U.S. patent application number 10/671694 was filed with the patent office on 2005-04-07 for micro-engineered reactors.
This patent application is currently assigned to ASTRAZENECA AB. Invention is credited to Shaw, John E.A., Shute, Richard E..
Application Number | 20050072686 10/671694 |
Document ID | / |
Family ID | 26245971 |
Filed Date | 2005-04-07 |
United States Patent
Application |
20050072686 |
Kind Code |
A1 |
Shaw, John E.A. ; et
al. |
April 7, 2005 |
Micro-engineered reactors
Abstract
The invention relates to a micro-engineered reactor device
comprising a closely coupled reactor and electrochemical cell, and
a method of using such a reactor for the synthesis of organic
compounds by a process involving an electrochemical reaction. The
synthetic processes are of a type in which a source material is
electrochemically converted to a reactive primary product which is
exposed at a reaction region within a channel, or chamber, to a
precursor material so that the primary product and precursor
material react to generate a secondary product.
Inventors: |
Shaw, John E.A.; (Middlesex,
GB) ; Shute, Richard E.; (Cheshire, GB) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
ASTRAZENECA AB
Soderstalje
SE
|
Family ID: |
26245971 |
Appl. No.: |
10/671694 |
Filed: |
September 29, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10671694 |
Sep 29, 2003 |
|
|
|
PCT/GB02/01608 |
Apr 5, 2002 |
|
|
|
Current U.S.
Class: |
205/334 ;
204/242 |
Current CPC
Class: |
B01J 2219/00853
20130101; C07F 7/2208 20130101; C07C 1/26 20130101; C25B 3/13
20210101; B01J 2219/00936 20130101; B01J 2219/00889 20130101; C07F
9/5352 20130101; B01J 2219/00835 20130101; B01J 2219/0086 20130101;
B01J 2219/00995 20130101; C07F 1/00 20130101; C07F 1/04 20130101;
C25B 3/00 20130101; B01J 2219/00867 20130101; C07F 3/02 20130101;
B01J 2219/00873 20130101; B01J 19/0093 20130101; C07C 1/26
20130101; C07C 15/04 20130101 |
Class at
Publication: |
205/334 ;
204/242 |
International
Class: |
C25D 017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 12, 2001 |
GB |
0109239.4 |
Oct 31, 2001 |
GB |
0126182.5 |
Claims
1. A micro-engineered reactor for performing chemical synthesis,
said reactor comprising: (a) a reaction chamber and an
electrochemical cell in close communication with the interior of
the reaction chamber; (b) said reaction chamber being of
micro-engineered dimensions and having micro-engineered inlet and
outlet conduits for conveying fluids to, and from, the reaction
chamber; (c) said cell comprising at least two electrodes
positioned and arranged relative to each other to define a space
between them, which, in at least one mode of use of the cell,
receives an ionically conductive fluid that is, or contains, a
redox-active source material, and forms an electrically conductive
path between the electrodes through which an electrical current
passes when an electrical potential is applied to the electrodes so
as to electrolyse the source material and form a primary product
at, or adjacent to, a surface of an electrode within the interior
of the reaction chamber; (d) means for introducing into the
reaction chamber a precursor material that will react with the
primary product to produce a secondary product, and (e) means for
conveying the secondary product away from the reaction chamber
through said outlet conduit.
2. A reactor according to claim 1 wherein at least one of the
electrodes has a surface at which, in use, the primary product is
formed, and the surface is located within, or forms a part of a
boundary wall of, the reaction chamber.
3. A reactor according to claim 1 wherein at least one of the
electrodes has a surface at which, in use, the primary product is
formed, made of, or coated with, a sacrificial material that will
react with the source material to form the primary product,
4. A reactor according to claim 3 wherein the cell further includes
an electro-depositing means for selectively applying an electrical
charge to each of the electrodes in the presence of an ionically
conductive fluid that contains ions of the sacrificial material,
thereby to cause the sacrificial material to be deposited on the
electrode or electrodes and replenish the sacrificial material that
is consumed by the electrolysis.
5. A reactor according to claim 4 wherein the electro-depositing
means is operable to deposit the sacrificial material on the
surface of the respective electrode or electrodes prior to, or
during reaction of the sacrificial material with the source
material to form the primary product.
6. A reactor according to claim 4 wherein the electro-depositing
means is operable to deposit the sacrificial material on the
surface of the respective electrode or electrodes prior to, or
during reaction of the sacrificial material with the source
material to form the primary product.
7. A reactor according to claim 4 wherein the electro-depositing
means comprises means for applying a negative charge to one of the
electrodes and a positive charge to the other electrode, and a
fluid supply means is provided for introducing a source of an
organic fluid containing a salt in which a cation is the
sacrificial material to be deposited on the negatively charged
electrode, and a means is provided for generating an electrical
field between the two electrodes so as to cause electro-deposition
of the material on to the surface of the negatively charged
electrode.
8. A reactor according to claim 4 wherein the electro-depositing
means comprises means for applying a negative charge to one of the
electrodes and a positive charge to the other electrode, and a
fluid supply means is provided for introducing a source of an
organic fluid containing a salt in which an anion is the
sacrificial material to be deposited on the positively charged
electrode, and a means is provided for generating an electrical
field between the two electrodes so as to cause electro-deposition
of the material on to the surface of the positively charged
electrode.
9. A reactor according to claim 7 wherein the organic fluid that
contains the ions of the sacrificial material is also the organic
reagent that will react with the deposited material to produce the
primary product.
10. A reactor according to claim 7 wherein the organic fluid that
contains the ions of the sacrificial material is also the precursor
that will react with the deposited material to produce the
secondary product.
11. A reactor according to claim 1 wherein at least one of the
electrodes is made of a fluid permeable material and defines a part
of the boundary wall of the reaction chamber through which a fluid
source material permeates to react at a surface of the fluid
permeable electrode that is in communication with the interior of
the reaction chamber to form the primary product.
12. A reactor according to claim 11 wherein a second chamber is
formed on a side of the fluid permeable electrode that is remote
from the interior of the reaction chamber, and an electrode of the
cell is located in the second chamber, said fluid permeable
electrode being made of a material that allows a primary product
created by electrolysis of a source material within the second
chamber to permeate through the permeable electrode into the
interior of the reaction chamber and to react with the precursor
material to form the secondary product.
13. A reactor according to claim 11 wherein the second chamber has
an inlet conduit for the supply of fluid containing fresh source
material to the second chamber and an outlet for removal from the
second chamber of fluids depleted of said source material.
14. A reactor according to claim 11 wherein a fluid permeable ionic
or electronic conductor is provided between the electrodes so as to
define a first region on one side of the conductor where an ion
conductive solution is retained in contact with the one of the
electrodes, and a second region on the other side of the said
conductor, where the conductor is in contact with the source
material.
15. A reactor according to claim 14 wherein the conductor is
mercury or an amalgam.
16. A reactor according to claim 1 wherein the cell is a
rechargeable cartridge.
17. A reactor according to claim 1 wherein there is provided a
fluid pumping means connected to the reactor for pumping the fluids
though the reactor.
18. A reactor according to claim 1 wherein the source material and
the precursor are present in a common fluid.
19. A reactor according to claim 1 wherein the source material is
present in a first fluid and the precursor is present in a second
fluid.
20. A reactor according to claim 1 wherein the outlet conduit of
the reaction chamber is divided into two or more discrete outlet
paths.
21. A reactor according to claim 20 wherein at least one or more
discrete outlet paths are connected to an inlet conduit of another
reactor constructed in accordance with claim 1.
22. A reactor according to claim 20 wherein one of the electrodes
of the cell is located in, or forms part of, the wall of the
reaction chamber and one of the electrodes of the cell is located
in or forms part of the wall of a conduit defining one of the
discrete outlet paths.
23. A reactor according to claim 1 wherein the reaction chamber is
constructed, dimensioned and arranged to define a plurality of
adjacent flow paths through the reaction chamber via respective
pairs of an inlet conduit and an outlet-conduit.
24. A reactor according to claim 1 wherein there is provided an ion
permeable barrier located between an anode and a cathode of the
cell so as to define an anodic compartment adjacent the anode on
one side of the ion permeable barrier and a cathodic compartment
adjacent the cathode on the other side of the ion permeable
barrier.
25. A reactor according to claim 24 wherein the barrier is selected
from the following materials, namely a porous or permeable sheet, a
dialysis membrane, an ion exchange membrane, a region of gelled
electrolyte or a region of immobilised electrolyte.
26. A reactor according to claim 1 wherein at least one of the
electrodes is a porous block through which fluids may flow.
27. A reactor according to claim 1 wherein there is provided a
first discrete inlet conduit for supplying the source material, a
second discrete inlet conduit for supplying the precursor, and a
third discrete conduit for supplying a flushing fluid for removing
the secondary product from the reaction chamber.
28. A reactor according to claim 27 wherein valve means are
provided for selectively opening and closing each of the first,
second or third inlet conduits.
29. A reactor according to claim 1 wherein one or more reference
electrodes means is provided in the reaction chamber or cell for
monitoring and controlling the electrical potential applied to the
electrodes of the cell.
30. A reactor according to claim 29 wherein one or more monitoring
electrode means is provided for monitoring the composition of the
products produced in the reactor.
31. A reactor according to claim 1 wherein there is provided
within, or adjacent to, the reaction chamber, a heat exchanger for
controlling the temperature of at least a region of the interior of
the reaction chamber.
32. A reactor according to claim 1 wherein the output conduit is
connected in flow series to an inlet conduit of another reactor
constructed in accordance with claim 1.
33. A reactor according to claim 32 wherein a plurality of series
connected reactors are provided on a common structure.
34. A reactor according to claim 32 wherein one or more arrays of
series connected reactors are arranged relative to another one or
more arrays of series connected reactors on a common structure.
35. A method of performing chemical synthesis comprising the steps
of: (a) providing a reactor constructed in accordance with claim 1
(b) presenting a source material to the space between at least two
electrodes; (c) electrolysing the source material to form a primary
product at, or adjacent to, a surface of the electrode that
communicates with the interior of the reaction chamber; and, (d)
contacting the primary product in the reaction chamber with a
precursor that will react and/or mix with the primary product to
produce a secondary product.
36. A method according to claim 35 including the step of removing
the secondary product from the reaction chamber.
37. A method according to claim 36 including the step of reacting
the secondary product with a material that is a precursor for use
in a further reaction, or a series of further reactions, to produce
a final product.
38. A method for preparing a synthetic organic compound comprising
the steps of: (a) providing a micro-engineered reactor constructed
in accordance with claim 1 wherein at least one of the electrodes
is made of, or coated with, a sacrificial material that will react
with the precursor to form the secondary product; (b) presenting a
source material to at least the electrode that consists of, or has
deposited thereon, the sacrificial material; (c) electrolysing the
source material and allowing the electrolysed source material to
react with the sacrificial material to form the primary product at,
or adjacent to a surface of the electrode; and, (d) contacting the
primary product in the reaction chamber with a precursor that will
react with the primary product to form the said organic
compound.
39. A method for preparing a synthetic organic compound comprising
the steps of: (a) providing a micro-engineered reactor constructed
in accordance with claim 1 wherein at least one of the electrodes
is made of, or coated with, a sacrificial material that will react
with the precursor to form the secondary product; (b) presenting an
organic source material to at least the electrode that consists of,
or has deposited thereon, the sacrificial product; (c)
electrolysing the source material and allowing the source material
to react with the sacrificial material to form the secondary
product at, or adjacent to a surface of the electrode; and, (d)
contacting the primary product in the reaction chamber with a
precursor that will react with the primary product to form the said
organic compound.
40. A method according to claim 38 further including the step of
replenishing the consumed sacrificial material by electro
depositing material on at least one of the electrodes.
41. A method according to claim 40 wherein the sacrificial material
is deposited on the respective electrode or electrodes by
connecting the electrodes to an electrical supply whereby one of
the electrodes forms a cathode and the other forms an anode, and
the method includes the steps of presenting to the cathode, a fluid
containing a salt in which a cation is the sacrificial material,
and applying an electrical field between the cathode and an anode
thereby to deposit the sacrificial material on the cathode.
42. A method according to claim 40 wherein the sacrificial material
is deposited on a surface of the respective electrode by connecting
the substrate to an electrical supply whereby one of the electrodes
forms a cathode and the other forms an anode, and the method
includes the steps of presenting to the anode, an ionically
conductive fluid containing a salt in which an anion is the
sacrificial material, and applying an electrical field between the
cathode and an anode thereby to deposit the sacrificial material on
the anode.
43. A method according to claim 41 wherein a fluid containing the
salt is presented to the electrodes whilst simultaneously applying
an electrical charge to the electrodes thereby to deposit the
sacrificial material onto at least one electrode, and the source
material is subsequently presented to the electrodes and allowed to
react electrolytically with the sacrificial material to form the
primary product
44. A method according to claim 41 wherein a fluid containing the
salt is presented to the electrodes whilst simultaneously applying
an electrical charge to the cathode thereby to deposit the
sacrificial material onto at least one electrode, and the source
material is presented to the electrodes simultaneously with the
salt, and allowed to react with the deposited sacrificial material
to form the primary product.
45. A method of performing chemical synthesis, comprising the steps
of: (a) providing a reactor constructed in accordance with claim 1
(b) introducing into the second chamber a fluid containing said
source material; (c) electrolysing said source material in said
second chamber so as to produce said primary product at a surface
of the fluid permeable electrode that is in communication with the
interior of the reaction chamber; and (d) contacting the primary
product in the reaction chamber with a precursor that will react
and/or mix with the primary product to produce a secondary
product.
46. A method according to claim 35 for the synthesis of lithium, or
sodium, or potassium alkyls wherein the source material is derived
from solutions of lithium, or sodium, or potassium salts, or solid
or polymeric ion conductors thereof, and the precursor is an alkyl
halide that reacts with the source material to form lithium, or
sodium, or potassium alkyls as the secondary product.
47. A method according to claim 35 for the synthesis of Sodium
Napthalenide wherein the source material is sodium, the precursor
is napthalene and the secondary product is sodium Napthalenide.
48. A method according to claim 35 for the synthesis of potassium
Napthalenide wherein the source material is potassium, the
precursor is napthalene and the secondary product is potassium
Napthalenide.
49. A method according to claim 35 for the synthesis of Sodium
anthacenide wherein the source material is sodium, the precursor is
anthracene and the secondary product is sodium anthacenide.
50. A method according to claim 35 for the synthesis of potassium
anthacenide wherein the source material is potassium, the precursor
is anthracene and the secondary product is potassium
anthacenide
51. A method according to claim 35 for the synthesis of Sodium
phenanthrenide wherein the source material is sodium, the precursor
is phenanthrene and the secondary product is sodium
phenanthrenide
52. A method according to claim 35 for the synthesis of Potassium
phenanthrenide wherein the source material is potassium, the
precursor is phenanthrene and the secondary product is potassium
phenanthrenide
53. A method according to 35 for the conversion of organotin
compounds wherein the source material is sodium, the precursor is
an organotin compound.
54. A method according to claim 53 for carrying out the conversion
of organotin compounds by a reaction of the type
Na.sup.++e.sup.-(from electrode).fwdarw.Na.sup.o
(CH.sub.3).sub.3Sn--Sn(CH.sub.3).sub.3+2Na.sup-
.o.fwdarw.2(CH.sub.3).sub.3Sn.sup.-Na.sup.+
55. A method according to claim 54 wherein the sodium compound is
further reacted with an organo halide in accordance with the
following formula:
(CH.sub.3).sub.3Sn.sup.-Na.sup.++CH.sub.2=CH--CH--Cl.fwdarw.(CH.sub.3).su-
b.3Sn--CH.sub.2-CH.dbd.CH+Na.sup.+Cl.sup.-
56. A method according to claim 35 for the generation of sodium,
lithium or potassium alkoxide or phenoxide in accordance with
formula Na/K/Li.sup.++e.sup.-(from electrode).fwdarw.Na/K/Li.sup.o
Na/K/Li.sup.o+R .sup.-OH.fwdarw.Na/K/Li.sup.+ -OR+H.sub.2 where
R=CH.sub.3, C.sub.2H.sub.5, C.sub.3H.sub.7, C.sub.4H.sub.9, Ph,
substituted Ph, heteroaryl, or substituted heteroaryl
57. A method according to claim 35 for the removal of halides from
aromatics by sodium metal in accordance with the reaction
Na.sup.++e.sup.-(from electrode).fwdarw.Na.sup.o
.sub.6-nNa.sup.o+C.sub.6-
H.sub.nCl.sub.6-n+solvent.fwdarw.C.sub.6H.sub.6+NaHal+solvent where
Hal=Cl, Br, or I
58. A method according to claim 35 for carrying out a Birch
Reduction of compounds in accordance with the reaction:
3C.sub.6H.sub.6 (benzone)+2Na+C.sub.2H.sub.5 OH (in liquid
ammonia).fwdarw.C.sub.6H.sub.8 (1,4 cyclohexadiene).
59. A method according to claim 35 for the generation of Grignard
reagents in accordance with the reaction: RX+Mg (in
ether).fwdarw.R--Mg--X where R=C.sub.6H.sub.5, and X=Cl, Br, or
I
60. A method according to claim 59 wherein the reaction is:
C.sub.6H.sub.5Br+Mg.fwdarw.C.sub.6H.sub.5MgBr.
61. A method according to claim 35 for the generation of
halogenated products wherein the source material is a soluble
halide, the primary product is a halogen produced by the
electrochemical oxidation of the soluble halide, and the halogen is
reacted with an organic precursor to produce a secondary
halogenated product by addition to unsaturated bonds or by
substitution.
62. A method according to claim 35 for the generation of
halogenated products wherein the source material is a soluble
halide, the primary product is a halogen produced by the
electrochemical oxidation of the soluble halide, and the halogen is
reacted with an inorganic precursor to produce an inorganic
reactive intermediate.
63. A method according to claim 61 wherein the halogen is chlorine,
the inorganic precursor is phosphorus, and the secondary product is
PCl.sub.3 or PCl.sub.5.
64. A method according to claim 61 wherein the secondary product is
reacted in the reaction chamber with a carboxylic acid to generate
acyl chloride products.
65. A method according to claim 35 for the generation of ylids from
phosphonium salt cations by the Wittig reaction and the reaction of
ylids and aldehyde to generate alkenes in accordance with the
formulae
(C.sub.6H.sub.5).sub.3P.sup.+CH.sub.2C.sub.6H.sub.4NO.sub.2+e.sup.-.fwdar-
w.(C.sub.6H.sub.5).sub.3P.sup.+C.sup.-HC.sub.6H.sub.4NO.sub.2
(C.sub.6H.sub.5).sub.3P.sup.+C.sup.-HC.sub.6H.sub.4NO.sub.2+HCOC.sub.6H.s-
ub.4NO.sub.2.fwdarw.NO.sub.2C.sub.6H.sub.4CHCHC.sub.6H.sub.4NO.sub.2
66. A reactor according to claim 8 wherein the organic fluid that
contains the ions of the sacrificial material is also the organic
reagent that will react with the deposited material to produce the
primary product.
67. A reactor according to claim 8 wherein the organic fluid that
contains the ions of the sacrificial material is also the precursor
that will react with the deposited material to produce the
secondary product.
68. A reactor according to claim 21 wherein one of the electrodes
of the cell is located in, or forms part of, the wall of the
reaction chamber and one of the electrodes of the cell is located
in or forms part of the wall of a conduit defining one of the
discrete outlet paths.
69. A method according to claim 39 further including the step of
replenishing the consumed sacrificial material by electro
depositing material on at least one of the electrodes.
70. A method according to claim 42 wherein a fluid containing the
salt is presented to the electrodes whilst simultaneously applying
an electrical charge to the electrodes thereby to deposit the
sacrificial material onto at least one electrode, and the source
material is subsequently presented to the electrodes and allowed to
react electrolytically with the sacrificial material to form the
primary product.
71. A method according to claim 42 wherein a fluid containing the
salt is presented to the electrodes whilst simultaneously applying
an electrical charge to the cathode thereby to deposit the
sacrificial material onto at least one electrode, and the source
material is presented to the electrodes simultaneously with the
salt, and allowed to react with the deposited sacrificial material
to form the primary product.
72. A method according to claim 62 wherein the halogen is chlorine,
the inorganic precursor is phosphorus, and the secondary product is
PCl.sub.3 or PCl.sub.5.
73. A method according to claim 62 wherein the secondary product is
reacted in the reaction chamber with a carboxylic acid to generate
acyl chloride products.
Description
[0001] The invention relates to micro-engineered reactors for use
in the synthesis of organic compounds by a process involving an
electrochemical reaction, and to methods of using such
micro-engineered reactors. The synthetic processes are of a type in
which a source material is electrochemically converted to a
reactive primary product which is exposed at a reaction region
within a channel, or chamber, to a precursor material so that the
primary product and precursor material react to generate a
secondary product.
[0002] Electrochemical reactions are relatively little used in
organic synthesis. This is due to a variety of limitations, which
include the identification of few clean and direct electrochemical
conversions of organic species, limitation to polar ionically
conductive media which are incompatible with many organo-synthetic
processes, and relatively low ionic conductivity of organic
solutions, which can limit current and throughput. It is possible
to increase current by increasing applied potentials but this tends
to increase heating of the ionically conducting fluid body and
introduce difficulties in achieving controlled potentials at the
electrodes and clean electrochemical processes.
[0003] There are however, many widely used synthetic reactions,
which utilise reactive high-energy reactants. Examples of such
reactants are organometallic materials such as lithium or sodium
alkyls, and Grignard reagents. Long term storage of such materials
can be impractical or hazardous and they are often synthesised
shortly before use from precursor reagents and active metals. The
active metals, used in the synthesis of the organometallics,
especially the alkali metals, may themselves be hazardous or
difficult to handle, and may on storage accumulate corrosion
products that interfere with their use in organic syntheses. The
active metals are normally supplied by the producers as sheet, rod,
or granules which may have to be cut or otherwise mechanically
processed in dry oxygen free or otherwise protected environments
before being employed in organic synthesis to produce sufficient
clean active surface area. The handling and processing of these
active metals can be hazardous and adds to process complexity and
to the cost of generating the desired organometallic reagents.
Active metals for use in the synthesis of organometallic species
according to conventional procedures can be or are generated
electrochemically. It is an advantage of the proposed devices that
such material is generated in situ as a primary product for
reaction with a precursor reagent. The proposed devices allow the
controlled generation of active metals and their derivatives in
enclosed structures minimising hazards associated with handling
excess material and exposure to contaminants.
[0004] Micro-fabrication techniques are known in the semiconductor
industry for the manufacture of integrated circuits and the
miniaturise of electronics. It is also possible to fabricate
intricate fluid flow systems with channel sizes as small as a
micron (10.sup.-6 metre). These devices can be mass-produced
inexpensively and are expected to soon be in widespread use for
simple analytical tests. See, e.g., Ramsey, J. M. et al. (1995),
"Microfabricated chemical measurement Systems," Nature Medicine
1:1093-1096; and Harrison, D. J. et al. (1993), "Micro-machining a
miniaturised capillary electrophoresis-based chemical analysis
system on a chip," Science 261:895-897. Miniaturisation of
laboratory techniques is not a simple matter of reducing their
size. At small scales different effects become important, rendering
some processes inefficient and others useless. It is difficult to
replicate smaller versions of some devices because of material or
process limitations. For these reasons it is necessary to develop
new methods for performing common laboratory tasks on the
micro-scale.
[0005] Devices made by micro-machining planar substrates have been
made and used for chemical separation, analysis, and sensing. See,
e.g., Manz, A. et al. (1994), "Electro-osmotic pumping and
electrophoretic separations for miniaturised chemical analysis
system," J. Micromech. Microeng. 4:257-265. In addition devices
have been proposed for preparative, analytical and diagnostic
methods which bring two streams of fluid in laminar flow together
which allows molecules to diffuse from one stream to the next,
examples are proposed in WO9612541, WO9700442 and U.S. Pat. No.
5,716,852.
[0006] In this disclosure, the terms "microfabricated" and
"micro-engineered" includes devices capable of being fabricated on
plastic, glass, silicon wafers or any other material readily
available to those practising the art of microfabrication, such as
photolithography, screen printing, wet or dry isotropic and
anisotropic etching processes, reactive ion etching (RIE), laser
assisted chemical etching (LACE), laser and mechanical cutting of
metal, ceramic, and plastic substrates, plastic laminate
technology, LIGA, thermoplastic micropattern transfer, resin based
microcasting, micromolding in capillaries (MIMIC), and, or other
techniques known within the art of microfabrication. As in the case
of silicon microfabrication, larger wafers can be used to
accommodate a plurality of the devices of this invention in a
plurality of configurations. A few standard wafer sizes are 3" (7.5
cm), 4" (10 cm), 6" (15 cm), and 8" (20 cm). Application of the
principles presented herein using new and emerging microfabrication
methods is within the scope and intent of the present invention.
Microfabricated devices may be created through combinations of
manufacturing processes such as: (1) photolithography, the optical
process of creating microscopic patterns (2) etching, the process
that removes substrate material and (3) deposition, the process
whereby materials with a specific function can be coated onto a
surface of the substrate.
[0007] Connections with liquid reservoirs external to the device
may be made by a variety of means including adhesive bonding to
fine tubes and capillaries, anodic or other bonding to manifold
structures linked to macroscopic unions, or methods in accordance
with Mourlas N. J. et al. Proceedings of the .mu.TAS'98 Workshop,
Kluwer Academic Publishers 27-, and references cited therein.
[0008] An object of the present invention is to provide a
micro-engineered reactor, and method of using such a
micro-engineered reactor, suitable for the synthesis of organic
compounds involving reaction with a material produced in situ by
electrochemical means that overcomes at least some of the problems
encountered in the past, and exploits the advantages of
micro-engineered flow passages.
[0009] By employing reactors of micro-engineered dimensions, it is
possible to achieve short ionically conductive pathways limiting
resistive voltage drops and heating. The short distance across
fluids to surfaces that can be cooled avoids excessive temperature
rises, either from ohmic (Joule) heating or from reactions of
high-energy products. Flowing reagents through relatively narrow
channels or chambers allows rapid diffusive transfer of reagents to
surfaces so that precursor reagents can be efficiently and rapidly
presented to the primary electrochemical products, such as reactive
metal layers. Generating the active primary product and subsequent
products in the reactor device as required, avoids the accumulation
of hazardous inventory and the device provides a level of
confinement and avoids dangers inherent in handling of the
materials.
[0010] By using micro-engineering techniques, the depths of
features are generally defined by etching or deposition of material
and it is possible to form conduits or flow channels with depth
dimensions down to .about.1 .mu.m. In general in the present
invention, the term "micro-engineered" refers to channels with
depths of 0.1 to 1000 .mu.m. Although channel depths up to 1000
.mu.m allow significantly greater throughputs, and lower flow
resistance, the preferred range of sizes are between 1 to 500 .mu.m
and especially 30 to 300 .mu.m. Channel widths and lengths are
generally defined by lithographic techniques, and may range from a
few micrometers to centimetre dimensions. By using combinations of
such conduits or flow channels, transit and mixing times of the
order of seconds down to milliseconds in liquids, and microseconds
in gases may be achieved.
[0011] The use of electricity to drive redox reactions is also well
understood and is applied in electrolytic extraction of aluminium
metal from ore using molten electrolyte, electroplating and
rechargeable batteries. An electrochemical redox process is one in
which one or more electrons is transferred between an electrode and
a chemical species in an electrochemical cell. Chemical species
which are able to gain or loses electrons in this way are redox
active species. Such species may be transformed to other species by
the transfer of electronic charge and may undergo further
transformations including rearrangements, reaction, and phase
changes.
[0012] A further object of the present invention is to provide a
new use of the basic technique of using electricity to drive a
redox process within a reactor device to produce in situ a reactive
product that is reacted within the device as part of a synthetic
reaction.
[0013] Operation of reactor devices according to the present
invention involves a number of transport processes that are
affected by the construction and dimensions of the reactor device
so that the preferred dimensions are within the range appropriate
for micro-engineering techniques. Processes involved typically
include electro-migration, electrodeposition, and diffusion of
materials and reagents to reaction sites such as electrodes and
electrodeposits, mixing of fluid reagent streams, reaction, and
heat generation or consumption and heat transport. As described
later, the conditions for rapid ion migration, material transfer by
diffusion, and heat transfer across fluid layers in a reactor, are
improved, and the ratio of reaction flux to reaction zone volume
can be enhanced where cross layer thickness are in the
microengineering range from 1 .mu.m to 1000 .mu.m, and preferably
in the range 30 .mu.m to 300 .mu.m.
[0014] According to one aspect of the present invention there is
provided a micro-engineered reactor device that is suitable for the
electrochemical synthesis of organic compounds.
[0015] According to another aspect of the present invention there
is provided a method of using the micro-engineered reactor for the
purpose of manufacturing organic compounds.
[0016] The present invention will now be described by way of
examples, with reference to the accompanying drawings, in
which:--
[0017] FIGS. 1a and 1b show schematically, two types of
micro-engineered reactor device incorporating the present
invention.
[0018] FIGS. 2 to 17 show schematically micro-engineered reactor
devices incorporating embodiments of the present invention.
[0019] In the FIGS. 1a to 17 the reactor devices are shown in cross
section such that channel heights and lengths are represented
schematically. Channel widths are not indicated but may be similar
to the heights of the reactor, or greater, up to the limits imposed
by widths of materials or substrates used to fabricate reactor
devices.
[0020] In general terms, the present invention has a wide
application to the synthesis of organic compounds by reaction with
a reactive primary product generated electrochemically from a
source material. In general terms a source material is
electrochemically converted to a reactive primary product which is
exposed to a precursor material at a reaction region within a
channel, or chamber, so that the primary product and precursor
material react to generate a secondary product. For, example, the
precursor material may consist of, or include a fluid organic
reagent. The organic reagent may be dissolved in a solvent. In one
example, the primary product is a reactive metal electrochemically
generated from a source material which may be a salt or other redox
active compound of the metal. The precursor and primary product
react to form a secondary product, which may be an organometallic
compound.
[0021] The source material may be resident at, or adjacent to, an
electrode and may be transferred to the electrode region by fluid
flow. Preferably the source material is one that is mobile and may
possibly be dissolved in a solvent. The source material will
preferably be a salt or other redox active compound capable of
being converted by electrolysis to form the primary product.
[0022] The reactor device may include provision for reaction of the
secondary product with further reactants, either within the
channel, or chamber, where the secondary product is formed, or in
other channels, or chambers, to which the secondary product is
conveyed by fluid flow. The device will have not less than two
spaced electrodes, the working and counter electrodes, between
which an ionically conductive material is presented, and an
electrical current passed through the electrodes and the
intervening ionically conductive materials (or phases) during the
electrochemical generation of the primary product. The primary
product is formed electrochemically at the working electrode. Other
redox processes will occur at the counter electrode.
[0023] The ionically conductive material may consist of, or include
the source material and may include solvents and supporting
electrolytes and redox active material to support electrochemical
processes at the counter electrode. Solvents used for source
material, supporting electrolyte, and precursor material, may be
the same or different materials, and may be miscible or immiscible.
Polar aprotic solvent may be especially favoured for providing
ionically conducting phases.
[0024] The process carried out in the micro-engineered reactor
device will be a combination of an electrochemical redox process
which generates a primary product, such as a reactive metal deposit
or other highly reactive or unstable electrochemically generated
species, and reaction of the primary product with supplied reagent
or precursor material to generate a secondary product such as an
organometallic species, within the same micro-engineered reactor
device, or similar micro-engineered reactor devices.
[0025] Although the preferred embodiment of the invention is
intended for the synthesis of organomettalic compounds by the
electrochemical generation of reactive metals as primary products
and their reaction to produce organometallics as secondary
products, the generation of non metallic primary products for
subsequent reaction is included. Such primary products may be
electrochemically generated non-metallic materials, including
elements and compounds, and may include species or materials
generated by direct electrochemical oxidation or reduction of
organic species including organic ions, and may include free
radical species. Primary products may remain at least temporarily
where formed at, or adjacent to, an electrode until exposed and
reacted with precursor material to form secondary products that may
be conducted from the reaction site by fluid flow. Alternatively,
primary products generated in a first part of the reactor device,
or similar micro-engineered reactor devices, may be carried
dissolved, or in suspension, in a fluid phase (e.g. as particulate
or colloidal metal), and conveyed by fluid flow from that first
part of the reactor device, or devices, to a second part for mixing
and reaction to form secondary products. The secondary products may
themselves be used as reactants to generate tertiary products
either within the device or after transfer to another device or
environment.
[0026] In some cases, it may be that the processes of formation of
primary and secondary products and any intermediate forms are not
resolved, and it is not necessary that they be resolved to achieve
the purpose of the invention.
[0027] In the preferred embodiments of the invention, the proposed
micro-engineered reactor device has conduits to carry one or more
reactant solutions into a chamber containing one or more electrodes
and transfer product solutions from the chamber. The conduits and
chamber are formed by micro-engineering techniques.
[0028] The active metals for use in the synthesis of organometallic
species can be generated electrochemically and it is an advantage
of the proposed reactor devices that such material is generated in
situ as a primary product for reaction with a precursor reagent.
Application of the precursor reagent to the electrolytically
generated primary product is performed either immediately or after
a short delay, producing a secondary product such as a reactive
organometallic species. The reactor device may be a convenient
source on demand of reagents such as organometallics from readily
available and non-hazardous precursors. A further advantage is that
the secondary products may be utilised in situ avoiding storage
losses and hazards.
[0029] The reactor devices proposed allow a series of source or
precursor materials or reagents to be brought together in a
controlled manner with electrolytic processes applied only as
required. It is thus possible to employ redox active reagents and
generate redox active products whilst controlling which are exposed
to electrochemical conversion processes.
[0030] Electronic circuits for passing charge through the reactor
device may be operated to control potentials and current and vary
these over time. These may include potentiostatic and galvanostatic
circuits.
[0031] Reactor devices according to the present invention may be
operated in two modes. In the first mode (hereinafter called "the
continuous mode", the electrochemical generation of primary product
and supply of precursor are carried out at the same time allowing
continuous reaction and generation of secondary product. In the
second mode, hereafter called "the discontinuous mode", the
electrochemical generation of primary product is carried out in a
first time period and supply of precursor carried out in a second
time period. Primary product is accumulated in the first period and
reaction of accumulated primary product with precursor to generate
secondary product occurs within the second period. First and second
periods may be repeated alternately. Other time periods may
separate first and second, and second and first periods. Flushing
or cleaning solutions may be applied to the reactor device during
these other periods. Operation in discontinuous mode allows
different solvent systems to be used during the processes of
primary product formation and of reaction of primary product with
precursor to form secondary product. This extends the range of
chemistries, which can be used as the optimum conditions, and
solvent environment may not be the same for the processes of
primary product formation and of reaction of primary product with
precursor to form secondary product.
[0032] Two basic geometries or types are preferred for the reactor
devices of the present invention. Devices of the first type or
geometry (shown schematically in FIG. 1a) incorporate an
electrochemical cell, where at least some of the space between the
working and counter electrodes is occupied by fluid containing
source material, ionically conductive material, and redox active
material to support electrochemical processes at the counter
electrode, which materials may be the same or different, such that
an ionically conductive path links the electrodes to carry current
between the electrodes, and that space is also occupied by
precursor for the reagent to be generated, either at the same time
or at different times as discussed above. The electrodes may be
disposed on opposite sides of a chamber or flow channels as
indicated diagrammatically in FIGS. 1a and 1b or side by side on a
wall of a chamber or flow channel.
[0033] Reactor devices of the second type or geometry (shown
schematically in FIG. 1b), incorporate an electrochemical cell
where the space used for ion conduction during the electrochemical
generation of the primary product, and the space for precursor
addition and transfer, are separated by a structure which at least
includes an electrode structure at which the primary product is
generated, and where such separating structure allows for material
transfer enabling primary product and precursor to be brought
together.
[0034] Devices of the second type or geometry may be run in
continuous or discontinuous mode as for devices of the first type
or geometry. With the second type of geometry, there is no need to
clear electrolyte out of the precursor or product fluid flow path.
However, it may be convenient to run the device in a discontinuous,
or pulsed, mode, to allow sufficient primary product (such as
alkali metal) to build up on the working electrode, or allow
alternation of supply of precursor material, and of source material
where the source material is supplied in a fluid, and that fluid is
different to that for precursor supply, or to allow changes in the
solvent used for transporting precursor to the working electrode
and the product from it. Structures with multiple fluid inlets and
outlets may also be used for devices of the second type or
geometry.
[0035] Referring to FIGS. 1a and 1b, the reactor device, of the
first type is shown schematically in FIG. 1a, and comprises a
chamber 11 in which are located two electronically conductive
structures or substrates that form two electrodes, the working
electrode 13, and the counter electrode 14. In use the electrodes
13, 14 are connected to an electrical supply so that a potential is
applied between the electrodes 13, 14. The chamber 11 has an inlet
12 for receiving one or more fluids, which fluid or fluids are
utilised in electrochemical product formation and reaction in
chamber 11.
[0036] A first fluid entering chamber 11 consists of, or contains,
an ionically conductive material, and a source material such as,
for example, a metal salt dissolved in an organic fluid, so that
there exist an ionically conducting pathway through chamber 11
between electrodes 13 and 14. Consequent to current passage between
electrodes 13 and 14, the electrochemical formation of a primary
product such as, for example a metal, causes the metal 16 to
deposit on the electrode 13.
[0037] A second fluid entering chamber 11 that may be the same as
the first fluid or combined with the first fluid stream, consists
of, or contains, a precursor reactant, (such as, for example, an
alkyl halide). The precursor reagent reacts with the primary
product to form a secondary product, (such as, for example, an
organometallic compound). The second fluid (precursor reactant)
flows though chamber 11 along a fluid pathway 17 adjacent to
electrode 13 that may occupy all, or part only, of chamber 11.
[0038] The primary product 16 electrochemically deposited on one or
more surfaces of the substrate 13 is, in use, exposed to the
precursor reagent in the chamber 11. The primary product 16 reacts
with the precursor reagent to form the secondary product. The
source material and the ion conductive material may be the same, or
different, materials, and if different materials, they must both be
present in the chamber 11 when current is passed to form primary
product 16.
[0039] The source material and precursor material may be conveyed
in the same or different fluids, at the same time or at different
times. The chamber 11 has an outlet 15, through which reaction
product such as, for example, an organometallic compound is
removed. Spent fluid or fluids containing depleted source material
and precursor reagent may leave chamber 11 through outlet 15. The
function of inlet 12 and outlet 15 may be changed from time to time
by reversing fluid flow through chamber 11.
[0040] The second type or geometry of reactor device is shown
schematically in FIG. 1b. In this type of device the volume used
for ion conduction is separated from that used for precursor
addition and transfer.
[0041] The reactor device of the second type comprises a chamber 11
in which is located two electronically conductive substrates
forming electrodes, working electrode 13, and counter electrode 14.
In use the electrodes 13, 14 are connected to an electrical supply
so that a potential is applied between the electrodes 13, 14. The
chamber 11 has an inlet 12 for receiving one or more fluids which
are carried through chamber 11 to an outlet 15 along a fluid
pathway 17 adjacent to electrode 13 but not between electrodes 13
and 14.
[0042] The reactor device of the second type shown in FIG. 1b
involves a separation of the volumes within the chamber 11. The
volume 11a that is used for ion conduction is separated from the
volume 11b that is used for the reaction of the precursor and
reagent addition and transfer of the products of the reaction by
the working electrode 13 which is permeable to allow material
transfer across the electrode 13. In this way the primary product
and precursor reactant are brought into contact within the volume
11b to form secondary product which may be transferred into the
adjacent fluid flow path 17.
[0043] The permeability of the electrode 13 may be achieved by
using as structure with pores, or vias, such as a mesh or an array
of strips, or by using an electrode material that is inherently
permeable to the primary product or the fluid containing precursor
reagent and secondary product.
[0044] A further requirement of the second type of geometry is that
a counter electrode 14 is located within the chamber 11, but out of
the flow path 17 of the precursor reagent, and that that region 18
of chamber 11, between electrodes 13 and 14, contains ionically
conductive material, at least during the electrolytic generation of
primary product 16 at electrode 13.
[0045] Region 18 may be furnished with inlet and outlet tubes not
shown in FIGS. 1a and 1b, or may be occupied by a static ion
conductive phase which may be a fluid, semi-solid, or solid ion
conductor. The ion conductive phase may contain or consist of the
source material. Source material for electrochemical conversion to
primary product may be introduced to region 18 or the flow path 17
depending on the selected chemistry. Preferably this arrangement
allows primary products, produced at the working electrode 13 by
the electrochemical reaction on the source material by passage of
electrical current through the ion conductive material between
electrodes 13 and 14, to be presented through the electrode 13 and
interact with precursor reagent in the adjacent flow path 17.
[0046] Electrical current passage between electrodes 13 and 14
through region 18 of chamber 11 causes electrochemical formation of
a primary product such as, for example, a metal deposit 16, at
electrode 13. The fluid entering chamber 11 along flow path 17
adjacent to electrode 13 is, or contains, a precursor reactant such
as, for example, an alkyl halide, to form a secondary product such
as, for example, an organometallic compound, by reaction with the
primary product.
[0047] The fluid pathway 17 may not occupy that part of chamber 11
between electrodes 13 and 14. The primary product 16
electrochemically deposited on one or more surfaces of the
substrate 13 is, in use, exposed to the precursor reagent in the
chamber 11. The primary product 16 as, for example, a sacrificial
layer of a metal on electrode 13 will react with the precursor
reagent to form the secondary compound.
[0048] As explained above with regards to devices of the first
type, with devices of the second type, the source material and
precursor material may be conveyed in the same or different fluids,
at the same time or at different times.
[0049] The chamber 11 has an outlet 15, through which reaction
product such as, for example, an organometallic compound is
removed. Spent fluid or fluids containing depleted source material
and precursor reagent may leave chamber 11 through outlet 15. The
function of inlet 12 and outlet 15 may be changed from time to time
by reversing fluid flow through chamber 11.
[0050] For devices of both the first and second type, the source
material and ion conductive material may be the same, or different,
and if different, must both be present in the chamber 11 when
electrical current is passed between the electrodes 13, 14 to form
primary product 16. The source material and precursor material may
enter the chamber in the same or different fluids at the same or
different times.
[0051] The primary product 16 is generated from the source material
by charge transfer at the working electrode 13. Where the primary
product 16 is generated by a reductive process, as where the
primary product is a metal produced by electrochemical reduction of
a metal salt or compound at the working electrode 13, that working
electrode is connected as a cathode. This is achieved by connecting
the electrodes 13 and 14 of the electrochemical cell into an
external electrical circuit which maintains a potential bias
between the electrodes such that conventional current flows from
the working electrode 13 into the external circuit. Most generally
this corresponds to the working electrode 13 as cathode being
biased at a potential negative with respect to the counter
electrode 14 as anode as indicated schematically in FIGS. 1a and
1b.
[0052] Alternatively, where the primary product 16 is generated by
an oxidative process, as where the primary product is for example a
halogen generated from a halide salt source material at the working
electrode 13, that working electrode is connected as an anode. This
is achieved by connecting the electrodes 13 and 14 of the
electrochemical cell into an external electrical circuit which
maintains a potential bias between the electrodes such that
conventional current flows from the counter electrode 14 into the
external circuit. Most generally this corresponds to the working
electrode 13 as cathode being biased at a potential positive with
respect to the counter electrode 14 as cathode.
[0053] In operation the primary product 16 such as, for example, a
sacrificial metal layer is electrochemically deposited on the
electrode 13 by connecting the electrode 13 as a cathode and the
electrode 14 as an anode in an electrical circuit. An ionically
conductive material is presented in the space between the
electrodes 13 and 14 and a source material that may be a salt or
redox active compound of the metal is presented at least to the
working electrode 13. Application of a potential difference between
the electrodes 13, 14, causes an electrical current to flow between
the anode and cathode, thereby causing the primary product 16 (such
as, for example a metal) to be electro-deposited on the working
electrode 13.
[0054] In discontinuous mode operation, the electrochemical
generation of primary product 16 is carried out in the absence of
precursor reagent until sufficient primary product has been
deposited on the working electrode 13. The electrical potential
maintaining current through the cell between the anode and cathode
is removed, and the organic precursor reagent is caused to flow
through the chamber 11 along flow path 17 to react with the primary
product 16. This mode of operation is effectively a "discontinuous"
or batch process.
[0055] In the embodiment just described, the primary product 16 is
deposited prior to introducing the precursor reagent into the
chamber 11. In an alternative embodiment, continuous mode
operation, the primary product 16 may be electrochemically
generated at the same time as carrying out the passage of precursor
reagent through fluid path 17 and reaction of the precursor reagent
with the primary product 16. This mode of operation is effectively
a "continuous" process.
[0056] Operation of various embodiments of the invention and the
structures of various micro-engineered reactor devices constructed
in accordance with the present invention, are illustrated in FIGS.
2 to 17.
[0057] FIG. 2 shows schematically a continuous process in a reactor
of the first type where there is a continuous flow through the
chamber 11 of ionically conductive reagent mix containing source
material, which may be a salt (e.g. M.sup.+Y.sup.-) and a precursor
reagent (e.g. R--X). Source material (e.g. M.sup.+Y.sup.--) is
caused to flow in flow path 17 between energised electrodes 13 and
14 to produce electrolytic primary product 16 (e.g. M.sup.o) in
flow path 17 at or adjacent to electrode 13, which primary product
can then react with organic precursor reagent (e.g. R--X) to
produce useful secondary product (e.g. M-R). The primary product is
formed on the working electrode as an adherent deposit (as
represented schematically in the upper half of FIG. 2), or it may
pass into the fluid flow as solution or suspension as represented
schematically in the lower half of FIG. 2. It is not necessary that
an electrolytic intermediate primary product 16 (e.g. M.sup.o) be
identifiably formed. The useful secondary product (e.g. M-R) may be
carried by fluid flow to a subsequent junction 19 to which a
further reactant (e.g. R'-W) is brought through conduit 20 for
mixing and reaction (e.g. M.fwdarw.R--R'). Tertiary product R--R'
is carried away in flow through output conduit 21. Reagent R'--W
and tertiary product R--R' mat be compounds which would be subject
to alteration if they passed through the electrochemical cell
section e.g. where R'--W could not be introduced in the feed stream
to the electrochemical cell. The simplest structure achieving the
above is represented diagrammatically in FIG. 2 where the indicated
process involves reduction of M.sup.+ at the negatively polarised
working electrode 13 operating as the cathode.
[0058] Alternative processes may involve reaction with primary
product 16 formed by an oxidative process (e.g. Cl.sub.2 generated
from source material containing Cl.sup.-) formed where the
positively biased working electrode 13 operates as the anode.
[0059] Although electrochemical conversion of a singly charged
positive ion M.sup.+ is shown, the process is applicable to source
materials containing multiply charged, negatively charged, and even
neutral species as long as they are electrochemically active. The
charge and the relative importance of electrophoretic migration,
diffusion, and advective processes may affect the material transfer
to electrodes. In the simple structure shown schematically in FIG.
2, the anode and cathode both directly contact the reagent stream
and products from both the anodic region and the cathodic region
will be carried into subsequent reaction zones. These may include
side products from both anodic and cathodic electrode regions. Side
products from the counter electrode 14 that are not directly
involved in the required reaction may be diverted from subsequent
reaction zones by suitable flow arrangements.
[0060] Methods of diverting unwanted products from the reactor
zones are indicated diagrammatically in the device of FIG. 3. This
may involve separating flows from around the counter electrode 14
and the working electrode 13 with the required products leaving
chamber 11 through outlet 15, and unwanted products from the region
adjacent to electrode 14 passing along an output conduit 22.
[0061] Electrodes may be positioned outside the flow stream leading
to subsequent reaction sites as indicated in FIG. 4:
[0062] As indicated in FIG. 4, the counter electrode 14 may be
positioned in an outlet conduit 22 outside the flow stream 17
adjacent to electrode 13 as long as a sufficiently ionically
conductive pathway can be maintained between electrodes 13 and 14.
Unwanted products are carried away through conduit 22 without
contaminating the desired products passing through outlet 15.
[0063] As in indicated FIG. 5, the feed streams to the anode 14 and
cathode 13 may be different, with flow of source material and
precursor reagent from inlet 12 flowing into the chamber 11
adjacent to electrode 13, and fluid from inlet 23 flowing past
electrode 14. The two fluids may be of different composition and
may be immiscible as long as both have sufficient ionic
conductivity to maintain a conductive path between anode 14 and
cathode 13.
[0064] As well as separating the products from the two electrodes
by flow arrangements as indicated above, the fluid paths could be
controlled by addition of an ion permeable barrier between the
anodic and cathodic regions. This might be a porous sheet, dialysis
membrane, ion exchange membrane, or region of gelled or otherwise
immobilised electrolyte.
[0065] As well as separating the products from the two electrodes
13, 14 by flow arrangements as indicated above, the fluid paths
could be controlled positioning an ion permeable barrier 24 between
the regions adjacent to the electrodes 13, 14. This barrier 24
divides the chamber 11 into cathode and anode compartments as shown
in FIG. 6. The barrier 24 could be a porous sheet, dialysis
membrane, ion exchange membrane, or a region of gelled or otherwise
immobilised electrolyte.
[0066] One or more of the electrodes may be constructed as a porous
or mesh type electronically conductive structure as shown in FIG.
7. This can increase electrode surface area and a porous body may
be used to establish a region within the chamber 11 through which
part of the fluid passes. Within a porous electrode structure the
diffusion and thermal conduction distances through solution to the
electrode material are decreased. In the device of FIG. 7 the
working electrode 13 for primary product formation and reaction
takes the form of an electronically conductive porous body. Such a
porous electrode could be used in combination with an ion permeable
membrane of the type represented in FIG. 6.
[0067] In the reactor devices shown in FIGS. 2 to 17, the
dimensions of the channels through which the fluids flow, are such
that reagents flowing past the working electrode 13 or electrode 14
may effectively be carried, for example, by diffusion, to the
electrode surface to react with the respective electrode. The
electrodes 13, 14 may form part of the channel wall (as shown in
FIGS. 2 to 6) or may be discrete structures separate from the
channel or chamber walls. The electrodes may additionally be
constituted as porous blocks or meshes of electronically conductive
material. Fluid may be passed over the surface of a porous
electrode or be pumped to flow through the porous electrode so that
electrode processes and electrode position may occur at the pore
walls.
[0068] Variants with porous electrodes may be based on other
options described here and used with continuous or discontinuous
operation.
[0069] Although shown for continuous operation, the structure of
FIGS. 2 to 7 above may also be employed for discontinuous
operation. In this mode, an electrical current is passed between
the electrodes 13, 14 to produce a primary product, for example a
metal such as lithium, which is retained at, or adjacent to the
working electrode 13. The region adjacent electrode 13 is thus
loaded with the primary product. Subsequently, a precursor reagent,
or solution of that precursor reagent, is presented to the
electrode 13 that is loaded with primary product, such that, the
reagent reacts with the primary product to produce a secondary
product.
[0070] The reaction between primary product and precursor reagent
need not involve electrical current passing through the device, and
the precursor reagent solution need not be ionically conductive.
This secondary product may dissolve in a fluid containing the
precursor reactant, and may be carried by that fluid to a further
reaction site within the device. Alternatively, the primary product
when formed may be deposited within the chamber 11 or outlet
channel 15 or in a receptacle at the exit from outlet channel
15.
[0071] Another fluid may be passed in contact with the secondary
product, either deposited in the device or held in the fluid in
which it is generated, to receive the secondary product by
dissolution or transfer between fluids, and carry the secondary
product from the electrode region, and that flow may carry the
secondary product to a further reaction site externally or within
the device.
[0072] Operation of a reactor device in discontinuous mode using
two fluids passing alternately through the reactor device is
illustrated in FIG. 8.
[0073] In FIG. 8A, an ionically conductive solution from inlet 23
(solution of M.sup.+Y.sup.-, e.g. a Lithium salt) flows through the
chamber 11 and an electrical current is passed between the
electrodes 13, 14, to cause the accumulation of a primary product
16 (M.sup.o e.g. deposition of Lithium metal at the cathode) at the
electrode 13. Once sufficient deposit has built up, the electrical
current is stopped, and the fluid flows are changed, as indicated
in FIG. 8B, so that electrolyte flow from inlet 23 is terminated
and a precursor reagent fluid (R--X solution) is introduced through
inlet 12. The reagent fluid reacts with the primary product 16
deposited on cathode 13 generating a product which is carried to a
junction 19 with a second reagent flow from inlet conduit 20
allowing mixing and reaction at and beyond the junction 19.
[0074] As represented in FIGS. 8A and 8B, the junctions between
different fluid flows are open, and flow control is exercised by
changing pressures and flows at the inlets 12, 23 and 20. For
micro-devices this is often adequate, and may be used where a small
level of contamination of one fluid with another may be tolerated.
It may however be advantageous to insert valve structures at one or
more of the junctions inlets 12, 23 and 20 to control the flows of
fluids and to control contact between the fluids.
[0075] In those instances, where the solution conveying the
precursor reagent to the electrode 13 loaded with primary product
does not dissolve or carry away the secondary product that is
formed, a third fluid may be introduced into the cycle through an
inlet 24 as indicated in FIG. 9. The use of a third fluid stream
may prove useful even where the product can be dissolved or carried
away in the second fluid. Greater control and flexibility of system
operation may be achieved by interposing a solvent or different
fluid between the tonically conducting fluid introduced through
inlet 23 and a precursor introduced through inlet 12. This may also
ensure that mixing between those fluids is minimised thereby
reducing product contamination and side reactions.
[0076] Arrangements for linking inlets 12, 20, 23, or 24 of various
fluid sources may be chosen for convenience in fabrication or
sequence of operation as shown in FIG. 10, and may include use of
valves 25 as shown in FIG. 10. In FIG. 11, the valve is shown as a
rotary valve for selectively connecting one of the inlets 12, 23,
or 24 to the chamber 11.
[0077] FIG. 12 shows a reactor device of the second type or
geometry based on the design represented in FIG. 1b. In the reactor
device of FIG. 12 the chamber 11 is divided by the electrode 13,
into a region 18 containing ionically conducting material for
providing an ionic conduction path for electrolysis and a fluid
path 17 for carrying the precursor reagent. Regions 17 and 18 are
separate but adjacent, and are separated by a permeable working
electrode 13, which must be porous, or otherwise permeable, to
allow primary product 16 and precursor reagent to contact and react
to form the secondary product.
[0078] As shown in FIG. 12, fluid flow along pathway 17 carries
secondary product to junction 19 to mix and react with another
reagent from entrance 20. The working electrode 13 may be in the
form of a porous block through which fluid flowing along the flow
path 17 passes in a manner similar to that shown for devices of the
first type in FIG. 7. Similarly, the counter electrode 14 may be in
the form of a porous block through which are passed ionically
conductive fluid containing material to support electrochemical
processes at the counter electrode. Similarly there may be multiple
entrances to that part of the chamber 11 occupied by fluid flow 17
so as to allow changes of reactant and solvent in a similar way to
that described above in relation to that the devices of FIGS. 9 and
10. Such arrangements may incorporate valves as in FIG. 11.
[0079] In reactor devices of the type represented in FIG. 12,
ionically conductive fluid, which may contain source material for
the electrolytic generation of the primary product and other
species to support electrolytic reaction at the counter electrode
14, may flow to contact electrode 14. This fluid is brought into
and out of region 18 of chamber 11 by conduits 26 and 27. Ionically
conductive fluid may occupy region 18 up to the electrode 13, or
there may be a solid or semi-solid ion conductor layer 28
intervening between the ionically conductive fluid and electrode 13
as shown in FIG. 12.
[0080] FIG. 13 shows schematically a variation of the reactor
device of FIG. 12 in which there is provided a permeable layer of
ionic or electronic conductor 29 between a fluid ion conductive
solution contacting electrode 14, and ion conductor layer 28, which
may be fluid, solid or semi-solid, contacting electrode 13. Also
represented in FIG. 13 is a variation on the construction of
electrode 13 such that it takes the form of a mesh or set of
interconnecting strips allowing deposition of primary product 16
over the surface of ion conductor 28 in the vias through electrode
13. The permeable layer 29 may be an electronic conductor such as,
for example, Mercury (or a structure containing Mercury or an
amalgam) where the transferring species is a mercury soluble metal
such as sodium. Presence of a selectively permeable layer as
indicated for layer 29 allows use of chemically incompatible
ionically conductive materials on either side of the layer. For
example an aqueous salt solution can contact electrode 14 and
sodium beta alumina contact electrode 13 but the two electrolytes
should not directly contact due to hydrolysis reactions which would
damage the sodium beta alumina. An intervening layer chemically
compatible with both ion conductive layers and which transfers
sodium or sodium ions allows use of such chemically incompatible
layers in combination. In principle multiple layers of conductors
with suitable permeability and chemical compatibility may be
employed.
[0081] In principle, the reactor devices of the second type may be
used with both solid and fluid electrolytes, but it is advantageous
to employ ionic conductor adjacent to the working electrode 13
which is either a solid or semi-solid such as an electrolyte fluid
immobilised by a porous structure or gel. The arrangements
represented in FIGS. 12 and 13 may be used for carrying out a
process such as organometallic reagent production. Electrolysis in
the ion conduction pathway section generates reduction product
M.sup.o (e.g. Lithium metal) at the porous electrode, which reacts
with precursor R--X (e.g. an alkyl halide) generating the reagent
M-R (e.g. alkyl lithium compound). Side products including M-X
(e.g. lithium halide) may also be produced. Product M-R and side
products generated in the same region may be carried away in the
fluid flow as shown in FIGS. 12 and 13.
[0082] A variety of structures and materials may be used to form
the electrolytic cell and ion conducting pathway as long as they
maintain ionic or electronic continuity between electrodes 13 and
14 and allow transfer of species required to allow the electrolytic
formation of primary product at electrode 13.
[0083] Truly solid-state ion conductors based on ceramic or
crystalline materials tend to have transport number at or near 1
for the mobile ion, which reduces problems with concentration
polarisation within the electrolyte. Examples such as
.beta.-Alumina, or Nasicon are attractive as Na.sup.+ conductors
with transport number of 1. Conductivities rise with temperature
but values as high as .about.10.sup.-3 siemens/cm at room
temperature are achieved so that limitations on throughput due to
low conductivities are not excessive. Lithium and potassium
analogues of the ceramic sodium ion conductors also, though usually
with somewhat lower conductivities. Li.sub.3N crystals have high
Lithium ion conductivity perpendicular to the c axis. A range of
Lithium conductors based on mixed oxide (Si, Ge, P, Zn, Ge, and V)
matrices is also known. Other truly solid ion conductors are for
Ag.sup.+, Cu.sup.+, H.sup.+ cations, and F.sup.-, and O.sup.2-
anions. The anionic conductor, such as LaF.sub.3, and doped
ZrO.sub.2 are likely to prove of limited utility for organic
synthesis due to relatively low conductivity at moderate
temperatures, but may be applicable for high temperature reactions.
Some Ag.sup.+ ion conductors, especially those related to AgI (e.g.
silver rubidium iodide) have quite high conductivities, and may be
useful in formation of organo-silver compounds or as electrolytes
for use in combination with other source materials for generating
other organometallics. Cu.sup.+ conductors are also known but are
generally of lower conductivity than analogous Ag.sup.+ conductors.
Solid state proton conductors have conductivities which in many
cases depend on the presence of water and for the most part will be
limited to use with water compatible chemistries, may provide a
means of carrying out electrochemical hydrogenations or even
dehydrogenations in devices of the second type or geometry.
[0084] Polymer based ion conductors are widely applied in the
battery industry for Li.sup.+ ions in particular. They are probably
more truly immobilised liquid electrolytes as there is some anionic
migration that can lead to polarisation. Examples have been applied
in rechargeable systems where Li metal is deposited as either free
metal or within graphitic matrices. There may be more limitations
with the use of such polymeric systems arising from polymer and
Lithium salt solubility in the fluid used to carry precursor to,
and product from the working electrode. Polymer and solvent systems
may generally be characterised as ether/polyether type materials
that could be compatible with a range of lithium metal based
organic synthetic processes. Lithum ion conductors in combination
with graphite matrices to form Lithium or other species permeable
electrodes are suitable for use in devices of the second type or
geometry.
[0085] The same liquid electrolytes used for reactor devices of the
first type or geometry may be used in devices of the second type or
geometry with the porous working electrode, perhaps on a porous
substrate, held at the interface between the electrolyte and
precursor/product transport fluid(s). This may be an immiscible
fluid interface or may exist as a graded interface within the
porous electrode where the fluids are miscible or have some mutual
solubility.
[0086] The reactor device of the present invention can link to a
mixer/reactor stage for rapid consumption of the product reagent as
indicated in FIGS. 12 and 13.
[0087] The counter electrode 14 within the electrochemical cell
will require a source of the ions to be transferred. This may be
provided by the electrode material itself (e.g. if it is an alkali
metal, or alloy or amalgam of an alkali metal, or an electronically
conductive intercalation compound of an alkali metal). A solution
of the relevant ions may be provided as a layer adjacent to the
counter electrode and waste products removed to avoid polarisation
and contamination problems. This replenishment, either continuously
or intermittently may be achieved as indicated in FIGS. 12 and 13
through conduits 26, 27.
[0088] Although the number of types of ions which may be used
within the ionically conductive phase in the electrochemical cell
may be quite limited, it will be possible in some cases to generate
organometallic reagents of other metals by providing those metals
in compounds within the flow 17 adjacent to electrode 13. These
source materials in solution may be employed either alone or
simultaneously with precursor reagent as indicated earlier for
discontinuous or continuous mode operation of the synthetic
devices.
[0089] FIGS. 1a to 12 and the description pertaining to those
figures have shown only two electrodes in each device. It is to be
understood that that reactor devices according to the invention may
have, and could be constructed with, multiple electrodes carrying
out the functions of the working electrodes 13 and counter
electrodes 14 shown in FIGS. 1a to 13.
[0090] As shown diagrammatically in FIG. 14, further electrodes 30,
31 may be incorporated to carry out other functions. One or more
reference electrodes may be incorporated in a device to allow the
monitoring and control of the working electrode potential. Such a
reference electrode will contact the ionically conductive phase
between electrodes 13 and 14, and where it is to be used as part of
a circuit to control working electrode potential, then the
reference electrode 30 will most usually be placed relatively
closely to electrode 13 as shown in FIG. 14. Other electrodes 31
may be positioned in the fluid flow stream to monitor potentials
which allow sensing of fluid composition, and other non
electrochemical sensors, for example optical or thermal sensors,
may also be used. In operation the output from sensors in the
device may be used to control potentials applied and current passed
through the device and to control fluid input and output rates.
[0091] As shown diagrammatically in FIG. 15, a heat exchanger
structure 32 may be incorporated in the device. Such thermal
control structures may include fluid cooled or heated structures as
well as electrical heaters and Peltier coolers and multiple heat
control structures may be distributed throughout the device. Such
thermal control structures may be positioned adjacent reaction
zones as indicated schematically in FIG. 15 where a heat exchanger
is shown adjacent to the chamber 11 and particularly adjacent one
or more of the electrodes, and a further heat exchanger structure
33 adjacent to the reaction zone following junction 19.
[0092] As shown diagrammatically in FIG. 16, where the primary
product 16 is not deposited adherently to the working electrode 13
but taken up into the fluid flow 17, fluid consisting of or
containing precursor reagent may be passed into the reaction
chamber at a junction 34 through an entry conduit 35 downstream of
the primary product generation region to mix and react with the
primary product at and adjacent to the junction 34.
[0093] As shown diagrammatically in FIG. 17 the region where
primary product is formed and or reacted with precursor reagent may
be subjected to some radiative stimulus e.g. UV light through a
window or aperture 36 from a source 37. Such stimulus may be to
enhance formation or reaction of the primary product or as part of
a sensor system to monitor reaction.
[0094] The use of additional electrodes, thermal control
structures, and supplementary radiative stimulus as represented in
FIGS. 14, 16, and 17 may be applied to devices of both first and
second types.
[0095] In reactor devices of the second type the face or surface of
an electrode at which the primary product is formed may be
different to that to which precursor material is initially
presented. In such arrangements the electrode structure at which
primary product is formed must be such as to allow material
transfer between faces or surfaces of the electrode to enable
contact between primary product and the precursor material.
Electrodes that are permeable to the primary product may achieve
this or where electrodes are formed with materials or structures
providing pores or vias through the electrodes through which
primary product or precursor or fluids containing primary product
or precursor can pass. Physical pores or vias may be provided by
forming the electrodes from porous materials or as meshes or
strips.
[0096] Where the primary product is an amalgam forming metal, the
electrode permeable to the primary product may be formed at least
partially as a film or layer of Mercury. A porous body or sheet of
material that is wetted by mercury may support the mercury layer.
Graphite is permeable to some metallic and some non-metallic
species such as Lithium and Fluorine, and Graphite layers or films
may be used to form permeable electrodes where such species are the
primary product. Where the primary product is hydrogen, the
electrode permeable to the primary product may be formed as a film
or layer of Palladium or other metals (e.g. Lanthanides, and their
alloys, Misch metal) having high hydrogen permeability. Hydrogen
permeable metals may act as catalysts for the hydrogenation or
reduction of precursor reagents.
[0097] Most generally, the materials used for electrode
construction in the devices will conduct electrical charge
exclusively by electronic means. Such electrode materials include
metals, many semiconductors, conductive carbons, and some
electronically conductive polymers and ceramics. In device of
second type geometry with such electrodes the primary product must
be formed at a contact between the electrode and ionically
conductive material. In such cases the electrode must be permeable
to the primary product or be formed with materials or structures
providing pores or vias through the electrodes through which
primary product or precursor and secondary product, or fluids
containing products or precursor can pass.
[0098] Alternatively the materials used for electrode construction
may be mixed conduction materials. Mixed conduction materials are
those which are able to conduct electricity by both ionic and
electronic pathways. In devices of second type geometry the ionic
conductivity of such mixed conduction type electrodes can allow
generation of the primary product at the face away from the ion
conductive material which constitutes the electrolyte layer in the
electrochemical cell. Where such mixed conduction electrodes are
used the electrode within a device of second type geometry need not
be permeable to primary product or precursor or secondary product
or solutions thereof. Tungsten bronzes are a well-known class of
mixed conduction material. Sodium tungsten bronzes, which may be
represented by the formula Na.sub.xWO.sub.y, have composition
ranges where both electronic and Na.sup.+ ion conduction
occurs.
[0099] In the reactor devices show in FIGS. 1a to 17 the face, or
surface, of an electrode at which the primary product is formed may
be the same as that to which source material is presented. This
will usually be the case where the source material is supplied to
the same surface or face as the ionically conducting phase
intervening between electrodes though which the electrolytic
current is passed. This will include cases where the source
material constitutes part of the ionically conducting phase.
[0100] Alternatively, in reactor devices of the second type, the
face, or surface, of an electrode, at which the primary product is
formed, may be different to that to which source material is
initially presented, so long as the electrode structure, or
material, is such as to allow transfer of the source material to
the site of primary product formation. This may be achieved by
electrodes that are permeable to the source material, or fluid
containing the source material, or where the electrodes are formed
with pores or vias passing through the electrodes through which
source material, or fluids containing source material, can pass.
Physical pores or vias may be provided by forming the electrodes
from porous materials or as meshes or strips.
[0101] The source material may be a salt or redox active compound
for conversion to the primary product, or fluid containing source
material and is preferably at least part of the ionically
conductive material intervening between electrodes during the
electrochemical generation of primary product. The source material
which is converted electrochemically to the primary product may
provide all or part of the ionic conductivity, or the ionic
conductivity may be provided by supporting electrolyte ions which
may not be involved in the electrochemical process at one or more
of the electrodes.
[0102] Alternatively, the source material or that fluid containing
source material, and the ionically conductive material between the
electrodes may be different provided that, during the electrolytic
process, the source material can access at least part of the
junction between ionically conductive material and any electrode at
which the primary product is to be formed. This may be achieved
where the source material and ionically conductive material, each
of which may be in solid or fluid form, both contact the same
electrode surface. The source material and ionically conductive
material may be either mixed miscible or immiscible phases or
contact the electrode as strips or streams.
[0103] Alternatively access by source material to at least part of
the junction between ionically conductive material and any
electrode at which the primary product is to be formed may be
achieved by electrodes at the boundary between the source material,
or fluid containing the source material, and the ionic conductor
material being formed as strips or meshes or with pores or vias
through the electrode or where the electrode material is permeable
to the source material. The ionically conductive material may be a
fluid or alternatively may be a solid such as a ceramic ion
conductor or semi-solid material such as an ion conductive polymer
or gel. Alternatively a combination of solid or semi-solid, and
fluid ion conductive phases may be used as an ion conductive
structure or assembly of phases intervening between electrodes to
allow electrochemical generation of the primary product. The solid
or semi-solid ion conductor materials may contain mobile species
that are converted at an electrode to the primary product. The
mobile species within a solid or semi-solid ion conductor which are
converted at an electrode to the primary product may include the
ions which maintain conductivity, as for example the sodium ions in
sodium beta alumina. Where those mobile species constitute the
source material, other supply of source material, in for example a
fluid phase, is optional. Additionally the electrode material may
be a mixed ion and electronic conducting material and the mobile
ions within that constitute the source material as long as they can
be replenished from adjacent phases which may be the ion conductive
material or fluid containing the relevant ions or source
thereof.
[0104] The reactor device of the present invention involves regions
for electrochemical generation of primary product, and for reaction
of primary product with precursor reagent to generate secondary
product. These regions may be the same or different and further
regions and reaction zones and for mixing and reaction of products
and reagents may be incorporated into the device. The device may
contain regions for controlling the temperature of the
electrochemical generation and reaction zones. Heat may be
generated in the electrochemical cell by the combination of current
and cell resistance, by the electrochemical transformations, and by
chemical reactions such as those between primary products and
precursor reagents.
[0105] Operation of reactor devices according to the present
invention involves a number of transport processes that are
affected by the construction and dimensions of the reactor so that
the preferred device dimensions are within the range appropriate
for micro-engineering techniques. Processes involved typically
include electro-migration, electrodeposition, and diffusion of
materials and reagents to reaction sites such as electrodes and
electrodeposits, mixing of fluid reagent streams, reaction, and
heat generation or consumption and heat transport. In general, as
will be shown below, rates of material transport and formation, and
transfer of heat from, or to, the fluids and reaction sites is
improved by fabricating devices where distances across structures
and fluid flows are small and fall within the range applicable to
micro-engineering techniques.
[0106] Typically the generation of primary products involves
electro-migration of ions carrying the electrolytic current and
electromigration or diffusion of source materials to the electrode
at which the primary product is formed. The primary products may
remain where formed or transfer into a fluid flow to be carried to
a separate reaction site. Within the ionically conducting body or
layer, heat will be evolved due to resistive heating at a rate
given by the product of the current and the voltage drop. Heat may
also be generated, or, less commonly absorbed, as a result of the
electrochemical reactions at the electrodes including conversion of
source material to primary product. Maintenance of a desired
temperature regime will be aided by minimising thermal transport
distances across fluids and walls to heat exchangers, heat sinks,
or heat sources.
[0107] Precursor materials are brought by fluid flow to the primary
product, either at the deposition site or a separate reaction site.
In either case the precursor materials must be brought into contact
with the primary product and this will typically involve diffusive
transfer across the stream carrying the precursor material to
transfer the precursor material to the surface of the primary
product or to mix the precursor material and primary product
streams where both are held in a fluid phase. Rates of reaction
between primary product and precursor can be transport limited, and
such transport limitations on rates will be reduced by minimising
material transport distances across fluid layers.
[0108] Some generation or absorption of heat will be associated
with reaction of primary product and precursor material to produce
a secondary reaction product. Where the primary product is a
reactive material such as an alkali metal deposit the reaction will
generally be exothermic. Whether heat is evolved or absorbed,
maintenance of stable temperature regimes is improved by short
thermal transport distances from the reaction site to heat
exchangers, sinks, or sources across intervening fluid layers and
wall materials.
[0109] Reaction of secondary reaction product carried by flow to a
further reaction site will similarly involve mixing, heat
generation or absorption and heat transfer and enhancement of rates
of diffusive transport and thermal conduction will be achieved by
minimising the relevant transport distances.
[0110] The speed and efficiency of each of the processes described
is affected by the device geometry and dimensions and preferably
devices of micro-engineered dimensions are employed to enable rapid
and efficient mass and heat transport.
[0111] For electrochemical reagent generation the preferred
dimensions are governed especially by the requirement to maximise
current to increase production rate while avoiding excessive
voltage drops and heat generation within the body of the
electrochemical cell and at electrodes. Close coupling of the
electrochemical cell to cooling surfaces allows fast heat removal
but the ionically conducting electrolyte layers should be
sufficiently thin to ensure that heat generated within the
electrolyte can be efficiently removed. For devices employing
relatively poorly ionically conductive non-aqueous electrolyte
phases, it is desirable to minimise electrical resistance between
electrodes by arranging that the electrolyte layer thickness should
be low. This condition applies where the electrolyte is a fluid or
for polymer immobilised electrolytes.
[0112] Ceramic ion conductors are commonly operated at elevated
temperatures to increase ionic conductivity and their thermal
conductivity is generally relatively high. However it is still
preferable that such electrolyte layers are employed as moderately
thin structures within the synthetic devices to reduce operating
voltages required at the relatively low temperatures compatible
with synthetic organic chemistry. Electrochemical reactions are
located at or very near electrode surfaces and the transfer of ions
and source materials for generation of primary products is a
controlling factor in the rate of product generation for devices
according to the present invention.
[0113] As explained above, using micro-engineering techniques it is
possible to form conduits or flow channels with depth dimensions
down to .about.1 .mu.m. Though, in general, channels with depths of
10-100 .mu.m are more conveniently fabricated, and allow
significantly greater throughputs, and lower flow resistance.
Channel widths and lengths are generally defined by lithographic
techniques, and may range from a few micrometers to centimetre
dimensions. By using combinations of such conduits or flow
channels, transit and mixing times of the order of seconds down to
milliseconds in liquids, and microseconds in gases may be
achieved.
[0114] Material transfer to and from electrodes across the
ionically conductive electrolyte or flow streams may occur by
either electromigration, or diffusion. For thin electrochemical
cells it is facile to provide relatively large electrical field
gradients with only moderate potentials applied across the cell;
under such conditions transport by electromigration will be fast.
Typically ionic mobilities will be of the order .about.10.sup.-4
cm.sup.2V.sup.-1s.sup.-1, or 1 .mu.m/s for a field gradient of 1
V/cm. It is not difficult to provide field gradients of 10-1000
V/cm in relatively thin (.about.<1 mm) electrochemical cells
with the result that electromigration times across fluid or solid
electrolyte layers of less than 1 second are readily
accessible.
[0115] Regions for reaction or mixing may be considered as a
channels or chambers of depth d and length I, where t is the
transit time for fluid flowing along the length of a channel.
Temperature changes can be related to the residence time t over
which the processes causing heat generation or consumption occur,
to the heat generation or consumption rates, to the thermal
capacity of fluids and other materials in the device, and to the
thermal time constant for cooling processes which will be a
function of thermal diffusivity, and dimensions such as distance
across fluid and other layers to conductive heat sink structures.
In order that close control be exercised over the temperatures
within the material transport and reaction regions, it is should be
ensured that thermal time constants associated with a region are
low.
[0116] If any of the materials, such as the source materials,
electrolytes, reagents, products or solvents are thermally labile
then temperature rises should be limited. In any case the yields or
rates of processes generating first and second products are likely
to be temperature dependent and so control of temperature in the
device is desirable. In general temperature control is improved by
maintaining short thermal transfer distances and is therefore
readily improved in micro-engineered devices. The performance of
the heat transfer process may generally be related to a
dimensionless parameter of the form .mu.t/d.sup.2 where .mu. is
thermal diffusivity, t is time allowed for heat transfer, and d is
distance to a conductive heat sink surface. Where
.mu.t/d.sup.2>.about.1 then thermal equilibrium has been largely
achieved. Taking t in .mu.t/d.sup.2=1 as a thermal time constant
and rearranging gives t=(d.sup.2/.mu.) and clearly this is
decreased for small values of d. Some example values relating
thermal diffusivities, conduction lengths and time constants are
tabulated below.
[0117] These values indicate that for short thermal response times
of less than one second, liquid layer thickness should be 100 .mu.m
or less. For cases where energy transfer rates are low these
constraints may not apply. In practice where a structure and its
contents form a composite layer with different values of .mu. and
d, the evaluation of the heat transfer characteristics is
inevitably more complex but it is commonly adequate to identify the
most thermally resistant layer and base design calculations on
that. Where layers of reagent fluids and solvent are involved, it
will usually be adequate to ensure that those are sufficiently thin
to avoid maintaining excessive temperature differences, and to
contain them by more conductive structures, such as thin metal,
glass, or ceramic constructions, linked to heat sinks or sources
such as heat exchangers, heat pipes, Peltier coolers, or resistive
heaters.
[0118] On the micro scale smaller quantities of liquid are used and
diffusional distances within the liquid are dramatically lowered
allowing for rapid diffusion. The diffusion rate may be affected by
many different factors such as chemical kinetic factors and
transport of dissolved material in the solvent by convective,
advective, or diffusive processes. Within the microfabricated
devices, the cross channel dimensions generally ensure that low
Reynolds laminar flow conditions apply. Mixing and reaction of
species from adjacent flow streams or for species to contact and
react with deposits on walls or electrodes it is necessary for
those species to cross the flow streams. Turbulent fluid transport
is generally absent in devices of micro-engineered dimensions so
that movement of species across flow streams proceeds my molecular
migration mechanisms such as diffusion or electromigration. Where
diffusive transfer is the limiting factor then the rate of
diffusion is related to the length of the path through which the
molecule diffuses and the geometry of the liquid body. Diffusive
transfer rates will generally be inversely related to the path
length or square of the path length depending on whether the
conditions for steady state or transient diffusion apply.
[0119] Diffusive transfer will be required where the species to be
electrochemically transformed is uncharged, or does not travel
through the field region, and also for uncharged species involved
in non electrochemical processes taking place at the electrode.
Diffusive transfer is involved where the source material is not a
charged species which can be brought by electromigration to the
electrode for conversion, and diffusive transfer can still be
controlling for charged species where other ionic species, as
supporting electrolyte, carry most of the current and reduce field
gradients. Further the precursor materials required to react with
primary product to generate secondary product will in general not
be charged species. The length of time diffusively transferred
source and precursor materials need to be resident adjacent to the
working electrode can be estimated on the basis of diffusion
processes where the distance to the electrode surface across a flow
carrying such materials is taken as the characteristic distance for
diffusion calculations. Although a full analysis of the diffusion
process can be complex, it is generally adequate to consider the
diffusive process will be close to complete when the dimensionless
parameter Dt/d.sup.2.about.>1. This corresponds to near
equilibrium, or completion of the diffusive process. (D is
diffusion coefficient, t is time allowed for mass transfer, and d
is the distance across fluid to the surface (electrode) at which
conversion takes place.). Values for residence time based on
diffusion provide minimum guide values as longer times may be
required if reaction kinetics at the electrode surface are not
sufficiently fast, and if other mass transfer process introduce
delays e.g. dissolution of solid reactive products and their
diffusive transfer from the surface.
[0120] Acceptable values for the reactor device dimensions and
residence time within the electrochemical conversion stage will
depend on the stability of the reactive product to be formed, and
the desired throughput.
[0121] Typically diffusion coefficients (D) in non-viscous fluids
for low to moderate molecular weight species of the size range of
interest (Molecular weights of a few hundred of chemicals) will be
in the range 10.sup.-5 to 10.sup.-7 cm.sup.2s.sup.-1. Taking a
value for D of 5.times.10.sup.-6 cm.sup.2s.sup.-1, the approximate
time t for diffusive transfer times across a path length (l) may be
derived from expressions of the type Dt/d.sup.2=0.01 to 1, where
Dt/d.sup.2=0.01 approximates to a diffusion front reaching a
distance d from source plane, and Dt/d.sup.2=1 corresponds to near
completion of the diffusive process (concentration gradient across
d being nearly eliminated). Approximate times t for reaching
diffusive equilibration (Dt/d.sup.2=1) at different path lengths
(d), in which the dissolved material must travel, based on
d=5.times.10.sup.-6 or 5.times.10.sup.-7 cm.sup.2s.sup.-1 are
tabulated below in the table of diffusive mixing times:
1 t seconds t seconds for for d micrometers D 10.sup.-6
cm.sup.2s.sup.-1 Dt/d.sup.2 = 1 D 10.sup.-6 cm.sup.2s.sup.-1
Dt/d.sup.2 = 1 1 5 0.002 0.5 0.02 3 5 0.018 0.5 0.18 10 5 0.2 0.5 2
30 5 1.8 0.5 18 60 5 7.2 0.5 72 100 5 20 0.5 200 300 5 180 0.5 1800
1000 5 2000 0.5 20000
[0122] About 50% of the diffusive transfer will occur in about a
tenth of the above times (corresponding to Dt/d.sup.2.about.0.1).
On the basis of the above table relatively rapid equilibration by
diffusion alone will occur within 100 seconds where the required
transport distance d is of the order of or less than 100 .mu.m. The
relevant distance d for the mixing of two fluid streams will be
that from the furthest edge of the channel where the two fluids
meet. For transfer of material to or from a surface, such as to a
primary product deposit on an electrode, d is the distance across
the fluid stream or layer to that surface. In micro-engineered
devices where distance d is made small, the diffusion controlled
transport, mixing, and reaction times are decreased and controlled
by the distance d.
[0123] For processes operating under transport control, reactant
consumption and product flux from the reaction zone of a device
depends on the transit time for fluid flow through the reaction
zone and on the time for completion of cross flow diffusive
processes in that zone. Selecting flow rates so that reaction zone
fluid flow transit times and cross flow diffusion completion times
are similar will result in reaction flux per unit volume of device
improving as distance d is decreased. This may result in greater
heat fluxes from reaction and/or ohmic (Joule) heating but as
thermal time constants similarly decrease with d the temperatures
within the device do not rise excessively. Values of dimension d in
the range 1000 to 50 .mu.m correspond approximately to diffusion
limited reaction fluxes equivalent to current density values of
0.001 to 1 Amp/cm.sup.2, an acceptable range for electrodes in
micro-engineered devices. For devices with larger value for d the
reaction flux rates will be tend to be lower due to diffusion
limitation and so production rates per unit device volume will be
lower. It is an advantage therefore that the distance across
channels or chambers for mixing or transfer of reagent to reactive
deposits be low and this dimension in devices according to the
present invention should be 10 to 3000 .mu.m, and preferably in the
range 30 to 300 .mu.m.
[0124] Where mixing processes other than diffusive mixing are
ineffective, the preferred approximate maximal distance across a
channel, or chamber, in the direction which material is required to
diffuse is 300 .mu.m. Required residence time within a channel or
chamber sufficient to allow diffusive mixing will depend on the
value of that dimension. This dimension along with channel width
determines the cross sectional area of the channel, and fluid
throughput will depend on the cross sectional area and length of a
channel or chamber and on the fluid flow speed. Although channel
length may be quite extended, especially if drawn tubular
structures are used in the construction. However where the channels
or chambers are required to incorporate micro-engineered structures
such as electrodes, and especially if they are to be rendered by
conventional micro-engineering techniques on substantially planar
substrates, it is desirable that overall lengths and widths be
limited. Typically flow speeds readily achievable for liquids in
micro-fluidic systems without excessive pressure drives range up to
10 cm/s, and are preferably in the range 0.01 to 1 cm/s.
Appropriate lengths for channels or chambers in which diffusive
processes are allowed to proceed to completion will range up to 10
cm, and preferably lie in the range 0.1 to 3 cm.
[0125] It is not necessary for the purposes of the present
invention that laminar flow conditions are maintained for fluid
flows within the device. Channels and chambers may be made large
enough to support turbulent mixing with distances across channels
of greater than 0.1 cm and more conventionally of 1 cm or greater
generally being required. Where mixing is to be induced by simple
flow of fluids through channels and chambers, the mixing and mass
transfer across flow will not be efficient at these dimensions.
However efficient mixing may be induced by employing pulsed or
reciprocating flows or by employing mechanical agitation of fluid
by structures such as stirring paddles or magnetic stirring
bars.
[0126] The dimensions in the mixer/reaction stages will be governed
by the same sort of diffusion processes as indicated above for the
electrochemical primary product generation stage and reaction with
precursor to generate secondary product. Where two laminar streams
run together, the diffusion distance d controlling mixing time will
again be the channel depth. Where reaction is very fast and one
stream has an excess of reagent then the rate limiting diffusion
distance will tend to reduce to that fraction of the channel width
corresponding to fluid from the second stream. This will be the
case for single and multiphase flows. For multiphase processes the
limiting mass transfer distances and times may be altered somewhat,
but if the phases are immiscible liquid it is likely that the total
result will not change substantially, except as indicated above or
if inter-phase transfer is kinetically hindered. If one phase is
gaseous then mass transfer limitations are likely to reside
entirely in the liquid phase, and be set by the distances across
that phase. Reactions may of course not be mass transport limited.
Where kinetic limitations apply for single phase reactions it may
be adequate to carry out partial or complete mixing in
micro-engineered structures and then transfer the product to a
holding container for process completion. For multiphase processes
the degree of subdivision of the phases and the interface geometry
will depend critically on how the fluids are contained and
moved.
[0127] The above indicates that for reaction times in the 0.1-10
second range, channel depths of .about.10-1000 .mu.m are indicated,
and that preferably channel depth will be in the range 30 to 300
.mu.m. The earlier table on diffusive mixing times indicated that
if mixing and reaction in millisecond time scales are required for
liquid reagents, then the channel depth would have to be .about.1
.mu.m. Total flow rates achievable under those conditions would be
quite low (-1 cc/h or less for 1 cm wide channels). The table below
shows values for fluid throughput and transit times for channels
some example dimensions. The combinations of transit times and
diffusion distances correspond to significant to full diffusive
mixing for species of moderate molecular weights. Limitations to
channel length and therefore available transit times at any given
flow rate will depend on the size of the structure that can
conveniently be fabricated. Values for the required drive pressure
for laminar flows in these channels are indicated in the table
below.
2 Flow rate Channel height Pressure drop cc/hour Mean transit and
Diffusion Channel bar (for 1 cm Time distance transit length (for
viscosity width) t sec d micrometers cm 1 cPoise) 1 0.1 7 0.04
3.7E-03 10 0.1 7 0.39 3.7E-01 100 0.1 7 3.93 3.7E+01 1000 0.1 7
39.28 3.7E+03 1 1 22 0.12 3.7E-04 10 1 22 1.24 3.7E-02 100 1 22
12.42 3.7E+00 1000 1 22 124.22 3.7E+02 1 10 71 0.39 3.7E-05 10 10
71 3.92 3.7E-03 100 10 71 39.28 3.7E-01 1000 10 71 392.83
3.7E+01
[0128] It is clear for these short to moderate transit times that
flow rates will generally need to be restricted to less than 100
cc/hour if channel lengths or pressure drops are not to be
excessive. These flow rates are for 1 cm width channels and relate
linearly to channel width.
[0129] Multiphase reaction depends on being able to maintain a
useful inter-phase contact area. This becomes more difficult as
dimensions are reduced. While microcontactors and mesh structures
of the type described previously (see International Patent
Publication No WO 97/39814)) may be applied where channel depths
are 20 .mu.m or greater, the balance between pressures required to
drive flow and surface tension forces below that point would tend
to produce slugging flow in the phases. Reaction may be maintained
in slugging flow but slug dimensions will control rates and flow
rates and recirculation induced within the slugs and not according
to the diffusive processes appropriate to simple laminar flows.
[0130] The electrolysis cell may constitute a rechargeable and or
demountable cartridge that can be removed to enable the primary
product (e.g. a metal deposit) or source material to be replenished
way from the process generating the secondary product (e.g. an
organometallic product), or alternatively, to enable the primary
product (metal deposit) to be consumed in generating a secondary
product (e.g. an organometallic product) away from site of the
electrochemical process.
[0131] A fluid pumping means is preferably connected to the reactor
device, including to the electrochemical cell where fluid
electrolytes or sources of redox active materials are employed.
Such fluid pumping means may, as appropriate to the selected
fluids, include centrifugal pumps, diaphragm pumps, peristaltic
pumps, electrosmotic flow generating structures,
magnetohydrodynamic pumps, syringe pumps, and fluid reservoirs
positioned to maintain hydrodynamic heads to drive fluid flow.
Valves and flow regulators may be included in fluid pathways
leading to and from the device.
[0132] In the reactor devices described in FIGS. 1a to 17, the
electrode 13 at which primary product is formed is termed "the
working electrode" and is shown as being held at negative
potentials (i.e. cathodic) whilst the electrode 14 is held at a
positive potential (anodic). This will be consistent with
generation of alkali metals from their compounds and salts, but
working electrodes may be held at whatever potential is consistent
with the conversion of source material to primary product, and this
may include positive potentials. The figures are generally
represented as simple planar assemblies but other geometries
including cylindrical assemblies and stacked sheets may be
employed.
[0133] Multiple anodes and cathodes and arrays of such electrodes
may be employed, and devices may incorporate one or more reference
electrodes allowing the potentials of other electrodes to be
monitored or controlled.
[0134] Examples of types of chemistry that could be carried out in
synthetic devices incorporating electrochemical cells according to
this invention are described below to illustrate but not to limit
the invention.
[0135] 1 Formation of Sodium, Lithium, or Potassium Alkoxide or
Phenoxide.
[0136] Electrolysis is carried out in reactor devices of first or
second types to produce lithium metal as the primary product.
Solutions of lithium salts or Lithum ion solid or polymeric
conductors may be used to provide ion conductive material and
source material. Alkyl halide in solution as precursor reactant is
flowed up to contact lithium metal electrodeposited on a cathode to
react with the lithium and form lithium alkyls that may be carried
away in solution by a solvent. Stages in the chemistry are
represented below. The process may be applied to other organohalide
precursor materials such as sodium or potassium or lithium as long
as sodium/lithium/potassium does not directly attack parts or other
substituents of the organic group. This process is shown below.
Na/K/Li.sup.+Y.sup.-+e.sup.-(at
cathode)-.fwdarw.Na/K/Li.sup.o(metal)
[0137] where Y.sup.- is an anion such as CF.sub.3CO.sub.2.sup.-
Na/K/Li.sup.o(metal)+R.sup.-OH.fwdarw.Na/K/Li.sup.+OR+H.sub.2
[0138] where R.dbd.CH.sub.3, C.sub.2 H.sub.5, C.sub.3 H.sub.7,
C.sub.4H.sub.9, Ph, substituted Ph, or heteroaryl, or substituted
heteroarylyl,
[0139] With lithium precursors, solubility of side product lithium
halides may be an issue. Lithium bromide and iodide are relatively
soluble in many organic solvents, may not interfere with subsequent
reactions of lithium alkyls, and organo-iodides and bromides are
therefore the preferred precursor reactants. It is preferable to
ensure that excess Li metal is available to avoid consumption of
lithium alkyl produced by further reaction with precursor
(R--X+Li-R.fwdarw.Li.sup.+X.sup.-+R--R), and this may be achieved
by carrying out an initial electrode charging process to build up a
Li.sup.o deposit or by employing discontinuous mode operation.
Lithium salt electrolysis and lithium alkyl formation may be
carried out in ether solvents allowing continuous operation of
devices of the first type, but discontinuous operation and devices
of the second type may also be employed.
[0140] The sodium, potassium or Lithium alkyl produced may be
carried by fluid flow to a mixer stage to carry out a wide range of
chemistries established for those reagents.
[0141] 2 Sodium Naphthalenide Formation.
[0142] Electrolysis depositing sodium metal may be combined with a
flow of naphthalene solution to generate the sodium naphthalenide
product that may be used subsequently as a reagent. This process
does not involve generation of low solubility halides or problems
with reaction of product and precursor (naphthalene). Devices of
the second type based on sodium beta alumina as ion conductor are
suitable. The overall reaction may be written as:
Na.sup.++e.sup.-(from working electrode).fwdarw.Na.sup.o
Na.sup.o+C.sub.10H.sub.8(naphthalene).fwdarw.Na.sup.+C.sub.10H.sub.8.sup.--
(sodium naphthalenide)
[0143] Sodium naphthalenide appears to exist as Na.sup.+ associated
with a radical anion. Similar reagent are derived from anthracene
(hence sodium anthracenide), and others related to aromatic
precursors. Similar reagents may be derived from lithium and other
electropositive metals.
[0144] Similarly potassium napthalenide may be synthesised using
potassium as the source material, and napthalene as the precursor.
Also sodium napthelinide can be synthesised using sodium as the
source material and napthalene as the precursor.
[0145] 3 Synthesis of Sodium/Potassium/Lithium Anthracenides.
[0146] The present invention can be used for the synthesis of
sodium anthracenide, potassium anthracenide, or lithium
anthrecenide by using sodium, potassium, or lithium as the source
material and antracene as the precursor.
[0147] 4 Synthesis of Sodium/Potassium/Lithium Phenanthrenides.
[0148] The present invention can be used to synthesise sodium
phenanthrenide, or potassium phenanthrenide or lithium
phenanthrenide by using sodium, or potassium or lithium as the
source material and phenanthrenide as the precursor.
[0149] 5 Conversion of Organo Tin Compounds.
[0150] An example reaction would be of the type below:
Na.sup.++e.sup.-(from electrode).fwdarw.Na.sup.o
(CH.sub.3).sub.3Sn--Sn(CH.sub.3).sub.3+2Na.sup.o.fwdarw.2(CH.sub.3).sub.3S-
n.sup.-Na.sup.+
[0151] The sodium compound can then be reacted at a later
mixer/reactor stage e.g. with organo-halides to add a further
organic group to the tin.
(CH.sub.3).sub.3Sn.sup.-Na.sup.++CH.sub.2=CH--CH--Cl.fwdarw.(CH.sub.3).sub-
.3Sn--CH.sub.2-CH.dbd.CH+Na.sup.+Cl.sup.-
[0152] 6 Generation of Sodium/Potassium/Lithium Alkoxides or
Phenoxides.
[0153] Sodium alkoxides or potassium alkoxides or lithium alkoxides
can be synthesised using the present invention. In accordance with
the following process
Na/K/Li.sup.++e.sup.-(from electrode).fwdarw.Na/K/Li.sup.o
Na/K/Li.sup.o+R.sup.-OH.fwdarw.Na/K/Li.sup.+-OR+H.sub.2 where
R.dbd.CH.sub.3, C.sub.2H.sub.5, C.sub.3H.sub.7, C.sub.4H.sub.9, Ph,
substituted Ph, heteroaryl, or substituted heteroaryl.
[0154] Sodium ethoxide and other alkoxides which could be similarly
produced e.g. isopropoxide, are widely used in chemical synthesis.
Hydrogen gas evolved during synthesis will generally not interfere
with other reactions but may cause unwanted flow disturbance in the
device. Mixtures of alkoxides and salts may be produced from esters
without hydrogen evolution.
[0155] 7 Removal of Halides from Aromatics by Sodium Metal.
[0156] Halides can be removed from aromatics using the present
invention in accordance with the following process
Na.sup.++e.sup.-(from electrode).fwdarw.Na.sup.o
.sub.6-nNa.sup.o+C.sub.6H.sub.nCl.sub.6-n+solvent.fwdarw.C.sub.6H.sub.6+Na-
Hal+solvent
[0157] where Hal=Cl, Br, or I.
[0158] For example, Na+C.sub.6H.sub.nCl.sub.6-n+sodium
metal+(proton source solvent, e.g.
alcohol).fwdarw.C.sub.6H.sub.6+NaCl.
[0159] The addition of a proton source may need to be spatially
separated by adding it at a mixer stage following the reaction of
aromatic halide with the electro deposited sodum metal.
[0160] 8 Birch Reduction 1
[0161] Reactions of this type may be possible in type devices of
the second type with solid sodium ion conductor if compatibility
with the solvent can be established, or alternatively sodium salts
soluble in liquid ammonia could be used as electrolyte and source
material in devices of the first type.
[0162] An example is:--
C.sub.6H.sub.6(benzone)+2Na+C.sub.2H.sub.5OH(in liquid
ammonia).fwdarw.C.sub.6H.sub.8(1,4 cyclohexadiene)
[0163] The reaction goes via radical anion that abstracts protons
from alcohol.
[0164] 9 Generation of Grignard reagents.
[0165] The overall reaction is:
RX+Mg(in ether).fwdarw.R--Mg--X where R=C.sub.6H.sub.5 and X=Cl,
Br, or I
[0166] An example is
.C.sub.6H.sub.5Br+Mg.fwdarw.C.sub.6H.sub.5MgBr.
[0167] The reaction is carried out in ether solvents, and solvents
such as ethers facilitate the reaction in that they co-ordinate Mg
and stabilise the reagent. While electrolytic deposition of
Mg.sup.o from organic solutions is possible, it may also be
produced by reduction of dissolved magnesium compound by alkali
metal such as sodium which may therefore be employed as the primary
product as indicated for other reaction sequences.
[0168] Similarly for making organometallic reagents for metals
whose ions are not mobile within reasonably conductive solid
phases, e.g. metals with multiply-charged ions such as Mg, Zn, Cd,
Sn, Al, the preferred method will be to provide those metals in
solution and either directly electro-deposit or carry out a
conversion using electro-deposited alkali metal in devices of
either first or second type.
[0169] 10 Generation of Halogenated Products
[0170] This could include generation of products containing
fluorine, chlorine, bromine or iodine. The primary product may be
elemental halogen such as chlorine produced by electrochemical
oxidation of a soluble halide.
2Cl.sup.--2e.sup.-(at anode).fwdarw.Cl.sub.2
[0171] The chlorine may react with a range of organic species to
produce direct chlorination products by addition (to unsaturated
bonds) or substitution. Alternatively the chlorine may be converted
to an inorganic reactive intermediate. For example PCl.sub.3 and
PCl.sub.5 may be formed as secondary products by reaction of
chlorine with phosphorus which may be supplied suspended or
dissolved in a fluid stream. These secondary products may be
reacted within the device with further reagents such as carboxylic
acids to generate products such as acyl chlorides.
[0172] 11 Generation of Ylids from Phosphonium Salt Cations by the
Wittig Reaction and Reaction of Ylid and Aldehyde to Generate
Alkenes. For Example: 2
[0173] It will be appreciated that the cartridge and methods
described above may be performed on the macro scale but especially
may be applied on the micro scale by generating microfabricated
cartridges or systems.
[0174] In this disclosure, the term "fluid" means a gas or
supercritical liquid or either an aqueous or non-aqueous liquid.
Preferably the fluids are liquids. Preferably a fluid containing
salt or other redox active compounds of the metal to be
electrodeposited is ionically conductive but may be non conductive
provided an ionically conductive material is provided to link the
working and counter electrodes.
[0175] Additional mixing elements may be added to the reactor
device if needed, such as, for example small vanes or deflectors
that are shaped and positioned in the chamber and/or the inlet to,
or outlet from, the chamber to cause the fluid to swirl or mix.
[0176] A number of chemistries may be considered for operation in
the reactor devices described, but the generation of alkali metals
electrochemically and their reaction with organic reagents to form
organometallic reagents such as sodium naphthalenide or lithium
alkyls are preferred.
[0177] Therefore such a reactor device may find use on the
laboratory bench of a synthetic chemist and be scaled up or scaled
out by use of multiple or array devices for manufacture methods.
For example the output conduit of a first reactor of the present
invention may be connected in flow series to an inlet conduit of
another reactor constructed in accordance with the present
invention.
[0178] Similarly, a plurality of series connected reactors may be
provided on a common structure. One or more arrays of series
connected reactors may be arranged relative to another one or more
arrays of series connected reactors on a common structure. This
concept is not unlike that of a components built on an integrated
circuit chip but in this case the components are micro-engineered
reactors.
[0179] Importantly reactor devices according to the invention may
be applied in the conversion of dangerous waste chemicals and
solvents into less dangerous forms, especially but not limited to
the conversion and clean up of halogenated products such as PCBs
(polychlorinated biphenyls) and CFCs (chlorinated fluorocarbons).
Such conversions may proceed by direct reaction of primary product
metal such as sodium with the chemical to be converted, or by
generation of a secondary product such as sodium naphthalenide that
is then mixed and reacted with the chemical to be converted. The
use of sodium naphthalenide as a decomposition/clean-up reagent for
PCBs has been reported, as has reactive dehalogenation of CFCs by
sodium metal. These wastes may be subjected to direct treatment in
devices according the present invention with electrochemically
generated alkali metal (e.g. sodium) or by means of cartridges with
electrochemically generated alkali metal according to the present
invention.
* * * * *