U.S. patent application number 11/336843 was filed with the patent office on 2006-06-15 for combinatorial preparation and testing of heterogeneous catalysts.
Invention is credited to Dirk Demuth, Hartmut Hibst, Ferdi Schueth, Stephan A. Schunk, Andreas Tenten.
Application Number | 20060127287 11/336843 |
Document ID | / |
Family ID | 36584132 |
Filed Date | 2006-06-15 |
United States Patent
Application |
20060127287 |
Kind Code |
A1 |
Hibst; Hartmut ; et
al. |
June 15, 2006 |
Combinatorial preparation and testing of heterogeneous
catalysts
Abstract
The array of heterogeneous catalysts and/or their precursors, is
made up of a body which has, preferably parallel, through-channels
and in which at least n channels comprise n different heterogeneous
catalysts and/or their precursors, where n is 2, preferably 10,
particularly preferably 100, in particular 1000, especially 10,000.
A process for preparing arrays comprising the following steps: a1)
preparing solutions, emulsions and/or dispersions of elements
and/or element compounds of the elements present in the catalyst
and/or catalyst precursor and, if appropriate preparing dispersions
of inorganic support materials, a2) if appropriate introducing
adhesion promoters, binders, viscosity regulators, pH regulators
and/or solid inorganic supports into the solutions, emulsions
and/or dispersions, a3) simultaneously or successively coating the
channels of the body with the solutions, emulsions and/or
dispersions, a predetermined amount of the solutions, emulsions
and/or dispersions being introduced into each channel to obtain a
predetermined composition and a4) if appropriate heating the coated
body in the presence or absence of inert gases or reactive gases to
a temperature in the range from 20 to 1500.degree. C. to dry, with
or without sintering or calcining, the catalysts and/or catalyst
precursors.
Inventors: |
Hibst; Hartmut;
(Schriesheim, DE) ; Tenten; Andreas; (Maikammer,
DE) ; Demuth; Dirk; (Mannheim, DE) ; Schueth;
Ferdi; (Oberursel, DE) ; Schunk; Stephan A.;
(Heidelberg, DE) |
Correspondence
Address: |
NOVAK DRUCE DELUCA & QUIGG, LLP
1300 EYE STREET NW
SUITE 400 EAST
WASHINGTON
DC
20005
US
|
Family ID: |
36584132 |
Appl. No.: |
11/336843 |
Filed: |
January 23, 2006 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09622173 |
Aug 14, 2000 |
|
|
|
PCT/EP99/00902 |
Feb 11, 1999 |
|
|
|
11336843 |
Jan 23, 2006 |
|
|
|
Current U.S.
Class: |
422/185 ;
422/139 |
Current CPC
Class: |
B01J 2219/00511
20130101; B01J 2219/00747 20130101; B01J 2219/0059 20130101; B01J
37/0215 20130101; B01J 2219/00585 20130101; B01J 19/0046 20130101;
B01J 2219/00306 20130101; B01J 37/0217 20130101; B01J 2219/00599
20130101; B01J 2219/00286 20130101 |
Class at
Publication: |
422/185 ;
422/139 |
International
Class: |
D21C 11/00 20060101
D21C011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 12, 1998 |
DE |
19805719.9 |
Feb 18, 1998 |
DE |
19806848.4 |
Dec 3, 1998 |
DE |
19855894.5 |
Claims
1-4. (canceled)
5. A process for preparing an array of heterogeneous catalysts
and/or their precursors made up of a body which has, preferably
parallel, through-channels and in which at least n channels
comprise n different heterogeneous catalysts and/or their
precursors, where n is at least 2, comprising the following steps:
a1) preparing solutions, emulsions and/or dispersions of elements
and/or element compounds of the chemical elements present in the
catalyst and/or catalyst precursor and, if appropriate preparing
dispersions of inorganic support materials, a2) if appropriate
introducing adhesion promoters, binders, viscosity regulators, pH
regulators and/or solid inorganic supports into the solutions,
emulsions and/or dispersions, a3) simultaneously or successively
coating the channels of the body with the solutions, emulsions
and/or dispersions, a predetermined amount of the solutions,
emulsions and/or dispersions being introduced into each channel to
obtain a predetermined composition and a4) if appropriate heating
the coated body in the presence or absence of inert gases or
reactive gases to a temperature in the range from 20 to
1500.degree. C. to dry, with or without sintering or calcining, the
catalysts and/or catalyst precursors.
6. A process for preparing an array of heterogeneous catalysts
and/or their precursors made up of a body which has, preferably
parallel, through-channels and in which at least n channels
comprise n different heterogeneous catalysts and/or their
precursors where n is at least 2, comprising the following steps:
b1) preparing solutions, emulsions and/or dispersions of elements
and/or element compounds of the chemical elements present in the
catalyst and/or catalyst precursor and, if appropriate preparing
dispersions of inorganic support materials, b2) if appropriate
introducing adhesion promoters, binders, viscosity regulators, pH
regulators and/or solid inorganic supports into the solutions,
emulsions and/or dispersions, b3) simultaneously or successively
coating catalyst supports present in the channels of the body with
the solutions, emulsions and/or dispersions, a predetermined amount
of the solutions, emulsions and/or dispersions being introduced
into each channel to obtain a predetermined composition on the
catalyst supports and b4) if appropriate heating the body
comprising the coated catalyst supports in the channels in the
presence or absence of inert gases or reactive gases to a
temperature in the range from 20 to 1500.degree. C. to dry, with or
without sintering or calcining, the catalysts and/or catalyst
precursors.
7. A process for preparing an array of heterogeneous catalysts
and/or their precursors made up of a body which has, preferably
parallel, through-channels and in which at least n channels
comprise n different heterogeneous catalysts and/or their
precursors, where n is at least 2, comprising the following steps:
c1) preparing solutions, emulsions and/or dispersions of elements
and/or element compounds of the chemical elements present in the
catalyst and/or catalyst precursor and, if appropriate preparing
dispersions of inorganic support materials, c2) mixing
predetermined amounts of the solutions, emulsions and/or
dispersions with or without precipitation aids in one or more
reaction vessels run in parallel, c3) if appropriate introducing
adhesion promoters, binders, viscosity regulators, pH regulators
and/or solid inorganic supports into the resultant mixture(s), c4)
coating one or more predetermined channels of the body with the
mixture or a plurality of mixtures, c5) repeating steps c2) to c4)
for other channels of the body until the channels containing the
respective predetermined catalyst and/or catalyst precursor
compositions are coated, c6) if appropriate heating the coated body
in the presence or absence of inert gases or reactive gases to a
temperature in the range from 20 to 1500.degree. C. to dry, with or
without sintering or calcining, the catalysts and/or catalyst
precursors.
8. A process for preparing an array of heterogeneous catalysts
and/or their precursors made up of a body which has, preferably
parallel, through-channels and in which at least n channels
comprise n different heterogeneous catalysts and/or their
precursors, where n is at least 2, comprising the following steps:
d1) preparing solutions, emulsions and/or dispersions of elements
and/or element compounds of the chemical elements present in the
catalyst and/or catalyst precursor and, if appropriate preparing
dispersions of inorganic support materials, d2) mixing
predetermined amounts of the solutions, emulsions and/or
dispersions with or without precipitation aids in one or more
reaction vessels run in parallel, d3) if appropriate introducing
adhesion promoters, binders, viscosity regulators, pH regulators
and/or solid inorganic supports into the resultant mixture(s), d4)
coating catalyst supports present in one or more predetermined
channels of the body with the mixture or one or more mixtures, d5)
repeating steps d2) to d4) for other channels of the body until the
catalyst supports present in the channels of the body are coated
with the respective predetermined catalyst compositions and/or
catalyst precursor compositions, d6) if appropriate heating the
body comprising the coated catalyst supports in the channels in the
presence or absence of inert gases or reactive gases to a
temperature in the range from 20 to 1500.degree. C. to dry, with or
without sintering or calcining, the catalysts and/or catalyst
precursors.
9. A process as claimed in claim 5, wherein the adhesiveness of the
channels of the body is increased prior to the coating by chemical,
physical or mechanical pretreatment of the inner walls of the
channels or by applying an adhesive coating.
10. A process for preparing an array of heterogeneous catalysts
and/or their precursors made up of a body which has, preferably
parallel, through-channels and in which at least n channels
comprise n different heterogeneous catalysts and/or their
precursors, where n is at least 2, comprising the following steps:
e1) preparing different heterogeneous catalysts and/or their
precursors in the form of unsupported catalysts having a
predetermined composition, e2) charging in each case one or more
predetermined channels of the body, which are secured against the
heterogeneous catalyst falling out, with in each case one or more
of the heterogeneous catalysts and/or their precursors having a
predetermined composition, e3) if appropriate heating the body
comprising the heterogeneous catalysts and/or their precursors in
the channels in the presence or absence of inert gases or reactive
gases to a temperature in the range from 20 to 1500.degree. C. to
dry, with or without sintering or calcining, the catalysts and/or
the precursors.
11. A process for preparing an array of heterogeneous catalysts
and/or their precursors made up of a body which has, preferably
parallel, through-channels and in which at least n channels
comprise n different heterogeneous catalysts and/or their
precursors, where n is at least 2, comprising the following steps:
f1) coating and if appropriate heating predetermined catalyst
supports to prepare predetermined supported catalysts in the manner
defined in claim 6 outside the body, f2) introducing the supported
catalysts into predetermined channels of the body, f3) if
appropriate heating the packed body in the presence or absence of
inert gases or reactive gases to a temperature in the range from 20
to 1500.degree. C. to dry, with or without sintering or calcining,
the catalysts.
12. A process as claimed in claim 11, wherein the external shape of
the supported catalyst at least essentially corresponds to the
shape of the channel interior in the body.
13. An array obtainable by a process as claimed in claim 5.
14. A process for determining the activity and/or long-term
stability of the catalysts in an array as claimed in claim 13,
comprising the following steps: g1) if appropriate activating the
catalysts in the body, g2) heating or cooling the body to a desired
reaction temperature, g3) passing a fluid reactant or a fluid
reaction mixture through-channels of the body, g4) discharge of the
reacted fluids from individual or a plurality of collective
channels of the body, g5) analysis of the discharged reacted
fluids, g6) id appropriate comparative evaluation of the analytical
results of a plurality of analyses.
15. A process as claimed in claim 14, wherein after heating or
cooling the body to a first reaction temperature in step g2), step
g3) to step g6) are carried out successively for a plurality of
different fluid reactants or fluid reaction mixtures, where in each
case a purge step with a purge gas can be introduced, and then the
body can be heated or cooled to a second reaction temperature and
the abovementioned reactions can be repeated at this
temperature.
16. A process as claimed in claim 14, wherein the fluid reactant or
fluid reaction mixture is a gas or gas mixture.
17. A process as claimed in claim 14, wherein the reaction is a
gas-phase oxidation.
18. A process as claimed in claim 17, wherein a reaction mixture
comprising molecular oxygen is used.
19. A process as claimed in claim 6, wherein the adhesiveness of
the catalyst support in the body is increased, prior to the
coating, by chemical, physical or mechanical pretreatment of the
catalyst support or by applying an adhesive layer.
20. A process as claimed in claim 5, wherein the process is carried
out in an automated manner.
Description
[0001] The invention relates to a process for the combinatorial
preparation and testing of heterogeneous catalysts and catalysts
obtained by this process.
[0002] To prepare and study novel chemical compounds, in addition
to classical chemistry which is directed towards the synthesis and
study of individual substances, combinatorial chemistry has
developed. In this approach, a multiplicity of reactants were
reacted in a one-pot synthesis and analyzed as to whether the
resultant reaction mixture displays the desired properties, for
example a pharmacological activity. If an activity was found for
such a reaction mixture, it was necessary to determine in a further
step which specific substance in the reaction mixture was
responsible for the activity. In addition to the high expenditure
for determining the actual active compound, it was difficult with a
multiplicity of reactants to exclude to unwanted side
reactions.
[0003] In another combinatorial synthesis approach, a multiplicity
of compounds were synthesized by specific dosage and reaction of a
number of reactants in a multiplicity of different reaction
vessels. In this process, preferably, in each reaction vessel one
reaction product is present, so that in the event of, for example,
a given pharmacological activity of a mixture, the starting
materials used for its preparation are known immediately.
[0004] In addition to the first applications of this more specific
combinatorial synthesis in the search for novel pharmacologically
active substances, very recently the synthesis method has also been
extended to low-molecular-weight organic compounds and to organic
and inorganic catalysts.
[0005] F. M. Menger et al., "Phosphatase Catalysis Developed via
Combinatorial Organic Chemistry", J. Org. Chem. 60 (1995) pages
6666 to 6667, describe the preparation of organic catalysts by
combinatorial processes. 8 functionalized different carboxylic
acids were bound to a polyallylamine via amide bonds. In addition,
different metal ions were bound to the polymer via complex
formation. The resultant polymers were then studied for their
phosphatase activity. There is no description given as to whether
the catalysts were obtained by an automated preparation process.
Only the preparation of individual catalysts is described.
[0006] C. L. Hill and R. D. Gall, "The first combinatorially
prepared and evaluated inorganic catalysts. Polyoxometalates for
the aerobic oxidation of the mustard analog tetrahydrothiophene
(THT)", J. Mol. Catalysis A: Chemical 114 (1996), pages 103 to 111
describe the combinatorial preparation and testing of
polyoxometalates, which were prepared by mixing different
proportions of solutions of the desired metal salts. Tungstate,
molybdate and vanadate solutions as well as a sodium hydrogen
phosphate solution were prepared for this. After the appropriate
solutions were metered, the pH was set to a predetermined value and
a reaction induced. The resultant catalysts were used in dissolved
form for the reaction. No description is given as to whether the
catalyst preparation was automated.
[0007] Processes for the specific metering of different amounts of
various liquid reactants into an array of reaction vessels, which
can resemble a spot plate, for example, are described in U.S. Pat.
No. 5,449,754. For this purpose, the printer head of an ink jet
printer, which is connected to reservoir solutions of the
reactants, is moved over the array using an XY positioner and the
release of the liquids is controlled by a computer.
[0008] F. C. Moathes et al., "Infrared Thermographic Screening of
Combinatorial Libraries of Heterogeneous Catalysts", Ind. Eng.
Chem. Res. 35, (1996), 4801 to 4803, describe the IR screening of
libraries of heterogeneous catalysts which comprise differing
elemental metals applied to aluminum oxide. Their catalytic
activity with respect to hydrogen oxidation was studied. The
individual catalysts were prepared by impregnating aluminum oxide
pellets in appropriate metal salt solutions, drying and
calcination. There is no specification here as to whether the
preparation was automated.
[0009] The differing pellets were laid down on a support at
predetermined positions and contacted with hydrogen under reaction
conditions. In the event of catalytic activity, the catalyst heated
up, and the heating was measured using an infrared camera, as
result of which the active catalysts could be determined.
[0010] B. E. Baker et al., "Solution-Based Assembly of Metal
Surfaces by Combinatorial Methods", J. Am. Chem.-Soc. 118, (1996),
pages 8721 to 8722 describe the preparation by combinatorial
processes of metal surfaces differing in composition. For this
purpose, a silane-coated glass plate is immersed at a predetermined
rate into a colloidal gold solution so as to give a gold
distribution gradient on the substrate. After withdrawing and
drying the plate, it is rotated around 90.degree. and immersed into
a silver ion solution, so that there is a further concentration
gradient on the plate. This results in a continuous change in
composition in the surface.
[0011] X.-D. Xiang et al., "A Combinatorial Approach for Materials
Discovery", Science 268, (1995), pages 1738 to 1740 describe the
preparation of BiSrCaCuO and YBaCuO superconductivity films on
substrates, a combinatorial array of different metal compositions
being obtained by physical masking processes and vapor deposition
techniques in the deposition of the appropriate metals. After the
calcination, different compositions are present at different
positions of the array and can be studied by microprobes, for their
conductivity for example.
[0012] WO 96/11878 describes, in addition to the preparation of
such superconductivity arrays, the preparation of zeolites, the
amounts required in each case being metered without prior mixing
from a plurality of metal salt solutions using an ink jet onto a
type of spot plate, a precipitation starting on addition of the
last solution. BSCCO superconductors can also be prepared by
separate metering of the individual nitrate solutions of the metals
required by spraying onto a type of spot plate and subsequent
heating.
[0013] Various types of heterogeneous catalysts can be prepared
using the known processes. However, testing the catalysts is
complex and frequently cannot be performed under realistic
conditions, e.g. using the required residence times of the
reactants on the catalyst, since the catalysts are present, for
example, on a relatively large, generally flat support and this
must be charged, for example, with a gas mixture to be reacted.
[0014] It is an object of the present invention to provide a
process for preparing arrays of inorganic heterogeneous catalysts
or their precursors in which the resultant catalysts can be tested
with low expenditure and under conditions which resemble an
industrial process. In addition, the disadvantages of the existing
systems are to be avoided. Corresponding arrays are also to be
provided.
[0015] We have found that this object is achieved by providing an
array of, preferably inorganic, heterogeneous catalysts and/or
their precursors made up of a body which has, preferably parallel,
through-channels in which at least n channels comprise n different,
preferably inorganic, heterogeneous catalysts and/or their
precursors, where n is 2, preferably 10, particularly preferably
100, in particular 1000, especially 10,000.
[0016] According to one embodiment of the invention, the body is a
tube-bundle reactor or heat exchanger and the channels are
tubes.
[0017] According to a further embodiment of the invention, the body
is a block made of a solid material which has the channels, in the
form of boreholes for example.
[0018] The heterogeneous catalysts and/or precursors are preferably
unsupported catalysts or supported catalysts and/or their
precursors and are present as a catalyst bed, tube-wall coating or
auxiliary support coating.
[0019] The term "array of inorganic heterogeneous catalysts or
their precursors" describes here an arrangement of different
inorganic heterogeneous catalysts or their precursors on
predetermined areas of a body which are spatially separate from one
another, preferably a body having parallel through-channels,
preferably a tube-bundle reactor or heat exchanger. The geometric
arrangement of the individual areas to one another can be chosen
freely in this case. For example, the areas can be arranged in the
manner of a row (quasi one-dimensional) or a chessboard pattern
(quasi two-dimensional). In a body having parallel
through-channels, preferably a tube-bundle reactor or heat
exchanger having a multiplicity of tubes parallel to one another,
the arrangement becomes clear when a cross-sectional area
perpendicular to the longitudinal axis of the tubes is considered:
an area results, in which the individual tube cross sections
reproduce the different areas separated from one another. The areas
or tubes can, for example for tubes having a circular cross
section, also be present in a dense packing, so that different rows
are arranged from areas staggered to one another.
[0020] The term "body" describes a three-dimensional object which
has a multiplicity (at least n) of through-channels. The channels
thus connect two surface areas of the body and run through the
body. Preferably, the channels are essentially, preferably
completely, parallel to one another. In this case, the body can be
made up of one or more materials and can be solid or hollow. It can
have any suitable geometric shape. Preferably it has two surfaces
parallel to one another in which in each case one orifice of the
channels is situated. The channels preferably run perpendicularly
to these surfaces. An example of a body of this type is a
parallelepiped or cylinder in which the channels run between two
parallel surfaces. However, a multiplicity of similar geometries is
also conceivable.
[0021] The term "channel" describes a connection running through
the body between two orifices situated on the body surface which,
for example, permits the passage of a fluid through the body. The
channel here can have any desired geometry. It can have a
cross-sectional area changing over the length of the channel or,
preferably; can have a constant channel cross-sectional area. The
channel cross section can have, for example, an oval, round or
polygonal outline with straight or rounded connections between the
corners of the polygon. Preference is given to a round or
equilateral polygonal cross section. Preferably, all channels in
the body have the same geometry (cross section and length) and run
parallel to one another.
[0022] The terms "tube-bundle reactor" and "heat exchanger"
describe collective parallel arrangements of a multiplicity of
channels in the form of tubes, where the tubes can have any desired
cross section. The tubes are arranged in a fixed spatial
relationship to one another, are preferably present spatially
separated from one another and are preferably surrounded by a shell
which encloses all of the tubes. By this means, for example, a
heating or cooling medium can be conducted through the shell, so
that all of the tubes can be heated or cooled uniformly.
[0023] The term "block of a solid material" describes a body of a
solid material (which in turn can be made up of one or more
starting materials) which has the channels, for example in the form
of boreholes. The geometry of the channels (boreholes) can here be
chosen freely as described above for the channels generally. The
channels (boreholes) need not be installed by boring, but can be
left open, for example even when forming the solid body/block, for
instance by extruding an organic and/or inorganic molding
composition (for example by an appropriate die geometry during
extrusion). In contrast to the tube-bundle reactors or heat
exchangers, the space in the body between the channels in the block
is always filled by the solid material. Preferably, the block is
made up of one or more metals.
[0024] The term "predetermined" means that, for example, a number
of different catalysts or catalyst precursors is introduced into a
tube-bundle reactor or heat exchanger in such a manner that the
assignation of the different catalysts or catalyst precursors to
the individual tubes is recorded and can later be retrieved, for
example, when determining the activity, selectivity and/or
long-term stability of the individual catalysts, in order to make
possible an unambiguous assignation of defined measured values to
defined catalyst compositions. Preferably, the catalysts or their
precursors are prepared and distributed to the different tubes of
the tube-bundle reactor under computer control, the respective
composition of a catalyst and the position of the tube in the
tube-bundle reactor into which the catalyst or catalyst precursor
is introduced is stored in the computer and can later be retrieved.
The term "predetermined" thus serves to differentiate from a chance
or random distribution of the generally different catalysts or
catalyst precursors to the tubes of a tube-bundle reactor.
[0025] The arrays according to the invention of, preferably
inorganic, heterogeneous catalysts and/or their precursors can be
prepared by a variety of processes:
[0026] Process a comprises the following steps: [0027] a1)
preparing solutions, emulsions and/or dispersions of elements
and/or element compounds of the elements present in the catalyst
and/or catalyst precursor and, if appropriate preparing dispersions
of inorganic support materials, [0028] a2) if appropriate
introducing adhesion promoters, binders, viscosity regulators, pH
regulators and/or solid inorganic supports into the solutions,
emulsions and/or dispersions, [0029] a3) simultaneously or
successively coating the channels of the body with the solutions,
emulsions and/or dispersions, a predetermined amount of the
solutions, emulsions and/or dispersions being introduced into each
channel to obtain a predetermined composition and [0030] a4) if
appropriate heating the coated body in the presence or absence of
inert gases or reactive gases to a temperature in the range from 20
to 1500.degree. C. to dry, with or without sintering or calcining,
the catalysts and/or catalyst precursors.
[0031] The process b comprises the following steps: [0032] b1)
preparing solutions, emulsions and/or dispersions of elements
and/or element compounds of the elements present in the catalyst
and/or catalyst precursor and, if appropriate preparing dispersions
of inorganic support materials, [0033] b2) if appropriate
introducing adhesion promoters, binders, viscosity regulators, pH
regulators and/or solid inorganic supports into the solutions,
emulsions and/or dispersions, [0034] b3) simultaneously or
successively coating catalyst supports present in the channels of
the body with the solutions, emulsions and/or dispersions, a
predetermined amount of the solutions, emulsions and/or dispersions
being introduced into each channel to obtain a predetermined
composition on the catalyst supports and [0035] b4) if appropriate
heating the body comprising the coated catalyst supports in the
channels in the presence or absence of inert gases or reactive
gases to a temperature in the range from 20 to 1500.degree. C. to
dry, with or without sintering or calcining, the catalysts and/or
catalyst precursors.
[0036] Process c) comprises the following steps: [0037] c1)
preparing solutions, emulsions and/or dispersions of elements
and/or element compounds of the chemical elements present in the
catalyst and/or catalyst precursor and, if appropriate preparing
dispersions of inorganic support materials, [0038] c2) mixing
predetermined amounts of the solutions, emulsions and/or
dispersions with or without precipitation aids in one or more
reaction vessels run in parallel, [0039] c3) if appropriate
introducing adhesion promoters, binders, viscosity regulators, pH
regulators and/or solid inorganic supports into the resultant
mixture(s), [0040] c4) coating one or more predetermined channels
of the body with the mixture or a plurality of mixtures, [0041] c5)
repeating steps c2) to c4) for other channels of the body until the
channels containing the respective predetermined catalyst and/or
catalyst precursor compositions are coated, [0042] c6) if
appropriate heating the coated body in the presence or absence of
inert gases or reactive gases to a temperature in the range from 20
to 1500.degree. C. to dry, with or without sintering or calcining,
the catalysts and/or catalyst precursors.
[0043] Preferably, it comprises the following steps: [0044] c1)
preparing solutions of element compounds of the chemical elements
present in the catalyst except for oxygen, and if appropriate
preparing dispersions of inorganic support materials [0045] c2)
mixing predetermined amounts of the solutions or dispersions with
or without precipitation aids in one or more reaction vessels run
in parallel with precipitation of the chemical elements present in
the catalyst, [0046] c3) if appropriate introducing adhesion
promoters, binders, viscosity regulators, pH regulators and/or
solid inorganic supports into the resultant suspension, [0047] c4)
coating with the suspension one or more predetermined tubes of the
tube-bundle reactor or heat exchanger, [0048] c5) repeating steps
c2) to c4) for different tubes of the tube-bundle reactor or heat
exchanger until the tubes containing the respective predetermined
catalyst compositions are coated, [0049] c6) heating the coated
tube-bundle reactor or heat exchanger in the presence or absence of
inert gases or reactive gases to a temperature in the range from 20
to 1500.degree. C. to dry, with or without sintering or calcining,
the catalysts.
[0050] Process d) comprises the following steps: [0051] d1)
preparing solutions, emulsions and/or dispersions of elements
and/or element compounds of the chemical elements present in the
catalyst and/or catalyst precursor and, if appropriate preparing
dispersions of inorganic support materials, [0052] d2) mixing
predetermined amounts of the solutions, emulsions and/or
dispersions with or without precipitation aids in one or more
reaction vessels run in parallel, [0053] d3) if appropriate
introducing adhesion promoters, binders, viscosity regulators, pH
regulators and/or solid inorganic supports into the resultant
mixture(s), [0054] d4) coating catalyst supports present in one or
more predetermined channels of the body with the mixture or one or
more of the mixtures, [0055] d5) repeating steps d2) to d4) for
other (that is generally the as yet uncoated) catalyst supports in
the channels of the body until (preferably all) the catalyst
supports present in the channels of the body are coated with the
respective predetermined (generally differing from one another)
catalyst compositions and/or catalyst precursor compositions,
[0056] d6) if appropriate heating the body comprising the coated
catalyst supports in the channels in the presence or absence of
inert gases or reactive gases to a temperature in the range from 20
to 1500.degree. C. to dry, with or without sintering or calcining,
the catalysts and/or catalyst precursors.
[0057] In this process, the adhesiveness of the channels (e.g. of
the inner surface of the tubes) of the body or of the catalyst
supports can be increased prior to the coating by chemical,
physical or mechanical pretreatment of the inner walls of the
channels (e.g. inner tubes) or the catalyst supports or by applying
an adhesive layer. This applies in particular to the processes a)
and c) and to b) and d) respectively.
[0058] Process e comprises the following steps: [0059] e1)
preparing different heterogeneous catalysts and/or their precursors
in the form of unsupported catalysts having a predetermined
composition, [0060] e2) charging in each case one or more
predetermined channels of the body, which are secured against the
heterogeneous catalysts falling out, with in each case one or more
of the heterogeneous catalysts and/or their precursors having a
predetermined composition, [0061] e3) if appropriate heating the
body comprising the heterogeneous catalysts and/or their precursors
in the channels in the presence or absence of inert gases or
reactive gases to a temperature in the range from 20 to
1500.degree. C. to dry, with or without sintering or calcining, the
catalysts and/or catalyst precursors.
[0062] Process f) comprises the following steps: [0063] f1) coating
and if appropriate heating predetermined catalyst supports to
prepare predetermined supported catalysts in the manner defined
above in processes b) and d) outside the body, [0064] f2)
introducing the supported catalysts into predetermined channels of
the body, [0065] f3) if appropriate heating the packed body in the
presence or absence of inert gases or reactive gases to a
temperature in the range from 20 to 1500.degree. C. to dry, with or
without sintering or calcining, the catalysts.
[0066] Preferably, the external shape of the supported catalysts
corresponds here to the shape of the channel interior in the body
at least essentially, preferably approximately or completely.
[0067] The invention also relates to inorganic heterogeneous
catalyst arrays which are obtainable by one of the abovementioned
processes. The arrays can also be prepared by any combination of
the abovementioned processes.
[0068] The processes are suitable for preparing a multiplicity of
catalyst systems, as are described, for example, in G. Ertl, H.
Knozinger, J. Weitkamp, editors, "Handbook of Heterogeneous
Catalysis", Wiley--VCH, Weinheim, 1997.
[0069] In addition, the invention relates to a process g) for
determining catalytic properties, in particular the activity,
selectivity and/or long-term stability of the catalysts described
above and below in an array described, which comprises the
following steps: [0070] g1) if appropriate activating the catalysts
in the body, [0071] g2) heating or cooling the body to a desired
reaction temperature, [0072] g3) passing a fluid reactant or a
fluid reaction mixture through (one, a plurality or all of the)
channels of the body, [0073] g4) (preferably separate) discharge of
the reacted fluids from individual or a plurality of collective
channels of the body, [0074] g5) (preferably separate) analysis of
the discharged reacted fluids, [0075] g6) if appropriate
comparative evaluation of the analytical results of a plurality of
analyses.
[0076] In a preferred process variant, after heating or cooling the
body to a first reaction temperature in step g2), steps g3) to g6)
are carried out successively for a plurality of different fluid
reactants or fluid reaction mixtures, where in each case a purge
step with a purge gas can be introduced, and then the body can be
heated or cooled to a second reaction temperature and the
abovementioned reactions can be repeated at this temperature.
[0077] At the start of the analysis, the collected gas stream of
the entire array can be analyzed to detect whether there has been
any reaction at all.
[0078] Thereafter, if a reaction is present, the discharges of the
individual tubes or a plurality of tubes can be analyzed to
determine an optimum catalyst using a minimum number of analytical
processes.
[0079] Flow can pass through individual tubes or a plurality or all
of the tubes collectively.
[0080] Preferably, the fluid reactant or fluid reaction mixture is
a gas or gas mixture.
[0081] The invention permits the automated preparation and
catalytic testing for the purpose of mass screening of
heterogeneous catalysts for chemical reactions, in particular for
reactions in the gas phase, very particularly for partial
oxidations of hydrocarbons in the gas phase by molecular oxygen
(gas-phase oxidations).
[0082] Suitable reactions for investigation are described in G.
Ertl, H. Knozinger, J. Weitkamp, editors, "Handbook of
Heterogeneous Catalysis", Wiley--VCH, Weinheim, 1997. Examples of
suitable reactions are principally listed in this reference in
Volumes 4 and 5 under numbers 1, 2, 3 and 4.
[0083] Examples of suitable reactions are the decomposition of
nitrogen oxides, the synthesis of ammonia, the oxidation of
ammonia, oxidation of hydrogen sulfide to sulfur, oxidation of
sulfur dioxide, direct synthesis of methylchlorosilanes, oil
refining, oxidative coupling of methane, methanol synthesis,
hydrogenation of carbon monoxide and carbon dioxide, conversion of
methanol to hydrocarbons, catalytic reforming, catalytic cracking
and hydrocracking, coal gasification and liquefaction, fuel cells,
heterogeneous photocatalysis, synthesis of MTBE and TAME,
isomerizations, alkylations, aromatizations, dehydrogenations,
hydrogenations, hydroformylations, selective or partial oxidations,
aminations, halogenations, nucleophilic aromatic substitutions,
addition and elimination reactions, oligomerizations and
metathesis, polymerizations, enantioselective catalysis and
biocatalytic reactions.
[0084] The invention is described in more detail below with
reference to preferred embodiments.
Preparation of the Inorganic Heterogeneous Catalyst Array
[0085] Firstly, two or more, preferably 10 or more, very
particularly preferably 100 or more, in particular 1000 or more,
especially 10,000 or more, liquid starting mixtures (termed
mixtures below) which comprise selected chemical elements of the
Periodic Table of the Elements are prepared in the form of
solutions, emulsions and/or preferably suspensions (dispersions),
the mixtures prepared generally differing in their chemical
composition or concentration. To test the reproducibility, a
plurality of mixtures of the same composition can also be used.
[0086] The liquid mixtures generally comprise a liquid chemical
component which is used as solvent, emulsifying aid or dispersant
for the other components of the mixture. As solvent or dispersant,
use is made of organic solvents, emulsifying aids and/or water,
preferably water.
[0087] Apart from the chemical elements of the solvent or
dispersant, the liquid mixtures comprise one or more, preferably 2
or more, particularly preferably 3 or more, chemical elements,
generally, however, no more than 50 different chemical elements
being present in an amount of in each case greater than 1% by
weight. Preferably, the chemical elements are present in the
mixtures very intimately mixed, e.g. in the form of a mixture of
various miscible solutions, intimate emulsions having a small
droplet size and/or preferably as a suspension (dispersion) which
comprises the chemical elements in question generally in the form
of a finely divided precipitate, e.g. in the form of a chemical
mixed precipitate. The use of brines and gels has proved
particularly useful, in particular of those which comprise the
chemical elements in question in a substantially homogeneous
distribution, and preferably those which show an adhesion and flow
behavior expedient for the coating. Suitable starting compounds for
the chemical elements selected are in principle the elements
themselves, preferably in finely divided form, furthermore all
compounds which contain the chosen chemical elements in a suitable
manner, such as oxides, hydroxides, hydroxideoxides, inorganic
salts, preferably nitrates, carbonates, acetates and oxalates,
organometallic compounds, alkoxides etc. The respective starting
compounds can be used in solid form, in the form of solutions,
emulsions and/or in the form of suspensions.
[0088] Preferred element compounds, in particular catalytically
active metals, are water-soluble oxides, hydroxides or salts of
organic or inorganic acids. Active metals are preferably located in
the subgroups of the Periodic Table of the Elements, for example in
subgroups 5 and 6 for oxidation catalysts and in the platinum group
for hydrogenation catalysts. The process according to the invention
also permits the screening of (atypical) elements which were not
previously considered to be catalytically active, in particular
metals or metal oxides.
[0089] In addition, the liquid mixture can comprise other compounds
which affect the adhesion properties and the flow behavior of the
liquid mixture on the channel interior or tube interior to be
coated or catalyst supports and thus affect the coating properties
of the liquid mixture. Organic compounds which may be mentioned
here are, for example, ethylene glycol or glycerol, as described in
DE-A 4 442 346, or, for example, maleic acid copolymers, and
inorganic compounds which may be mentioned are, for example,
SiO.sub.2, organosilicone compounds or siloxanes.
[0090] In addition, the mixtures can comprise known inorganic
support materials, such as Al.sub.2O.sub.3, ZrO.sub.2, SiO.sub.2,
Y.sub.2O.sub.3, TiO.sub.2, activated carbon, MgO, SiC or
Si.sub.3N.sub.4, which generally increase the surface area
accessible to the catalysis of the catalytically active chemical
elements present in the mixture and in addition can affect the
catalytic properties of the active composition present and which
likewise can affect the adhesion and flow properties of the
resultant mixture. Generally, coatings are obtained in this case
which comprise, in addition to the actual catalytic material, the
preferred oxide, nitride or carbide support material. However, when
the components are being mixed or during the subsequent heating of
the coating, said support material can also react with the chemical
elements used above it to form a novel solid material.
[0091] Furthermore, the mixtures used can additionally comprise an
inorganic and/or organic binder or a binder system which stabilizes
the mixture used. Binders suitable for this are, for example,
binders or binder systems which comprise metal salts, metal oxides,
metal hydroxide oxides, metal hydroxide oxide phosphates and/or
eutectic compounds melting at the service temperature of the
catalyst.
[0092] The mixture can in addition be set to a defined pH range by
adding acids and/or bases. In many cases, pH neutral suspensions
are used. For this purpose, the mixture can advantageously be set
to a pH between 5 and 9, preferably between 6 and 8. Special
results may be obtained by the process according to the invention
if the mixture has a high solids content of up to 95% by weight,
preferably from 50 to 80% by weight at low viscosity. If
precipitation is insufficient, precipitation aids, such as ammonia,
can be added.
[0093] In a preferred embodiment of the invention, the mixture is
stirred after, and generally also during, the preparation and its
flowability is measured continuously, but at least at the end of
the preparation. This can be done, for example, by measuring the
power consumption of the agitator unit. Using this measurement, the
viscosity of the suspension can be set, for example by adding
further solvents or thickeners, so as to result in optimum
adhesion, layer thickness and layer thickness uniformity on the
tube inner wall to be coated or on the auxiliary support (catalyst
support) to be coated.
[0094] In principle, the invention is not restricted to certain
catalyst materials and catalyst compositions. The preparation of
the mixture can be performed in parallel or successively and is
generally performed in automated form, e.g. using an automated
pipette or automated pipetting system or else an ink-jet process,
as described, for example, in U.S. Pat. No. 5,449,754.
[0095] To coat the tubes of the tube-bundle reactor or heat
exchanger by process variant a), solutions, emulsions or
suspensions of individual elements or element compounds can be
introduced into the tubes simultaneously or successively separated
from one another. Simultaneous introduction can be performed, for
example, using a modified ink-jet printer head which comprises
separate feed lines for the individual solutions, emulsions or
suspensions and permits the simultaneous atomization. Compared with
this process variant a, the process variant b is preferred, which
is carried out in particular as follows:
[0096] To prepare the catalysts or their precursors, solutions,
emulsions and/or suspensions of the required elements are firstly
prepared in separate vessels. These are frequently metal salt
solutions, for example nitrates. The amounts of the separate
solutions required to prepare a catalyst or catalyst precursor are
transferred in the desired ratio into a small separate reaction
vessel in which the components are intensively mixed. They can be
metered, for example, using automated pipettes or an ink-jet unit.
When the components are mixed, a reaction or precipitation of the
components can occur. Using precipitants such as ammonia,
precipitation is induced or completed if necessary, so that a
suspension of the mixed catalyst precursor material is frequently
present.
[0097] Since the suspension should have a suitable viscosity to be
able to be introduced into a tube of the tube-bundle reactor and
distributed, so as to give a distribution of the catalyst or
catalyst precursor on the tube inner wall as uniform as possible
and substantially adherent, if necessary the suitable suspension
viscosity can be set to the desired value as described above by
further additives. The suspension can be withdrawn from the
reaction vessel in this case, for example, using pipettes, and
distributed in the tube, as described below, by injection or
atomization. The reaction vessel can in this case be completely or
partially emptied. A plurality of reaction vessels can be operated
in parallel, or one reaction vessel, after partial emptying, can be
refilled with other components, to achieve an altered
composition.
[0098] The mixtures prepared are coated, preferably using an
injection process, onto various parts of an, in particular,
metallic tube reactor or heat exchanger, in particular onto the
tube inner walls of (preferably metallic) reaction tubes of a
tube-bundle reactor at a 10-2000 .mu.m thick layer, generally each
tube being coated with a mixture of differing composition (to test
reproducibility, a plurality of mixtures of the same composition
can also be used in a plurality of tubes).
[0099] To test layer thickness effects (such as transport effects),
the same catalyst compositions can also be applied at different
layer thicknesses to different tubes.
[0100] In a further variant of the invention, auxiliary supports
(preferably metallic or ceramic tubes) are used which have been
coated with the liquid mixture after, or preferably before,
insertion into the reaction tubes of a tube-bundle reactor.
[0101] Auxiliary supports which can be used here are tubes having
any desired cross section, preferably circular. The material of the
auxiliary supports can be chosen freely, for example the auxiliary
supports can be made of glass, metal, ceramics such as glass
ceramics, activated carbon, graphite or sintered quartz. The
material in this case can be densely sintered or porous. The tubes
in this case can also be segmented in such a manner that a
plurality of channels, preferably in parallel to one another,
extend in parallel to the longitudinal tube axis. The cross section
of such tubes can resemble a spoked wheel, for example. An outer
tube and an inner tube can also be connected by a multiplicity of
through-spokes.
[0102] The number of the spokes can be chosen freely here.
[0103] As porous materials, the auxiliary supports can also be
solid, provided that they preferably have a high porosity. They can
be made up, for example, from foams of the abovementioned
materials. The solid bodies can have any desired suitable shape.
Suitable shapes are, for example, cylinders, cones, disks, sheets
etc.
[0104] Suitable auxiliary supports are offered, for example, by
ROBU Glasfilter-Gerate GmbH, D-57644 Hattert as sintered filters,
by PoroCer Keramikmembranen GmbH, D-07629 Hermsdorf as tubular
membranes for cross flow filtration, by Tami Deutschland GmbH,
D-07629 Hermsdorf/Thuringen as ceramic tubular membranes for cross
flow filtration and by Hi-Tech Ceramics, a Vesuvius Group Company,
Alfred, N.Y. 14802, USA as RETICEL ceramics. Clearly, products from
other suppliers can also be used.
[0105] Examples of porous auxiliary metal supports are sintered
metals, metal gauzes, knitted metal fabrics, metal felts or wire
meshes. From the reaction aspect, precisely metals offer great
advantages with respect to their thermal conductivity, in
particular if large amounts of heat must be removed or an exact
temperature control is necessary.
[0106] Suitable porous activated carbon and graphite auxiliary
supports are known.
[0107] The arrays according to the invention are preferably
prepared using auxiliary supports of this type by process f), as
described above. In this process, the auxiliary supports are
preferably coated outside the body and if appropriate heated. After
the supported catalysts prepared in this way have been introduced
into the predetermined channels of the body, the packed body is if
appropriate heated to dry the catalysts, with or without sintering
or calcining. The above described supported catalysts can have here
the auxiliary supports as catalyst supports.
[0108] Coating the bodies or the preferred heat exchanger is
described in more detail below.
[0109] The parts of the, preferably metallic, heat exchanger which
have been coated with the liquid mixture prepared in advance are
preferably the tube inner walls of, preferably, metallic
tube-bundle reactors. The reaction tubes of the tube-bundle reactor
can have any desired cross section, but generally have a round and,
in particular, circular cross section. The inner diameter is
preferably from 0.2 to 70 mm, preferably from 1 to 25 mm,
particularly preferably from 3 to 10 mm. The tube-bundle reactor
can comprise up to 30,000 reaction tubes or more, preferably from
10 to 20,000, particularly preferably from 100 to 10,000 reaction
tubes, which are generally each provided with a coating of
differing composition.
[0110] The coating with liquid mixtures can be applied by sponging,
slurrying, brushing, centrifuging, spraying and/or dipping.
Furthermore, the mixture can be poured into the individual tubes
and centrifuged at rotary speeds from 200 to 1000 rpm, preferably
at rotary speeds from 300 to 800 rpm. In a preferred embodiment,
the coatings on the inner side of the reaction tubes are prepared
by spraying on the abovementioned liquid mixture. The sprayed-on
mixture material is forced in the course of this into the surface
roughnesses of the substrate, air bubbles below the coating being
prevented. The mixture used can then adhere completely to the
sprayed interior. However, in particular in the case of low
adhesion and/or low viscosity of the mixture, some of the mixture
can be discharged again by dripping off. The auxiliary supports to
be coated, e.g. in the form of inner tubes, can be completely or
only partially coated. In this case, in particular the respective
reactor tube inlet and reactor tube outlet can be spared from the
coating by a suitable apparatus, in order to prevent any
later-occurring sealing problems with the feed and discharge
apparatuses to be connected for the fluid. A coating has also
proved to be useful in which the mixture is sprayed into the
preheated tube or this mixture is introduced into the preheated
tube by dipping. For this purpose, the metallic base body, prior to
spraying the suspension, is preheated to from 60 to 500.degree. C.,
preferably from 200 to 400.degree. C., and particularly preferably
from 200 to 300.degree. C., and coated at this temperature with the
mixture described at the outset. In this case, a majority of the
volatile constituents of the mixture evaporates and a preferably
from 10 to 2000 .mu.m, particularly preferably from 20 to 500
.mu.m, thick layer of the catalytically active metal oxides forms
on the preferably metallic base body. This type of preparation can
be performed, for example as described in DE-A-2 510 994, with the
variant in which the mixture is not applied to a preheated support,
but to a preheated preferably metallic base body.
[0111] To achieve particularly thick layers or particularly
homogeneous coatings, the reaction tubes can be coated repeatedly
successively. In this case, separate drying steps and/or calcining
steps and/or sintering steps can be connected in-between the
individual coatings of a reaction tube. The inner wall, in the case
of spraying, is advantageously coated using one or more atomizer
lances, preferably using one or more movable atomizer lances. In
this case, the atomizer lance is drawn through the tube to be
coated at a defined constant or varying speed during the atomizing
operation, e.g. using an automatic apparatus.
[0112] The thickness of the applied layer after drying, with or
without calcining or sintering, is preferably from 10 to 2000
.mu.m, particularly preferably from 20 to 500 .mu.m.
[0113] In addition, before the coating on the inner tube, an
adhesion promoter and subsequently on this adhesion promoter a
covering layer which comprises a catalyst material and is
catalytically active can be applied. The adhesion promoter can
increase the adhesion of the catalytically active covering layer on
the inner tube. Moreover, when an adhesion promoter is used, the
service lives can be increased. Suitable adhesion promoters are
described above.
[0114] In addition, the adhesion of the catalytic layer can be
increased by a chemical, physical or mechanical pretreatment of the
inner tube prior to the coating. In the event of a chemical
pretreatment, the inner tubes can be pickled, for example by lyes
or preferably by acids. Furthermore, the inner tube can be
roughened by blasting with a dry blasting medium, in particular
corundum or quartz sand, to reinforce the adhesion. Furthermore,
cleansers which are a suspension of hard particles, e.g. corundum,
in a dispersion fluid, have also proved useful.
[0115] Furthermore, the coating on the preferably metallic inner
tube can comprise the constituents auxiliary support and a covering
layer which comprises a catalyst material and is catalytically
active, as is described, for example, in DE-A-19 600 685. In this
case, the auxiliary support preferably has an external shape which
at least essentially corresponds to the geometry of the surface to
be coated. Suitable auxiliary supports here are, for example,
metallic or ceramic bodies, e.g. wire braidings or metal or ceramic
tubes. In this case, at least the auxiliary support, and preferably
only the auxiliary support, is coated with the catalytically active
covering layer and the coated auxiliary support is arranged in the
entire reaction inner tube, or preferably in a part of the reaction
inner tube. In this tube-in-tube arrangement, the outer tube can
have, for example, a tapering at one end, in order to prevent the
inner tube from falling out, and at the other end the projecting
inner tube can be pushed into the outer tube, for example, by
springs or a springy material.
[0116] The particular feature of the process according to the
invention is that each auxiliary support in the tube-bundle reactor
used generally has a different composition or a different layer
thickness of the catalytic coating. Furthermore, the coated
auxiliary supports can readily be exchanged for other auxiliary
supports having different coatings. For example, by means of a
suitable reactor construction (provision of shut-off valves etc.)
changing individual auxiliary supports during the reactor operation
can be possible.
[0117] When the coated tube-bundle reactor is heated under vacuum
or a defined gas atmosphere to temperatures of from 20 to
1500.degree. C., preferably from 60 to 1000.degree. C.,
particularly preferably from 200 to 600.degree. C., very
particularly preferably from 250 to 500.degree. C., the coating
applied in advance is freed from preferably aqueous solvent by
drying. At an elevated temperature, furthermore, sintering or
calcining of the particles forming the coating can occur. In this
process, the actual catalytically active coating is generally
obtained.
[0118] To regulate the temperature, the reaction tubes are
preferably surrounded by a heat-carrier medium, for example by a
salt melt or liquid metal such as Ga or Na. In this case, the
liquid heat-carrier medium is fed and removed, preferably at
opposite points of the tube-bundle reactor, e.g. using a pump, in
order to lead it then through a (e.g. air-cooled) heat exchanger to
remove or deliver heat. The heat-carrier medium ensures, firstly,
that the temperature for the drying, for any following sintering of
the coating and subsequent fluid-phase test reaction, is set in the
reaction tubes. Secondly, the heat-carrier medium removes the heat
produced in the following test reaction and thus suppresses the
formation of hot spots along the catalyst coating, in which,
locally, a higher temperature prevails than in the remaining
catalyst coating.
[0119] This type of reaction procedure ensures that the heat
produced in the reaction is removed outstandingly well, so that
virtually no hot spots occur any longer.
[0120] In a further embodiment of the invention, the space between
the reaction tubes is filled with a solid material, preferably a
metal or a solid metal alloy. In this case, the tube-bundle reactor
transforms into a material block as described above, in particular
a metal block having channels or boreholes. The inner diameter of
the boreholes corresponds to the inner diameter of the reaction
tubes of the tube-bundle reactor here.
[0121] It is also possible to prepare differing heterogeneous
catalysts having a predetermined composition in the form of
unsupported catalysts or supported catalysts by known, for example
combinatorial, processes and to charge in each case one or more
predetermined tubes of the tube-bundle reactor or heat exchanger or
tubes or auxiliary supports to be introduced into these with each
of these preprepared heterogeneous catalysts. In this case, the
known types of shaped bodies can be used. For each individual tube,
it is possible to vary the bed height or the inert content of a bed
or to establish other bed parameters. Tubes thus filled with the
supported catalysts, which are secured from falling out, can be
introduced into the actual tube-bundle reactor. This permits the
simple exchange of individual catalyst packings.
[0122] The catalysts are tested by reacting fluid reactants or
reaction mixtures which are generally present in the liquid, or
preferably gaseous, state. Preferably, oxidation catalysts are
tested by supplying, in parallel or in succession, individual, a
plurality or all tubes of the coated tube-bundle reactor with a gas
mixture of one or more saturated, unsaturated or polyunsaturated
organic starting materials (e.g. hydrocarbons, alcohols, aldehydes
etc.), oxygen-containing gas (e.g. air, O.sub.2, N.sub.2O, NO,
NO.sub.2, O.sub.3) and/or, for example H.sub.2, with or without an
inert gas, e.g. nitrogen or a noble gas, at temperatures of from 20
to 1200.degree. C., preferably at from 50 to 800.degree. C.,
particularly preferably at from 80 to 600.degree. C., the separate
removal of the respective gas streams, performed in parallel or in
succession, from the individual, plurality or all reaction tubes of
the tube-bundle reactor being ensured by a suitable apparatus.
[0123] A gas mixture, consisting of, for example, an
oxygen-containing gas (e.g. air, O.sub.2, N.sub.2O, NO, NO.sub.2,
O.sub.3) and/or H.sub.2 and the organic starting material to be
reacted (for example propene or o-xylene) is, for example, passed
through the generally differently coated reaction tubes of the
tube-bundle reactor. In addition to said gaseous substances, other
gaseous substances, such as Cl- or P-containing substances, can
also be present. The gas mixture can be passed here in succession
through the individual reactor tubes. In the preferred embodiment,
the gas mixture is passed through the reaction tubes in such a
manner that the gas mixture flows through all tubes simultaneously.
In this case, during the start-up of the reaction, i.e. during the
time that the catalytic coatings are activated, the composition of
the feed, the temperature of the heat-exchange medium or the
reaction tube, the residence time of the feed and/or the pressure
of the total gas in the tube-bundle reactor can be changed. The
product gases leaving the respective reaction tube, which gases are
produced by reaction of the reaction gases used, are generally
removed separately, but may also be removed collectively, and are
analyzed by diverse probes or analytical methods, e.g. with respect
to their composition.
[0124] The coated tube-bundle reactor can also be supplied with
said gas mixture directly after the suspension coating (omitting
the drying and sintering or calcining), in this case the drying
process and following sintering process taking place under said gas
mixture. In this case, the composition of the inner tube coating
can change. In particular, oxidic coatings, under highly reducing
conditions, can partially or completely release their oxygen or,
under highly oxidizing conditions, can take up oxygen into their
structure.
[0125] A constant gas mixture can be fed to the individual
differently coated reaction tubes of the tube-bundle reactor, for
example via a gas supply hood which can be mounted essentially
gas-tightly onto the tube-bundle reactor.
[0126] The gases used can be mixed prior to the feed into the gas
supply hood, or not until this, e.g. using a static mixer.
[0127] The individual reaction gases can be removed via an
apparatus mounted essentially gas-tightly on the tube-bundle
reactor, the individual reaction gases of the individual, plurality
of, or all reaction tubes being removed separately and then
analyzed separately via a valve switching.
[0128] Another way of removing separately the individual exhaust
gases of the respective generally differently coated reaction tubes
is a, for example, computer-controlled mechanically moved "sniffing
apparatus" having a sniffing line for the gas to be taken off,
which line is positioned essentially automatically on, in, or over
the exit of the respective reaction tube and then takes off a
reaction gas sample. The positioning and takeoff of the respective
reaction gas is preferably carried out here in such a manner that
only the actual reaction gas to be analyzed later, and no
additional external gas from outside, passes into the sniffing
line. If the sniffing apparatus is positioned on the reaction tube
end, an essentially gas-tight application of the sniffing line to
the reaction tube end, e.g. by pressing the sniffing apparatus onto
the end face of the tube reactor, is advantageous. If the sniffing
apparatus is positioned in or above the exit of the respective
reaction tube, it is advantageous to suck the reaction gases into
the sniffing apparatuses via a reduced pressure set in the sniffing
line in such a manner that the amount of the sucked-in reaction
gases is limited, so that no additional external gases are drawn
into the sniffing line. In the event that the sniffing line is
positioned in the exit of the respective reaction tube, it has
proved particularly advantageous if the end of the sniffing line is
tapered in such a manner that inserting the sniffing line into the
end of the respective reaction tube ensures that the reaction gases
exiting from the reaction tube in question are essentially sealed
gas-tightly from the exterior. After reaction gas has been taken
off from the reaction tube in question of the tube-bundle reactor,
the sniffing apparatus is, preferably automatically, positioned on,
in or over another reaction tube, generally the next exit of a
further reaction tube, in order to effect the next gas takeoff. In
this manner, all exhaust gases of the reaction tubes can be
delivered separately for a sample and then analyzed. It is not only
possible for the positioning to move on, in or over the reaction
tube exit, and the tube-bundle reactor to remain fixed, but the
sniffing line can remain fixed during the positioning and for the
tube-bundle reactor to be moved correspondingly. During the
positioning, both the sniffing apparatus and the tube-bundle
reactor can also move. In a preferred process variant, the
tube-bundle reactor remains unchanged and only the sniffing
apparatus is moved during the positioning above or onto the
respective reaction tube ends. In another preferred process
variant, the tube-bundle reactor, during the positioning,
experiences a rotary movement around its axis, while the sniffing
line, during a positioning over the respective reaction tube ends,
carries out a linear motion in the direction toward the axis of
rotation of the tube-bundle reactor, while, when it is positioned
onto the respective reaction tube ends, the sniffing apparatus
carries out an additional motion parallel to the reactor axis. A
plurality of sniffing apparatuses can also be used simultaneously
for sampling the various reaction gases. In addition, a plurality
of combined tubes can also be sampled.
[0129] In a similar manner to the removal of gas via what are
termed sniffing lines, as an alternative to the gas supply hood,
the gas can be fed via such a principle, the individual tubes being
tested sequentially. Obviously, the exhaust gas sniffing line must
then be positioned synchronously with the feed line for fresh
gas.
[0130] The catalytic performance of the individual catalytic
coatings of the individual reaction tubes can be screened by
chemical analysis of the respective gas streams using suitable
methods known per se. The gas streams removed individually from the
individual reaction tubes of the tube-bundle reactor are in this
case analyzed individually for their composition, e.g. using
suitable apparatuses, e.g. via gas chromatography using flame
ionization detection and/or thermal conductivity detection, or, for
example using mass spectrometry. The gas composition obtained is
analyzed here in particular with respect to its relative content of
desired product, or of various desired products, and the resultant
concentrations related to the reacted starting material, values for
the respective conversion rates (activity) and product
selectivities being produced. In many cases it is useful here to
measure the product selectivities of the individual catalysts over
a relatively long time period of generally hours to a number of
weeks. In the selection of the catalyst coating most suitable for
the respective reaction, in order to limit the number of gas
analyses, it can be useful to make repeat measurements only on gas
compositions of selected reactor tubes which exceed a desired
limiting concentration or limiting selectivity of certain
products.
[0131] After the catalytic test, the catalytic inner coatings
applied can be removed, so that the remaining tube-bundle reactor
is again accessible to a renewed catalytic coating.
[0132] The catalyst coatings can be renewed by at least essentially
clearing off the old catalytically active covering layer of the
coating and applying a new catalytically active coating by
sponging, brushing, centrifuging, spraying and/or dipping.
Expediently, a choice is made of the same coating process which was
used to apply the catalytic coating previously removed. The old
catalytically active covering layer of the coating can be cleared
off in a simple manner in particular by blasting with a blasting
medium, e.g. corundum, silicon carbide, fine sand or the like.
Alternatively, treatment with steam or the use of chemical clearing
methods has also proved useful.
[0133] An efficient method of removing the inner coatings, for
example after the catalyst testing, is the use of brushing devices,
e.g. similarly to a bottle brush, in general in combination with
the described cleansers. Preference is given to the removal of the
inner coatings by an at least substantially automated route.
[0134] The process according to the invention can readily be
carried out in automated form by automated systems. Coating tubes
with the catalyst ensures an optimal flow of the fluid, causes only
a low pressure drop and prevents blockages in the individual
reaction tubes of the tube-bundle reactor.
[0135] The spatial separation and clear assignation of the tested
coatings offer the advantage of being able to test simultaneously,
using one apparatus (tube bundle), a number of materials, generally
corresponding to the number of tubes, in parallel with reduced cost
and time consumption.
[0136] Furthermore, in comparison with other systems, e.g.
perforated plates, CVD arrays, etc., the tube-bundle reactor offers
the advantage of testing in a manner as close as possible to an
industrial process (scale-up capacity is retained). An industrially
relevant optimization can be carried out very rapidly and
cost-effectively, in particular also, because a multiplicity of
catalysts can be tested in parallel/simultaneously under the same
conditions.
* * * * *