U.S. patent number 3,616,312 [Application Number 04/870,920] was granted by the patent office on 1971-10-26 for hydrazine manufacture.
This patent grant is currently assigned to Ionics, Incorporated. Invention is credited to Stuart G. McGriff, Wayne A. McRae.
United States Patent |
3,616,312 |
McGriff , et al. |
October 26, 1971 |
**Please see images for:
( Certificate of Correction ) ** |
HYDRAZINE MANUFACTURE
Abstract
Hydrazine is produced in a two chamber electrolytic cell with
anode and cathode chambers separated by an ion exchange membrane.
When using an anion exchange membrane, ammonia and nonaqueous
solvent are fed to the cathode compartment and hydrazine and
solvent are collected from the anode compartment. When using a
cation exchange membrane ammonia and nonaqueous solvent are fed to
the anode compartment while hydrazine is also removed from the
anode compartment. Similarly, alkyl hydrazines can be produced by
feeding a lower alkyl amine instead of ammonia.
Inventors: |
McGriff; Stuart G. (Alexandria,
VA), McRae; Wayne A. (Lexington, MA) |
Assignee: |
Ionics, Incorporated
(Watertown, MA)
|
Family
ID: |
27067146 |
Appl.
No.: |
04/870,920 |
Filed: |
September 16, 1969 |
Current U.S.
Class: |
205/432 |
Current CPC
Class: |
C25B
3/00 (20130101); C07C 241/02 (20130101); C07C
241/02 (20130101); C07C 241/02 (20130101); C01B
21/16 (20130101); C07C 243/10 (20130101); C07C
243/14 (20130101) |
Current International
Class: |
C01B
21/16 (20060101); C01B 21/00 (20060101); C25B
3/00 (20060101); B01k 003/00 (); B01k 003/08 ();
B01k 003/10 () |
Field of
Search: |
;204/18P,101,102,59
;23/190 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Mack; John H.
Assistant Examiner: Prescott; A. C.
Parent Case Text
This application is a division of Ser. No. 542,780 filed Apr. 15,
1966 now U.S. Pat. No. 3,496,091.
Claims
What is claimed is:
1. A process of electrolytically producing hydrazine from ammonia
in a two-chamber cell having a terminal anode and cathode electrode
and adjacently disposed anode and cathode chambers separated from
one another by an ion-permselective membrane comprising, passing an
ammonia-containing, nonaqueous fluid solvent into that electrode
chamber which is adjacent to the electrode having a charge opposite
in sign to the fixed charge on said membrane passing fluid solvent
into said other electrode chamber, passing a direct current across
the electrodes through said chambers and membrane to cause the
anodic formation of hydrazine, withdrawing the resulting anolyte
solution from said chamber, and separating and recovering said
hydrazine from said anolyte solution.
2. The process of claim 1 wherein the fluid solvent is selected
from the group consisting of dimethyl formamide, dimethyl
acetamide, dimethyl sulfoxide and mixtures thereof.
3. The process of claim 1 wherein the hydrazine is separated and
recovered from the withdrawn anloyte solution by distillation.
4. The process of claim 1 wherein the membrane is
cation-permselective and wherein the ammonia-containing fluid
solvent is passed into said anode chamber and the fluid solvent
into said cathode chamber.
5. The process of claim 1 wherein the membrane is
anion-permselective and wherein the ammonia-containing fluid
solvent is passed into said cathode chamber and the fluid solvent
into said anode chamber.
6. A process of electrolytically producing alkyl hydrazines in a
two-chamber cell having a terminal anode and cathode electrode and
adjacently permselective membrane comprising, passing a nonaqueous
fluid solvent containing a lower alkyl amine into that electrode
chamber which is adjacent to the electrode having a charge opposite
in sign to the fixed charge on said membrane, passing fluid solvent
into said other electrode chamber, passing a direct current across
the electrodes through said chambers and membrane to cause the
anodic formation of a lower alkyl hyrazine, withdrawing the
resulting anolyte solution from said chamber, and separating and
recovering said alkyl hydrazine from said anolyte solution.
7. The process of claim 6 wherein the lower alkyl amine is methyl
amine and the fluid solvent in dimethyl sulfoxide.
Description
This invention relates to novel apparatus and methods for producing
hydrazine by the electrolysis of ammonia solutions and, in
particular, to electrolytic cells utilizing electrolytes of solid
ion-exchange material for the production of anhydrous
hydrazine.
Hydrazine (M.sub.2 M.sub.4) finds its greatest use as a rocket
fuel, but also as an oxygen scavenger in boiler water; as an
intermediate in drug manufacture; as a plant growth retardant and
in rubber blowing. The recent developments in new catalysts make
hydrazine of increasing interest as a monopropellant and as a
source of energy for fuel cell applications. However, the present
cost of hydrazine is too high for widespread commercial use.
Almost all of the present production of hydrazine is based on the
chemical oxidation of ammonia or urea in aqueous solutions by
employing an oxidizing agent of an alkaline hypochlorite. The
hydrazine is obtained as a dilute aqueous solution containing many
contaminants and the commercial product of hydrazine hydrate or
anhydrous hydrazine is produced with difficulty and great expense.
Attempts have been made to produce hydrazine by electrolysis, using
a variety of operating conditions and starting materials, but none
appear to be sufficiently inexpensive for general use.
In the electrolysis of liquid ammonia, hydrazine is one of the
first products formed by the anodic oxidation of ammonia. Liquid
ammonia, like pure water, is a poor electrical conductor and is
only slightly ionized into ammonium and amide ions, as shown in the
following reaction: 2NM.sub.3 NM.sub.2 .sup.-+NM.sub.4 .sup.+.
During the electrolysis, the negatively charged amide ions are
discharged by oxidation at the anode with a pair combining to form
hydrazine. However, because of the poor conductance of liquid
ammonia, the prior art has resorted to adding soluble electrolytes
to the ammonia to form a solution having increased electrical
conductance. Such electrolytes, soluble in liquid ammonia, include,
for example, sodamide, (Na NM.sub.2) sodium hydroxide, ammonium
salts, including ammonium sulfonate and urea. Although the high
degree of dissociation of the electrolytes do in fact increase the
electrical conductivity of the resulting solution, their presence
can be detrimental to the production of hydrazine.
Hydrazine is thermodynamically unstable and therefore readily
susceptible to decomposition. Since hydrazine is more susceptible
to oxidation than ammonia, the hydrazine formed at the anode, if
allowed to remain in the area of the anode, will quickly decompose.
Many materials are known that will catalyze or accelerate this
decomposition, such materials being halide ions, heavy metal ions
and strong proton acceptors, such as the amide and hydroxide ions.
Additionally, certain materials used in the construction of the
anodes will more readily chemisorb hydrazine with its resultant
decomposition.
In accordance with the present invention, solutions of ammonia in
contact with an electrolyte of solid ion-exchange material are
subjected to electrolysis to produce hydrazine at the anode. The
electrolytic apparatus has a continuous bridge of a solid
ion-exchange resin between and in intimate contact with the spaced
cathode and anode electrodes. The ion-exchange material bridging
the space between the electrodes will function to provide an
hydroxide conducting path since the ammonia solution passing into
the cell will have a high electrical resistance. In the equilibrium
between the ion-exchange resin and a solution, the concentration of
mobile ions in the resin is not highly dependent upon the
concentration of ions in the surrounding solution, but is
essentially determined by the number of exchange sites within the
resin itself. Thus, in the case of an anion-permeable resin, it is
possible to have a high concentration of mobile negatively charged
amide ions (NM.sub.2 .sup.-) within the resin to obtain the
required electrical conductance without the addition of soluble
salts or electrolytes to the ambient solution. This technique
provides an available source of amide ions. The hydrazine formed at
the anode will dissolve in the liquid, and the resulting solution
will be removed from the cell before there is an substantial
contact between the hydrazine in solution and amide ions in the
resin. The result of this process is that hydrazine is formed in
the liquid solution with the solution isolating the hydrazine from
contact with catolytic materials which would cause excessive
decomposition.
Therefore, the object of this invention is to provide a novel
apparatus and process to produce hydrazine economically from liquid
ammonia solutions by electrolysis.
A further object is to produce hydrazine derivatives the the
process applicable to hydrazine by substituting amines in place of
ammonia.
A further object is to economically prevent the further
decomposition or oxidation of hydrazine once it is electrolytically
formed.
A further object is to utilize a solid electrolyte of ion-exchange
resin in contact with ammonia to manufacture hydrazine
electrolytically.
A further object is to employ a semiconducting anode for
electrolytically oxidizing ammonia into hydrazine.
These and various other objects, features and advantages of the
invention will appear more fully from the detailed description
which follows accompanied by the drawings. To better understand the
invention, the description is made with specific reference to
certain preferred embodiments; however, it is not to be construed
as limited thereto except as defined in the appended claims. By way
of example, the use of this invention will now be described in
detail with reference to the accompanying drawings in which:
FIG. 1 is an exploded perspective view of one embodiment of the
improved electrolytic cell of the present invention wherein the
solid electrolyte of ion-exchange resin is in the form of a
membrane having pebbled surfaces.
FIG. 2 is a sectional view of an assembled cell taken along lines
2-2 of FIG. 1, showing the membrane in contact with both
electrodes.
FIG. 3 is a modification of an ion-exchange membrane in which both
sides have a corrugated design.
FIG. 4 is a cross-sectional view of a corrugated ion-exchange
membrane taken along line 4-4 of FIG. 3.
FIG. 5 illustrated schematically the process for producing
hydrazine electrolytically by employing an anion-selective membrane
in the electrolytic cell and
FIG. 6 illustrates schematically an alternate process using a
cation-selective membrane.
As shown in the drawings and, in particular, in FIGS. 1 and 2, the
electrolytic cell is basically of a package or stack type. The
apparatus comprises a cathode 1, an anode 3, an embossed or
contoured ion-permselective membrane 5 and spacer members 6, all of
which are assembled between two terminal pressure end plates 7 and
8. A fluidtight stack is obtained by applying the proper pressure
against each end plate, as by bolts 9 and nuts 10. Means for
passing a DC potential transversely through the stack is provided
for through leads 11 and 12 from an outside source of electric
current (not shown).
The spacer members 6 are generally of an electrically nonconducting
plastic gasketing material such as polyethylene and have cutout
central portions 13 and 14 which form the cathode and anode
fluid-holding chambers, respectively. These chambers are confined
by the frame or border 15 of the spacer which also functions to
separate and gasket the substantially flat marginal area 25 of the
membrane with respect to the adjacent electrodes 1 and 3. The
spacers, electrodes and end plates are shown with apertures 16 for
directing a fluid to the cathode and anode chambers 13 and 14 and
further apertures 17 are provided for withdrawing fluid therefrom.
The apertures 16 and 17 in the frame 15 of the spacer are located
on substantially opposite sides of the cutout flow area. The
apertures 16 and 17 in the frame of the spacer communicate with the
respective cathode and anode chambers by slits or channels 20 cut
in the spacer material. Inlet means for passing fluid into the
cathode and anode chambers are provided by inlets 20 and 22
respectively, and outlet means for withdrawing the solutions are
provided at 23 and 24. The combination of a cathode and an anode
chamber, membrane and terminal electrodes form a single
electrolytic unit.
The single membrane 5 separating the electrode chambers 13 and 14
from each other is fabricated from an organic polymeric
cross-linked material and may be anion permselective or cation
perselective, both types of material being well known in the
art.
The manufacture and properties of ion-selective membranes are fully
disclosed in U.S. Pat. Nos. 2,702,272; 2,703;768; 2,731,408;
2,800,445; Re. 24,865, and many others. Ion-exchange membranes are
comprised of a solvated ion-exchange resin generally in sheet form
which may be reinforced by an inert woven fabric structure. Such
membranes generally comprise about 30 percent fabric by weight, 40
percent resin, and about 30 percent solvent, the solvent being
uniformly dispersed throughout the resin.
Cation membranes are typically cross-linked sulfonated polystyrene.
In the presence of inbibed solvent having at least a moderate
dielectric constant, for example, dimethyl formamide, the sulfonate
groups are dissociated into bound negatively charged ions and
mobile positively charged counter-ions. The positively charged
counter-ions are free to diffuse through the resin structure and,
under the influence of an electric potential, are substantially the
sole carrier of current. Typical positively charged counter-ions,
for example, are sodium and ammonium. Similarly, the anion
membranes may be a cross-linked polystyrene structure with
quaternary ammonium salt groups which dissociate into bound
positively charged quaternary ammonium ions and mobile negatively
charged counter-ions such as, for example, hydroxide, sulfate and,
in some nonaqueous solvents, the amide ion.
Generally, conventional ion-selective membranes are fabricated as
sheets having totally flat surfaces. However, the membranes of the
present invention are provided on both major faces with an elevated
central area integrated with and generally of the same polymeric
ion-exchange material as the substantially flat marginal sealing
area 25 of the membrane to form a single homogeneous piece. The
surface of the central area is embossed or contoured with a
plurality of projecting 26 and receding 27 portions. The receding
portions are so arranged as to form flow channels 28 between the
projections for the passage of fluid therethrough. As shown in the
drawings, the contoured central area of the membrane is pebbled
(FIG. 1) or corrugated (FIG. 3) but other various geometric
designs, such as ribs, studs, ridges and the like may be provided
on the surface.
When the elements comprising the electrolytic cell are assembled
into a fluidtight stack arrangement, the projecting central
portions 26 of the membrane will extend directly into the central
cutout portions 13 and 14 of the adjacent spacers which form the
cathode and anode chambers. The projections may be about the same
height as the spacer thickness. The height of the projections may
vary within wide limits but an extension of about 30 mils (0.030
inches) in a direction perpendicular to the flat surface of the
membrane would be satisfactory. Such a membrane embossed on both
sides and having a 30 mil thickness across the flat marginal area
would than have a total central area thickness of about 90 mils. On
assembly of the cell, the tips of the projections are caused to
press firmly against the surface of each adjacent electrode to form
an electrode-membrane interface 30 which makes electrical contact
and forms a continuous ion-conducting bridge between the electrode
pair. This arrangement will allow an electric current to be carried
between the electrodes, primarily by mobile ions of one sign
passing solely through the membrane structure. The recessed areas
or interstices between the projections form fluid-flow channels 28.
The fluids used in the cell need not necessarily be
electrolytically conducting since the electric current will be
carried within and across the bridge of ion-conducting membrane
material. The membranes can of course be of various thicknesses and
have pattern configurations other than those specifically described
herein. All other factors being equal, it is evident that the
greater the number of projections of membrane area contacting the
electrode surface, the smaller the power consumption of the
electrolytic cell.
The membranes may be fabricated by sandwiching the liquid polymer
mix between two glass plates having the desired patterned surface,
polymerizing the mix until solid, and then stripping off the glass
molding plates to leave a solid polymerized structure. The pattern
serves as the mold for the contoured central portion of the
membrane. There are glass molding plates of numerous design
patterns which are available commercially. The solid structure is
then treated with appropriate chemicals to make them either anion
or cation permselective as by quarternization or sulfonation. In
order to add strength and flexibility to the membrane, an inert
sheet of open-weave cloth or screen material may be incorporated as
a backing or reinforcing material within the membrane. In such a
method, the liquid mix is poured over the cloth fabric prior to
being sandwiched between the glass molding plates. Additionally, in
order to prevent or minimize fracturing of the projecting or raised
portions of the membrane, especially during assembly of the
electrolytic cell when the membrane is compressed between the pair
of electrodes. It is preferable that bits of fabric material or
fibers of glass or other material be suspended in the liquid
polymer mix before casting into a membrane. These fibers will
structurally reinforce the entire raised membrane area to impart
the necessary resistance to cracking.
The operation of the electrolytic apparatus, for example, in the
manufacture of hydrazine from ammonia, may be illustrated by
referring particularly to FIG. 5 wherein the membrane is
anion-selective and the mobile counter-ions are amide ions NH.sub.2
.sup.-).
A catholytic and an anolytic feed solution are directed into inlet
21 and 22 respectively, and caused to flow into the respective
cathode and anode chambers across the chambers via the interstices
or flow channels 28 formed by the projecting membrane portions and
out of the chamber by way of outlets 23 and 24 in the general
direction as shown by the arrows of the figures.
The catholytic feed solution is comprised of a nonaqueous inert
fluid solvent containing ammonia in dilute concentrations. The feed
to the anode chamber is pure anhydrous fluid solvent. The fluid
solvent should of course be a solvent for ammonia and hydrazine
and, preferably, should have at least a moderate dielectric
constant and have a negligible affinity for protons, and should not
substantially dissociate into an anion which would have a strong
affinity for protons. Another preferred requirement of the solvent
is that it has a higher boiling point than that of liquid hydrazine
(B.P. 113.5.degree. C.). This requirement evolves from the
consideration of recovering the hydrazine from the mixture of
hydrazine and solvent issuing as the effluent of the anode chamber.
Distillation is a preferred method since two liquids are involved
and of course recovery cost will be minimized if the hydrazine has
a substantially lower boiling point that the solvent to allow its
being boiled off from the bulk of solvent. Suitable solvents
meeting the preferred requirement are dimethyl acetamide, dimethyl
formamide, dimethyl sulfoxide, and the like.
The electrolysis is carried out using a source of direct current
and suitable electrode current densities. A range of about 10 and
100 amps/ft.sup.2 is preferred although current densities outside
this range are suitable. During electrolysis, the ammonia in the
catholytic solution is reduced at the cathodemembrane interface
into hydrogen gas and amide ions as follows:
2NH.sub.3 + 2e 2NH.sub.2 .sup.- + H.sub.2
The hydrogen gas is carried out of the chamber with the flowing
catholytic solution. This catholytic solution, now partially
depleted in ammonia, is removed from the cell at exit 23 and
directed to a gas-liquid separator (not shown) for removal of the
hydrogen gas. The solution may then be spiked with additional
gaseous or liquid ammonia and recycled back to the cathode chamber
of the cell for further processing.
The negatively charged amide ions formed at the cathode will, under
the influence of the electric current, migrate across the
anion-permselective membrane in the direction of the positively
charged anode. On reaching the anode-membrane interface, oxidation
of the amide ion will occur with a pair of amide ions combining to
form hydrazine as follows:
2NH.sub.2 .sup.- N.sub.2 H.sub.4 + 2e
In addition, small amounts of nitrogen and ammonia may also result
as products of the oxidation process. The hydrazine formed diffuses
out of the membrane, and is carried out of the anode chamber with
the flowing solvent to a gas separator (not shown) to remove any
nitrogen gas contained therein. The dissolved hydrazine is then
separated from the remaining solution by any suitable means, such
as distillation, freezing, membrane permeation, or the like. The
preferred method would be distillation whereby the solution is
stripped of its anhydrous hydrazine and traces of ammonia. Small
amounts of hydrazine hydrate may be present in the final product
due to unavoidable pickup of water in the system. The ammonia,
separated during distillation, may be added to the catholytic feed
solution, and the pure solvent remaining is recycled as the feed
solution to the anode chamber.
It is important that the hydrazine formed be removed from the
vicinity of the anode as quickly as possible. If allowed to remain
within the anode area, the hydrazine becomes susceptible to
oxidation and can readily decompose as follows:
N.sub.2 H.sub.4 + NH.sub.2 .sup.- N.sub.2 H.sub.3 .sup.- + NH.sub.3
+2
The extent of hydrazine decomposition depends among other things on
the anode current density and the concentration of the reactants
present at the anodemembrane interface. Where the cell employs an
anion-permeselective membrane, the reactants would be hydrazine
along with amide ions, and naturally the lower their concentration
at the interface, the less hydrazine decomposition. Further
prevention of hydrazine decomposition can be attained by
fabricating the anodes from a material on which hydrazine is not
readily chemisorbed. Such anodes may be constructed of impervious
graphite, platinum, electrolytic valve metals, such as titanium
coated with a precious metal of platinum, and the like. In place of
these conventional electrodes, it is further contemplated that
semiconducting electrodes be employed to further diminish the
hydrazine decomposition process. The preferred material for
semiconducting electrodes is impervious self-bonding carbide having
either the n- or p-type conduction. Hydrazine will be less strongly
absorbed on properly constructed semiconducting electrodes and
therefore less subject to electro-oxidation or decomposition.
The ion-exchange resin of the membrane does not act as a catalyst
in the decomposition of hydrazine. In fact, in its use as the
electrolyte of the cell, the concentration at the anode of strong
proton acceptors, such as the amide ion, is kept at a low level
since the only amide ions contacting the anode are those carrying
the electric current in their migration through the ion-exchange
membrane. Additionally, since the mobile amide ion is the only
conducting ionic species within the anion selective resin which
need be present in the process, hydrazine decomposition
attributable to heavy metal ions or halides will not occur as would
be the case where soluble salts are employed as the electrolyte of
the cell.
An alternate embodiment of the invention is diagrammatically
illustrated in FIG. 6. The membrane in this modification is cation
selective and is in the ammonium ionic form NH.sub.4 .sup.+).
Operation of this cell is similar to that of FIG. 5 except that the
feed solutions entering the electrode chambers are reversed; that
is, the solution of solvent and ammonia is fed to the anode
chamber, whereas the pure anhydrous-solvent is fed to the cathode
chamber. In the anode chamber, the ammonia is oxidized at the
anode-membrane interface to hydrazine and positively charged
ammonium ions as follows:
4NH.sub.3 N.sub.2 H.sub.4 + 2NH.sub.4 .sup.+ + 2e
To minimize the decomposition of the hydrazine, an excess of
ammonia is maintained at the membrane surface. Since ammonia is a
stronger base than hydrazine, the hydrazine will be in the free
base form and diffuse out of the resin to be carried out of the
anode chamber by the flowing anolyte.
The positively charged ammonium ions formed at the anode will
migrate through the cation membrane in the direction of the cathode
where they will be cathodically reduced at the cathode-membrane
interface to ammonium and hydrogen gas as follows:
2NH.sub.4 .sup.+ + 2e 2NH.sub.3 + H.sub.2
The hydrogen gas is then separated from the anolyte effluent
solution, the solution is spiked with additional ammonia and the
resulting solution of solvent and ammonia is recycled back to the
cell as the feed to the anode chamber.
The following examples are further illustrative of the practice of
this invention and are not intended to be limiting:
EXAMPLE 1
In a cell constructed as shown in FIG. 5, the membrane is a
trimethylaminated, chloromethylated copolymer of ethyl vinyl
benzene and divinyl benzene reinforced with woven polypropylene
fabric. The fixed charged groups are quaternary ammonium cations
(benzyl trimethyl ammonium). The total thickness of the membrane is
about 0.090 inch. The plane of the membrane is vertical and the
surfaces of the membrane in the central portion are raised into
ribs having a roughly triangular cross section and having their
long dimension in a vertical direction. The ribs project about
0.030 inch from the bulk of the membrane and are on centers of
about 0.035 inch. The central portion of the membrane is about 2
inches wide and 7 inches long. The flow in each compartment is
upward. The electrodes are smooth platinum and the spacer gaskets
are polypropylene. The membrane is converted to the hydroxide form
in water in the conventional way and then equilibrated with several
changes of methanol to replace the water and with several changes
of dimethyl formamide to replace the methanol. The membrane is then
assembled into the cell. To convert the membrane to the amide form,
a 5 percent solution of sodium amide in anhydrous dimethyl
formamide is passed upwardly through the cathode compartment at a
rate of about 3 grams per minute. Pure anhydrous dimethyl formamide
is passed upwardly through the anode compartment at a rate of about
3 grams per minute. A current of 3 amperes is applied for 2 hours
and then the current is turned off and the compartments rinsed with
anhydrous dimethyl formamide. In a production run the catholyte is
anhydrous dimethyl formamide containing about 5 percent anhydrous
ammonia by weight. The catholyte flows at a rate of about 3 grams
per minute. The anolyte is anhydrous dimethyl formamide and flows
at a rate of about 3 grams per minute. A current of about 3 amperes
is applied. After about 3 hours, about 180 grams of enolyte
effluent have been collected. Upon analysis by standard iodate
solution using amaranth as an indicator, it is found that the
collected anolyte contains about 3.75 grams of hydrazine. The
current efficiency is about 70 percent. The hydrazine is recovered
by fractional distillation.
EXAMPLE 2
In a cell constructed as shown in FIG. 6, the membrane is a
sulfonated terpolymer of vinyl toluene, ethyl vinyl benzene and
divinyl benzene reinforced with a woven fabric of glass fibers. The
fixed charged groups are sulfonate anions. The total thickness of
the membrane is about 0.090 inch. The plane of the membrane is
horizontal and the surfaces of the membrane in the central portion
are raised into small hillocks rising about 0.030 inch from the
surface of the membrane. The hillocks are about 0.060 inch in
diameter and are on centers of about 0.075 inch. The central
portion of the membrane is about 2 inches wide and 7 inches long.
The flow in each compartment is horizontal and in a composite
direction parallel to the long dimension of the central portion.
The electrodes are self-bonded silicon carbide having n-type
carriers. The gaskets are polytetrafluorethylene. The membrane is
converted to the ammonium form in water in the conventional way and
then equilibrated with several changes of methanol to replace the
water and with several changes of dimethyl acetamide to replace the
methanol. The membrane is then assembled into the cell. In a
production run, the catholyte is anhydrous dimethyl acetamide,
flowing at a rate of about 3 grams per minute. The enolyte is
anhydrous dimethyl acetamide containing about 5 percent anhydrous
ammonia by weight. The anolyte flows at a rate of about 3 grams per
minute. A current of about 3 amperes is applied. The product of the
first two hours of operation is discarded and the product of the
anolyte of the next three hours is collected. The amount collected
is about 180 grams. Upon analysis by standard iodate solution using
amaranth as an indicator, it is found that the collected anolyte
contains about 3.20 grams of hydrazine. The current efficiency is
about 60 percent. The hydrazine is recovered by fractional
distillation.
EXAMPLE 3
The cell of example 2 is operated with 10 percent methyl amine in
anhydrous dimethyl sulfoxide as the anolyte and impervious graphite
electrodes. The catholyte is anhydrous dimethyl sulfoxide. Dimethyl
hydrazine (probably the symmetrical compound) is recovered from the
anolyte. The current efficiency is about 70 percent.
* * * * *