Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B3/00—Electrolytic production of organic compounds
  • C25B3/20—Processes
  • C25B3/29—Coupling reactions
  • C25B3/295—Coupling reactions hydrodimerisation

Definitions

• This invention relates to a method for the manufacture of adiponitrile, the hydrodimer of acrylonitrile, characterized by electrolyzing a catholyte comprising an aqueous solution of alkyl, aryl or aralkyl quaternary ammonium sulfate and acrylonitrile in a divided cell, employing an anolyte of an aqueous solution of sulfuric acid and the anolyte being separated, by a cation-exchange membrane placed between the cathode compartment and the anode compartment, from the catholyte.
• a method for hydrodimerizing acrylonitrile by electrolyzing the catholyte comprising said quaternary ammonium sulfate used as the supporting electrolyte and acrylonitrile which is characterized by separating a cathode efiluent solution into two phases, i.e. aqueous and oil phases by adding acrylonitrile thereto and extracting adiponitrile from the resulting aqeuous solution phase.
• this invention relates to a method for electrolytically hydrodimerizing acrylonitrile to adiponitrile by using quaternary ammonium sulfate with can alkyl radical having no more than three carbon atoms bonded to nitrogen atom of quaternary ammonium as a supporting electrolyte, and electrolyzing the catholyte in which acrylonitrile is dissolved together with said supporting electrolyte.
• the electrolysis of this invention may be carried out advantageously in a high selectivity of adiponitrile even when the acrylonitrile concentration in the catholyte is as low as 3 to 10% by weight.
• a conventional method known to the trade is of such principle that an aqueous solution containing such salt as aryl-or alkaryl sulfonate or alkylsulfate of aliphatic amine or heterocyclic amine together with acrylonitrile is contacted with the cathode and electrolyzed to obtain hydrodimerization product of acrylonitrile. Further details of this method are found in US. Patents Nos. 3,193,481, 3,193,480 and 3,193,477. Basic invention of these known in the literature is that by increasing the solubility of acrylonitrile by the use of specific supporting salts, high selectivity of adiponitrile may be obtained. Such typical 3,497,429 Patented Feb.
• This invention is essentially different from said conventionally known methods in that it conducts electrolysis by using as the catholyte the aqueous solution containing alkyl, aryl and/ or alkaryl quaternary ammonium sulfate and acrylonitrile, and the concentration of acrylonitrile is substantially less than the solubility of acrylonitrile in water.
• the first advantage of the method of this invention consists in the use of the supporting electrolyte to facilitate the separation of the mixed solution of adiponitrile and acrylonitrile from the aqueous solution of supporting electrolyte and, as a result, when the effluent solution of the cathode compartment is separated into the supporting electrolyte, adiponitrile, acrylonitrile and Water so as to isolate adiponitrile as the product, the recovery of acrylonitrile and the supporting electrolyte can be conducted very easily and re-used as the catholyte components.
• the supporting electrolyte dissolves acrylonitrile to very high solubility in both water and organic substances, it is ditfuclt to separate the organic components containing adiponitrile and acrylonitrile (oil phase) from the aqueous solution of supporting electrolyte (aqueous phase). Moreover, even if the oil phase is separated from the water phase, the supporting electrolyte is contained in a considerably high concentration in the oil phase, and also adiponitrile and acrylonitrile is left in the aqueous phase. Thus, it is very difiicult to isolate adiponitrile efficiently from the oil phase.
• this invention uses said tetraammonium sulfate as the supporting electrolyte, the solubility of acrylonitrile and adiponitrile in the aqueous solution of the supporting electrolyte is substantially same as that in water and much lower than that of acrylonitrile using the supporting electrolyte of US. Patents Nos. 3,193,481, 3,193,480 and 3,193,477. Because of this lower solubility of acrylonitrile, the quaternary ammonium sulfate of this invention is convenient for the separation of the oil phase from the aqueous phase in the effluent of the cathode compartment.
• the supporting electrolyte of this invention has such characteristics that it is very easy to separate the oil phase of adiponitrile and acrylonitrile containing substantially negligible amount of supporting electrolyte from the aqueous phase composed of the aqueous solution of mainly supporting salt and having a low adiponitrile content.
• the isolation of the ingredients in the oil phase and the aqueous phase is generally accomplished by conventional separation or extraction method, such as cooling, heating and fractional distillation or the solvent extraction by use of either organic or inorganic solvent. In any form of such separating operation, because the supporting electrolyte of this invention has little affinity and low solubility with and in the organic components, it is easy to separate the organic components from the cathode effluent solution.
• the second advantage of this invention consists in the fact that because quaternary ammonium sulfate is used in the catholyte, sulfuric acid solution as the anolyte and the electrolysis is conducted in a divided cell separated by cation-exchange membrane placed between the cathode compartment and the anode compartment, the anions which can migrate from the cathode compartment to the anode compartment are sulfate ions which are identical with the anions existing from the beginning of the operation in the anode compartment. Therefore, even if the constituents of the anode compartment pass through the membrane due to the migration by electric current or diffusion, no difficulty such as erosion of anode occurs.
• Anode is usually made of lead, lead alloy, or platinum, and particularly lead alloy for industrial purposes.
• the lead alloy is corroded by the discharge of halide ion and sulfonic acid ion, whereas no such corrosion takes place at all where sulfate ion discharges at the anode.
• the third advantage of this invention consists in the fact that because the process for manufacturing quaternary ammonium sulfate is simple, and the supporting electrolyte of this invention can be manufactured less expensively than the conventional known tetraethylarnmonium p-toluenesulfonate. Moreover, the rate of the Hotfman decomposition reaction of quaternary ammonium sulfate is less than that of the conventional salt such as quaternary ammonium arylsulfonate or quaternary ammonium alkylsulfate, if the alkyl groups of quaternary ammonium salt is same.
• the fourth advantage of this invention consists in the fact that adiponitrile can be manufactured in a high yield from acrylonitrile without having a substantial yield of propionitrile even when the acrylonitrile concentration in the electrolyte is below 10%, especially if quaternary ammonium sulfate in which alkyl radical having a small number of carbon atoms, particularly not more than three carbon atoms is bonded to nitrogen atom, is used as the supporting electrolyte. Because in this case solubility of acrylonitrile in the electrolyte never is increased more than that in water in the concentration of salt less than 60%.
• the best yield of adiponitrile is obtained in the suitable range of C/C preferably from 0.4 to 1, wherein C is the solubility of acrylonitrile 1n the electrolyte, and C is the concentration of acrylonitrile in the electrolyte.
• C/C can be eas1ly adjusted because the C using quaternary ammonium sulfate is smaller than 10%.
• the fifth advantage of this invention consists in the fact that the high stability against the decomposition of the supporting electrolyte can be utilized for heating the catholyte and other solutions originating therefrom to hlgh temperatures for the purpose of isolating adiponitrile.
• the sixth advantage of this invention consists in the fact that the high specific conductivity of the supporting electrolyte serves to reduce the consumption of electriclty involved in the manufacture of hydrodimer.
• a solution composed of 30% of tetraethylammonium sulfate, the supporting electrolyte used for this invention, 8% of acrylonitrile and 62% of water has a specific resistance of 269 cm.
• the high specific conductivity of the supporting electrolyte of this invention can be explained by reasoning that cations of this invention occurring from the dissociation of the supporting electrolyte have substantially the same conductivity as those of the conventional known supporting electrolyte whereas anions of this invention are sulfate ion, which are smaller in dimen sions and consequently higher in mobility than p-toluenesulfonate ions or alkylsulfate ion of the conventional known method.
• the cell resistance is reduced remarkably and the selectivity of adiponitrile is increased when the electrolysis is carried out by using a quaternary ammonium sulfate having an alkyl group of not more than three carbon atoms, with the concentration of this suppotring salt in the electrolyte fixed below 40%.
• the aqueous solution of quaternary ammonium salt of this invention shows its minimum specific resistance in the salt concentration range of from 20 to 40% by weight.
• the method of this invention is effective in that the hydrodimerization of acrylonitrile can be accomplished in a substantially high yield with small power consumption, and that the dimerization can be conducted while preventing the formation of propionitrile and harmful side reaction at the anode. Further, in this invention the process of separating the product and the raw material can be simplified and recovery of the supporting electrolyte is simplified.
• the catholyte is a solution which contains a quaternary ammonium sulfate, acrylonitrile, and water, with the concentration of acrylonitrile ranging from 3 to 60% by weight, that of water corresponding to to 90% of the total weight of the catholyte, and that of quaternary ammonium sulfate in the range of from 1 to 60%.
• concentration of acrylonitrile ranging from 3 to 60% by weight, that of water corresponding to to 90% of the total weight of the catholyte, and that of quaternary ammonium sulfate in the range of from 1 to 60%.
• the solubility of acrylonitrile in the catholyte is increased.
• acrylonitrile is dissolved by about 8% by weight in the catholyte at 25 C.
• acrylonitrile can be dissolved to form homogeneous solution at whatever concentration desired at C.
• a quaternary ammonium salt of high affinity with water but comparatively less affinity with adiponitrile and acrylonitrile it is, therefore, advantageous to employ a quaternary ammonium compound such as tetramethylammonium sulfate or tetraethylarnmonium sulfate with a radical having less carbon atom bonded to nitrogen.
• the adiponitrile in the cathode compartment eflluent is extracted with acrylonitrile added, and in the tank there are produced an oil layer consisting of adiponitrile and acrylonitrile as an upper layer and an aqueous layer mostly composed of the supporting electrolyte and water together with decreased concentration of adiponitrile due to extraction by acrylonitrile as a lower layer.
• this lower layer is supplied to the cathode compartment and the electrolysis is continued, the adiponitrile formed by electrolysis is extracted by acrylonitrile and separated in the upper layer of the tank. It is possible in this invention to obtain with ease the product containing less supporting electrolyte by drawing off the upper layer alone.
• the solubility of acrylonitrile in the electrolyte is not substantially increased due to the addition of supporting salt beyond that in the water, and C/C representing a ratio of the concentration of acrylonitrile in the catholyte for electrolysis C to a solubility of acrylonitrile in the electrolyte C is easily adjusted to a suitable value near to 1, as compared with the case using a supporting electrolyte which substantially increase a solubility of acrylonitrile beyond that in the water.
• solubility of acrylonitrile is about 10% in a range of salt concentration from 0 to ity. This value shows substantially no increase of acrylonitrile solubility as compared with the solubility of acrylonitrile in water, 7.35% (weight) at C., 7.9% (weight) at C., and 9% (Weight) at 60 C.
• electrolysis in such special conditions facilitates the formation of acrylonitrile oligomer (e.g. hydrotrimer and hydrotetramer of acrylonitrile) as the concentration of acrylonitrile approaches near saturation. Furthermore, a lower concentration of acrylonitrile than saturation causes the formation of hydrogen gas, and leads to the formation of undesirable by-product propionitrile.
• acrylonitrile oligomer e.g. hydrotrimer and hydrotetramer of acrylonitrile
• the optimum point for an effective preparation of adiponitrile by using quaternary ammonium having an alkyl group of not more than three carbon atoms may be influenced by acrylonitrile concentration, current density agitating condition on anode surface, temperature, etc., but generally the optimum condition is in the range of about 3 to 10% acrylonitrile concentration, if the concentration of supporting salt is defined to cover a lower range than the concentration corresponding to the minimum specific resistivity of the electrolyte.
• the temperature of electrolysis in the present invention can be at any degree up to the boiling point of acrylonitrile, preferably in the range of 080 C. for better adjustment of solution and operation.
• a solvent to the anolyte for the purpose of improving the current efliciency in the formation of hydrodimer or the selectivity of acrylonitrile at the cathode, or for the purpose of improving or controlling the solubility of acrylonitrile into the catholyte.
• quaternary ammonium sulfates are generally suitable.
• Such salts can be alkyl quaternary ammonium salts, quaternary ammonium salts having alkyl and aralkyl groups, quaternary ammonium salts having aryl and/or alkyl groups, heterocyclic quaternary ammonium salts and alkylalkanol quaternary ammonium salts.
• quaternary ammonium compounds having alkyl groups those having methyl, ethyl, butyl, and/or propyl groups bonded to the nitrogen atom are the most convenient to use.
• Compounds of quaternary ammonium having the phenyl group and the naphthyl group are representative salts having aryl groups bonded to a nitrogen atom
• salts having the benzyl group and the methylbenzyl group are representative of the salts having aralkyl groups bonded to nitrogen.
• quaternary ammonium compounds are tetramethylammonium sulfate, tetraethylammonium sulfate, trimethylethylammonium sulfate, triethylmethylammonium sulfate, tetrapropylammonium sulfate, tetrabutylammonium sulfate, trimethylethylammonium sulfate, methylpyridinium sulfate, ethylpyridinium sulfate, trimethylbenzylammonium sulfate, triethylbenzylammonium sulfate, trimethylaniline sulfate and triethylaniline sulfate.
• an electrode which has high hydrogen overvoltage in order to prevent hydrogen formation at the cathode.
• metals such metals as copper, lead, tin and mercury or alloys of such metals.
• acrylonitrile is converted generally by 70 to 100% into adiponitrile, while a part of it may undergo side reaction for forming propionitrile, oligomer of acrylonitrile (such as hydrotrimer), or biscyanoethyl ether. It is necessary to control the occurrence of these side reactions as far as possible.
• the formation of propionitrile is easy to occur in the cathode compartment solution having a low pH value and in the electrolytic cell wherein the turbulence condition in the cathode compartment is not so strong as the supply enough acrylonitrile to the cathode, and also oligomer is liable to occur when the acrylonitrile concentration is high. Therefore, the concentration of acrylonitrile and the pH of the cathode compartment should be selected so as to minimize the yield of these side reactions.
• the eflluent solution from cathode compartment will have pH in the range of from 2 to 9.5, and it is proper to keep the concentration of acrylonitrile in the catholyte in the order of from 3 to 40%.
• the side reactions at the cathode are influenced by the pH, monomer concentration, etc., on the surface of the cathode, therefore, it is necessary to make suitable arrangements so that the electrolyte may be sutficiently agitated in the cell and on the surface of the electrode and the concentration gradient of hydroxyl ion and acrylonitrile on the cathode may be reduced sulficiently.
• the flow velocity suitable for this invention is in the range of from 0.1 to 200 cm./second, more desirably from 5 to 100 cm./second.
• Sulfuric acid solution is used as an anolyte.
• concentration of sulfuric acid can be selected in the range of from 1 to 60%, it is proper generally to select it in the range of from 1 to 20% because the corrosion of anode becomes heavier with the increasing sulfuric acid concentration.
• material of anode it is suitable to use platinum, nickel, nickel silicide, Duriron, lead, and lead alloys, particularly lead-antimony alloy.
• the ion-exchange membranes having sulfonic acid groups and carboxyl groups can be used, the most suitable membrane is the sulfonated styrene-divinylbenzene polymer.
• Such cation exchange membranes can be either homogeneous or heterogeneous.
• the cation exchange membrane is desired to have ideal characteristics as to transfer only hydrogen ions but prevent sulfate ion and other catholyte ingredient like acrylonitrile from migration to anode compartment. In the case of this invention, however, even if anions of the supporting electrolyte in the cathode compartment migrate through the membrane in a small amount and discharge at the anode, they will not induce harmful corrosion of the anode.
• the pH of the cathode compartment is changed through insufficient neutralization, required neutralization can be accomplished by adding any kind of acid from outside.
• EXAMPLE 1 The electrolytic cell was used, in which both the anode and cathode were of lead, the anode compartment and cathode compartment was divided by a cation exchange membrane of sulfonated 1 mm. thick divinylbenzenestyrene-butadiene copolymer and the distance between the membrane and the electrode was 1 mm.
• a cation exchange membrane of sulfonated 1 mm. thick divinylbenzenestyrene-butadiene copolymer and the distance between the membrane and the electrode was 1 mm.
• As an anolyte 0.5 N sulfuric acid solution was circulated.
• the catholyte was circulated in the cathode compartment at a flow velocity of 20 cm./sec. and electrolyzed at the temperature of electrolyte of 40 C. The current density was amp./dm. for both electrode.
• the efiluent of cathode compartrnent was separated into two phases by adding acrylonitrile to the cathode efiluent.
• adiponitrile formed at the cathode was extracted with acrylonitrile as the upper oil phase.
• the lower phase was recirculated to the cathode compartment.
• Tetrapropylammonium sulfate was used to support electrolyte in catholyte.
• the composition of the upper oil phase was 60.7% of adiponitrile, 8% of oligomer, biscyanoethyl ether and ropionitrile, 0.4% of supporting electrolyte, 24.6% of acrylonitrile and 6% of water.
• the composition of the lower phase was 6% of acrylonitrile, 12% of supporting salt, the rest being water and electrolytic products which were mainly adiponitrile and minor part of propionitrile, oligomer, biscyanoethyl ether and etc.
• EXAMPLE 2 An electrolytic cell was used, in which both the anode and cathode were of lead, the anode compartment and cathode compartment was divided by cation exchange membrane of sulfonated 1 mm. thick divinylbenzenestyrene-butadiene copolymer and the distance between the membrane and electrode was 1 mm.
• cation exchange membrane of sulfonated 1 mm. thick divinylbenzenestyrene-butadiene copolymer and the distance between the membrane and electrode was 1 mm.
• As an anolyte 0.5 N sulfuric acid solution was circulated and the catholyte was circulated in the cathode compartment at a flow velocity of 20 cm./sec. and electrolyzed at the temperature of 30 C., the current density was 10 amp./dm. for both electrodes.
• the electrolytic products were mainly adiponitrile and minor part of propionitrile, oligomer, biscyanoethyl ether and etc.
• the selectivity of the electro lytic reaction was as follows:
• EXAMPLE 3 Acrylonitrile percent weight 6.0-7.0 Supporting electrolyte do 29-30 Electrolytic products and water do The rest pH 8 a-Naphthylamine p.p.m 1,000
• EXAMPLE 4 The same electrolytic cell and anolyte as in the Example 2 were used.
• the catholyte was circulated in the cathode compartment at a flow velocity of 60 cm./sec. and electrolyzed at a temperature of 30 C.
• the current density was 10 arnp./dm. for both electrodes.
• EXAMPLE 6 An electrolytic cell was used, in which both the anode and cathode are of lead, the anode compartment and cathode compartment are divided by cation exchange membrane of sulfonated 1.mm..thick divinylbenzenestyrene-butadiene copolymer, and the distance between the membrane and electrode was 1 mm.
• cation exchange membrane of sulfonated 1.mm..thick divinylbenzenestyrene-butadiene copolymer
• the electrolytic products were mainly adiponitrile and minor parts of oligomer, biscyanoethyl ether and etc.
• the selectivityof electrolytic reaction was as follows:
• adiponitrile by electrolyzing in a divided cell the catholyte of an aqueous solution comprising acrylonitrile and quaternary ammonium sulfate having at least one radical selected from the group consisting of alkyl, aryl and aralkyl bonded to the nitrogen atom of said quaternary ammonium compound, sulfuric acid solution being used as an anolyte, and the anolyte being separated by a cation exchange membrane from the catholyte, the improvement comprising using a concentration of dissolved acrylonitrile in said catholyte of from 3 to 10% by weight.
• said quaternary ammonium sulfate is selected from the group consisting of tetramethylammonium sulfate, tetraethylammoniurn sulfate, trimethylethylammonium sulfate, triethylmethylammonium sulfate and tetrapropylammonium sulfate.

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• 1966
  • 1966-11-28 US US597207A patent/US3497429A/en not_active Expired - Lifetime
  • 1966-12-01 LU LU52478A patent/LU52478A1/xx unknown
  • 1966-12-01 DE DE1568054A patent/DE1568054C3/de not_active Expired
  • 1966-12-01 GB GB53869/66A patent/GB1169525A/en not_active Expired
  • 1966-12-01 GB GB53870/66A patent/GB1170436A/en not_active Expired
  • 1966-12-02 FR FR86000A patent/FR1503182A/fr not_active Expired
  • 1966-12-02 ES ES0334065A patent/ES334065A1/es not_active Expired
  • 1966-12-02 BE BE690607D patent/BE690607A/xx not_active IP Right Cessation
  • 1966-12-02 CH CH1727966A patent/CH469678A/fr unknown
  • 1966-12-05 FR FR86138A patent/FR1503244A/fr not_active Expired

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