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
  • C25B3/25—Reduction
• • 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
  • C25B3/01—Products
  • C25B3/03—Acyclic or carbocyclic hydrocarbons

Definitions

• This invention relates to a method of the production of dihydroaromatic hydrocarbons which comprises subjecting a catholyte composed of a heterogeneous mixture of an aromatic hydrocarbon and an aqueous solution of one or more quaternary ammonium salts to electrolysis carried out at a temperature from 30 to 100 C. and subsequently recovering the resulting dihydro aromatic hydrocarbon.
• This invention relates to a method of electrolytically reducing aromatic hydrocarbons to produce dihydro aromatic hydrocarbons.
• Electrolytic reduction of aromatic hydrocarbons has been carried out either by electrolysis of a non-aqueous solution using as a solvent ethylamine, ethylenediamine or the like such as those described in Journal of the American Chemical Society 86, 52.72 (1964) and J. Electrochem. Soc. 113, 1060 (1966) or by a method in which the electrolysis is carried out in an electrolytic bath using as a solvent an aprotic solvent such as tetrahydrofuran or diglyme containing a minor amount of water such as one described in J. Electrochem. Soc. 115, 266 (1968).
• This invention is concerned with a method of the production of dihydro aromatic hydrocarbons formed in a catholyte which is a heterogeneous mixture composed of an aqueous solution of one or more quaternary ammonium salts such as tetra-n-butyl ammonium sulfate and an aromatic hydrocarbon by carrying out the electrolysis under vigorous stirring in an electrolytic bath using mercury as a cathode and having a diaphragm of a material such as an ion exchange membrane.
• the aromatic hydrocarbon which may be employed in the method of the invention includes mononuclear aromatic hydrocarbons such as benzene or derivatives thereof such as toluene, ethylbenzene, xylenes and diethylbenzenes having alkyl group of carbon number 1-2 and polynuclear aromatic hydrocarbons such as naphthalene or derivatives thereof such as a-methylnaphthalene, fl-methylnaphthalene and a-ethylnaphthalene having alkyl group of carbon number 1-2, the amount of the hydrocarbon employed being preferably from 0.3 to 20 parts by Weight per parts by weight of the aqueous solution of one or more quaternary ammonium salts. Higher amounts of the hydrocarbon will result in lower electric conductivities while on the other hand lower amounts of the same will lower the current efficiency. Especially suitable is the use of an amount from 3 to 10 parts by weight.
• quaternary ammonium salt suitably used in the method of this invention are mentioned sulfates, halogenides, aliphatic sulfonates, cycloaliphatic sulfonates and the like.
• a quaternary ammonium hydroxide in place of the supporting salt, it is not preferable because of its high corrosivity.
• use of a small amount of a quaternary ammonium hydroxide in combination with the aforementioned quaternary ammonium salts is effective in the provision of stable electrolysis.
• the quaternary ammonium group are preferred those consisting of alkyl and cycloalkyl groups, those consisting mainly of n-butyl group such as methyltri-n-butyl ammonium, ethyl-tri-n-butyl ammonium, npropyl-tri-mbutyl ammonium, tetra-n-butyl ammonium and n-amyl-tri-n-butyl ammonium being suitable for practical use with good results.
• the quaternary ammonium salt is suitably employed at a concentration of several percent by weight or higher, preferably from about to 50% by weight, in view of electric conductivity of the electrolytic bath, and usually from 20 to 30% by weight.
• the temperature at which the method of the invention is effectively operated is a temperature from room temperature up to the boiling point of the catholyte, usually a temperature from 30 to 100 C. being suitable and a temperature from 50 to 80 C. being particularly preferable.
• the diaphragm used in this invention is desirably an ion exchange membrane.
• Materials such as an unglazed pottery plate of fine mesh or a glass filter which substantially prevent admixture between the catholyte and the anolyte and are well conductive when immersed in the electrolytic bath may also be used.
• the anolyte is preferably employed sulfuric acid.
• Other acids such as hydrochloric, hydrobromic, nitric and sulfonic acids may be used, which are preferably used with a cation exchange membrane in view of the control of a electrolyte concentration.
• Mercury is most suitable used as the anode with which the method of the invention can be effectively conducted.
• the quality of the cathode material does not directly affect the results of this invention and conventional insoluble materials such as platinum and graphite may be used.
• the range of current density at which the method of this invention can be efiiciently carried out is from 0.5 a./dm. to 100 a./dm. and the range between 2 and 50 a./dm. is particularly preferred.
• the dihydro aromatic hydrocarbons thus produced which are sparingly soluble in the aqueous solution of quaternary ammonium salts, are separated for the most part as the liquid upper layer together with the unreacted aromatic hydrocarbon when allowed to stand for a while outside the electrolysis system.
• the dihydro aromatic hydrocarbons therefore, can be easily recovered by conventional purifying procedures such as fractional distillation of the upper layer portion.
• the electrolysis can be continued by recyclizing the separated liquid lower layer in admixture with a fresh starting aromatic hydrocarbon for use as the catholyte.
• the system is organic solvent free there can be no loss of the solvent at all in the electrolysis step and the step for recovering the dihydro aromatic hydrm rbon according to the present invention, whereas it is impossible or extremely difiicult in the prior methods using an organic solvent to recover the solvent which tends to leak into the anode chamber.
• the recovery, if any, is usually associated with a considerable loss of the organic solvent.
• the electric conductivity of the electrolytic bath used in this invention is very high as exemplified below.
• the dihydro aromatic compounds are useful as the starting material for polymers and organic chemicals.
• Example 1 An H-shaped electrolytic cell composed of pure mercury and platinum respectively as the cathode and anode, a strongly acid cation exchange membrane in H form parting the anode chamber and the cathode chamber and a stirrer provided in the cathode chamber was used.
• the anolyte was employed 2 N aqueous sulfuric acid and as the catholyte a heterogeneous mixture of tetra-n-butyl ammonium sulfate, tetra-n-butyl ammonium hydroxide, water and benzene in a weight ratio of 20:1:7lz8.
• Example 2 The same electrolytic cell and anolyte as in Example 1 were used.
• the catholyte was employed a 40:5 1:811 heterogeneous mixture of tetra-n-butyl ammonium bromide, Water, toluene and tetra-n-butyl ammonium hydroxide.
• Electrolysis was made under vigorous stirring while maintaining the temperature of the catholyte at C.
• Current density on the mercury surface was about 8 a./dm. and current intensity 0.3 F. per mole of the toluene.
• Gaschromatographic analysis of the catholyte after the electrolysis indicated formation of methylcyclohexa-1,4-diene at a current efficiency of 45%.
• Example 3 The same electrolytic cell and anolyte as in Example 1 were used. As the catholyte was employed a 40:1:51z8 heterogeneous mixture of tetra-n-butyl ammonium bromide, tetra-n-butyl ammonium hydroxide, water and p-xylene was employed. Electrolysis was made under vigorous stirring while maintaining the temperature of the catholyte at 80 C. Current density was 6 a./dm. and current intensity 0.4 F. per mole of the p-xylene. Analysis of the catholyte after the electrolysis indicated formation of dimethylcyclohexadiene at a current efficiency of 38%.
• Example 4 The same electrolytic cell as in Example 1 was used.
• As the anolyte was employed 2 N aqueous nitric acid.
• Electrolysis was made at a current density on the cathode surface of 10 a./dm. while maintaining the catholyte at 55 C. under stirring to such a degree as giving an emulsion. Current intensity was 0.25 F. per mole of benzene.
• Analysis of the catholyte after the electrolysis indicated formation of cyclohexa-l,4-diene at a current efi'iciency of 68% and a selectivity of 92%.
• Example 5 A horizontal electrolytic cell partitioned into the upper and lower chambers by a cation exchange membrane was used in which pure mercury was placed in the lower chamber for use as the cathode and a platinum net in the upper chamber for use as the anode.
• 0.5 N aqueous sulfuric acid was circulated between the anode chamber and the anolyte storage.
• the cathode chamber and the catholyte storage was placed 6 'kg. of a heterogeneous mixture of tetra-n-butyl ammonium bromide and sulfate, water and benzene at a weight ratio of 20: 1:69: 10, respectively, which was vigorously circulated through a heat exchanger for electrolysis while maintaining the temperature at 65 C.
• Example 6- The same electrolytic cell and anolyte as in Example 1 were used.
• the catholyte Was employed a 40:57z3 by weight heterogeneous mixture of tetra-nbutyl ammonium bromide, water and naphthalene.
• Electrolysis was made while maintaining the temperature of the catholyte at 80 C. under vigorous stirring. Current density on the mercury surface was about 8 a./dm. and current intensity 0.5 F. per mole of the naphthalene.
• Gaschromatographic analysis of the catholyte after the electrolysis indicated formation of 1,4-dihydronaphthalene at a current intensity of 72%. Selectivity of the formation of 1,4-dihydronaphthalene was 88%.
• Example 7 The same electrolytic cell and anolyte as in Example 1 were used.
• the catholyte was employed a 4225325 by weight mixture of ethyl-tri-n-butyl ammonium sulfate, water and a-methylnaphthalene.
• Electrolysis was made while maintaining the temperature of the catholyte at 75 C. under vigorous stirring. Current density on the mercury surface was 6 a./d1n. and current intensity 0.8 F. per mole of the ct-methylnaphthalene.
• Gaschromatographic analysis of the catholyte after the electrolysis indicated formation of 1-methy1-5,8-dihydronaphthalene at a current efliciency of 70% and a selectivity of 89%.
• Example 8 The same electrolytic cell and anolyte as in Example 1 were used. As the catholyte was employed a 35:51:14 by weight heterogeneous mixture of n-amyltri-n-butyl ammonium chloride, water and benzene. Electrolysis was made while maintaining the temperature of the catholyte at 67 C. under vigorous stirring. Current density on the mercury surface was 10 a./dm. and current intensity 0.5 F. per mole of the benzene. Gaschromatograp hic analysis of the catholyte after the electrolysis indicated formation of cyclohexa-1,4diene at a current efficiency of and a selectivity of 90.5%.
• Method of the production of dihydro aromatic hydrocarbons which comprises subjecting an organic solvent free catholyte composed of a heterogeneous mixture of an aromatic hydrocarbon to be reduced selected from the group consisting of benzene, naphthalene and alkyl derivatives thereof having 1 to 2 carbon atoms and an aqueous solution of at least one alkyl or cycloalkyl quaternary ammonium salt in which the alkyl or cycloalkyl groups contain from 1 to about 6 carbon atoms to electrolysis carried out at a temperature from 30 to C.
• an organic solvent free catholyte composed of a heterogeneous mixture of an aromatic hydrocarbon to be reduced selected from the group consisting of benzene, naphthalene and alkyl derivatives thereof having 1 to 2 carbon atoms and an aqueous solution of at least one alkyl or cycloalkyl quaternary ammonium salt in which the alkyl or cycloalkyl groups contain from 1 to about 6 carbon
• aromatic hydrocarbon is selected from the group consisting of benzene and alkyl derivatives thereof having 1 to 2 carbon atoms.
• Method according to claim 2 wherein the said quaternary ammonium salt is selected from the group consisting of methyl-tri-n-butyl ammonium salts, ethyl-tri-nbntyl ammonium salts, n-propyl-tri-n-butyl ammonium salts, tetra-n-butyl ammonium salts and n-amyl-tri-n-butyl ammonium salts and hydroxides derived therefrom.
• aromatic hydrocarbon is selected from the group consisting of naphthalene and alkyl derivatives thereof having 1 to 2 carbon atoms.
• Method according to claim 1 including the further steps of dividing the resulting electrolyte into two layers and subsequently recovering the resulting dihydro aromatic hydrocarbon.

Landscapes

• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=14327509

Family Applications (1)

Country Status (2)

Cited By (3)

Families Citing this family (1)

• 1969
  • 1969-12-22 JP JP44102440A patent/JPS4835063B1/ja active Pending
• 1970
  • 1970-12-16 US US98931A patent/US3700572A/en not_active Expired - Lifetime

Also Published As

Similar Documents