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

• the invention relates to a method for reducing anode corrosion in an electrolytic cell employed to electrohydrodimerize acrylonitrile to adiponitrile.
• an electrolytic cell employed to electrohydrodimerize acrylonitrile to adiponitrile.
• a process has been developed whereby acrylonitrile can be electrohydrodimerizedto adiponitrile in a dually-compartmented cell.
• the compartments are a cathode and an anode compartment and are separated by a cation permselective membrane.
• An anolyte composed of an aqueous solution of sulfuric acid is continuously circulated through the anode compartment.
• Sufficient electrical potential is established between the anode and cathode to produce unidirectional electrical current. Under the influence of such current acrylonitrile is electro'hydrodimerized at the cathode to produce adiponitrile which is then recovered.
• the anode of the cell generally employed to accomplish acrylonitrile electrohydrodimerization is made from lead, lead'rsilver alloy, lead-antimony alloy, platinum, stainless steel, and other like materials.
• the most commonly employed anode material is a lead-silver alloy.
• certain deleterious ions invade the anode compartment. Among these are included nitrate, perchlorate, and chlorate ions.
• nitric acid is an oxidizing agent. These acids were found to be extremely corrosive of the anodes used in the electrolytic cell.
• the most concentrated deleterious ion is nitrate which forms nitric acid and is itself formed by the oxidation of acrylonitrile which has invaded the anode compartment and been oxidized at the anode.
• the above general object is accomplished by intimately contacting the sulfuric acid anolyte with a water insoluble organic solution of a high molecular weight amine. Thereafter, the water insoluble organic solution of a high molecular weight amine is separated from the anolyte.
• the amines here employed must be highly selective for nitric, perchlorate, and chlorate ions, must be substantially water insoluble, be low in cost, be highly miscible with low cost solvents, be capable of regeneration with common reagents, and be free from emulsion forming tendencies.
• These criteria are met by primary, secondary, and tertiary amines having a molecular weight from about 250 to about 500.
• these amines are unifunctional, i.e., they contain only one ionizable group per molecule. Such amines can be used singly or as a mixture. Mixtures of amines are much more easily obtainable on a commercial basis.
• Amberlite LA-l is a mixture of N dodecenyl-N-trialkylmethylamines having a molecular weight from about 351-393, a neutral equivalency of 380410, a freezing point below C., a pour point below 20 C. and a steady state solubility in IN sulfuric acid in parts per million of 15 and an acid binding capacity of 2.5-2.7 milliequivalents per gram.
• Amberlite LA2 is a mixture of N-lauryl-N-trialkylamine having a molecular weight from about 35 3-395, a neutral equivalency of 350-380, a freezing point below 10 C., an acid binding capacity of 2.6-2.8 milliequivalents per gram, and a steady state solubility in IN H 50 in parts per million of 0.
• high molecular weight primary amines examples include 1-(3-ethylpentyl)-4-ethyloctylamine, l heptyloctylamine, and l-nndecyllaurylamine.
• Other secondary amines of high molecular weight besides those described before include bis-(1-isobutyl-3,5-dimethylhexyl) amine, di-n-decylamine, dilaurylamine, N-(l-undecyllauryl) laurylamine, N-benzyl-(l-nonyldecyl) amine, and N benzyl-l-undecyllaurylamine.
• a few of the many tertiary amines are trilaurylamine, tri-n-octylamine, didodenyl-n-butylamine, butylidaurylamine, and tribenzylamine.
• the amnies here employed can be in the free base form, or in the salt form. It is possible to use the salt form and exchange an anion for the deleterious anions. However, by far the most practical procedure is to use the amines in the free base form to thereby neutralize and remove the deleterious acids found in the anolyte.
• the organic solvents employed herein to produce organic solutions of amines must meet two general requirements. First, the solvent must be substantially water insoluble and second the amine employed must be highly soluble in the solvent.
• the generally useful organic solvents are included petroleum distillates, aromatic and aliphatic hydrocarbons, and high molecular weight alcohols. Specifically useful materials include benzene, xylene, and kerosene. It must be clearly understood, however, that there is a broad range of water insoluble materials whose usefulness should be apparent to one skilled in the art to which the present invention pertains.
• the organic solvent plus amine soluble therein, which in contact with water forms an organic phase, must be only slightly soluble if not completely insoluble in acidic aqueous solutions, especially aqueous sulfuric acid solution.
• An aqueous to organic phase ratio greater than about :1 is undesirable and should be avoided.
• the instant process can be practiced on a batch basis or it can be practiced in a continuous fashion.
• the main requirement is that whatever method be employed the aqueous and organic phases be thoroughly and intimately contacted.
• Various methods of contacting include counter flow in packed columns, contact in a vessel mechanically agitated, or in centrifugal contact apparatus. Many contact methods should be apparent to those skilled in the art.
• the high molecular weight amines here employed have become loaded with deleterious ions they can then be recharged by contact with a number of alkaline materials including anhydrous ammonia, aqueous ammonia, sodium hydroxide solution, and other materials. If, in the poorer procedure, an anion exchange procedure is used then the proper recharging anion must be provided. Once the material 'has been recharged it is generally preferred that the organic solution containing amine be water-washed prior to its reuse for deleterious ion removal.
• Example Two volumes of a N organic solution of high molecular weight amine having the trademark Amberlite LA-2 (described hereinbefore) dissolved in xylene were contacted in a separatory funnel with 5 volumes of anolyte containing 500 milliequivalents per liter (2.5%) of sulfuric acid and 9.3 milliequivalents per liter of nitrate ion along with a small quantity of non-deleterious ions. After separating and analyzing the aqueous phase it was found that the nitrate level in the anolyte had been reduced to 2.9 millicquivalents per liter by this single stage extraction procedure. A loss of only 8% sulfuric acid was sustained.
• test anode-panels of lead containing 1% silver were conatcted with the treated anolyte in a beaker test at a current density of 0.15 ampere per square centimeter of effective anode surface.
• the corrosion rate was found to be 0.2 inch per year as compared with a corrosion rate of 2.5 inches per year when untreated anolyte containing deleterious ions was employed.
• the contaminated organic solution of amine was regenerated with 0.27 volume of 0.46 N aqueous ammonia. Stoichiometrically this was of the amount required. Thereafter the regenerated amine solution was water washed three times using 0.1 volume of water per wash, thereby reducing the ammonium ion content to about 0.5 milliequivalent per liter.
• Organic amine solution recovery for reuse was about 99%.

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

Priority Applications (10)

Applications Claiming Priority (1)

Publications (1)

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Cited By (5)

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Citations (4)

• 1965
  • 1965-07-26 US US474934A patent/US3402112A/en not_active Expired - Lifetime
• 1966
  • 1966-07-11 GB GB31072/66A patent/GB1150303A/en not_active Expired
  • 1966-07-12 LU LU51543D patent/LU51543A1/xx unknown
  • 1966-07-14 IL IL26151A patent/IL26151A/en unknown
  • 1966-07-20 NL NL6610248A patent/NL6610248A/xx unknown
  • 1966-07-22 FR FR70473A patent/FR1487571A/fr not_active Expired
  • 1966-07-25 CH CH1078366A patent/CH456565A/fr unknown
  • 1966-07-25 AT AT707466A patent/AT264493B/de active
  • 1966-07-26 DE DE19661593054 patent/DE1593054A1/de active Pending
  • 1966-07-26 BE BE684628D patent/BE684628A/xx unknown

Patent Citations (4)

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