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 present invention is concerned with a process .for the production of adiponitrile from acrylonitrile.
• Another process consists in hydrodimerizing acrylonitrile by the electrolysis of a inixture of acrylonitrile and of a small quantity of water saturated by an electrolyte, such as lithium bromide, on a platinum electrode (Belgian Pat. specification No. 649,625).
• the electrolyte used according to the process of Belgian Pat. specification No. 684,436 is responsible for the corrosion of the iron oxide anode and that, if the salts of the electrolyte are replaced wholly or partially by the alkali metal salts of polycondensed phosphoric acids, it is possible to maintain substantially all of the advantages of this process, while reducing the corrosion of the iron oxide anode to an amount which is technically acceptable.
• the process according to the present invention for the hydrodimerization of acrylonitrile to adiponitrile by the direct electrolytic route, by passing a direct electrical current through an electrolytic cell having the anode and cathode in contact with the electrolytic medium comprises using an initial electrolysis medium consisting essentially of (a) acrylonitrile, (b) water, (c) at least one alkali salt selected from the group consisting of the alkali salts of condensed polyphosphoric acids of the formula:
• alkali salts of condensed polyphosphoric acids of formula (1) there are intended the sodium, potassium, lithium, ammonium and quaternary ammonium salts of acids, such as pyrophosphoric acid (H,P O,-), triphosphoric acid (H P O tetraphosphoric acid (H -P 0 polyphosphoric acids containing from 5 to 100 phosphorus atoms, and mixtures thereof.
• acids such as pyrophosphoric acid (H,P O,-), triphosphoric acid (H P O tetraphosphoric acid (H -P 0 polyphosphoric acids containing from 5 to 100 phosphorus atoms, and mixtures thereof.
• 'By alkali salts of polymetaphosphoric acids of formula (11) there are intended the sodium, potassium, lithium, ammonium and quaternary ammonium salts of acids, such as dimetaphosphoric acid (H P- O), tn'metaphosphoric acid (11 F 0 tetrametaphosphoric acid (H,P.oa). metaphosphoric acids containing from 5 to 100 phosphorus atoms and mixtures thereof.
• alkali salts of the condensed polyphosphoric acids of formula (1) and of the metaphosphoric acids of formula (11) may also be used in the form of mixtures with one another in any desired proportions; furthermore, there can be used the alkali salts of these acids such as are available commercially, for example, under the names of Graham's salt, Kurrol salt, sodium hexametaphosphate, SQ salt sold by Monsanto (Na,,P 0 and the like.
• acidic salts of alkali metals and of polyacids there are intended the salts of a polyacid, such as sulfuric acid, boric acid, perboric acid, phosphoric acid, oxalic acid or the like, which is incompletely substituted, containing at least one hydrogen cation.
• a polyacid such as sulfuric acid, boric acid, perboric acid, phosphoric acid, oxalic acid or the like, which is incompletely substituted, containing at least one hydrogen cation.
• monoand disodium orthophosphates, monoand dipotassium orthophosphates, sodium hydrogen sulfate, monopotassium oxalate and the like as well as mixtures thereof.
• the salts used according to the present invention may replace wholly the partially substituted salts of alkali metals and of polyacids, especially the acidic alkali metal orthophosphates.
• the salts according to the present invention are more expensive, especially with regard to the alkali orthophosphates, and as, on the other hand, their lower ionization, increases the terminal voltage, it is intended, according to the present invention, to use mixtures, on the one hand, of acidic salts of alkali metal and of polyacid and, on the other hand, of salts of acids according to formulas (l) and (11) in which the amount of polyphosphates according to the present invention is sufficient to maintain the corrosion of the anode at an acceptable level.
• the amount of polyphosphate may be relatively low, without prejudicing the anticorrosive effect.
• the ratio by weight between the acidic salts of alkali metal and of polyacid and of the polyphosphates used according to the present invention may be 99.9/01 to 0/100, advantageously 99/1 to /20, and preferably 95/5 to /15.
• the concentration by weight of the polyphosphates (or of the mixture of polyphosphates and of acidic salts of alkali metal and of polyacid) in the aqueous electrolytic solution may'vary from 0.5 percent up to the concentration corresponding to saturation.
• quaternary ammonium salts or pyridinium salts such as acidic bistetraethyl-amrnonium phosphate, penta-tetraethyl-ammonium tripolyphosphate or acidic bis-methyl-pyridinum phosphate or the like.
• concentration of these surface-active substances in the aqueous electrolytic solution may vary from 0.05 to 5 percent by weight, preferably from 0.2 to 2 percent
• the initial electrolytic solution essentially contains water.
• a small quantity of a base or of an acid in order to maintain a definite pH value, this pH value advantageously being maintained between 5 and 10, preferably between 8 and 9.
• a mixture of emulsified acrylonitrile and of the initial aqueous electrolytic solution is circulated through the electrolysis apparatus, the volumetric ration between the aqueous phase and the acrylonitrile phase being maintained within the limits of 1:1 and 6: l.
• This anode is surrounded by two cathodes made of graphite and of the same dimensions, placed on both sides of the anode at a distance ofl cm.
• the supply of current is made by means of steel threaded rods screwed to the upper part ofeach electrode.
• the assembly of the three electrodes is fixed vertically in the beaker.
• the apparatus is provided with [.8 liters of the electrolytic solution to be tested. A temperature of 20 C. is maintained and there is passed through a continuous current of 14 amperes. The current density is in the region of 7 amperes/dmf". Every 24 hours, the electrolysis is interrupted for the time necessary to remove the anode, rinse it, dry and weigh it. The anode is then replaced and the electrolysis resumed under the same conditions.
• the first experiment is a comparative one carried out with an TABLE I Experiment number KzEPO 5.6 5.6 5.3 4.8 KsPzOnL 0. 06 0.3 1.14 (Et NhllPOt 1 1 1 1 Hexarnetaphosphatc Phosphate SQ NB P207 Rate of corrosion, mmJyear:
• the temperature during the electrolysis is maintained within the limits of 0 C., to 40 C., preferably within the region of room temperature.
• the linear velocity of circulation of the emulsified mixture is between 0.1 and l m./sec.
• an electrolysis apparatus without a diaphragm, having graphite cathodes and magnetite anodes, with or without a metallic support.
• the current density is l20 amperes/dm. and the voltage is comprised between 4 and volts preferably between 4 and 7 volts.
• the process according to the present invention is equally applicable to anodes made of materials other than iron oxide, for example, anodes made of metallic iron or the like.
• the electrolysis is carried out in a manner such that the conversion of the acrylonitrile is -70 percent, preferably -50 percent. Below 20 percent, the economy of the process according to the present invention or the production ratio is too poor for industrial use, while when the conversion is increased beyond 70 percent, the selectivity of adiponitrile is less good.
• the process according to the present invention may be carried out as well discontinuously as continuously.
• the apparatus for measuring the rate of corrosion of the anodes comprises a beaker provided with means for cooling and a mechanical stirrer.
• the magnetite anode subjected to the experiments is a square plate of steel or of Armco iron, the edges of which are 10 cm. long and the thickness of which is l cm., entirely covered with a coating of magnetite with a thickness of about 1 mm., obtained by the superficial oxidation of the metal in water vapor at a temperature of 1,000 C.
• the composition of the electrolyte is of the type used in Belgian Pat. specification No. 684,436; it contains, in particular, acidic dipotassium orthophosphatev
• the second experiment which is according to the present invention, a part of the acidic dipotassium orthophosphate of the first experiment is replaced by potassium tripolyphosphate.
• the whole of the dipotassium orthophosphate is replaced by potassium tripolyphosphate.
• the electrolysis device functions in a continuous manner, with a constant supply of acrylonitrile and of water (to compensate for the electrolytic decomposition of this latter) and a continuous removal, by decantation, of an organic phase containing unchanged acrylonitrile,
• the pH value is permanently controlled and maintained at 8.4.
• AN Acrylonitrile.
• ADN Adiponitrile.
• PN Propionitrile.
• ADNlAN Percent of the number of moles of ADN formed referred to the number of moles of AN supplied.
• PNlAN Percent of the number of moles of PN formed, referred to the number of moles of AN supplied.
• Yield ADN/Elec. Ratio in percent between the number of moles of ADN formed and the number of taradays provided to the cell in the course of the electrol sis.
• the experiment was carried out in a tubular electrolytic cell constituted by a cylindrical anode made of molten magnetite surrounded by a graphite tube which functions both as cathode and as container.
• the anode has a diameter of 6 cm. and an effective length of 61 cm., i.e., a surface of 11.3 dm. dm.?
• the cathode has an interior diameter of7 cm., i.e.. an effective surface of l3.2 dm.?
• the distance between the electrodes is 0.5 cm.
• the cell proper is completed by a tubing system with pumps, hydrocyclone and filter allowing the circulation of the reaction medium between the electrodes and the collection of the solid products resulting from the corrosion of the anode (phosphate+iron hydroxide). Cooling is effected by circulating brine in a double jacket surrounding the graphite tube.
• Process of hydrodimerization of acrylonitrile to adiponitrile by the direct electrolytic route by passing a direct electrical current through an electrolytic cell having the anode and cathode in contact with the electrolytic medium, which comprises using an initial electrolysis medium consisting essentially of (a) acrylonitrile, (b) water, (c) at least one alkali salt selected from the group consisting of the alkali salts of condensed polyphosphoric acids of the formula in which n has a value of from 2 to I00, and the alkali salts of polymetaphosphoric acids of the formula n n fln in which n has a value of from 2 to I00, (d) a surface-active substance, and (e) at least one acidic salt of an alkali metal and ofa polyacid, the ratio by weight of (e) to (c) being comprised between 99.9/0.l and 0/l00.
• Process as claimed in claim I in which the concentration 5.
• Process as c laimed in claim 1, in which the salts of formu la (1) are selected from the group consisting of sodium, potassium, lithium, ammonium and quaternary ammonium salts of pyrophosphoric, triphosphoric, tetraphosphoric and polyphosphoric acids containing from 5 to 100 phosphorous atoms and mixtures thereof.
• salts offormula (II) are selected from the group consisting of sodium, potassium, lithium, ammonium and quaternary ammonium salts of dimetaphosphoric, trimetaphosphoric, tetrametaphosphoric acids and metaphosphoric acids having 5 to 100 phosphorous atoms and mixtures thereof.
• the surface-active substance is selected from the group consisting of acidic bistetraethyl-ammonium phosphate, penta-tetraethyl-ammonium tripolyphosphate and acidic bis-methylpyridinium phosphate.
• the acidic salt of an alkali metal and of a polyacid is selected from the group consisting of acidic salts of sulfuric, boric, perboric, phosphoric and oxalic acids, which are incompletely substituted, containing at least one hydrogen cation.
• the acidic salts of an alkali metal and of a polyacid is selected from the group consisting of acidic sodium and potassium salts of orthophosphoric acid, sodium hydrogen sulfate and 8 monopotassium oxalate.

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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)
• Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

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Cited By (9)

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• 1968
  • 1968-06-06 GB GB2705168A patent/GB1233266A/en not_active Expired
• 1969
  • 1969-06-02 NL NL6908359.A patent/NL159366B/xx not_active IP Right Cessation
  • 1969-06-02 FR FR6918295A patent/FR2010513A1/fr not_active Withdrawn
  • 1969-06-02 LU LU58763D patent/LU58763A1/xx unknown
  • 1969-06-04 US US830521A patent/US3616321A/en not_active Expired - Lifetime
  • 1969-06-04 CH CH848569A patent/CH502312A/fr not_active IP Right Cessation
  • 1969-06-04 AT AT532169A patent/AT289056B/de not_active IP Right Cessation
  • 1969-06-04 IL IL32339A patent/IL32339A/en unknown
  • 1969-06-04 BG BG012388A patent/BG16183A3/bg unknown
  • 1969-06-04 PL PL1969134011A patent/PL80063B1/pl unknown
  • 1969-06-05 NO NO02331/69A patent/NO130430B/no unknown
  • 1969-06-05 CS CS399669A patent/CS154624B2/cs unknown
  • 1969-06-05 SE SE08003/69A patent/SE367820B/xx unknown
  • 1969-06-05 BE BE734090D patent/BE734090A/xx not_active IP Right Cessation

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