Patent GB-859401-A (GB)
Title: Process for the manufacture of pure chloroprene
Inventor: SENNEWALD KURT
IPC: C07C17/38
Filed: 1957-02-25
Abstract: <PICT:0859401/IV(b)/1> In a process for the manufacture of pure chloroprene the gas mixture containing chloroprene and monovinyl-acetylene, which results from the reaction of monovinyl-acetylene and hydrogen chloride in contact solutions consisting of aqueous solutions of cuprous chloride containing considerable amounts of hydrochloric p  acid is de-acidified by washing it with water, the washed gas mixture, which contains in addition to unreacted monovinyl-acetylene between about 2 and about 25 % by volume of chloroprene and between about 0,1 and 5 % by volume of higher boiling impurities resulting from the reactions, is conducted to a fractional condensation in which the mixture is separated into higher boiling constituents, pure monovinyl-acetylene, and chloroprene saturated with monovinyl-acetylene from which the monovinyl-acetylene is then distilled off, in the fractionation stages with partial condensation of the higher boiling constituents and then of the chloroprene, an additional gas current being maintained consisting of at least one inert gas which may comprise monovinyl-acetylene or nitrogen which promotes the driving off of the uncondensed gases, while the penetration of atmospheric oxygen into the fractionation stages is prevented by working at least under normal pressure, preferably under elevated pressure, at least one substance inhibiting polymerisation being introduced into each of the fractionation stages; the percentages by volume being calculated on the total volume of monovinyl-acetylene, chloroprene and higher boiling constituents. Advantageously the distillation in which the chloroprene is separated from higher boiling impurities is carried out in a current of monovinyl-acetylene and the subsequent elimination of monovinyl acetylene from chloroprene in a current of nitrogen. Other inert gases which may be used as alternatives to nitrogen are carbon monoxide, carbon dioxide, hydrogen, methane, argon and helium.  Such inert gases are washed free from monovinyl acetylene by means of chloroprene, acetone, methanol and aromatic hydrocarbon oils.  The gas mixture after washing with water, is optionally dried with calcium chloride prior to the first distillation.  The polymerisation inhibitor specified is phenothiazine optionally in chloroprene solution.  n-Butane may be employed as diluent in the distillation stages to reduce explosion risk, and may be pure or may contain at least one aliphatic hydrocarbon such as butylene, propane, isobutane, isopentane and pentane.  In the apparatus shown monovinyl acetylene and hydrogen chloride are passed through pipes 1 and 2 to reactor 3 and the products with unreacted monovinyl acetylene pass through pipe 4 to water-washing and drying columns 5 and 6 and thence through pipe 7 into column 8 fitted with condenser 9 whilst monovinyl acetylene is passed in through pipe 11.  High boiling impurities leave through pipe 13 whilst chloroprene and monovinyl-acetylene pass through pipe 14 to column 15 where monovinyl acetylene leaves overhead and is recycled partly to reactor 3 and partly through drier 22 to the bottom of column 8.  Liquid chloroprene containing dissolved monovinyl acetylene leaves column 15 and passes through syphon 23 to column 24, through which nitrogen is circulated from which part of the chloroprene is removed through pipe 30 as product and the remainder passes through tube 32 to column 34 wherein the nitrogen from column 24 is washed to remove monovinyl acetylene and recycled to column 24.  Chloroprene containing monovinyl acetylene is passed through pipe 39 to column 8. Examples are furnished.ALSO:<PICT:0859401/III/1> In a process for the manufacture of pure chloroprene, the gas mixture containing chloroprene and monovinyl-acetylene, which results from the reaction of monovinyl-acetylene and hydrogen chloride in contact solutions consisting of aqueous solutions of cuprous chloride containing considerable amounts of hydrochloric acid, is de-acidified by washing it with water and the washed gas mixture, which contains in addition to unreacted monovinyl-acetylene between about 2 and 25% by volume of chloroprene and between about 0.1 and 5% by volume of higher boiling impurities resulting from the reaction, is conducted to a fractional condensation in which the mixture is separated into higher boiling constituents, pure monovinyl-acetylene, and chloroprene saturated with monovinyl-acetylene, from which the monovinyl-acetylene is then distilled off, in the fractionation stages with partial condensation of the higher boiling constituents and then of the chloroprene, an additional gas current being maintained consisting of at least one inert gas, which may comprise monovinyl-acetylene or nitrogen, which promotes the driving off of the uncondensed gases, while the penetration of atmospheric oxygen into the fractionation stages is prevented by working at least under normal pressure, preferably under elevated pressure, at least one substance inhibiting polymerization being introduced into each of the fractionation stages. Advantageously the distillation in which the chloroprene is separated from higher boiling impurities is carried out in a current of monovinyl-acetylene and the subsequent elimination of monovinyl-acetylene from chloroprene in a current of nitrogen. Other inert gases which may be used are carbon monoxide, carbon dioxide, hydrogen, methane, argon and helium.  Such inert gases are washed free from monovinyl-acetylene by means of chloroprene, acetone, methanol and aromatic hydrocarbon oils.  The gas mixture, after washing with water, is optionally dried with calcium chloride prior to the first distillation.  The polymerization inhibitor specified is phenothiazine, optionally in chloroprene solution.  n-Butane may be employed as diluent in the distillation stages to reduce explosion risk and may be pure or may contain at least one aliphatic hydrocarbon such as butylene, propane, isobutane, isopentane or pentane.  In the apparatus shown monovinyl-acetylene and hydrogen chloride are passed through pipes 1, 2 to reactor 3 and the products with unreacted monovinyl-acetylene pass through pipe 4 to water-washing and drying columns 5, 6 and thence through pipe 7 into column 8 fitted with condenser 9 whilst monovinyl-acetylene is passed in through pipe 11.  High-boiling impurities leave through pipe 13 whilst chloroprene and monovinyl-acetylene pass through pipe 14 to column 15, where monovinyl-acetylene leaves overhead and is recycled partly to reactor 3 and partly through drier 22 to the bottom of column 8.  Liquid chloroprene containing dissolved monovinyl-acetylene leaves column 15 and passes through syphon 23, to column 24 through which nitrogen is circulated and from which part of the chloroprene is removed through pipe 30 as product, the remainder passing through tube 32 to column 34 wherein the nitrogen from column 24 is washed to remove monovinyl-acetylene and recycled to column 24. Chloroprene containing monovinyl-acetylene is passed through pipe 39 to column 8. Examples are given.