Patent GB-902399-A (GB)
Title: Process for isolating and purifying chloroprene
IPC: C07C17/38
Filed: 1958-12-05
Abstract: A process for isolating and purifying chloroprene from gas mixtures containing chloroprene and monovinyl acetylene, said mixtures being obtained from the reaction of monovinyl acetylene and hydrogen chloride in the presence of aqueous cuprous chloride solution followed by deacidification by washing with water, drying if desired, and separation under atmospheric or elevated pressure by fractional distillation while preventing penetration of atmospheric oxygen, an additional gas current being maintained in the distillation stages and polymerization inhibitors being added for stabilizing the liquid phases of the distillation, is characterized by separating the main part of the mono-vinyl lacetylene portion contained in the starting gas mixture from the chloroprene and the impurities in a first distillation stage, the chloroprene and impurities being obtained as a sump saturated with dissolved mono-vinyl acetylene, separating the chloroprene from the impurities in a second distillation stage by means of a gas current consisting of a subsidiary cycle of monovinyl acetylene and expelling the monovinyl which is still dissolved in the chloroprene taken from the second distillation stage in a third distillation stage by means of a current of oxygen-free inert gas conducted in a cycle.  A dilution gas, e.g. n-butane, may be added to the monovinyl acetylene for desensitizing purposes, drying may be effected with anhydrous calcium chloride, phenothiazine may be employed as polymerization inhibitor and nitrogen may be employed as oxygen-free gas in the third cycle.  An example is furnished and an apparatus for carrying out the process is described with reference to a drawing (not shown).ALSO:A process for isolating and purifying chloroprene from gas mixtures containing chloroprene and monovinyl acetylene, said mixtures being obtained from the reaction of monovinyl acetylene and hydrogen chloride in the presence of aqueous cuprous chloride solution followed by de-acidification by washing with water, drying, if desired, and separation under atmospheric or under elevated pressure by fractional distillation, while preventing penetration of atmospheric oxygen, an additional gas current being maintained in the distillation stages and polymerization inhibitors being added for stabilizing the liquid phases of the distillation, is characterized by separating the main part of the monovinyl acetylene portion contained in the starting gas mixture from the chloroprene and the impurities in a first distillation stage, the chloroprene and impurities being obtained as a sump saturated with dissolved monovinyl acetylene, separating the chloroprene from the impurities in a second distillation stage by means of a gas current consisting of a subsidiary cycle of monovinyl acetylene and expelling the monovinyl acetylene which is still dissolved in the chloroprene taken from the second distillation stage in a third distillation stage by means of a current of oxygen-free inert gas conducted in a cycle.  A dilution gas e.g. n-butane may be added to the monovinyl acetylene for desensitising purposes, drying may be effected with anhydrous calcium chloride, phenothiazine is specified for use as polymerization inhibitor and nitrogen may be employed as the oxygen free gas in the third cycle.  An example is furnished and an apparatus for carrying out the process is described with reference to a Figure (not shown).