GB798027A - Process for the production of dichlorbutenes - Google Patents

Abstract

Dichlorobutenes are prepared by the noncatalytic additive chlorination of butadiene in the vapour phase by a process which comprises contacting chlorine with butadiene in the ratio of at least one mol. of butadiene per mol. of chlorine in an unpacked reaction zone at a temperature within the range of about 280 DEG to 400 DEG C. for not more than 12 seconds. A large excess of butadiene may be used and serves to absorb the heat of reaction or the butadiene may be diluted with an inert diluent such as nitrogen. The butadiene is preferably preheated before passing into the reaction zone and is rapidly and thoroughly mixed with the chlorine. The reaction may be carried out at subatmospheric, superatmospheric or, preferably, atmospheric pressure, and may advantageously be carried out in an adiabatic manner with a rise in temperature within the specified limits. The products may be separated by any suitable means, such as continuous distillation, whereby the dichlorobutenes, i.e. 1 : 4-dichlorobutene-2 and 3 : 4-dichlorobutene-1 are recovered substantially pure. The excess butadiene is also recovered and may, after washing free of hydrogen chloride and drying, be recycled. In examples, preheated butadiene and chlorine were passed through a heated tubular glass or steel reactor at various temperatures and with contact times within the limits defined above, the dichlorobutenes being separated by fractional distillation. The Provisional Specification further defines the low and high boiling fractions also obtained in the fractional distillation as 1-chlorobutadiene and chloroprene (low boiling) and tetrachlorobutane (high boiling). Specification 798,028 is referred to.