Polyisobutylene process

Claim 1

A continuous process for preparing low molecular weight polyisobutylene having an M n in the range of 700 to 3,000 and a molecular weight distribution less than about 2.0 from a feedstream mixture of C 4 hydrocarbons containing at least about 6% by weight isobutylene in a continuous stirred reactor maintained at a reaction temperature of about -50° to +30° C., the reactor having a feedstream inlet and a separate AlCl 3 catalyst inlet, which comprises injecting gaseous HCl, in an amount of 25 to 200 ppm parts by weight of feedstream and in the absence of AlCl 3 , into said feedstream at a point prior to its entry into the reactor in a manner sufficient to permit substantially complete reaction of the HCl with isobutylene to form t-butyl chloride before contact with AlCl 3 such that the resulting pre-reacted feedstream at the point of reactor entry contains less than 1.0 ppm HCl, and simultaneously adding the pre-reacted feedstream and the AlCl 3 catalyst to the reactor and contacting the pre-reacted feedstream with said catalyst in the reaction mixture to form the polyisobutylene, withdrawing the reaction mixture from the reactor, quenching the reaction with aqueous alkali and separating therefrom the polyisobutylene product.