Process for producing butylene polymers having molecular weights in the range of from about 400 to 5000 molecular weight

A process for preparing isobutylene polymers from a hydrocarbon feed stream comprising a C.sub.4 -C.sub.5 hydrocarbon mixture containing up to 12(wt)% cis-2-butene, up to 15(wt)% trans-2-butene and up to 35% (wt)% isobutylene, which method comprises:

• (a) fractionating said feed stream comprising said C.sub.4 -C.sub.5 hydrocarbon mixture to remove no more than about 50(wt)% of said cis-2-butene of said C.sub.4 -C.sub.5 hydrocarbon mixture;
• (b) reacting in liquid phase the overhead fraction from said fractionating of said feed stream comprising said C.sub.4 -C.sub.5 hydrocarbon mixture containing isobutylene and an aluminum chloride catalyst at a temperature of from about 0.degree. F. to about 75.degree. F. to polymerize said isobutylene and form a reaction mixture consisting of isobutylene polymers of molecular weight of from 900 to about 5000 and unreacted hydrocarbons including butene-1, cis-2-butene and trans-2-butene;
• (c) flash distilling said reaction mixture to recover polybutene polymers of molecular weights of from about 900 to about 5000 from unreacted hydrocarbon mixture fraction (ii);
• (d) reacting in liquid phase said fraction (ii) with a catalyst system consisting of aluminum chloride and a promoter at a temperature of from about 30.degree. F. to about 140.degree. F. to polymerize butylenes in said fraction (ii) and form a reaction product mixture containing butylene polymers;
• and
• (e) separating polybutene-1 polymers having the molecular weights in the range of about 400-900 from said product mixture.