Abstract: A process flow is presented for a hydrocarbon conversion process in which a relatively volatile hydrocarbon is separated from less volatile feed and product hydrocarbons present in a reaction zone effluent stream. The preferred usage is in the alkylation of benzene with propylene. The reaction zone effluent stream is passed into a lower portion of a rectified separation zone. Recycle aromatic hydrocarbon is passed into a contact exchanger/absorber present in the top portion of the rectified separation zone. The liquid collected at the bottom of the contact exchanger is removed as a sidecut stream and passed into the reaction zone.

Abstract: Insertion of about one-half of a small diameter distillation column through the bottom of a larger diameter column permits the fractionation of a feed stream fed to the small column into three distinct high purity streams within one vessel. An annular space between the two columns functions as a stripping section which produces a pure stream of intermediate boiling range material. Open communication between the columns at the top of the small column eliminates the requirement of having a separate reflux system for the small column.