Integrated process for c.sub.4, c.sub.5 and c.sub.6 isomerization

Abstract

A process is disclosed for the isomerization of a C.sub.4 feedstock and a C.sub.5 -C.sub.6 feedstock that reduces equipment and operating expenses by utilizing a process flow scheme that provides beneficial heat integration and facilitates the use of a common recovery zone while permitting a wide variation in the relative ratio of a C.sub.4 to a C.sub.5 -C.sub.6 feedstock. The isomerization of the C.sub.4 feedstock takes place in a separate reaction zone. The effluent from the C.sub.4 isomerization zone is heat exchanged against or mixed with the C.sub.5 -C.sub.6 feedstock ahead of an additional isomerization zone that converts the C.sub.5 -C.sub.6 hydrocarbons, and if present, normal C.sub.4 hydrocarbons, to more highly branched hydrocarbons. Effluents from both isomerization zones enter a common separation section that removes light gases from the isomerate product. This invention simplifies the simultaneous isomerization of C.sub.4 and C.sub.5 -C.sub.6 feedstocks. If offers significant cost and operational advantages to newly designed units and is beneficial in the revamp of existing isomerization units to either add or improve butane isomerization capabilities. For example, butane isomerization capability may be incorporated into an existing C.sub.5 -C.sub.6 isomerization unit by adding as few pieces of major equipment as a butane drier, a feed exchanger, and one or two reactors.