Isomerization process

In a process of isomerization of C.sub.4, C.sub.5 and C.sub.6 hydrocarbons in which C.sub.5 and C.sub.6 hydrocarbons are isomerized in the presence of a metallic halide catalyst and hydrogen-to-hydrocarbon molar ratio of about 0.6 to 1.8 and in the absence of C.sub.4 hydrocarbons, wherein the improvement, comprising the steps of

• charging a first feedstream containing C.sub.5 and higher molecular weight hydrocarbons and at least 20% C.sub.6 hydrocarbons to a first isomerization reaction zone in the presence of hydrogen and with an isomerization catalyst at conditions of temperature and pressure sufficient to effectuate isomerization whereby a first effluent stream is produced;
• charging a second feedstream containing C.sub.4 hydrocarbons to a second isomerization reaction zone in the presence of hydrogen and an isomerization catalyst at conditions of temperature and pressure sufficient to effectuate isomerization whereby a second effluent stream is produced;
• conveying the first and second effluent streams to a high pressure separator to produce a hydrogen-rich recycle stream and a product stream containing C.sub.4, C.sub.5 and higher molecular weight hydrocarbons;
• recycling at least a part of the hydrogen-rich recycle stream for admixture with the first feedstream and the second feedstream whereby a common hydrogen-rich recycle stream is shared during isomerization;
• conveying the product stream to a stabilizer section to remove gaseous and low-boiling components formed during isomerization;
• and
• fractionating the product stream to separate the product stream into at least one C.sub.4 hydrocarbon stream and at least one higher molecular weight hydrocarbon stream.

An integrated process of isomerization of C.sub.4, C.sub.5 and C.sub.6 hydrocarbons in which the C.sub.4 hydrocarbons are isomerized in the absence of the C.sub.5 and C.sub.6 and higher molecular weight hydrocarbons, comprising the steps of:

• charging a first feedstream containing C.sub.5 hydrocarbons and at least 20% C.sub.6 hydrocarbons to a first isomerization reaction zone in the absence of C.sub.4 hydrocarbons and in the presence of hydrogen and an isomerization catalyst at conditions of temperature and pressure sufficient to effectuate isomerization whereby a first effluent stream is produced;
• charging a second feedstream containing C.sub.4 hydrocarbons to a second isomerization reaction zone in the absence of C.sub.5 and C.sub.6 and higher molecular weight hydrocarbons and in the presence of hydrogen and an isomerization catalyst at conditions of temperature and pressure sufficient to effectuate isomerization whereby a second effluent stream is produced;
• separating a hydrogen-rich recycle stream from the first effluent stream;
• recycling at least a part of the hydrogen-rich recycle stream for admixture with the first feedstream and the second feedstream whereby a common hydrogen-rich recycle stream is shared during isomerization providing an integration of the C.sub.4 isomerization and the C.sub.5 and C.sub.6 isomerization steps which reduces overall hydrogen requirements;
• conveying the first and second effluent streams to a stabilizer section to remove gaseous and low-boiling components formed during isomerization and produce a product stream containing C.sub.4, C.sub.5 and C.sub.6 hydrocarbons;
• and
• fractionating the product stream to separate the hydrocarbons into at least one C.sub.4 hydrocarbon stream and at least one stream containing higher molecular weight hydrocarbons.