Processes and apparatuses for isomerizing hydrocarbons

Abstract

Processes and apparatuses for isomerizing hydrocarbons are provided. In an embodiment, a process for isomerizing hydrocarbons includes providing a first hydrocarbon feed that includes hydrocarbons having from 5 to 7 carbon atoms. The first hydrocarbon feed is fractionated to produce a first separated stream that includes hydrocarbons having from 5 to 6 carbon atoms and a second separated stream that includes hydrocarbons having 7 carbon atoms. The first separated stream is contacted with a benzene saturation catalyst at benzene saturation conditions to produce an intermediate stream and subsequently isomerized in the presence of a first isomerization catalyst and hydrogen under first isomerization conditions to produce a first isomerized stream. The second separated stream is isomerized in the presence of a second isomerization catalyst and hydrogen under second isomerization conditions that are different from the first isomerization conditions to produce a second isomerized stream.

What is claimed is: 
     
         1 . A process for isomerizing hydrocarbons, wherein the process comprises:
 providing a first hydrocarbon feed comprising hydrocarbons having from  5  to  7  carbon atoms;   fractionating the first hydrocarbon feed to produce a first separated stream comprising hydrocarbons having from 5 to 6 carbon atoms and comprising benzene and a second separated stream comprising hydrocarbons having 7 carbon atoms;   contacting the first separated stream with a benzene saturation catalyst at benzene saturation conditions to produce an intermediate stream comprising cyclohexane;   isomerizing the intermediate stream in the presence of a first isomerization catalyst and hydrogen under first isomerization conditions to produce a first isomerized stream; and   isomerizing the second separated stream in the presence of a second isomerization catalyst and hydrogen under second isomerization conditions to produce a second isomerized stream.   
     
     
         2 . The method of  claim 1 , wherein first isomerization conditions comprise a temperature of about 130° C. to about 210° C. 
     
     
         3 . The process of  claim 1 , wherein the second isomerization conditions comprise a temperature of about 100° C. to about 120° C. 
     
     
         4 . The process of  claim 1 , wherein the benzene saturation conditions comprise a temperature of about 130° C. to about 160° C. and a pressure of about 18 Kg/cm 2  g to about 22 Kg/cm 2  g. 
     
     
         5 . The process of  claim 1  further comprising passing the intermediate stream to a first flash drum, prior to isomerization of the intermediate stream, to separate a first flash drum overhead stream comprising butane and lighter boiling hydrocarbons and gases. 
     
     
         6 . The process of  claim 1  further comprising stabilizing the first isomerized stream and the second isomerized stream to provide a common overhead stream comprising hydrocarbons having less than or equal to 4 carbon atoms and a first isomerized stabilized stream comprising branched hydrocarbons and a second isomerized stabilized stream comprising branched hydrocarbons. 
     
     
         7 . The process of  claim 6 , wherein the first isomerized stream and the second isomerized stream are stabilized in a split shell stabilizer, wherein a first side of the split shell stabilizer is configured to stabilize the first isomerized stream and a second side of split shell stabilizer is configured to stabilize the second isomerized stream. 
     
     
         8 . The process of  claim 6  further comprising providing the first isomerized stabilized stream to a deisohexanizer to provide a deisohexanier recycle stream comprising linear hexane, cyclic hydrocarbons, and monomethyl-branched pentane and a first isomerate product, wherein the deisohexanier recycle stream combines with the first separated stream. 
     
     
         9 . The process of  claim 6  further comprising providing the second isomerized stabilized stream to a deisoheptanizer to provide a deisoheptanizer recycle stream comprising linear heptanes and cyclic hydrocarbons and a second isomerate product, wherein the deisoheptanizer recycle stream combines with the second separated stream. 
     
     
         10 . The process of  claim 9 , wherein the first isomerized stabilized stream and the second isomerized stabilized stream are provided to a split shell column comprising the deisohexanizer and the deisoheptanizer. 
     
     
         11 . The process of  claim 6  further comprising passing the second isomerized stream through a second flash drum prior to stabilizing the second isomerized stream. 
     
     
         12 . The process of  claim 1 , wherein the first isomerization catalyst is one of a zirconia containing catalyst or a chlorided alumina catalyst. 
     
     
         13 . The process of  claim 1 , wherein the second isomerization catalyst is one of a zirconia containing catalyst or a chlorided alumina catalyst. 
     
     
         14 . A process for isomerizing hydrocarbons, wherein the process comprises:
 providing a first hydrocarbon feed comprising hydrocarbons having from 5 to 7 carbon atoms;   fractionating the first hydrocarbon feed to produce a first separated stream comprising hydrocarbons having from 5 to 6 carbon atoms and comprising benzene and a second separated stream comprising hydrocarbons having 7 carbon atoms;   contacting the first separated stream with a benzene saturation catalyst at benzene saturation conditions to produce an intermediate stream comprising cyclohexane;   separating a first flash drum overhead stream comprising butane and lighter boiling hydrocarbons and gases from the intermediate stream in a first flash drum to provide a net first flash drum bottoms stream;   isomerizing the net first flash drum bottoms stream in the presence of a first isomerization catalyst and hydrogen under first isomerization conditions to produce a first isomerized stream; and   isomerizing the second separated stream in the presence of a second isomerization catalyst and hydrogen under second isomerization conditions to produce a second isomerized stream;   separating a second flash drum overhead stream comprising butane and lighter boiling hydrocarbons and gases from the second isomerized stream in a second flash drum to provide a second flash drum bottoms stream;   stabilizing the first isomerized stream and second flash drum bottoms stream to provide a first isomerized stabilized stream and a second isomerized stabilized stream; and   passing the first isomerized stabilized stream and the second isomerized stabilized stream to a split shell column comprising a deisohexanizer and a deisoheptanizer to provide a net isomerate product.   
     
     
         15 . An apparatus for isomerizing hydrocarbons, wherein the apparatus comprises:
 a first fractionation unit adapted to fractionate a first hydrocarbon feed comprising hydrocarbons having from 5 to 7 carbon atoms to produce a first separated stream comprising hydrocarbons having from 5 to 6 carbon atoms and a second separated stream comprising hydrocarbons having 7 carbon atoms;   a benzene saturation reactor in fluid communication with the first fractionation unit to produce an intermediate stream comprising cyclohexane;   a first isomerization unit in fluid communication with the benzene saturation reactor and adapted to receive and isomerize the intermediate stream in the presence of a first isomerization catalyst and hydrogen under first isomerization conditions to produce a first isomerized stream; and   a second isomerization unit in fluid communication with the first fractionation unit and adapted to receive and isomerize the second separated stream in the presence of a second isomerization catalyst and hydrogen under second isomerization conditions to produce a second isomerized stream.   
     
     
         16 . The apparatus of  claim 15  further comprising a first flash drum in fluid communication with the benzene saturation reactor. 
     
     
         17 . The apparatus of  claim 15  further comprising a split shell stabilizer comprising a first side and a second side, wherein a first side of the split shell stabilizer is in fluid communication with the first isomerization unit and a second side of split shell stabilizer is in fluid communication with the second isomerization unit. 
     
     
         18 . The apparatus of  claim 17  further comprising a split shell column comprising a deisohexanizer and a deisoheptanizer, wherein the deisohexanizer is in fluid communication with the first side of the split shell stabilizer and the deisoheptanizer is in fluid communication with the second side of the split shell stabilizer. 
     
     
         19 . The apparatus of  claim 15  further comprising a second flash drum, wherein the second flash drum is in fluid communication with the second isomerization unit. 
     
     
         20 . The process of  claim 19 , where in the second flash drum is stacked with the first flash drum.