Treatment of alkylation catalyst poisons with dehydrogenation

Abstract

Methods and processes for reducing alkylation catalyst poisoning are described herein. Such methods generally include contacting ethylbenzene with a dehydrogenation catalyst to form a dehydrogenation output stream within a dehydrogenation system and passing at least a portion of the dehydrogenation output stream to an alkylation system, wherein the at least a portion of the dehydrogenation output stream contacts an alkylation catalyst. The at least a portion of the dehydrogenation output stream includes a level of impurities resulting from offtest and wherein the level of impurities is sufficiently low to result in essentially no observed effect on the alkylation catalyst life in comparison with an alkylation system feed absent offtest.

1 . A dehydrogenation process comprising: 
 introducing an alkyl aromatic hydrocarbon into a dehydrogenation system;    contacting the alkyl aromatic hydrocarbon with a dehydrogenation catalyst to form a dehydrogenation output stream comprising a vinyl aromatic hydrocarbon;    passing at least a portion of the dehydrogenation output stream to a separation system, wherein the separation system comprises a first separation column and at least one additional separation column;    withdrawing offtest from the dehydrogenation process; and    introducing the offtest into at least one of the additional separation columns.    
   
   
       2 . The process of  claim 1 , wherein the separation system comprises three separation columns.  
   
   
       3 . The process of  claim 1  further comprising introducing steam into the dehydrogenation system.  
   
   
       4 . The process of  claim 3 , wherein the steam to alkyl aromatic hydrocarbon weight ratio is from about 0.01:1 to about 15:1.  
   
   
       5 . The process of  claim 1 , wherein the alkyl aromatic hydrocarbon comprises ethylbenzene.  
   
   
       6 . The process of  claim 5 , wherein the vinyl aromatic hydrocarbon comprises styrene.  
   
   
       7 . The process of  claim 6 , wherein the output stream further comprises ethylbenzene.  
   
   
       8 . The process of  claim 1  further comprising passing an overhead fraction from the first separation column to an alkylation system and passing a bottoms fraction from the first separation column to the at least one additional separation column.  
   
   
       9 . The process of  claim 8 , wherein the overhead fraction contacts an alkylation catalyst within the alkylation system.  
   
   
       10 . The process of  claim 9 , wherein the alkylation catalyst comprises a molecular sieve catalyst.  
   
   
       11 . The process of  claim 9 , wherein the overhead fraction comprises benzene and impurities.  
   
   
       12 . The process of  claim 9 , wherein the impurities comprise nitrogen containing compounds.  
   
   
       13 . The process of  claim 8 , wherein the overhead fraction fewer impurities than an overhead fraction in an identical system having offtest fed to the first separation column.  
   
   
       14 . A method for reducing alkylation catalyst poisoning comprising: 
 contacting ethylbenzene with a dehydrogenation catalyst to form a dehydrogenation output stream within a dehydrogenation system;    passing at least a portion of the dehydrogenation output stream to an alkylation system, wherein the at least a portion of the dehydrogenation output stream contacts an alkylation catalyst; and    wherein the at least a portion of the dehydrogenation output stream comprises a level of impurities resulting from offtest and wherein the level of impurities is sufficiently low to result in essentially no observed effect on the alkylation catalyst life in comparison with an alkylation system feed absent offtest.    
   
   
       15 . The method of  claim 14 , wherein the dehydrogenation output stream comprises benzene.  
   
   
       16 . The method of  claim 14 , wherein the alkylation catalyst comprises a zeolitic alkylation catalyst.