Propylene production process

Abstract

Processes and systems for forming propylene are described herein. The processes generally include reacting a metathesis feed stream including at least 95 wt. % 2-butene with ethylene in the presence of a metathesis catalyst to form a metathesis product stream including propylene, and recovering propylene from the process.

What is claimed is: 
     
         1 . A process for forming propylene comprising:
 separating a butene feed stream in a butene fractionation system that, in operation, separates 1-butene from 2-butene;   recovering 2-butene from the butene fractionation system and utilizing the 2-butene to form a metathesis feed stream comprising at least 95 wt. % 2-butene;   reacting the metathesis feed stream with ethylene in the presence of a metathesis catalyst to form a metathesis product stream comprising the propylene; and   recovering the propylene from the process.   
     
     
         2 . The process of  claim 1 , wherein the metathesis feed stream reacts with the ethylene in the absence of an amount of isomerization catalyst sufficient to isomerize butene. 
     
     
         3 . The process of  claim 1 , wherein the metathesis feed stream reacts with the ethylene in the absence of an isomerization catalyst. 
     
     
         4 . The process of  claim 1 , wherein the metathesis feed stream consists essentially of 2-butene. 
     
     
         5 . The process of  claim 1 , wherein the metathesis feed stream comprises at least 98 wt. % 2-butene. 
     
     
         6 . The process of  claim 1 , wherein the metathesis feed stream comprises a molar ratio of 2-butene:1-butene of at least 49:1. 
     
     
         7 . The process of  claim 1 , wherein the metathesis feed stream comprises less than 5 wt. % 1-butene. 
     
     
         8 . The process of  claim 1  further comprising:
 contacting a first feed stream comprising ethylene with a dimerization catalyst to form a dimerization product stream comprising 2-butene, wherein the butene feed stream comprises the dimerization product stream. 
 
     
     
         9 . The process of  claim 8 , wherein the dimerization catalyst is selected from metal oxides, nickel complexes, aluminum complexes and combinations thereof. 
     
     
         10 . The process of  claim 1 , wherein the metathesis catalyst comprises a transition metal oxide. 
     
     
         11 . The process of  claim 1 , wherein the metathesis catalyst comprises tungsten oxide. 
     
     
         12 . The process of  claim 1 , wherein the metathesis product stream comprises less than 1 mol. % pentene. 
     
     
         13 . The process of  claim 1 , wherein the metathesis product stream further comprises C 2  to C 6  olefins and wherein recovering the propylene comprises fractionating within a propylene fractionation system the metathesis product stream to form a propylene product stream, at least one recycle stream comprising olefins selected from butene, ethylene and combinations thereof, and a bottoms stream comprising olefins selected from C 5  olefins, C 6+  olefins and combinations thereof. 
     
     
         14 . The process of  claim 13  further comprising passing the recycle stream from the propylene fractionation system to the metathesis reaction without passing through an isomerization reaction. 
     
     
         15 . The process of  claim 13 , wherein the propylene fractionation system comprises:
 a first stage that, in operation, separates ethylene from other components present in the metathesis product stream to form a de-ethenized product stream; and   a second stage that, in operation, separates propylene from C4 and heavier olefins in the de-ethenized product stream.   
     
     
         16 . The process of  claim 1 , wherein the process produces at least 100 MM lbs/yr of propylene. 
     
     
         17 . The process of  claim 1 , wherein the metathesis reaction exhibits a propylene selectivity of at least 95%. 
     
     
         18 . A process for forming propylene comprising:
 reacting a first feed stream comprising ethylene with a dimerization catalyst to form a dimerization product stream;   fractionating the dimerization product stream to form a 2-butene stream;   reacting the 2-butene stream with ethylene in the presence of a metathesis catalyst to form a metathesis product stream comprising the propylene, wherein the 2-butene stream reacts with the ethylene in the absence of an amount of isomerization catalyst sufficient to isomerize butene; and   recovering the propylene from the process, wherein the process produces at least 100 MM lbs/yr of the propylene.   
     
     
         19 . The process of  claim 18 , wherein the metathesis reaction exhibits a propylene selectivity of at least 95%. 
     
     
         20 . The process of  claim 18 , wherein the metathesis catalyst comprises a transition metal oxide. 
     
     
         21 . The process of  claim 18 , wherein the metathesis product stream comprises less than 1 mol. % pentene. 
     
     
         22 . The process of  claim 18 , wherein the metathesis feed stream consists essentially of 2-butene.