Oxygenate conversion to olefins with metathesis

Abstract

A processing scheme and system for enhanced light olefin production, particularly for increased relative yield of propylene, involves oxygenate conversion to olefins and subsequent oxygenate conversion effluent stream treatment including cross-metathesis of 1-butene with 2-butene, metathesis of 2-butene with ethylene, conversion or removal of at least a portion of the isobutene, and/or isomerization of at least a portion of 1-butene to 2-butene to produce additional propylene. The processing scheme and system may further involve a reaction with distillation column for the metathesis of butenes with ethylene to produce propylene and/or a reaction with distillation column for the conversion of isobutenes with an oxygenate-containing material to produce a tertiary ether or alcohol.

1 . A process for producing light olefins from an oxygenate-containing feedstock, the process comprising:
 contacting the oxygenate-containing feedstock in an oxygenate conversion reactor with an oxygenate conversion catalyst and at reaction conditions effective to convert the oxygenate-containing feedstock to an oxygenate conversion effluent stream comprising light olefins and C 4 + hydrocarbons, wherein the light olefins comprise ethylene and the C 4 + hydrocarbons comprise butenes including a quantity of 1-butenes and a quantity of isobutenes;   separating the oxygenate conversion effluent stream in a separation zone and forming a first process stream comprising at least a portion of the butenes, including at least a portion of the quantity of 1-butenes and at least a portion of the quantity of isobutenes, from the oxygenate conversion effluent stream;   contacting at least a portion of the butenes from the first process stream with a metathesis catalyst in a metathesis zone at effective conditions to produce a metathesis effluent stream comprising propylene; and   recovering propylene from the metathesis effluent stream.   
     
     
         2 . The process of  claim 1 , wherein the first process stream further comprises a quantity of 2-butenes and wherein upon contact with the metathesis catalyst at least a portion of the 1-butenes and at least a portion of the 2-butenes from the first process stream cross-metathesize to produce propylene. 
     
     
         3 . The process of  claim 1 , additionally comprising introducing a quantity of ethylene into the metathesis zone to metathesize at least a portion of the butenes from the first process stream to produce propylene. 
     
     
         4 . The process of  claim 1  further comprising:
 isomerizing at least a portion of the 1-butenes from the first process stream to form an isomerized stream comprising a quantity of 2-butenes; and   metathesizing at least a portion of the quantity of 2-butenes from the isomerized stream in the metathesis zone to produce the metathesis effluent stream.   
     
     
         5 . The method of  claim 1  wherein at least a portion of the quantity of isobutenes is removed from the first process stream by reacting at least a portion of the quantity of isobutenes with methanol in an isobutene conversion zone to form a second process stream comprising methyl tert-butyl ether. 
     
     
         6 . The process of  claim 1  wherein the metathesis zone comprises a reaction with distillation column containing a fixed bed of the metathesis catalyst and wherein upon contact with the metathesis catalyst at least a portion of the quantity of butenes from the first process stream is metathesized with ethylene in the fixed bed to produce the metathesis effluent stream and a metathesis bottoms stream comprising a quantity of unreacted butenes. 
     
     
         7 . The process of  claim 6  wherein the separating step additionally forms a third process stream comprising at least a portion of the ethylene from the oxygenate conversion effluent stream and wherein at least a portion of the ethylene from the third process stream is introduced into the reaction with distillation column to metathesize with at least a portion of the butenes from the first process stream to produce propylene. 
     
     
         8 . The process of  claim 6  additionally comprising:
 recycling at least a portion of the metathesis bottoms stream to the oxygenate conversion zone.   
     
     
         9 . A process for producing light olefins from an oxygenate-containing feedstock including at least a quantity of methanol, the process comprising:
 contacting the oxygenate-containing feedstock in an oxygenate conversion reactor with an oxygenate conversion catalyst and at reaction conditions effective to convert the oxygenate-containing feedstock to an oxygenate conversion effluent stream comprising light olefins and C 4 + hydrocarbons, wherein the light olefins comprise ethylene and the C 4 + hydrocarbons comprise a quantity of butenes including a quantity of 1-butenes and a quantity of isobutene;   treating the oxygenate conversion effluent stream and forming a first process stream comprising at least a portion of the butenes including a quantity of isobutenes and a quantity of 1-butenes from the oxygenate conversion effluent stream;   converting at least a portion of quantity of isobutenes from the first process stream in an isobutene conversion zone to form a second process stream including a quantity of 1-butenes and a third process stream including a conversion product;   isomerizing at least a portion of the 1-butenes from the second process stream in an isomerization zone to form an isomerized stream comprising a quantity of 2-butenes;   contacting at least a portion of the quantity of 2-butenes from the isomerized stream with ethylene in a metathesis zone at effective conditions to produce a metathesis effluent stream comprising propylene; and   recovering propylene from the metathesis effluent stream.   
     
     
         10 . The process of  claim 9  wherein the treating step additionally forms a fourth process stream comprising at least a portion of the ethylene from the oxygenate conversion effluent stream and wherein at least a portion of the ethylene from the fourth process stream is introduced into the metathesis zone to metathesize at least a portion of the quantity of 2-butenes to produce propylene. 
     
     
         11 . The process of  claim 9  wherein the converting step comprises introducing a portion of the oxygenate-containing feedstock into the isobutene conversion zone wherein during an isobutene conversion reaction at least a portion of the quantity of isobutenes is converted to produce a conversion product comprising methyl tert-butyl ether. 
     
     
         12 . The process of  claim 9 , wherein the converting step comprises dimerizing at least of the portion of isobutenes from the first process stream in the isobutene conversion zone to produce the conversion product. 
     
     
         13 . The process of  claim 9  wherein the C 4 + hydrocarbons from the oxygenate conversion effluent stream additionally comprise a quantity of 2-butenes and wherein during the metathesis step, at least a portion of the quantity of 2-butenes is also metathesized with ethylene in the metathesis zone to produce additional propylene included in the metathesis effluent stream. 
     
     
         14 . The process of  claim 9  wherein the metathesis effluent stream additionally comprises a quantity of butenes, the process further comprising:
 separating at least a portion of the quantity of butenes from the metathesis effluent stream; and   recycling at least a portion of the separated butenes to the isobutene conversion zone.   
     
     
         15 . The process of  claim 9  wherein the metathesis zone comprises a reaction with distillation column containing a fixed bed of the metathesis catalyst and wherein upon contact with the metathesis catalyst at least a portion of the quantity of 2-butenes from the isomerized stream is metathesized with ethylene in the fixed bed to produce the metathesis effluent stream comprising propylene and a metathesis bottoms stream. 
     
     
         16 . The process of  claim 15  additionally comprising:
 recycling at least a portion of the metathesis bottoms stream to the oxygenate conversion zone.   
     
     
         17 . A system for producing light olefins from an oxygenate-containing feedstock, the system comprising:
 a reactor for contacting an oxygenate-containing feedstock with an oxygenate conversion catalyst and converting the oxygenate-containing feedstock to form an oxygenate conversion effluent stream comprising light olefins and C 4 + hydrocarbons, wherein the light olefins comprise ethylene and the C 4 + hydrocarbons comprise a quantity of butenes including a quantity of 1-butenes and a quantity of isobutenes;   a separation zone for separating the oxygenate conversion effluent stream and forming a first process stream comprising at least a portion of the quantity of butenes, including at least a portion of the quantity of 1-butenes and at least a portion of the quantity isobutenes, from the oxygenate conversion effluent stream;   a metathesis zone for contacting at least a portion of the butenes from the first process stream with a metathesis catalyst to produce a metathesis effluent stream comprising propylene; and   a recovery zone for recovering propylene from the metathesis effluent stream.   
     
     
         18 . The system of  claim 17  additionally comprising:
 an isomerization zone for isomerizing at least a portion of the quantity of 1-butenes from the first process stream to form an isomerized stream comprising a quantity of 2-butenes, the isomerization zone interposed between the separation zone and the metathesis zone.   
     
     
         19 . The system of  claim 18  additionally comprising:
 an isobutene conversion zone for converting at least a portion of the quantity of isobutenes from the first process stream to produce a second process stream including a portion of the quantity of 1-butenes and a third process stream comprising a conversion product, the isobutene conversion zone interposed between the separation zone and the isomerization zone.   
     
     
         20 . The system of  claim 17  wherein the metathesis zone comprises a reaction with distillation column containing a fixed bed of the metathesis catalyst wherein at least a portion of the quantity of butenes from the first process stream is contacted with ethylene to produce the metathesis effluent stream comprising propylene.