Propylene production
A process for producing propylene from ethylene and a feed stream comprising 1-butene is disclosed. The feed stream is contacted with an isomerization catalyst to produce an isomerized stream. The isomerized stream is reacted with ethylene in a distillation column reactor containing a metathesis catalyst to generate a reaction mixture; and the reaction mixture is concurrently distilled to produce an overhead stream comprising ethylene and propylene, and a bottoms stream comprising 1-butene, 2-butene, and C 5 and higher olefins. Propylene is separated from the overhead stream.
1 . A process for producing propylene comprising:
(a) contacting a feed stream comprising 1-butene with an isomerization catalyst to obtain an isomerized stream comprising 2-butene;
(b) reacting the isomerized stream and ethylene in a distillation column reactor containing a metathesis catalyst to generate a reaction mixture, and concurrently distilling the reaction mixture to produce an overhead stream comprising ethylene and propylene, and a bottoms stream comprising 1-butene, 2-butene, and C 5 and higher olefins; and
(c) separating the overhead stream into propylene and ethylene.
2 . The process of claim 1 further comprising distilling the bottoms stream to obtain a light stream comprising 1-butene and 2-butene, and a heavy stream comprising the C 5 and higher olefins.
3 . The process of claim 2 wherein the bottoms stream is distilled at a temperature in the range of 50 to 170° C..
4 . The process of claim 2 wherein the bottoms stream is distilled at a pressure in the range of 1,000 to 2,000 kPa.
5 . The process of claim 2 further comprising recycling the light stream to step (a).
6 . The process of claim 1 further comprising recycling the separated ethylene to step (b).
7 . The process of claim 1 wherein the isomerization catalyst is an acidic catalyst.
8 . The process of claim 1 wherein the isomerization catalyst is an acidic ion-exchange resin.
9 . The process of claim 1 wherein the isomerization catalyst is a basic catalyst.
10 . The process of claim 1 wherein the isomerization catalyst comprises magnesium oxide.
11 . The process of claim 1 wherein the isomerization catalyst is a hydroisomerization catalyst.
12 . The process of claim 11 wherein the hydroisomerization catalyst comprises Pd and alumina.
13 . The process of claim 1 wherein the metathesis catalyst comprises a transition metal oxide comprising an element selected from the group consisting of cobalt, molybdenum, rhenium, tungsten, and mixtures thereof.
14 . The process of claim 1 wherein the metathesis catalyst comprises rhenium oxide and alumina.
15 . The process of claim 1 wherein the step (b) is conducted at a temperature in the range of 40 to 150° C..
16 . The process of claim 1 wherein the step (b) is conducted at a pressure in the range of 1,500 to 3,500 kPa.
17 . The process of claim 1 wherein the isomerized stream is fed to the distillation column reactor above the catalyst bed.
18 . The process of claim 1 wherein the ethylene is fed to the distillation column reactor below the catalyst bed.
19 . The process of claim 1 wherein step (c) is performed by distillation at a temperature in the range of −20 to 100° C. and a pressure in the range of 3,000 to 4,500 kPa.