Production of high purity butene-1 from an n-butane feedstock

• US 4,558,168 A
• Filed: 06/19/1985
• Issued: 12/10/1985
• Est. Priority Date: 06/19/1985
• Status: Expired due to Fees

• Current Assignee: Houdry, Inc.
• Original Assignee: Air Products and Chemicals Incorporated (Linde Plc)
• Inventors: Schwartz, William A., Spence, David C., Gussow, Stanley
• Primary Examiner(s): Gantz, D. E.
• Assistant Examiner(s): Pal, A.
• Application Number:
  US06/746,605
• Time in Patent Office: 174 Days
• Field of Search: 585/324, 585/314, 585/315, 585/654, 585/655, 585/809, 585/833, 585/836
• US Class Current: 585/324
• CPC Class Codes: C07C 11/08 with four carbon atoms
• CPC Class Codes: C07C 11/167 1, 3-Butadiene

Abstract

This invention relates to a process for producing a high purity butene-1 product from n-butane via a dehydrogenation process. In one embodiment of the process the n-butane is dehydrogenated over a chromia-alumina catalyst and any butadiene formed hydrogenated to monoolefins. The monoolefins are separated and the butene-1 separated from isobutylene by reacting the isobutylene with methanol to form methyl tertiary butyl ether. The methyl tertiary butyl ether is separated from the butene-1 leaving it as a high purity product. Alternatively, the dehydrogenated product from the reactor may be contacted with a solvent to extract butadiene followed by hydrogenation, separation of monoolefins and conversion to methyl tertiary butyl ether.

Claims

1. A process for producing high purity butene-1 from an n-butane containing feedstock which comprises the steps:

(a) dehydrogenating a feed stock containing n-butane in the presence of a chromia-alumina catalyst thereby producing a reaction product containing butene-1, butene-2, isobutene, butadiene and by product heavies;

(b) hydrogenating the butadiene product produced to produce additional butene-1 and butene-2;

(c) fractionating the reaction product from the butadiene hydrogenation step to produce an overhead stream comprising butene-1 and isobutene and a bottoms fraction comprising n-butane, butene-2 and any other heavies;

(d) reacting the overhead fraction from step (c) containing isobutene and butene-1 with methanol to form methyl tertiary butyl ether;

(e) fractionating the methyl tertiary butyl ether from the reaction product in step (d) to produce a bottoms comprising methyl tertiary butyl ether and an overhead fraction comprising butene-1 and isobutane;

(f) separating the isobutane from the butene-1 and recycling the isobutane to dehydrogenation zone described in step (a).

2. The process of claim 1 wherein the feedstock comprises from about 60 to 100% n-butane and the balance comprising C₃ to C₅ hydrocarbon.

3. A process for producing butene-1 and butadiene from a feedstock containing n-butane which comprises the steps:

(a) dehydrogenating a feedstock containing n-butane in the presence of a chromia-alumina catalyst to produce a reaction product containing butene-1, butene-2, butadiene, and unreacted material;

(b) distilling the reaction product from step (a) in a distillation column separating butene-2 from butadiene and butene-1, the butene-2, being removed as a bottoms fraction and the butene-1 and butadiene as an overheads fraction;

(c) treating the bottoms fraction from the distillation column in a deoiler thereby removing butene-2 as an overhead fraction and any C₅ plus material as a bottoms fraction;

(d) separating the overhead fraction from the distillation column by contacting with a solvent selective for butadiene into a high purity butadiene product and a raffinate stream containing butene-1, isobutane, isobutene and a small portion of residual butadiene;

(e) passing the raffinate stream from the butadiene extraction through a hydrogenation zone thereby hydrogenating residual butadiene to form butene-1 and butene-2;

(f) fractionating the reaction product from the hydrogenation in step (e) generating an overhead containing butene-1, isobutane and isobutene;

(g) contacting the isobutene and butene-1 in the overhead from step (f) with methanol in a methyl tertiary butyl ether unit thereby forming methyl tertiary butyl ether;

(h) fractionating the reaction product from the methyl tertiary butyl ether unit separating methyl tertiary butyl ether from the reaction product; and

(i) fractionating the overhead fraction containing butene-1 and isobutane thereby producing an overhead containing isobutane for recycle to the dehydrogenation zone and a high purity butene-1 as a bottoms fraction.

4. A process for producing butene-1 from a feedstock containing n-butane and other C₂ to C₆ hydrocarbons which comprises the steps:

(a) dehydrogenating a feedstock containing n-butane in the presence of a chromia-alumina catalyst to produce reaction product containing butene-1, butene-2, butadiene, and unreacted materials;

(b) hydrogenating the butadiene product produced in the dehydrogenation step to produce additional butene-1 and butene-2;

(c) fractionating the reaction product from the butadiene hydrogenation step to produce an overhead stream comprising butene-1, butene-2, and isobutene and a bottoms fraction containing C₅ plus hydrocarbons;

(d) contacting the overhead stream from the fractionation of step (c) with a solvent selective for extracting butene-1 from butene-2 and saturated hydrocarbons;

(e) separating the butene-2 from the saturates by fractionation;

(f) isomerizing the butene-2 from the butene-1 extraction by contact with an isomerization catalyst and recycling the isomerization reaction product to the feed to the deoiler in step (c);

(g) contacting the butene-1 from the extraction in step (d) with methanol to convert the isobutylene to methyl tertiary butyl ether thereby generating a reaction product containing said ether and unreacted butene-1;

(h) fractionating the methyl tertiary butyl ether from the reaction product in step (g) to produce a bottoms comprising methyl tertiary butyl ether and an overhead fraction comprising butene-1; and

then

(i) recovering said butene-1 and methyl tertiary butyl ether.