Low temperature process for separating hydrocarbons

• US 4,455,444 A
• Filed: 11/12/1982
• Issued: 06/19/1984
• Est. Priority Date: 07/30/1981
• Status: Expired due to Fees

• Current Assignee: UOP Des Plaines IL A NY General Partnership
• Original Assignee: UOP Llc (Honeywell International Inc.)
• Inventors: Kulprathipanja, Santi, Neuzil, Richard W.
• Primary Examiner(s): Gantz, Delbert E.
• Assistant Examiner(s): Pal, A.
• Application Number:
  US06/441,142
• Time in Patent Office: 585 Days
• Field of Search: 585/826, 585/827, 585/828, 208/310 Z, 208/310 R
• US Class Current: 585/826
• CPC Class Codes: C07C 7/13 by molecular-sieve technique
• CPC Class Codes: C07C 9/00 Aliphatic saturated hydrocarbons
• CPC Class Codes: C10G 25/003 Specific sorbent material, not covered by C10G25/02 or C10G25/03

Abstract

A process for separating a normal paraffin hydrocarbon from a mixture of the same with a cyclic and/or branched chain paraffin hydrocarbon. The process comprises contacting the mixture at a temperature of from about 120° C. to about 140° C. with a zeolite free molecular sieve comprising silicalite. The normal paraffin hydrocarbon is selectively retained and will preferably be recovered from the molecular sieve by displacement with a displacement material.

Claims

1. A process for separating a normal C₁₇ or lighter paraffin hydrocarbon from a mixture of the same with another structural class of hydrocarbon selected from cyclic hydrocarbons other than benzene and branched chain paraffin hydrocarbons, which comprises contacting said mixture at a temperature of from about 120°

C. to about 140°

C. with zeolite free molecular sieve comprising silicalite to effect the selective retention of said normal hydrocarbon by said molecular sieve.

2. The process of claim 1 wherein said normal paraffin hydrocarbon is recovered by displacement with a displacement material at a temperature of from about 120°

C. to about 140°

C. and a pressure sufficient to maintain liquid phase.

3. The process of claim 2 wherein said displacement material comprises a normal hydrocarbon having a boilinq point at least about 5°

C. different than the boiling point of the normal hydrocarbon being separated.

4. The process of claim 3 wherein said displacement material comprises a mixture of iso-octane and normal hydrocarbon.

5. The process of claim 4 wherein said displacement material comprises a mixture of iso-octane and normal olefin.

6. The process of claim 1 wherein said contacting occurs at a pressure sufficient to maintain liquid phase.

7. A process for separating a normal paraffin hydrocarbon from a mixture of the same with a cyclic hydrocarbon other than the benzene, or branched chain paraffin hydrocarbon, which process employs a zeolite free molecular sieve comprising silicalite, which process comprises the steps of:

(a) maintaining net fluid flow through a column of said molecular sieve in a single direction, which column contains at least three zones having separate operational functions occurring therein and being serially interconnected with the terminal zones of said column connected to provide a continuous connection of said zones;

(b) maintaining a retention zone in said column, said zone defined by the molecular sieve located between a feed input stream at an upstream boundary of said zone and a raffinate output stream at a downstream boundary of said zone;

(c) maintaining a purification zone immediately upstream from said retention zone, said purification zone defined by the molecular sieve located between an extract output stream at an upstream boundary of said purification zone and said feed input stream at a downstream boundary of said purification zone;

(d) maintaining a displacement zone immediately upstream from said purification zone, said displacement zone defined by the molecular sieve located between a desorbent input stream at an upstream boundary of said zone and said extract output stream at a downstream boundary of said zone;

(e) passing said feed mixture into said retention zone at a temperature of from about 120°

C. to about 140°

C. and a pressure sufficient to maintain liquid phase to effect the selective retention of said normal paraffin hydrocarbon by said molecular sieve in said retention zone and withdrawing a raffinate output stream from said retention zone;

(f) passing a displacement material into said displacement zone at a temperature of from about 120°

C. to about 140°

C. and a pressure sufficient to maintain liquid phase to effect the displacement of said normal hydrocarbon from the molecular sieve in said displacement zone;

(g) withdrawing an extract output stream comprising said normal paraffin hydrocarbon and displacement material from said displacement zone;

(h) withdrawing a raffinate output stream comprising said branched chain paraffin hydrocarbon or cyclic hydrocarbons from said displacement zone; and

(i) periodically advancing through said column of molecular sieve in a downstream direction with respect to a fluid flow in said retention zone the feed input stream, raffinate output stream, displacement fluid input stream, and extract output stream to effect the shifting of zones through said molecular sieve and the production of extract output and raffinate output streams.

8. The process of claim 7 wherein said displacement material comprises a hydrocarbon or mixture of hydrocarbons having a boiling point at least about 5°

C. different than the boiling point of the C₆ hydrocarbon being separated.

9. The process of claim 8 wherein said displacement material comprises a mixture of iso-octane and normal hydrocarbon.

10. The process of claim 9 wherein said displacement material comprises a mixture of iso-octane and normal olefin.

11. The process of claim 7 further characterized in that it includes the step of maintaining a buffer zone immediately upstream from said displacement zone, said buffer zone defined as the molecular sieve located between the displacement fluid input stream at a downstream boundary of said buffer zone and a raffinate output stream at an upstream boundary of said buffer zone.