Vacuum swing adsorption process for separating propylene from propane

• US 6,296,688 B1
• Filed: 11/30/1999
• Issued: 10/02/2001
• Est. Priority Date: 11/30/1999
• Status: Expired due to Fees

• Current Assignee: UOP Llc (Honeywell International Inc.)
• Original Assignee: UOP Llc (Honeywell International Inc.)
• Inventors: Wilson, Stephen T., Cheng, Linda S.
• Primary Examiner(s): Spitzer, Robert H.
• Application Number:
  US09/449,656
• Time in Patent Office: 672 Days
• Field of Search: 95/96--07, 951/10, 951/11, 951/44, 959/00, 959/02
• US Class Current: 95/101
• CPC Class Codes: B01D 2253/104 Alumina
• CPC Class Codes: B01D 2253/304 Linear dimensions, e.g. particle shape, diameter
• CPC Class Codes: B01D 2256/24 Hydrocarbons
• CPC Class Codes: B01D 2259/40052 Recycled product or process gas
• CPC Class Codes: B01D 2259/404 using four beds
• CPC Class Codes: B01D 2259/4068 using more than ten beds
• CPC Class Codes: B01D 53/0476 Vacuum pressure swing adsorption
• CPC Class Codes: B01J 20/0248 Compounds of B, Al, Ga, In, Tl B01J20/08 takes precedence
• CPC Class Codes: B01J 20/0292 Phosphates of compounds other than those provided for in B01J20/048
• CPC Class Codes: Y10S 95/902 Molecular sieve

Abstract

A vacuum swing adsorption process is provided for the separation of propylene from a feedstream comprising propylene and propane using an adsorbent comprising AlPO-14 to produce a high purity propylene product stream at high recovery. The vacuum swing adsorption process of the present invention can be employed in a variety of petroleum refining and petrochemical processes to purify and separate propylene from mixtures of propylene and propane alone or in combination with fractionation.

Claims

1. A vacuum swing adsorption process For the separation of propylene from a feedstream comprising propylene and propane to produce a high purity propylene product, said process comprising:

a) passing the feedstream at effective adsorption conditions in an adsorption step to a first adsorption bed of a plurality of adsorption beds, each of said adsorption beds containing a selective adsorbent comprising AlPO-14 to produce a raffinate stream, comprising propane;

b) terminating the passing of the feedstream to the first adsorption bed and co-currently purging the first adsorption bed at a co-purge pressure essentially equal to an adsorption pressure with a recycle stream to provide a purge gas stream comprising propane;

c) co-currently venting the first adsorption bed to a vent pressure and withdrawing a vent stream;

d) co-currently depressurizing the first adsorption bed to a provide-purge pressure lower than the vent pressure to produce a provide-purge gas and passing the provide-purge gas to another adsorption bed;

e) further co-currently depressurizing the first adsorption bed in a first equalization step to an equalization pressure lower than the provide-purge pressure to produce an equalization gas and passing the equalization gas to another adsorption bed;

f) counter-currently depressurizing the first adsorption bed in an evacuation step to a desorption pressure to provide a first desorption stream comprising propylene;

g) counter-currently purging the first adsorption bed with a vacuum purge gas stream from another adsorption bed to produce a second desorption stream comprising propylene;

h) counter-currently repressurizing the first adsorption bed in a second equalization step to about the equalization pressure;

i) further counter-currently repressurizing the first adsorption bed to about the adsorption pressure with at least a portion of the raffinate stream;

j) compressing the first desorption stream and the second desorption stream to provide the high purity propylene product;

k) recycling at least a portion of the high purity propylene product to provide the recycle stream; and

l) repeating steps (a) to (k) for each of the adsorption beds to provide a continuous process.

2. The vacuum swing adsorption process of claim 1 wherein the effective adsorption conditions include a propylene partial pressure comprising between about 0.5 and about 4 bar.

3. The vacuum swing adsorption process of claim 1 wherein the effective adsorption conditions include an adsorption temperature less than 120°

C.

4. The vacuum swing adsorption process of claim 1 wherein the desorption pressure comprises between about 0.01 and about 0.5 bar.

5. The vacuum swing adsorption process of claim 1 wherein the vacuum purge gas comprises the provide-purge gas.

6. The vacuum swing adsorption process of claim 1 wherein the high purity propylene product comprises at least 95 mol-% propylene.

7. The vacuum swing adsorption process of claim 1 wherein a ratio of the propylene recovered to the propylene in the feedstream is greater than about 80%.

8. The vacuum swing adsorption process of claim 1 wherein the plurality of adsorption beds comprises at least 4 adsorption beds.

9. The vacuum swing adsorption process of claim 1 wherein the plurality of adsorption beds comprises from 4 to 12 adsorption beds.