Process for separating propylene from propane

• US 6,293,999 B1
• Filed: 11/30/1999
• Issued: 09/25/2001
• 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: Cheng, Linda S., Wilson, Stephen T.
• Primary Examiner(s): Spitzer, Robert H.
• Application Number:
  US09/451,567
• Time in Patent Office: 665 Days
• Field of Search: 95/96--07, 951/10, 951/11, 951/44, 959/00, 959/02
• US Class Current: 95/96
• CPC Class Codes: B01D 2253/108 Zeolites
• CPC Class Codes: B01D 2253/116 Molecular sieves other than zeolites
• CPC Class Codes: B01D 2253/25 Coated, impregnated or composite adsorbents
• CPC Class Codes: B01D 2253/308 Pore size
• CPC Class Codes: B01D 2256/24 Hydrocarbons
• CPC Class Codes: B01D 2257/7022 Aliphatic hydrocarbons
• CPC Class Codes: B01D 2259/4003 with two sub-steps
• CPC Class Codes: B01D 2259/40052 Recycled product or process gas
• CPC Class Codes: B01D 2259/40064 Five
• CPC Class Codes: B01D 2259/40079 Co-current
• CPC Class Codes: B01D 2259/40081 Counter-current
• CPC Class Codes: B01D 2259/4009 using hot gas
• CPC Class Codes: B01D 2259/404 using four beds
• CPC Class Codes: B01D 2259/41 using plural beds of the same adsorbent in series
• CPC Class Codes: B01D 53/0462 Temperature swing adsorption
• CPC Class Codes: B01D 53/047 Pressure swing adsorption
• CPC Class Codes: B01D 53/0476 Vacuum pressure swing adsorption
• CPC Class Codes: Y10S 95/902 Molecular sieve

Abstract

A process is provided for the concentration and recovery of propylene from propane using an adsorbent comprising AlPO-14 at adsorption temperatures less than 120° C. and an adsorption pressure comprising a propylene partial pressure between about 0.5 bar and about 4 bar. The AlPO-14 adsorbent can be employed as a selective adsorbent for the separation of propylene from mixtures thereof with propane in vacuum swing adsorption processes, thermal swing adsorption processes, and combinations thereof. A simulated moving bed process using vacuum swing adsorption is used to remove propylene from a C₃ hydrocarbon stream comprising propylene and propane and recover a high purity propylene product at a high recovery rate. The simulated moving bed 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 process for adsorptive separation of propylene from a feedstream comprising propylene and propane, said process comprising:

a) passing the feedstreani at an effective sorption temperature less than 120°

C. and a sorption pressure to a sorption zone wherein said sorption zone comprises AlPO-14, to adsorb at least a portion of the propylene and withdrawing an unadsorbed stream comprising propane; and

b) desorbing at least a portion of the propylene from the sorption zone and withdrawing a desorbed stream.

2. The process of claim 1 wherein step (b) comprises reducing pressure of the sorption zones.

3. The process of claim 1 wherein step (b) comprises a combination of reducing pressure and heating of the sorption zone.

4. The process of claim 1 wherein step (b) comprises heating of the sorption zone.

5. The process of claim 1 wherein the sorption zone is selected from the group consisting of a pressure swing adsorption, vacuum swing adsorption, and temperature swing adsorption.

6. The process of claim 1 wherein the sorption zone is selected from the group consisting of temperature swing adsorption, pressure swing adsorption, vacuum swing adsorption, and combinations thereof.

7. The process of claim 1 wherein the effective sorption temperature ranges between about 25°

C. and 120°

C. and the sorption pressure comprises a propylene partial pressure between about 0.5 bar and about 4 bar.

8. The process of claim 1 wherein the effective sorption temperature ranges between about 70°

C. and about 100°

C. and the sorption pressure comprises a propylene partial pressure between about 0.5 bar and about 2 bar.

9. The process of claim 1 wherein step (b) comprises depressutizing the sorption zone to an effective desorption pressure comprising a propylene partial pressure between about 0.01 bar and about 0.5 bar.

10. A simulatedmoving bed process for the purification of propylene from a feedstream comprising propane and propylene, said process comprising:

a) introducing a feedstream and a first co-purge effluent stream at an effective adsorption pressure and adsorption temperature to a first adsorption bed of a plurality of at least tour adsorption beds containing an AlPO-14 small pore aluminophosphate adsorbent for the selective adsorption of propylene, said first co-purge effluent stream being withdrawn from a second adsorption bed and withdrawing a raffinate stream comprising propane from the first adsorption bed;

b) co-purging a second adsorption bed with a second co-purge effluent stream withdrawn from a third adsorption bed and withdrawing the first co-purge effluent stream;

c) co-purging the third adsorption bed with a compressed recycle stream and withdrawing the second co-purge effluent stream;

d) isolating and counter-currently depressurizing a fourth adsorption bed to an effective desorption pressure in an evacuation step to recover a propylene product stream;

e) recompressing at least a portion of the propylene product stream to provide the compressed recycle stream,

f) counter-currently repressurizing the fourth adsorption bed with at least a portion of the raffmate stream to provide a repressurized fourth adsorption bed; and

g) advancing the fcedstream to the repressurized fourth adsorption bed and switching the positions among said plurality of adsorption beds such that each of said adsorption beds effectively advances by one adsorption bed with respect to the first adsorption bed to provide a continuous process.

11. The simulated moving bed process of claim 10 wherein the propylene product stream comprises greater than about 95 mol-% propylene and is recovered at a recovery comprising greater than about 85%.

12. The simulated moving bed process of claim 10 wherein the adsorption temperature comprises less than 120°

C. and the adsorption pressure comprises a propylene partial pressure between about 0.5 and about 4 bar.

13. The simulated moving bed process of claim 10 wherein the adsorption temperature comprises between 25°

C. and 120°

C. and the adsorption pressure comprises a propylene partial pressure between about 0.5 and about 4 bar.

14. The simulated moving bed process of claim 10 wherein the adsorption temperature comprises less than 100°

C. and the adsorption pressure comprises a propylene partial pressure between about 0.5 and about 4 bar.

15. The simulated moving bed process of claim 10 wherein the desorption pressure comprises a propylene partial pressure between about 0.01 bar and about 0.5 bar.