Gasoline production by olefin polymerization

Abstract

A process unit for the zeolite-catalyzed conversion of light refinery olefins from an FCC unit such as ethylene, propylene, and butylene to gasoline boiling range motor fuels comprises at least two sequential, serially connected reactors connected in parallel to a fractionation section with at one or two fractionators for separating the reactor effluents into product fraction with an optional recycle stream or streams. The configurations according to this scheme allow the adjustment of reactor temperature and/or pressure and/or space velocity to be based on the reactivities of the olefin compounds present in the LPG streams so that the gasoline produced in each reactor will be separated immediately, to reduce over-polymerization of the gasoline in the low severity reactor and to ensure that gasoline formed in the low severity reactor will not be sent to the higher severity reactor e.g. with a higher reactor temperature, where excessive polymerization to undesirable higher molecular with products may take place.

Description

DRAWINGS

FIG. 1 shows a process schematic for an olefin polymerization unit for converting light refinery olefins to motor gasoline with two serially connected reactors and a fractionation section comprising a common fractionator.

FIG. 2 shows a process schematic for an olefin polymerization unit for converting light refinery olefins to motor gasoline with two serially connected reactors and a fractionation section comprising a common fractionator which supplies recycle to the first reactor.

FIG. 3 shows a process schematic for an olefin polymerization unit for converting light refinery olefins to motor gasoline with two serially connected reactors and a fractionation section comprising two fractionators.

FIG. 4 shows a process schematic for an olefin polymerization unit for converting light refinery olefins to motor gasoline with two serially connected reactors and a fractionation section comprising two fractionators with the second fractionator supplying recycle to the second reactor.

FIG. 5 shows a process schematic for an olefin polymerization unit for converting light refinery olefins to motor gasoline with two serially connected reactors and a fractionation section comprising two fractionators, each supplying recycle to its own associated reactor.

Claims

1. A process unit for the conversion of FCC refinery gas feed stream containing light C3-C4 olefins into a gasoline boiling range product which comprises: at least two reactors each containing a fixed bed of a solid, porous, molecular sieve olefin polymerization catalyst, each reactor having a feed inlet and an effluent outlet, the reactors being serially connected for sequential flow of the olefin feed from one reactor to the next,a fractionation section connected to the effluent outlets of each reactor to receive the effluent from each reactor.

2. A process unit according to claim 1 in which the molecular sieve olefin polymerization catalyst material comprises a zeolite.

3. A process unit according to claim 2 in which the molecular sieve olefin polymerization catalyst comprises a zeolite of the MWW family.

4. A process unit according to claim 1 in which the olefin condensation catalyst comprises a zeolite of the MCM-22 family.

5. A process unit according to claim 4 in which the olefin condensation catalyst comprises a regenerated catalyst.

6. A process unit according to claim 1 which comprises a first stage reactor having a feed inlet and an effluent outlet connected to the inlet of a first fractionator which is in the fractionation section and which has a feed inlet, a heavy fraction outlet and a light fraction outlet which is connected to the feed inlet of a second stage reactor having a feed inlet and an effluent outlet which is connected to the feed inlet of the first fractionator.

7. A process unit according to claim 6 which includes a recycle conduit connected to the light fraction outlet of the first fractionator and to the feed inlet of the first stage reactor for passing light fraction from the first fractionator as recycle to the first stage reactor.

8. A process unit according to claim 1 which comprises a first stage reactor having a feed inlet and an effluent outlet connected to the inlet of a first fractionator which is in the fractionation section and has a feed inlet, a heavy fraction outlet and a light fraction outlet which is connected to the feed inlet of a second stage reactor having a feed inlet and an effluent outlet which is connected to the feed inlet of a second fractionator in the fractionation section.

9. A process unit according to claim 8 which includes a recycle conduit connected to the light fraction outlet of the second fractionator and to the feed inlet of the second stage reactor for passing light fraction from the second fractionator as recycle to the second stage reactor.

10. A process unit according to claim 9 which includes a recycle conduit connected to the light fraction outlet of the first fractionator and to the feed inlet of the first stage reactor for passing light fraction from the first fractionator as recycle to the first stage reactor.

11. A process for the conversion of an FCC light gas stream containing light C3-C4 olefins into a gasoline boiling range product which comprises: feeding the light gas stream containing the light olefins into the feed inlet of a first reactor containing a fixed bed of a solid, porous molecular sieve olefin polymerization catalyst to polymerize the olefins in the feed under a first set of reaction conditions to form an effluent comprising polymerized product in the gasoline boiling range formed from the light olefins,passing the first stage reactor effluent to a feed inlet of a fractionation section and fractionating the first stage effluent stream to form a heavy fraction comprising gasoline boiling range product and a light fraction comprising unreacted olefins, passing light fraction from the fractionation section to the feed inlet of a second stage reactor containing a fixed bed of a solid, porous molecular sieve olefin polymerization catalyst to polymerize the olefins in the feed under a second set of reaction conditions which are more severe than those of the first set to form a second stage reactor effluent comprising polymerized product in the gasoline boiling range formed from the unreacted light olefins, passing the second stage reactor effluent to a feed inlet of the fractionation section;fractionating the second stage reactor effluent in the fractionation section to form a heavy fraction comprising gasoline boiling range product and a light fraction comprising unreacted olefins.

12. A process according to claim 11 in which light fraction from the fractionation section is recycled to the feed inlet of the first stage reactor.

13. A process according to claim 11 in which the fractionation section comprises a first fractionator and a second fractionator and light fraction is fed from the first fractionator to the feed inlet of the second stage reactor and the second stage reactor effluent is fed to a feed inlet of the second fractionator to form the heavy fraction comprising gasoline boiling range product and the light fraction.

14. A process according to claim 13 in which light fraction from the second fractionator is recycled to the feed inlet of the second stage reactor.

15. A process according to claim 14 in which light fraction from the first fractionator is recycled to the feed inlet of the first stage reactor and light fraction from the second fractionator is recycled to the second stage reactor.

16. A process according to claim 11 in which the molecular sieve olefin polymerization catalyst material comprises a zeolite.

17. A process according to claim 16 in which the molecular sieve olefin polymerization catalyst comprises a zeolite of the MWW family.

18. A process according to claim 17 in which the olefin condensation catalyst comprises a zeolite of the MCM-22 family.

19. A process according to claim 18 in which the olefin condensation catalyst comprises a regenerated MCM-22 catalyst.

20. A process according to claim 11 in which the first stage polymerization is carried out at a temperature from 150° to 200° C., a pressure up to 3500 kPag and a space velocity of 5 to 30 hr−1 WHSV and the second stage under conditions of relatively higher severity.