Optimized inert gas partial pressure in a gas phase polymerization process

Patent metadata

Field	Value
Publication number	US-11618793-B2
Application number	US-202117444094-A
Country	US
Kind code	B2
Filing date	Jul 30, 2021
Priority date	Aug 27, 2020
Publication date	Apr 4, 2023
Grant date	Apr 4, 2023

Abstract

Gas phase polymerization processes include contacting an input stream comprising a monomer and an induced condensing agent in the presence of an inert gas with a catalyst in a fluidized bed reactor to produce a polymer, unreacted monomer, and an output gas; recycling a recycle stream of the unreacted monomer from the reactor to the input stream; venting at least a portion of the output gas from the reactor; and maintaining a partial pressure of the inert gas in the reactor above a reference inert gas pressure to decrease losses of the recycle stream with the vented output gas. The processes may include controlling the inert gas partial pressure to vary the total reactor pressure up to the maximum safe pressure, without causing carry-over of product polymer.

First claim

What is claimed is:

1. A gas phase polymerization process, comprising:
contacting an input stream comprising a monomer and an induced condensing agent in the presence of an inert gas with a catalyst in a fluidized bed reactor to produce a polymer, unreacted monomer, and an output gas;
recycling a recycle stream of the unreacted monomer from the reactor to the input stream;
venting at least a portion of the output gas from the reactor; and
maintaining a partial pressure of the inert gas in the reactor above a reference inert gas pressure to decrease losses of the recycle stream with the vented output gas.

2. The gas phase polymerization process of claim 1 , further comprising maintaining a total reactor pressure above a reference total reactor pressure.

3. The gas phase polymerization process of claim 1 , further comprising maintaining a partial pressure of the monomer in the reactor at a reference monomer pressure and maintaining a partial pressure of the induced condensing agent in the reactor at a reference induced condensing agent pressure.

4. The gas phase polymerization process of claim 2 , wherein maintaining the total reactor pressure comprises controlling the venting of at least some of the output gas from the reactor.

5. The gas phase polymerization process of claim 1 , wherein the venting comprises passing the produced polymer, at least a portion of the unreacted monomer, at least a portion of the induced condensing agent, and at least a portion of the output gas to a product discharge system.

6. The gas phase polymerization process of claim 1 , where the venting comprises stripping the unreacted monomer from at least a portion of the output gas in a stripping column.

7. The gas phase polymerization process of claim 1 , wherein the venting comprises directly venting at least a portion of the output gas from the reactor.

8. The gas phase polymerization process of claim 2 , wherein the total reactor pressure is up to a maximum safe pressure for the reactor.

9. The gas phase polymerization process of claim 8 , wherein the maximum safe pressure is less than the rated pressure for the reactor.

10. The gas phase polymerization process of claim 9 , further comprising activating a relief device when the total reactor pressure exceeds the rated pressure.

11. The gas phase polymerization process of claim 1 , wherein the process is a polyolefin polymerization process wherein the monomer comprises an olefin and the polymer comprises a polyolefin.

12. The gas phase polymerization process of claim 1 , wherein the process is a polyethylene polymerization process, wherein the olefin comprises ethylene and the polymer comprises polyethylene or a polyethylene copolymer.

13. The gas phase polymerization process of claim 1 , wherein the inert gas is nitrogen.

14. The gas phase polymerization process of claim 1 , wherein the monomer comprises at least one of ethylene, 1-butene, 1-hexene, or combinations thereof.

15. The gas phase polymerization process of claim 1 , wherein the induced condensing agent comprises at least one of isobutene, isopentane, or combinations thereof.

16. The gas phase polymerization process of claim 1 , wherein the catalyst comprises at least one of a Ziegler-Natta catalyst, a metallocene catalyst, a chromium catalyst, or combinations thereof.

17. A gas phase polyethylene polymerization process, comprising:
contacting an input stream comprising ethylene and an induced condensing agent in the presence of nitrogen with a Ziegler-Natta, metallocene, or chromium catalyst in a reactor to form (i) a polyethylene homopolymer or copolymer, (ii) unreacted ethylene, and (iii) an output gas;
recycling a recycle stream of the unreacted ethylene from the reactor to the input stream;
venting at least a portion of the output gas from the reactor; and
maintaining a partial pressure of the nitrogen in the reactor above a reference nitrogen partial pressure to decrease losses of the recycle stream with the vented output gas.

18. The gas phase polymerization process of claim 17 , further comprising maintaining a partial pressure of the ethylene in the reactor at a reference ethylene pressure and maintaining a partial pressure of the induced condensing agent in the reactor at a reference induced condensing agent pressure.

19. The gas phase polymerization process of claim 17 , further comprising maintaining a total reactor pressure above a reference total reactor pressure.

20. A gas phase polyolefin polymerization process, comprising:
contacting an input stream comprising an olefin monomer and an induced condensing agent in the presence of nitrogen with a Ziegler-Natta, metallocene, or chromium catalyst in a reactor to form a polyolefin, unreacted olefin, and output gas;
recycling a recycle stream of the unreacted olefin monomer from the reactor to the input stream;
venting at least a portion of the output gas from the reactor;
maintaining a partial pressure of the nitrogen in the reactor above a reference inert gas pressure to decrease losses of the recycle stream with the vented output gas; and
maintaining a total reactor pressure above a reference total reactor pressure, while maintaining a partial pressure of the olefin monomer in the reactor at a reference olefin monomer pressure and maintaining a partial pressure of the induced condensing agent in the reactor at a reference induced condensing agent pressure.

Assignees

• Exxonmobil Chemical Patents Inc

Inventors

• Lucas Michael D
• Bernard-Brunel Anne
• Impelman Ryan W
• Beh Keng-Hua
• Singh Sr Diwaker
• Chong Rui Hoong
• Brandl Corrine L
• Sotomayor Luis A

Classifications

• C08F210/16

  Copolymers of ethene with alpha-alkenes, e.g. EP rubbers · CPC title

• B01J8/1809

  Controlling processes · CPC title

• C08F210/02 Primary

  Ethene · CPC title

• C08F2/34 Primary

  Polymerisation in gaseous state · CPC title

• B01J2208/00539

  Pressure · CPC title