High condensing mode polyolefin production under turbulent conditions in a fluidized bed

• US 6,391,985 B1
• Filed: 10/21/1999
• Issued: 05/21/2002
• Est. Priority Date: 10/21/1999
• Status: Expired due to Term

• Current Assignee: Union Carbide Corporation (Dow, Inc.)
• Original Assignee: Union Carbide Chemicals & Plastics Technology Corporation (Dow, Inc.)
• Inventors: Blood, Mark Williams, Goode, Mark Gregory, Sheard, William George
• Primary Examiner(s): Wu, David W.
• Assistant Examiner(s): CHEUNG, WILLIAM K
• Application Number:
  US09/422,458
• Time in Patent Office: 943 Days
• Field of Search: 526/59, 526/61, 526/70, 526/68, 526/72, 526/351, 526/352, 526/348
• US Class Current: 526/70
• CPC Class Codes: B01J 2208/00584 Controlling the density
• CPC Class Codes: B01J 8/003 in a downward flow
• CPC Class Codes: B01J 8/1809 Controlling processes
• CPC Class Codes: C08F 10/00 Homopolymers and copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
• CPC Class Codes: C08F 110/02 Ethene
• CPC Class Codes: C08F 110/06 Propene
• CPC Class Codes: C08F 2/34 Polymerisation in gaseous state
• CPC Class Codes: C08F 210/06 Propene
• CPC Class Codes: C08F 210/08 Butenes
• CPC Class Codes: C08F 210/16 Copolymers of ethene with alpha-alkenes, e.g. EP rubbers
• CPC Class Codes: C08F 2500/08 Low density, i.e. < 0.91 g/cm3
• CPC Class Codes: C08F 2500/18 Bulk density

Abstract

A fluidized bed olefin polymerization process is operated in the turbulent regime while utilizing greater than 17.5% liquid in the recycle fluid to remove the heat of reaction. The ratio of fluidized bed density to settled bed density may, contrary to prior art predelictions, be maintained at lower than 0.59.

Claims

1. Method of achieving a high level of liquid in recycle fluid in the operation of a fluidized bed olefin polymerization reactor comprising adjusting conditions in said reactor to pass from a bubbling operating mode with a condensing liquid level in said recycle fluid of less than 17.5 weight percent to a turbulent operating mode, and increasing the liquid level in said recycle fluid to at least 17.5 weight percent.

2. Method of claim 1 wherein said adjusting of conditions includes adjusting the superficial gas velocity to at least 1.01 times U_c.

3. Method of claim 2 wherein said adjusting of conditions includes adjusting the superficial gas velocity to at least 1.1 times U_c.

4. Method of claim 1 wherein said liquid level in said recycle fluid is increased to at least 17.5 weight percent after achieving said turbulent operating mode.

5. Method of claim 1 wherein the olefin polymerized in said reactor comprises ethylene.

6. Method of claim 1 wherein the olefin polymerized in said reactor comprises propylene.

7. Method of claim 1 wherein the liquid recycled includes hydrocarbons having molecular weights between 42 and 100.

8. Method of claim 1 wherein the recycled liquid includes hydrocarbons having molecular weights between 42 and 60.

9. Method of claim 1 wherein said liquid level is increased to at least 20%.

10. Method of claim 1 wherein said liquid level is increased to at least 25%.

11. Method of claim 1 wherein said liquid level is increased to 30-90%.

12. Method of conducting an exothermic olefin polymerization reaction in a fluidized bed comprising maintaining turbulent conditions therein while removing the heat of reaction by recycling fluid from said fluidized bed, said recycled fluid containing at least 17.5% liquid after cooling and condensing.

13. Method of claim 12 wherein said turbulent conditions include a superficial gas velocity between 1.01×

U_c and U_k.

14. Method of claim 12 wherein said turbulent conditions include a superficial gas velocity between 1.1×

U_c and 0.9×

U_k.

15. Method of claim 12 wherein said turbulent conditions include a ratio of fluidized bulk density to settled bulk density (FBD/SBD) of less than 0.59.

16. Method of claim 12 wherein the level of liquid in said recycled fluid is greater than 20 weight percent based on the total weight of said recycled fluid.

17. Method of claim 12 wherein the level of liquid in said recycled fluid is in the range of about 30 to 90 weight percent liquid based on the total weight of said recycled fluid.

18. Method of claim 12 wherein said recycled fluid includes about 1 to 90 mole percent of a condensing agent selected from the group consisting of propane, butane, isobutane, pentane, isopentane, hexane, heptane, octane and mixtures thereof.

19. A process for polymerizing alpha-olefins in a gas phase reactor having a fluidized bed and a fluidizing medium wherein the fluidizing medium serves to control the cooling capacity of said reactor, the process comprising employing in the fluidizing medium a level of liquid entering the reactor which is greater than 17.4 weight percent based on the total weight of the fluidizing medium and wherein the superficial gas velocity is at least at the velocity of transition from the bubbling regime to turbulent fluidization and is below the transport velocity, and the ratio of the resin fluidized bulk density to the settled bulk density is less than 0.59.

20. Process of claim 19 wherein the ratio of fluidized bulk density to settled bulk density is from 0.4 to 0.58.