Process for monomer recovery from a polymerization process

• US 8,636,831 B2
• Filed: 01/16/2009
• Issued: 01/28/2014
• Est. Priority Date: 01/18/2008
• Status: Active Grant

• Current Assignee: Total Petrochemicals Research Feluy (Totalenergies Se)
• Original Assignee: Total Petrochemicals Research Feluy (Totalenergies Se)
• Inventors: Damme, Eric, Van Der Schrick, Bernard
• Primary Examiner(s): Wu, David W
• Assistant Examiner(s): Eng, Elizabeth
• Application Number:
  US12/811,848
• Publication Number:
  US 20110046323A1
• Time in Patent Office: 1,838 Days
• Field of Search: None
• US Class Current: 95/186
• 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 210/16 Copolymers of ethene with alpha-alkenes, e.g. EP rubbers
• CPC Class Codes: C08F 6/001 Removal of residual monomers by physical means
• CPC Class Codes: C08J 11/02 of solvents, plasticisers or unreacted monomers
• CPC Class Codes: C08J 2323/02 not modified by chemical after treatment
• CPC Class Codes: C08L 23/00 Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers

Abstract

The present relates to a process for optimizing the recovery of unreacted monomers from a polymerization process, wherein said process comprises the steps of

• • recovering a fluid stream generated by the separation of the polyolefin product from the polymerization fluid comprising unreacted monomers and optionally comonomers;
  • contacting said fluid stream in an absorption zone with a scrub liquid comprising at least one C_4-10 hydrocarbons, thereby absorbing at least a portion of the unreacted monomers in said scrub liquid; and
  • withdrawing from said absorption zone (i) a vapor overhead comprising light gas and (ii) an absorber bottoms scrub liquid comprising said C_4-10 hydrocarbons and said unreacted monomer; thereby recovering said unreacted monomer in said absorber bottoms scrub liquid comprising said C_4-10 hydrocarbons.

The present invention also concerns a process for the recovery of unreacted monomers from a gas phase or slurry polymerization process, and also concerns a process for the production of polyolefins.

Claims

1. A process for the recovery of unreacted monomers from a slurry polymerization process comprising:

(a) recovering a fluid stream from a polymer slurry comprising essentially liquid diluent, unreacted monomer, comonomers and solid polyolefin particles, by separating at least a majority of the diluent and unreacted monomer and comonomers from said polyolefin solid particles;

(b) distilling said fluid stream, and withdrawing from said distillation a bottom stream comprising C_4-10 hydrocarbons, and an overhead stream comprising unreacted monomer and diluent;

(c) distilling said overhead stream and withdrawing (i) a bottom stream comprising substantially olefin-free hydrocarbon diluent, optionally a side stream comprising hydrocarbon diluent, and (ii) an overhead vapor stream comprising unreacted monomer and light gas;

(d) contacting said removed overhead vapor stream in a gas-liquid absorption zone with a scrub liquid comprising at least one C_4-10 hydrocarbons, thereby absorbing at least a portion of the unreacted monomers in said scrub liquid; and

(e) withdrawing from said absorption zone (i) a vapor overhead and (ii) an absorber bottoms scrub liquid comprising said C_4-10 hydrocarbons and said unreacted monomer, wherein the bottom stream of step (b) comprising C_4-10 hydrocarbons, is combined with makeup scrub liquid and cooled to provide said scrub liquid feed to said gas-liquid absorption zone.

2. The process of claim 1, wherein said absorber bottoms scrub liquid is recycled to the polymerization reaction.

3. The process of claim 1, wherein said overhead vapor stream of step (c) comprising unreacted monomer and light gas is compressed and cooled prior to treatment in said gas-liquid absorption zone.

4. The process of claim 1, wherein said unreacted monomer is recovered from said absorber bottoms scrub liquid by first flashing to a reduced pressure said absorber bottoms scrub liquid, and separating the resulting flashed stream into a vapor containing the unreacted monomer and a liquid comprising said C_4-10 hydrocarbons.

5. The process of claim 4, wherein said vapor containing the unreacted monomer is compressed and recycled to said polymerization process.

6. The process of claim 4, wherein said liquid comprising said C_4-10 hydrocarbons is cooled and pumped back to said absorption zone as the scrub liquid.