Continuous ethylene tetramerization process

Patent metadata

Field	Value
Publication number	US-9688588-B2
Application number	US-201314443838-A
Country	US
Kind code	B2
Filing date	Dec 4, 2013
Priority date	Dec 21, 2012
Publication date	Jun 27, 2017
Grant date	Jun 27, 2017

Abstract

A continuous flow process for the oligomerization of ethylene using a chromium catalyst having a phosphorus-nitrogen-phosphorus (“P—N—P”) ligand provides high selectivity to the desired tetramer (1-octene) with reduced production of coproduct C 10 + oligomers. Prior art processes that maximize catalyst activity have provided comparatively poor product selectivity. In particular, the production of larger amounts of C 10 + oligomers have been observed under conditions that maximize activity. The present process resolves this problem through the use of a combination of low catalyst concentration and by limiting the octene concentration in the reactor.

First claim

The invention claimed is:

1. A continuous flow process for the oligomerization of ethylene, said process comprising
I) adding ethylene and solvent to a single mixed reactor and contacting said ethylene under continuous flow oligomerization conditions with
1) a diphosphine catalyst defined by the formula (R1)(R2)-P1-bridge-P2(R3)(R4) wherein R1, R2, R3 and R4 are independently selected from the group consisting of hydrocarbyl and heterohydrocarbyl and the bridge is a moiety that is bonded to both phosphorus atoms;
2) a source of Cr; and
3) an activator

II) removing a product discharge stream comprising hexene, octene, C10+ oligomers and solvent from said reactor; and
III) controlling the flow of said solvent and ethylene to said reactor such that the product discharge stream contains from 2 to 25 weight % octene, based on the weight of hexene, octene, C10+ oligomers and solvent; and

wherein said process is further characterized by i) being conducted at a catalyst concentration of from 0.3 to 5 micromolar Cr and ii) said diphosphine catalyst is prepared and activated in-situ by combining said Cr, said activator, ethylene, and a ligand defined by the formula (R1)(R2)-P1-bridge-P2(R3)(R4) wherein R1, R2, R3 and R4 are independently selected from the group consisting of hydrocarbyl and heterohydrocarbyl and the bridge is a moiety that is bonded to both phosphorus atoms, within said single mixed reactor and wherein said solvent is selected from the group consisting of saturated C 6 to C 20 aliphatics and saturated aliphatics.

2. The process of claim 1 wherein said activator comprises an aluminoxane plus an alkyl aluminum.

3. The process of claim 2 wherein said aluminoxane consists essentially of methylaluminoxane and said alkyl aluminum consists essentially of triethylaluminum (TEA)TEAL.

4. The process of claim 3 wherein the total amount of aluminum contained in said aluminoxane plus said triethylaluminum is sufficient to provide an Al: Cr molar ratio of from 500:1 to 2000:1.

5. The process of claim 1 when conducted at a pressure of from 2 to 20 MPa.

6. The process of claim 1 when conducted at a temperature of from 30 to 70° C.

7. The process of claim 1 wherein said solvent is selected from the group consisting of cyclohexane and heptane.

8. The process of claim 1 wherein the concentration of ethylene in said mixed reactor is from 5 to 20 weight %.

9. The process of claim 1 when conducted at a temperature of from 35 to 45° C., an ethylene concentration of from 5 to 20 weight % and wherein said solvent is selected from the group consisting of cyclohexane and heptane.

Assignees

• Nova Chemicals International Sa

Inventors

• Zoricak Peter
• Brown Stephen John
• Chisholm P Scott

Classifications

• C07C2/36 Primary

  as phosphines, arsines, stilbines or bismuthines · CPC title

• C07C2/34 Primary

  Metal-hydrocarbon complexes · CPC title

• C07C2531/14

  of aluminium or boron · CPC title

• Y02P20/52

  using catalysts, e.g. selective catalysts · CPC title

• C07C2531/22

  Organic complexes · CPC title