Surface conditioning in olefin dimerization reactors

A method for dimerizing at least one .alpha.-olefin in an olefin dimerization circulating loop reactor, comprising the steps of:

• (a) contacting the surface of said reactor with a first homogeneous catalyst component comprising a complex of divalent nickel, and a second soluble homogeneous catalyst component comprising an alkyl aluminum halide, wherein the alkyl group has from 1 to 10 carbon atoms;
• (b) introducing at least one .alpha.-olefin having from 2 to 20 carbon atoms into said reactor;
• (c) operating said reactor for a first period of time ranging from about 0.1 to about 25 hours, under conditions as will result in the dimerization of said .alpha.-olefin, while controlling the feed rates of said catalyst components such that the average molar ratio of the aluminum in said alkyl aluminum halide to said divalent nickel in said complex (Al/Ni mol ratio) is maintained for the first period of time in a first range of ratio values which is effective to improve the selectivity and/or yield of dimer during a second period of time;
• (d) subsequently adjusting said Al/Ni mol ratio of the catalyst to a second value, higher than said the average ratio value during said first period of time, for dimerization operations during a second period of time;
• and
• (e) operating said reactor to produce dimer for said second period of time.

A method for dimerizing at least one .alpha.-olefin in a cleaned reactor comprising the steps of:

• (a) contacting the surface of said reactor with a homogeneous catalyst selective to dimerization and having a first catalyst component comprising a complex of divalent nickel and a second catalyst component comprising an alkyl aluminum halide, wherein the alkyl group has from 2 to 20 carbon atoms;
• (b) introducing at least one .alpha.-olefin having from 2 to 20 carbon atoms into said reactor under such conditions as will result in the dimerization of said .alpha.-olefin;
• (c) operating said reactor with the feed rates of said first and second catalyst components controlled so that the average value of the Al/Ni mol ratio of said second catalyst component to said first catalyst component is below a first value for a first period of time sufficient to pre-condition the interior surface of said reactor by contact with said first catalyst component;
• and
• (d) thereafter operating said reactor for a second period of time with said molar catalyst feed rates controlled to maintain an average value of said Al/Ni mol ratio higher than the average value of said Al/Ni mol ratio during said first period of time.

A method for dimerizing at least one .alpha.-olefin in a reactor comprising the steps of:

• (a) contacting the surface of said reactor with a homogenous catalyst selective to dimerization, comprising at least one complex of a divalent metal selected from the group consisting of nickel, cobalt and iron as first catalyst component and at least one organoaluminum compound as second catalyst component, wherein the feed rates of said first and second catalyst components are adjusted so as to give a molar ratio of aluminum in said second catalyst component to the divalent metal in said first catalyst component being below a first value;
• (b) introducing at least one .alpha.-olefin having from 2 to 20 carbon atoms into said reactor;
• (c) operating said reactor under such conditions as will result in the dimerization of the .alpha.-olefin, with said molar ratio of aluminum to the divalent metal of the catalyst being below said first value, for a first period of time ranging from about 0.1 to about 25 hours so as to pre-condition the interior surface of said reactor;
• and
• (d) thereafter operating said reactor for a second period of time with the feed rates of said first and second catalyst components adjusted so as to give a molar ratio of aluminum to said divalent metal of the catalyst being at a second value which is higher than said first value.