Reduced Polymer Formation For Selective Ethylene Oligomerizations

A reaction system comprising:

• a reaction zone comprising ethylene, an organic reaction medium, a catalyst system, a C3+ olefin, and optionally hydrogen and having a C3+ olefin:ethylene weight ratio that decreases from a value of equal to or greater than 0.5:1 to a value less than 0.2:1 over a period of time;
• a first reaction zone inlet connected to the reaction zone and configured to introduce the catalyst system comprising i) a chromium component comprising a heteroatomic ligand chromium compound complex, and ii) an aluminoxane to the reaction zone;
• a second reaction zone inlet connected to the reaction zone and configured to introduce ethylene and optionally hydrogen to the reaction zone;
• a third reaction zone inlet connected to the reaction zone and configured to introduce at least a portion of the organic reaction medium to the reaction zone;
• a C3+ olefin feed line in fluid communication with the first reaction zone inlet, the second reaction zone inlet, the third reaction zone inlet, or a fourth reaction zone inlet, wherein the C3+ olefin feed line is configured to introduce the C3+ olefin to the reaction zone;
• and
• one or more reaction zone outlets connected to the reaction zone and configured to discharge a reaction zone effluent comprising an ethylene oligomer product from the reaction zone,
• wherein the C3+ olefin in the reaction zone that is used to determine the C3+ olefin:ethylene weight ratio in the reaction zone is not an ethylene oligomer formed in-situ within the reaction zone,
• wherein the heteroatomic ligand chromium compound complex has the formula
• where
• each X1s is independently selected from the group consisting of N, P, O, and S;
• L1s is a C1 to C20 organylene linking group, a C1 to C30 amin-di-yl group, or a C1 to C30 phosphin-di-yl group linking X1ss;
• each m is independently 1 or 2;
• each R1s is independently a C1 to C20 organyl group;
• X is a halide, a C1 to C20 carboxylate, a C1 to C20 β-diketonate, or a C1 to C20 hydrocarboxide;
• and
• p is from 2 to 6.

A reaction system comprising:

• a reaction zone comprising ethylene, an organic reaction medium, a catalyst system, a C3+ olefin, and optionally hydrogen and having a C3+ olefin:ethylene weight ratio that decreases from a value of equal to or greater than 0.5:1 to a value less than 0.2:1 over a period of time;
• a first reaction zone inlet connected to the reaction zone and configured to introduce ethylene, at least a portion of the organic reaction medium, optionally hydrogen, and the catalyst system comprising i) a chromium component comprising a heteroatomic ligand chromium compound complex, and ii) an aluminoxane to the reaction zone;
• a C3+ olefin feed line in fluid communication with the first reaction zone inlet or a second reaction zone inlet, wherein the C3+ olefin feed line is configured to introduce the C3+ olefin to the reaction zone;
• and
• one or more reaction zone outlets connected to the reaction zone and configured to discharge a reaction zone effluent comprising an ethylene oligomer product from the reaction zone,
• wherein the C3+ olefin in the reaction zone that is used to determine the C3+ olefin:ethylene weight ratio in the reaction zone is not an ethylene oligomer formed in-situ within the reaction zone,
• wherein the heteroatomic ligand chromium compound complex has the formula
• where
• each X1s is independently selected from the group consisting of N, P, O, and S;
• L1s is a C1 to C20 organylene linking group, a C1 to C30 amin-di-yl group, or a C1 to C30 phosphin-di-yl group linking X1s s;
• each m is independently 1 or 2;
• each R1s is independently a C1 to C20 organyl group;
• X is a halide, a C1 to C20 carboxylate, a C1 to C20 β-diketonate, or a C1 to C20 hydrocarboxide;
• and
• p is from 2 to 6.