Oligomerization catalyst system activation and related ethylene oligomerization processes and reaction systems

A process comprising:

• a) forming a first mixture in an activation vessel, the first mixture comprising:
• 1) a first catalyst system comprising i) a first heteroatomic ligand chromium compound complex and a first organoaluminum compound, or ii) a first heteroatomic ligand, a first chromium compound, and a first organoaluminum compound,
• 2) a first feed comprising ethylene, a second catalyst system comprising i) a second heteroatomic ligand chromium compound complex and a second organoaluminum compound, or ii) a second heteroatomic ligand, a second chromium compound, and a second organoaluminum compound, a second organic reaction medium, a second oligomer product, and optionally hydrogen,
• 3) optionally, a first organic reaction medium, and
• 4) optionally, hydrogen;
• b) maintaining the first mixture in the activation vessel for an average residence time;
• c) introducing into a reaction zone:
• i) ethylene,
• ii) the first mixture from step b),
• iii) the second organic reaction medium, and
• iv) optionally, hydrogen;
• and
• d) forming an oligomer product in the reaction zone;
• wherein a portion of a reaction zone effluent is fed to the activation vessel as the first feed, and
• wherein the average residence time of the first mixture in the activation vessel is in a range from 10 sec up to a period of time sufficient to form an amount of a first oligomer product in the activation vessel equal to 5% of an amount of the oligomer product formed in the reaction zone.

A reaction system comprising:

• (a) an activation vessel configured to form a first mixture, wherein the activation vessel is further configured for an average residence time of the first mixture in the activation vessel;
• (b) one or more activation vessel inlets configured to introduce i) ethylene and a catalyst system mixture, or ii) ethylene and components of a catalyst system mixture, into the activation vessel;
• (c) an activation vessel outlet configured to withdraw the first mixture from the activation vessel;
• (d) a reaction zone configured to contact ethylene, the first mixture, a second organic reaction medium, and optionally hydrogen to form an oligomer product;
• (e) one or more reaction zone inlets configured to introduce ethylene, the second organic reaction medium, and the first mixture from the activation vessel outlet into the reaction zone;
• and
• (f) a reaction zone outlet configured to withdraw a reaction zone effluent stream containing the oligomer product from the reaction zone;
• wherein the average residence time of the first mixture in the activation vessel is in a range from 10 sec up to a period of time sufficient to form an amount of a first oligomer product in the activation vessel equal to 5% of an amount of the oligomer product formed in the reaction zone.