Abstract: A pre-formation unit, includes: a first vessel comprising a solution of co-catalyst and modifier; a second vessel comprising chromium compound and ligand; wherein the first and second vessel are connected via lines to a mixing unit, wherein each line has a flow control valve; wherein the mixing unit is connected via a line having a flow control valve to an oligomerization reactor; wherein gas inlets are each connected to the first vessel and to the second vessel, and wherein a portion of each of the first vessel, the second vessel, the mixing unit, and the flow control valves are within a temperature controlled enclosure.