Polyolefin production with chromium-based catalysts

A method of treating a chromium-based catalyst for polyolefin production, the method comprising:

• adding a charge of chromium-based catalyst to a mix vessel;
• introducing a reducing agent into the mix vessel through a conduit extension that extends at least 0.5 inch into the mix vessel and terminates in a designated vapor space of the mix vessel;
• directing the reducing agent toward a location of a mixture level in a range of 20% to 80% of a perpendicular distance from a vertical centerline of the mix vessel to an inside surface of a wall of the mix vessel to give a desired flow index response from the reduced chromium-based catalyst;
• and
• agitating a mixture of the chromium-based catalyst, reducing agent, and a solvent in the mix vessel to disperse the reducing agent in the mixture to promote reaction of the reducing agent with the chromium-based catalyst to give a reduced chromium-based catalyst.