Abstract: A process is provided to produce a catalyst system. The process comprises blending a first component and a second component. The first component of the catalyst system comprises chromium on a support. The amount of chromium on the support is from about 0.05 to about 5 weight percent based on the weight of the support. The support comprises fluorided alumina. The support has a surface area from about 200 to about 550 square meters per gram and a pore volume from about 0.7 to about 2.5 cubic centimeters per gram. The first component is activated at a temperature in the range of about 500° C. to about 900° C. The second component is a transition metal halide catalyst. A process comprising polymerizing ethylene or copolymerizing ethylene and at least one other monomer using the catalyst system to produce ethylene polymers is also provided.