Silica-supported polyolefin catalyst system

An olefin polymerization catalyst system comprising a silica support, a catalyst precursor compound, and an activator, the silica support comprising a plurality of silica gel particles, wherein:

• each particle comprises a rigid network of amorphous silica;
• the particles are spherical, single gel particles;
• the particles have an average aspect ratio of about 1.2 or less;
• the particles have an average pore volume of from about 1.4 ml/g to about 3 ml/g;
• the particles have an average surface area from about 200 m2/g to about 950 m2/g;
• and
• the particles have a median particle size from about 4 μm to about 100 μm.

An olefin polymerization catalyst system comprising a silica support and a chromium compound, the silica support comprising a plurality of silica gel particles, wherein:

• each particle comprises a rigid network of amorphous silica;
• the particles are spherical, single gel particles;
• the particles have an average aspect ratio of about 1.2 or less;
• the particles have an average pore volume of from about 1.4 ml/g to about 3 ml/g;
• the particles have an average surface area from about 200 m2/g to about 950 m2/g;
• and
• the particles have a median particle size from about 4 μm to about 100 μm.

An olefin polymerization catalyst system comprising a silica support, a magnesium halide, a transition metal compound, a cocatalyst, and an electron donor compound, the silica support comprising a plurality of silica gel particles, wherein:

• each particle comprises a rigid network of amorphous silica;
• the particles are spherical, single gel particles;
• the particles have an average aspect ratio of about 1.2 or less;
• the particles have an average pore volume of from about 1.4 ml/g to about 3 ml/g;
• the particles have an average surface area from about 200 m2/g to about 950 m2/g;
• and
• the particles have a median particle size from about 4 μm to about 100 μm.