Process for preparing a support for olefin polymerization catalysts

A process for preparing an essentially spherical support for olefin polymerization catalysts, which comprises:

• a) preparing a hydrogel comprising a cogel of silicon oxide and at least one further metal oxide,
• b) optionally, washing the hydrogel until the content of alkali metal ions is less than 0.1% by weight, based on the weight of solids,
• c) extracting water from the hydrogel until the water content is less than 5% by weight, based on the total content of liquid, and
• d) drying the hydrogel to form a xerogel,
• wherein step (c) comprises:
• (1) at least one first extraction down to a water content of less than 50% by weight with a first organic solvent followed by
• (2) at least one second extraction with a second organic solvent,
• wherein each of the first and second organic solvents is at least partially miscible with water and is selected from R′OH wherein R′ is an organic radical having 1-6 carbon atoms;
• and
• wherein the second organic solvent has at least one carbon atom more or at least one branch, including the heteroatoms, more than the first organic solvent.