Method of making polymers and copolymers of 1-olefins

The method of making polymers of 1-olefins of 2-8 carbon atoms and copolymers of said olefins and 1-olefins of 2-20 carbon atoms which comprises polymerizing said olefins under polymerizing conditions with an improved catalyst prepared by the method comprising:

• preparing (1) a mixture by dispersing on a finely divided, difficult to reduce, inorganic support of the class consisting of silica, alumina, thoria, zirconia, titania, magnesia and mixtures thereof a tetra or lower valent organic chromium compound capable of reacting with the support at an elevated temperature;
• (2) calcining (1) in air or inert atmosphere and at an elevated temperature of 80.degree.-260.degree. C. for 15 minutes to 4 hours to bond said chromium compound on said support;
• (3) reacting the product of (2) with an alkyl ester of titanium, boron, vanadium or mixtures thereof or boric acid at an elevated temperature;
• and
• (4) immediately activating the product of (3), without reducing, with a dry gas that contains oxygen by heating at an elevated temperature said product of (3) in said gas.