Ethylene polymerization process

In a Particle Form Process for the polymerization of ethylene, the improvement which comprises employing as the polymerization catalyst a catalyst prepared by

• (a) Admixing an inorganic chromium compound with an aqueous slurry of an inorganic carrier containing aluminum and phosphorus moieties to provide about 0.1-4.0% by weight chromium based on the total solids,
• (b) Spray drying the slurry of (a), and
• (c) Activating the dry catalyst of (b) by heating to a temperature of about 350.degree.-950.degree. C.;
• said slurry of step (a) having been prepared by preparing an acidic aqueous solution containing Al.sup.+++ cations and PO.sub.4.sup.--- anions in proportions such that the aluminum and phosphorus are present in an atomic ratio in the range of about 5:1 to 1:1;
• and precipitating the inorganic carrier by feeding the aqueous solution containing Al.sup.+++ cations and PO.sub.4.sup.--- anions to an aqueous medium with stirring while simultaneously feeding to such medium an alkaline solution, the feed streams being controlled so as to provide a pH in the range of about 7.0-11.0.