Method for the treatment of a catalytic component on a porous metal oxide support for the polymerization of olefins in the gas phase and method of polymerizing olefins

A method for the manufacture of a homopolymer of ethylene or a copolymer of ethylene and a C.sub.3 to C.sub.12 alpha olefin comprising carrying out the polymerization in the gas-phase in the presence of a morphology protected granular catalyst prepared by first forming a granular catalytic component by impregnating a porous metal oxide support with at least one titanium compound, magnesium compound, and chloride compound, and prepolymerizing ethylene or a monomer mixture of ethylene and least one C.sub.3 to C.sub.12 alpha olefin, at least partially in suspension, in the presence of said impregnated porous metal oxide support and least one alkylaluminum compound, of the formula Al(R").sub.c X.sup.1.sub.d H.sub.e in which X.sup.1 is Cl or R", R" is a C.sub.1 to C.sub.14 unsaturated hydrocarbon radical, with o<d<1.5, o<3<1, and c+d+e=3, complexed with at least one electron donor, the monomer or monomer mixture being introduced into the reaction during the first hour of prepolymeriztion at a flow rate equal to or less than 10 NL h.sup.-1 .times.g.sup.-1 of catalytic component on the porous metal oxide support.