Abstract: A catalyst which is able to express a high oligomerizing activity of ethylene and a method for the production of &agr;-olefin where ethylene is oligomerized using said catalyst are provided. The present invention relates to a catalyst for the production of &agr;-olefin obtained by contacting (a) clay, clay mineral or ion-exchange layer compound with (b-1) a transition metal complex of Groups 4 to 6 of the Periodic Table and also relates to a method for the production of &agr;-olefin by oligomerization of ethylene using said catalyst. The present invention further relates to a catalyst for the production of &agr;-olefin obtained by contacting (a) clay, clay mineral or ion-exchange layer compound with (b-2) a transition metal complex of Groups 8 to 10 of the Periodic Table and also relates to a method of the production of &agr;-olefin by oligomerization of ethylene using said catalyst.

Abstract: A process to produce high melt flow propylene polymer comprises polymerizing propylene in the presence of a titanium-containing, magnesium-containing, high activity catalyst and an aluminum alkyl cocatalyst in a gas phase system which uses condensed liquid to control temperature wherein the external catalyst modifier is a tetraalkylorthosilicate, preferably tetraethylorthosilicate, at process conditions of temperature, hydrogen concentration, and Si/Mg, Al/Mg and Al/Si atomic ratios, to produce a high melt flow propylene polymer at high yield.