Process for the polymerization of olefins

DETAILED DESCRIPTION We claim: 1.
Process for the synthesis of an olefinic polymer or copolymer in which one or more olefins are polymerized in the presence of a catalyst system, which comprises contacting said olefins with said catalyst system and recovering said polymer or copolymer therefrom, said catalyst system consisting of an active solid hydrocarbon and having been prepared by forming a homogeneous pulverulent composition by combining (a) a component comprising a transition metal compound wherein said metal is chosen from Ti, V, Zr and Cr, in the form of particles having an average diameter of between 0.
1 and 500 microns, (b) an inert porous organic or inorganic solid support in the form of a powder wherein said powder has a mean particle diameter of from 1 to 5,000 microns, and (c) a liquid phase containing at least one compound chosen from the organometallic compound of the metals of group I to III of the Periodic Table of the Elements, the amounts of the component comprising the transition metal compound and of the organometallic compound or compounds being such that the ratio of the number of atoms of the metal or metals of groups I to III of the Periodic Table to the number of atoms of transition metal is between 0.
1 and 800, while the amount of support powder is adjusted so that the mixture produced remains in pulverulent form, and polymerizing, in contact with the above pulverulent composition, one or more C.
sub.
2 to C.
sub.
12 olefins so that an active solid hydrocarbon containing an amount by weight of transition metal of between 10 and 50,000 ppm is produced, this polymerization being carried out in the gas phase at a temperature below the melting point of the active solid hydrocarbon, whilst an hourly conversion of the C.
sub.
2 to C.
sub.
12 olefin or olefins of less than 500,000 g per gram of transition metal is maintained.
2.
Process according to claim 1, wherein a monoolefin is polymerized in contact with the active solid hydrocarbon, the said monoolefin being selected from the group consisting of ethylene, propene or but-1-ene