Process for preparing a solid metallocene catalyst system, unsupported, and their use in the polymerization of olefins

Process for the preparation of a catalyst system heterogeneous olefin polymerization, without support, comprising an organometallic compound of a transition metal of Group 3 to 10 of the Periodic Table (IUPAC 2007) or of an actinide or lanthanide in the form of particles solid, comprising the steps of a) preparing a solution of catalyst components, including an aluminoxane, a compound that is effective to form clathrates with aluminoxane and an organometallic compound of a transition metal of Group 3 to 10 of the Periodic Table (IUPAC 2007) or of an actinide or lanthanide, in a hydrocarbon solvent, yielding a two phase system with an upper solvent layer, which is separated, b) preparing a system liquid / liquid emulsion comprising a continuous phase wherein said solution of the catalyst components forms a dispersed phase in the form of droplets, c) solidifying said dispersed phase to convert dich as droplets to solid particles and optionally recovering said particles to obtain said catalyst system.