Crystalline propylene polymers and copolymers in the form of spherical particles at high porosity

Crystalline propylene homopolymers with an isotactic index greater than 90 and crystalline copolymers of propylene with ethylene or a CH.sub.2 .dbd.CHR olefin or mixtures thereof containing over 85% by weight of propylene and having an isotactic index greater than 85, where R is an alkyl radical with 2-8 carbon atoms, said homopolymers and copolymers being in the form of spherical particles having an average diameter of from 50 to 5000 microns, a porosity, expressed in void percentage, greater than 15%, and a pore volume distribution such that more than 90% of the pores have a diameter greater than one micron.