A new process for the sequential copolymerization of olefins has been devised (Multicatalysts Reactor Granule Technology); it allows the synthesis of thermoplastic polyolefin elastomers having polypropylene from Ti-based catalysts and ethylene-propylene rubbers from metallocenes. Such new materials have been cured with peroxides an the relevant mechanical properties measured in comparison with those of heterophasic copolymers synthesized with traditional catalysts. It resulted that the new materials present an improved balance between strength and elasticity, especially at high temperature.