Solid form of a stabilizer for organic polymers consisting of one or more tocopherols, as such or in formulation, absorbed on porous polypropylene with a high crystallinity, in a quantity ranging from 30% to 85% by weight. The above tocopherols, as such or in formulation, can also be used in a mixture with other stabilizers such as, for example, secondary antioxidants containing phosphorous or sulfur, sterically hindered phenols and sterically hindered amines.