A catalyst is a substance that changes the rate of a reaction. In the petroleum industry, the catalysts are commonly used for Fluid Catalytic Cracking (FCC) and Hydro Catalytic Cracking (HCC), each of them applied in a specific stage. These catalysts are used to facilitate the molecular chains cracking, which will generate a mixture of hydrocarbons. However, the catalyst gradually loses its activity, either by changing its original molecular structure or by its contamination from other petroleum molecules. The application of ionizing radiation (medium-energy electron beam) over these spent catalysts was studied to contribute the extraction of metals or rare-earths of high added-value. Tests conducted with HCC catalysts were used the technique of electron beam irradiation (1.3 MeV) and had as a subject the extraction of Molybdenum. Energy Dispersive X-ray (EDX) analysis was performed on a Shimadzu EDX-720/800HS and X-ray Diffraction (XRD) analysis on a Rigaku MultiFlex. Electron beam irradiation had a positive contribution if compared to traditional thermal and chemical methods. In temperature around 750??C, HCC irradiated catalysts of the lower region have an extraction of Molybdenum (MoO3) yield twice higher compared to non-irradiated ones, in other words 57.65% and 26.24%, respectively.