Novel solution for removing poisonous silica from a Ni-Mo/Al2O3 industrial HDT spent catalyst

During hydrotreating, silica poisoning of catalysts represents a severe problem, because the silicone compounds that are present in coker naphtha feedstocks are adsorbed and transformed on the alumina surface, deactivating it. To provide a solution, in the present work, silica was selectively removed from an industrial Ni-Mo/Al2O3 spent catalyst by applying a depolymerization process with glycerol that resulted in the restoration of silicon retention capacity, hydrodesulfurization and hydrodenitrogenation activities and physical properties of the catalyst. Catalyst samples, before and after the removal of silica compounds, were studied by nuclear magnetic resonance spectroscopy (NMR), N2 physisorption, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), atomic absorption spectroscopy and scanning electron microscopy (SEM).