In situ magnetic resonance imaging study of the impregnation of γ-alumina pellets

In petroleum refining, γ-alumina is used as a solid support of molybdenum nickel/cobalt promoted catalysts for the hydrotreatment processes, such as hydrodesulfurization. The ever decreasing norms for the sulfur content in gasoline require better and more efficient catalysis, prompting extensive research on the materials and the factors influencing the activity, selectivity and stability of the catalytic processes. In the present study, Magnetic Resonance Imaging Single Point Imaging is tested as a tool to monitor the impregnation of γ-alumina pellets with Ni(NO3)2 aqueous solutions at varying Ni2+ concentration. The method enables a study in the presence of paramagnetic elements in the alumina support, in the conditions of very fast T1 and T2. It is shown that at higher concentrations of metal ions a homogenous distribution in the support is attained faster. A non-linear dependence is observed and a minimum ion concentration of 0.2 M is necessary for achieving short impregnation times of alumina pellets of millimeter size scale.