Formation of monolayer of molybdena over alumina by unconventional slurry impregnation or solvent assisted spreading method Original Research Article

Alumina supported molybdenum catalysts with variable loading and support particle size were prepared by the unconventional equilibrium adsorption in slurry MoO3/water. The method can be named either slurry impregnation method, SIM (when compared with impregnation in ammonium molybdate solution) or solvent assisted spreading, SAS (when compared with thermal spreading of MoO3). The maximum saturated adsorption loading achieved with alumina of surface area 172 m2 g−1 and particle size 0.16–0.32 mm was 14.4 wt% MoO3. No other crystalline phase beside γ-Al2O3 was found in XRD spectra of the catalysts. The XPS surface ratio MoAl in oxide form and the thiophene hydrodesulphurization activity in sulphide form increased linearly with the overall composition up to saturated adsorption loading. The hydrodesulphurization activity of the SIMSAS catalysts of corresponding loading was comparable or better than the activity of conventional commercial MoO3Al2O3 catalyst. All this indicated that the monolayer type catalysts are obtained by SIMSAS method. The electron probe micro analysis of the SIMSAS catalyst prepared from extrudates (1.5 mm) confirmed uniform cross sectional distribution of molybdena. This proved that the SIMSAS method can be used not only for small support particles but also for usual extrudates or tablets. The relation and advantage of the SIMSAS method as compared with other methods of preparation of monolayer molybdena catalysts were discussed.