FORMATION OF MONOLAYER OF MOLYBDENA OVER ALUMINA BY UNCONVENTIONAL SLURRY IMPREGNATION OR SOLVENT ASSISTED SPREADING METHOD

Alumina supported molybdenum catalysts with variable loading and suppo rt particle size were prepared by the unconventional equilibrium adsor ption in slurry MoO3/water. The method can be named either slurry impr egnation method, SIM (when compared with impregnation in ammonium moly bdate 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 m(2) g(-1) and particle size 0.16-0.32 mm was 14.4 wt% MoO3. No other crystalline phase beside gam ma-Al2O3 was found in XRD spectra of the catalysts. The XPS surface ra tio Mo/Al in oxide form and the thiophene hydrodesulphurization activi ty in sulphide form increased linearly with the overall composition up to saturated adsorption loading. The hydrodesulphurization activity o f the SIM/SAS catalysts of corresponding loading was comparable or bet ter than the activity of conventional commercial MoO3/Al2O3 catalyst. All this indicated that the monolayer type catalysts are obtained by S IM/SAS method, The electron probe micro analysis of the SIM/SAS cataly st prepared from extrudates (1.5 mm) confirmed uniform cross sectional distribution of molybdena. This proved that the SIM/SAS method can be used not only for small support particles but also for usual extrudat es or tablets. The relation and advantage of the SIM/SAS method as com pared with other methods of preparation of monolayer molybdena catalys ts were discussed.