EFFECT OF FLUORINE ON HYDRODESULFURIZATION AND HYDROGENATION ACTIVITY OF DOUBLY PROMOTED (ZN + CO) MOLYBDENA ALUMINA CATALYSTS

Fluorinated alumina (0-2.0 wt % F) has been used as a carrier for promoted (Co + Zn) molybdate catalysts. The preparations consisted of constant molydbenum (12 wt % MoO3) and promoter (CoO + ZnO) loading (4 wt % and atomic ratio Co/Zn = 1). The sulfided catalyst activity has been studied in the hydrodesulfurization of thiophene. It has been observed that the thiophene conversion attained a maximum at 0.0-0.4 wt % F. In addition to this, the thiophene conversion changed only slightly and linearly with H2 pressure. Textural and chemical characterization results revealed that Al2O3 carrier becomes attacked by (NH4)HF2 solution yielding pores of greater sizes and plugging those of lower diameter, and also some Al3+ ions are solubilized, which then precipitate as Al(OH)3 during the drying step over fluorinated alumina surface. As both Mo and promoter are incorporated in further impregnation steps, it is expected that a fraction of these ingredients can be lost through strong interaction with the resulting Al2O3 coating.