Nickel-Containing Polyoxotungstates Based on [PW9O34](9-) and [PW10O39](13-) Keggin Lacunary Anions Supported on Al2O3 for Dibenzothiophene Hydrodesulfurization Application

摘要

In the present study, different Al2O3-supported Ni-containing polyoxotungstates (POW) based on Keggin lacunary structures were synthesized in order to establish a correlation between the local conformation of the different Ni/POWs and the final catalytic performance of the corresponding supported NiW hydrodesulfiirization (HDS) catalysts. POWs containing various amounts of nickel (3, 4, or 9 Ni atoms per POW) were therefore prepared and supported on an Al2O3 support obtained by a sol-gel method using impregnation techniques in aqueous solutions at two different pH values (7 and 9). The as-obtained supported Ni-containing POWs were characterized after the drying (120 degrees C, 4 h) and calcination steps (400 degrees C, 4 h, air). The different solids were then sulfided using 10 mol % H2S in H-2 at 400 degrees C for 4 h and evaluated in the hydrodesulfurization of dibenzothiophene (DBT) at T = 300 degrees C and P = 30 bar H-2. Both the Ni localization inside the polyoxotungstate and the pH of the impregnation solution influence the degree of sulfidation and the intrinsic activity of the promoted phase, with Ni-3 POW/Al2O3 the most HDS active if impregnation occurs at pH 7. A direct correlation between the structure of the nickel-containing polyoxotungstate and the final HDS activity can be observed, opening the way for a rationalization of the preparation of this type of precursor.