Abstract
The Al(2)O(3) concentration effect over NiWS/Al (x) Zr(100-x) catalysts was investigated for deep hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT). The sol-gel method changed the wt % Al(2)O(3) concentrations used to synthesize the Al (x) Zr(100-x) supports. The NiWS/Al (x) Zr(100-x) catalysts were prepared with ammonium metatungstate hydrate and nickel(II) nitrate hexahydrate by sequential incipient impregnation, calcination, and H(2)S/H(2) activation. The catalytic evaluation data fit a pseudo-first-order trend in the 4,6-DMDBT HDS reactions. In the oxide phase, the catalysts presented Ni and W species in tetrahedral (td) and octahedral (oh) coordination, with the oh species prevailing as a function of the Al(2)O(3) amount. The lower amount of Al(2)O(3) can facilitate the "Type II" NiWS phase formation by weakening the interaction of the W-O-Al bond and promoting W and Ni species sulfidation. In the sulfide phase, catalysts with (oh) coordination and surface WO (X) species promote the formation of WS(2) and NiWS species during the catalyst activation step. This species favors the reaction yield, where the hydrogenation route is predominant, with the highest initial reaction rate using the NiWS/Al(25)Zr(75) catalyst. A direct correlation was found between high hydrogenation/hydrogenolysis ratio values and low Al(2)O(3) concentrations.