Support effects of NiW hydrodesulfurization catalysts from experiments and DFT calculations

Abstract

The present work deals with the effect of common carriers and binary mixed oxide materials in the preparation of oxide and sulfidic NiW catalysts. Experimental characterization and DFT theoretical study of the intrinsic support interaction of WS2 and Ni-WS2 clusters revealed that each oxide conferred to the NiW catalysts different activity, dispersion, promotion, total acidity and specific surface bonding. Initially, we present the binding energy obtained by routine UV–vis DRS of WOx polymeric species over the different supports as indicator of the dispersion by obtaining the next nearest neighbors (NW). These NW values seem to correlate well with the WS2 slab length reported in our previous work. The XPS results pointed to a better promotion of the active phase when catalysts were prepared over Al2O3-TiO2 and ZrO2-TiO2 mixed oxides. Besides, a correlation was confirmed between the total acidity observed by FTIR of adsorbed pyridine and the hydrodesulfurization of the DBT diesel model molecule. Additionally, DFT theoretical calculations revealed that the promoted cluster tends to be bent by the interaction with the support. This bending of the promoted WS2 slabs was observed experimentally in our materials, especially in the three more active NiW catalysts.