Active sites of sulfided NiMo/Al2O3 catalysts for 4,6-dimethyldibenzothiophene hydrodesulfurization-effects of Ni and Mo components, sulfidation, citric acid and phosphate addition

摘要

The active sites of the sulfided 5.2 wt%Ni9.8 wt%Mo/Al2O3 catalyst for the hydrodesulfurization of 4,6dimethyldibenzothiophene were studied using a high-pressure flow system. The catalysts were prepared by dry sulfidation or after the calcination of four sets of NiMo precursors with and without citric acid and phosphoric acid. The dry sulfidation Wing the precursor of nickel carbonate and molybdenum trioxide with citric acid and phosphate produced the HDS MoO3 is considered a precursor for the hydrogenation activity, and ammonium heptamolybdate is a precursor for the direct desulfurization activity. and the highest number of active sites of the Ni2+MoS2 slab (NiMoS phase) based on the NO and XPS. The sulfidation after calcination using nickel nitrate and ammonium hexamolybdate had the highest HDS rate for the desulfurization, and the number of sites of the MoS2 (Mo4+) slab covered with Ni sulfide (Ni2+). This site was stacked with 3.3 layers and 34 angstrom length for the 2% phosphorus catalyst and widely dispersed as multilayers, and increased when stacked by the phosphate addition and contained highly stacked slabs by the citric acid addition. (C) 2017 Elsevier B.V. All rights reserved.