Catalytic performance of CoMoW Sulfide catalysts supported on hierarchically structured porous silicas for HDS reactions

In this work, monolithic silica materials with hierarchical porosity were synthesized by the sol-gel method combined with a dual hard-soft templating route. Silica materials were used for the synthesis of hydro-desulfurization CoMoW-S catalysts by the immersion technique using transition metal salts as precursors, followed by oxidation and sulfidation in H2S/H-2 mixture. Styrene-HEMA copolymer hard template presented homogeneous well-defined spherical shape with an average diameter of about 800 nm. Samples prepared over the hard template presented similar morphology. The surface areas of all supports prepared resulted in around 800 m(2).g(-1) and decreased to 220 m(2).g(-1) on average after the sulfidation process. Small-angle X-ray diffraction confirmed the presence of the 2D hexagonal or Im3m array of mesopores in all samples. The CoMoW oxide state catalysts presented low intensity peaks assigned to the b-CoMo(W)O-4 phase and minor peaks related to MoO(3 )and polyoxides with the general formula MoxW1-xO3. The high conversion was obtained for catalysts supported on hierarchically structured porous silicas, even greater than that of the commercial catalyst used as reference (>30-50%). XPS results revealed that the degree of sulfidation and CoMoWS active species resulted higher in the CoMoW-HOPSCM catalyst compared to the CoMoW-MoNoSBA-15 sample, which in turn coincides with the catalytic activity results.