Mesoporous materials from zeolite seeds as supports for nickel-tungsten sulfide active phases Part 2. Catalytic properties for deep hydrodesulfurization reactions

The properties of nickel-tungsten sulfide supported on MCM-41 aluminosilicate materials assembled from beta-zeolite seeds (beta-MCM-41) were examined in the conversion of 4,6-dimethyldibenzothiophene (4,6-DMDBT) pure or in mixture with dimethyldisulfide, carbazole and tetralin. As reported in the part I, the properties of the acidic supports assembled from zeolite BEA seeds are strongly related to the preparation conditions, especially to the duration of the thermal treatment leading to the zeolite seeds. For this study, two materials were selected: one obtained after a short pre-treatment time (tseeds=6h), whose structure is essentially MCM-41-like, and the other, obtained after a long pre-treatment time (tseeds=16h) which is mostly zeolitic. In order to examine the effect of the acid function of the beta-MCM-41 material on the catalytic properties of the supported catalyst, beta-MCM-41-alumina supports were prepared by mixing the two oxides (0, 15, 50 and 85% beta-MCM-41). The important and regular increase of activity observed upon increasing the beta-MCM-41 content is due to an increase in the hydrogenation properties of the active phase, indicating an electronic effect of the acidity on the supported phase. It is particularly interesting to note that this advantage of the mesoporous support is maintained even in the presence of inhibitors. For zeolite-like support, the 4,6-DMDBT is also converted through isomerization.