Oxidation of tert-butanethiol with air using Mo-containing hydrotalcite-like compounds and their derived mixed oxides as catalysts

This contribution presents several aspects concerning the production and characterization of hydrotalcite-like compounds containing Mo-species in the interlayer region (Mo-HT), the corresponding derived mixed oxides (Mo-CHT) and their catalytic activity in the demercaptanization of gasoline contaminated by tert-butanethiol. Mo-HT samples were obtained using two different molybdenum sources, e.g. Na2MoO4 or (NH4)6Mo7O24 and two preparation procedures: (i) ionic exchange and (ii) coprecipitation at pH 10 under high supersaturation. The derived mixed oxides were obtained by calcination at 450 °C during 24 h. The solids have been characterized by chemical analysis, TG/DTA, XRD, SEM–EDX, FTIR, DR-UV–Vis and Raman spectroscopy as well as determination of base sites. The specific area of the solids was determined using the BET method. The best catalysts were found to be those containing higher amounts of Mo species with tetrahedral coordination obtained by calcination of the Mo-HT precursors prepared at pH 10, either by ionic exchange or by co-precipitation using Na2MoO4 as a molybdenum source. Meanwhile, the catalysts containing mainly octahedrally coordinated Mo species (obtained from Mo-HT prepared at pH 10 using (NH4)6Mo7O24·6H2O as molybdenum source) were characterized by a higher concentration of molybdenum species with octahedral coordination, lower number of base sites, smaller surface area, and a poor catalytic activity.