In-situ characterisation and catalytic testing of Co and Pd promoted tungsten carbide catalysts

Full text: Transition metal carbides are obtained when carbon atoms are incorporated into transition metal interstitial sites. It has been shown that these tungsten carbide catalysts can be used to convert cellulose which is the most abundant source of biomass into value added products which presents great potential for sustainable production of fuels and chemicals. In-situ PXRD studies of the effects of Pd and Co promoters on tungsten carbide catalysts showed the promoters effect not only the temperature that carburization occurs but also the phase of tungsten carbide that occurs. Carburization temperatures decreased in the following series non-promoted > Pd > Co. The non-promoted carburization produced both W2C and WC phases. These phases were also present in the Pd promoted catalyst but absent in the Co promoted case. The Co promoter not only produced a phase pure W2C but was also able to perform the carburization at the lowest temperature, some 110°C lower than the catalyst produced without a promoter. Both Ni and Pd promoters were able to lower the carburization temperature and formed a mixture of W2C and WC phases with the Pd promoter being the only one of the promoters identifiable in the PXRD scans. This may imply that the Pd is present in the catalyst in a different manner to that of the Co promoter. Co was found to be the best promoter as it acts to lower the carburization temperature while producing a phase pure product of W2C which is the most active tungsten carbide phase. (author)