Thermally Impregnated Ni−Olivine Catalysts for Tar Removal by Steam Reforming in Biomass Gasifiers

A novel and potentially economic preparation technique, thermally impregnation (TI), was developed to incorporate catalytic active materials (i.e., Ni) onto olivine. The approach allows for the synthesis of attrition-resistant Ni−olivine catalysts. Comparative studies were performed over Ni−olivine catalysts prepared by TI and traditional incipient wetness impregnation (IWI), as well as olivine without Ni. Various characterization techniques such as BET surface area analysis, temperature-programmed reaction/oxidation/reduction, XRD, and XPS were performed to examine the catalysts. The Ni−olivine catalyst prepared by TI demonstrated improved activity and “coke selectivity” compared to the olivine support, indicating that Ni is necessary for enhanced activity. Additionally, the Ni−olivine catalyst prepared by TI showed similar high-temperature activity and decreased coke deposition rates compared to similar formulations prepared by IWI. Stronger interactions between Ni and the olivine support for the TI catalyst were responsible for the improved catalytic properties compared to IWI catalysts. Moreover, effects of pretreatment and reaction parameters such as temperature and time-on-stream (TOS) were studied. The reaction network in simulated biomass-derived syngas was also investigated to probe the possible reactions occurring in a biomass gasifier. The Ni−olivine catalyst prepared by TI possessed catalytic activity for several reactions such as the water gas shift (WGS), reverse WGS, methanation, and Boudouard reactions.