(482d) Steam Reforming of Toluene and Biomass Tar over Biochar Supported Ni Nanoparticles: Effects of Ni Particle Size on Catalytic Activity and Stability

Du, Z., University of Minnesota
A series of biochar supported Ni catalysts (Ni/BC) were explored for steam reforming of toluene, with an emphasis on the effects of Ni particle size on the product distribution and catalytic stability. Metallic Ni nanoparticles were formed upon pyrolysis treatment of impregnated biomass via carbothermal reduction. The influence of preparation parameters (Ni loading amount and pyrolysis temperature) on the Ni particle size was examined. Ni/BC pyrolyzed at 600 oC with a Ni loading of 5% (5Ni-600/BC) displayed higher specific surface areas and higher metal dispersion (i.e. lower particle size) than other catalysts. In addition, 5Ni-600/BC showed superior catalytic performance in terms of initial activity (TOF) and stability over other Ni/BC catalysts, indicating the positive role of small particles with more corner and edge sites. Two conventional metal oxides supported Ni catalysts (Ni/ZrO2 and Ni/γ-Al2O3) were selected for comparison with 5Ni-600/BC in long-term stability tests. Although characterization of the spent catalysts revealed that 5Ni-600/BC experienced severe coke deposition and metal sintering, it performed more stable than the reference catalysts, which can be attributed to its significantly larger specific surface area available for coke tolerance. 5Ni-600/BC was further examined for its performance in steam reforming of real biomass tar. Compared with BC alone, Ni/BC not only reduced the overall amount of tar, but also cracked some large molecules into smaller ones. Our study demonstrated that Ni/BC is a cheap and easy-to-prepare catalyst with promising prospects for toluene/tar reforming. However, the catalyst stability still needs to be improved by inhibiting metal sintering and coke deposition in future work.