Low-Temperature Steam Reforming of Toluene and Biomass Tar over Biochar-Supported Ni Nanoparticles

Developing efficient, inexpensive, in situ tar reforming technologies under mild conditions is an important practical aspect of biomass gasification. In this study, a series of biochar-supported Ni catalysts (Ni/BC) were prepared via a simple one-step pyrolytic approach and first explored for steam reforming of toluene as a tar model compound at a relatively low temperature of 600 degrees C. The as-prepared catalysts can be directly used without a further reduction process. The abundant surface oxygen containing groups of the starting biomass and the high porosity of Ni/BC assisted with the dispersion of the Ni nanoparticles. The in situ generating process of metallic Ni nanoparticles via carbothermal reduction was manipulated to modulate the Ni particle size. A size-dependent behavior was observed, wherein 5Ni-600/BC (pyrolyzed at 600 degrees C, 5% Ni loading) with the smallest Ni particle size (4.2 nm) showed superior catalytic performance in terms of the initial intrinsic activity (turnover frequency value of 1.64 s(-1)) and stability over others, indicating the positive role of small particles with more corner and step sites, which was further proved by DFT calculations. In addition, 5Ni-600/BC was found to be effective in the steam reforming of real biomass tar by reducing both the tar amount and the molecular weight.