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

Du, Zhen-Yi, Zhang, Zhi-Hua, Xu, Chen, Wang, Xing-Bao, Li, Wen-Ying
ACS sustainable chemistry & engineering 2018 v.7 no.3 pp. 3111-3119
biomass, catalysts, catalytic activity, gasification, models, molecular weight, nanoparticles, nickel, oxygen, particle size, porosity, steam, temperature, toluene
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 °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 °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.