Low-temperature steam reforming of toluene as a biomass tar model compound over biochar-supported catalysts

Abstract

Abstract The removal of tar produced during biomass gasification is a significant challenge. Tar reforming is a highly effective way of eliminating tar. However, typical tar-reforming catalysts are prone to coke deposition and the sintering of active metal, especially at elevated temperatures. Consequently, it is crucial to develop highly active and stable catalysts under low reforming temperature. First, Ni, Co, and Fe-loaded wood chips biochar supported catalysts were synthesized via the wetness impregnation method. Toluene was chosen as a tar model compound. Overall, Ni/Biochar exhibited superior catalytic performance in toluene reforming compared to Co/Biochar and Fe/Biochar catalysts at a temperature below 500 °C. After active metal screening, 10 wt.% La and Ce-promoted biochar-supported Ni catalysts were also synthesized for tuning the metal–support interaction, basicity, and oxygen vacancy of the catalysts to enhance the low-temperature tar reforming performance. 10 wt.% La-doped 15 wt.% Ni/Biochar showed the best toluene reforming performance among the prepared catalysts, with a H2 yield of 87% and toluene conversion of 93% at reaction temperature of 400 °C. Moreover, this catalyst maintained uniform dispersion of Ni and La2O3 particles and did not show growth in Ni crystallite size and significant coke accumulation during 15 h continuous reforming reaction. The high catalytic activity and better stability of NiLa/Biochar were attributed to a small Ni particle size (9.05 nm), uniform dispersion of metal, strong metal-support interaction, high basicity (2.95 mmol g–1), and abundance of oxygen vacancies (84.1%), which promoted the activation, adsorption, and dissociation of H2O molecules as well as the removal of deposited coke. Graphical Abstract

Keywords

• Biochar
• Catalyst
• Hydrogen
• Promoter
• Tar reforming