Enhancing performance of Ni/La2O3 catalyst by Sr-modification for steam reforming of toluene as model compound of biomass tar

Abstract

Steam reforming of biomass tar with toluene as the model compound was studied using Sr-doped Ni/La₂O₃ catalysts prepared using two methods, i.e. co-impregnation of Sr and Ni on La₂O₃ support (Ni–Sr/La₂O₃ catalyst) and sequential impregnation of Sr on Ni/La₂O₃ catalyst (SNL catalyst), which were then calcined at various temperatures (500, 700, and 900 °C). These two types of catalysts are found to possess better catalytic performance than the undoped Ni/La₂O₃ catalyst at the same calcination temperature due to the presence of Sr, which helps in water adsorption at low steam/carbon (S/C) ratio. Moreover, the catalytic performance for catalysts calcined at various temperatures decreases following this trend: 500 °C > 700 °C > 900 °C due to lower BET surface area and lower surface active metal available for reaction. In addition, it is also observed that the Sr/Ni/La₂O₃ catalyst has better performance than the Ni–Sr/La₂O₃ catalyst at the same calcination temperature. Further characterization results suggest that in the Ni–Sr/La₂O₃ catalyst, the Sr is present between Ni and La₂O₃ support. On the other hand, Sr in the Sr/Ni/La₂O₃ catalyst is thought to be located on the surface of Ni/La₂O₃ due to the preparation method. This study shows that more Sr on the catalyst surface has better catalytic activity and stability in steam reforming of toluene.