Catalytic pyrolysis of toluene as biomass tar model component using Ni/HZSM-5 modified by CeO2 and MgO promoters

Abstract

Thermochemical conversion technology is a promising chemical method for removal of biomass tar. In this study, Ni/HZSM-5 catalyst modified by CeO2 and MgO promoters were prepared by ultrasonic-assisted excessive impregnation method. Toluene was selected as the representative model component of biomass tar, and the pyrolysis experiments were carried out in a tubular fixed bed reactor. Fresh and reacted catalysts have been characterized. The results revealed a similar initial activity for different loadings of same promoter. The stability of Ni-Ce catalysts increased gradually with increasing of Ce loading. In particular, Ni-4%Ce/HZSM-5 catalyst has the best catalytic activity with the toluene conversion of 94.5%, the yield of total gas of 107 mL/g, the gaseous efficiency of 68 wt.%. The BET surface areas as large as 206.9 m2/g with an average pore size of 3.2 nm assisted NiO particles dispersed on the surface of HZSM-5 support. Although the performance of Ni-4%Ce/HZSM-5 catalyst was better, the surface of its also formed char with an elongated fiber. However, the low-catalytic performance of Ni-Mg/HZSM-5 was due to the instability of active center NiO-MgO solid solution. This study revealed the influences of promoter types, promoter loadings, and the potential mechanism of similar catalytic performance on the preparation process of Ni-based catalysts.