Effects of loading methods and oxidation degree of support on the tar reforming activity of char-supported Ni catalyst using toluene as a model compound

Abstract

It is necessary to remove the tars present in gasification systems of biomass or low-rank coal to prevent the blockage and corrosion of downstream equipment. In this study, catalysts were prepared using different Ni loading methods: impregnation, pressure impregnation, and ion exchange methods using coal char as a catalyst support for tar removal. The catalyst prepared by ion exchange method showed considerably better performance for the steam reforming of toluene (model tar) compared with the other two catalysts. The oxygen-containing groups of low-rank coal acted as cation-exchange sites, and the oxidation significantly increased the number of oxygen-containing groups. Therefore, the intrinsic correlation between oxidation degree of support and catalytic property was further explored. ICP analysis, XRD spectroscopy, and TEM images confirmed that Ni loading and Ni crystallite size (NCS) significantly depended on the oxidation degree of support. When coal was oxidized with 30% H2O2 and 30% HNO3, the Ni loadings of catalysts were 9.9 wt% and 12.1 wt%, and the NCS were 3.5 nm and 4.5 nm, respectively. Compared to HNO3, the catalyst prepared using H2O2 pretreatment exhibited a higher toluene removal efficiency.