Optimizing Ni dispersion and stability over SiO2 supported Ni–La2O3 catalysts by preparation method for enhancing H2 selectivity and durability on steam reforming of methylcyclohexane

Abstract

In the application of catalytic liquid hydrocarbons steam reforming to hydrogen production, Ni-based catalysts are easy to sintering and carbon deposition owing to poor stability and Ni nanoparticles aggregation at high temperature. Hence, the preparation of well-dispersed and stable Ni nanocatalyst has become research focus. In this work, different preparation methods are adopted to optimize Ni dispersion and stability in SiO2 supported Ni–La2O3 catalysts. Moreover, methylcyclohexane steam reforming is used to evaluate their catalytic behaviors. Structure-activity correlation suggests that the catalyst prepared by sol-gel shows larger pore structure, higher dispersion of Ni nanoparticles, smaller particle size (∼3 nm) and strong interaction of metal-support because of its unique network structure. Meanwhile, it exhibits 100% gas yield and 68% H2 selectivity at 750 °C during activity testing. The gas yield of stability testing remains above 60% after running 50 h at 750 °C and carbon formation rate is only 8.86 mg/gCat·h. Besides, ReaxFF molecular dynamics simulation results substantiate that smaller Ni size can afford more active sites to improve methylcyclohexane conversion, consistent with experimental results. This study can provide guidance on preparation of highly dispersed and stable Ni-based catalysts and analysis of methylcyclohexane steam reforming reaction pathway.