Oxygen-Vacancy-Rich Co–Ce/C for Highly Stable Catalytic Steam Reforming of Toluene at Low Temperature

Developing highly active catalysts, which possess highly dispersed small active particles, strong metal–support interaction (MSI) and abundant oxygen vacancies, has attracted much attention in the steam reforming of biomass tar. In this study, a series of Ce-promoted lignite-char-supported Co catalysts (Co–Ce/C) was prepared via ion exchange combined with an impregnation method. A smaller average metal particle size (4.22 nm), higher reduction degree (90%), larger number of oxygen vacancies (58%) and stronger MSI were obtained when the Ce content was 5 wt %. For steam reforming of toluene, Co-5Ce/C exhibited the highest activity, such that toluene conversion and H2 yield reached 100% and 4137 μmol·min–1·gCo –1, respectively, and good stability such that the toluene conversion remained at 92% after 100 h of continuous reaction at 450 °C. The low apparent energy (45.8 kJ/mol) was consistent with the high activity of Co-5Ce/C, while less carbon deposition and slighter growth of metal particle size (5.45 nm) over the spent catalyst corresponded to its good stability. In short, the formation of oxygen vacancies due to the introduction of Ce not only increased the dispersion of active metal but also promoted the adsorption and activation of H2O molecule and accelerated the carbon removal. The reported catalyst can be promising for highly efficient conversion of the real biomass tar, especially at relatively low temperatures.