Plasma-catalytic benzene steam reforming over Ce doped Ni-HAP catalysts: Insights into enhanced oxygen activity

Non-thermal plasma (NTP) coupled Ni-based catalysts show significant potential in reforming of biomass tar for syngas production. Carbon deposition on catalysts remains a troubling problem. Ce doping can contribute to the improvement of oxygen vacancies and oxygen activity, which is expected to solve this challenge. In this study, Ce-doped Ni-based catalysts with HAP as support have been prepared. Benzene was selected as a tar model and the effects of Ni/Ce, steam to carbon ratio (S/C), reaction temperature, discharge power, Ni/Ce intervention order and catalysts preparation method on catalytic activity and stability were investigated in NTP-catalytic system. The results show that Ni3/Ce5-HAP-C exhibits the best catalytic activity at a reaction temperature of 450 degrees C, an S/C of 1.6, and a discharge power of 86 W with benzene conversion of 94.99 %, total gas yield of 3501.20 mL/g(benzene) and energy efficiency of 8.75 g/kWh. An increase in Ce proportion significantly enhances the reducibility of the metal oxides and the mobility of the oxygen species, and effectively reduces the catalyst carbon deposition. The increase in temperature significantly enhances the catalyst reactivity and selectivity. The order of metal intervention of Ce followed by Ni proves to be favorable for the Ni-Ce bimetallic catalysts, and the first intervening Ce is able to enhance the lattice oxygen activity and the dispersion of Ni metal. Characterization of the spent catalysts indicates that graphitic carbon is the main type of carbon deposition, and reducing the conversion of benzene and its intermediates into graphitic carbon is crucial to enhance the stability of the catalysts.