Microwave reforming with char-supported Nickel-Cerium catalysts: A potential approach for thorough conversion of biomass tar model compound

Abstract Tar abatement and removal is most challenging facing industrialization of biomass gasification technology and its cost-effective removal is indispensably dreamed. Thorough, low-cost and stable removal of toluene, a major compound of biomass tar, was achieved by the microwave catalytic reforming method. A self-designed microwave tube furnace was employed, and toluene was converted with char-supported nickel-iron and nickel-cerium catalysts in an ex situ hot gas conditions. Under the optimal conditions, a 100% toluene conversion efficiency could be achieved, and the hydrogen concentration in the product gas could reach 28.2 vol%. The energy efficiency was 98.97 g/kW h. According to duration tests, the conversion efficiency of nickel-cerium catalysts could still be higher than 90%, even after 8-h successive runs. Comprehensive characterizations of fresh and spent catalysts were conducted, showing agglomeration was the main challenge instead of carbon deposition, which was previously commonly believed. Furthermore, in the pursuit of advancing industrial tar abatement, the depletion and thermal stability of char-supported catalysts were evaluated through a custom-designed gasification-atmosphere-thermogravimetry-mass spectrum analysis. The study provided a breakthrough for the integration of thermal, catalysis and microwave effects for toluene conversion, and the mechanism of char-supported catalysis under specific microwave conditions was also highlighted.