Microwave-Assisted Camellia oleifera Abel Shell Biochar Catalyzed Fast Pyrolysis of Waste Vegetable Oil to Produce Aromatic-Rich Bio-Oil

In this work, Camellia oleifera Abel shell was used as a feedstock to prepare biochar by HNO₃ impregnation and pyrolysis. The biochar was used for the catalytic pyrolysis of waste vegetable oil to prepare bio-oil. Experimental results showed that HNO₃ solution treatment had an important effect on the groups and structure of the biochar catalyst. When the solid/liquid ratio of pretreatment was 1:3, the Brunauer–Emmett–Teller specific surface area of the 1:3–600°C biochar is 392.65 m²/g, which is approximately 677 times higher than that of untreated biochar. Moreover, the biochar catalyst had a remarkable catalytic performance. The selectivity of the monocyclic aromatic hydrocarbon in the bio-oil was up to 78.82%, and the oxy-compound could be completely removed at the catalytic temperature of 600°C. However, the increase of the catalyst-to-waste vegetable oil ratio and catalytic temperature decreased the bio-oil yield.