Two-step fast pyrolysis of torrefied corncobs and waste cooking oil under different atmosphere for hydrocarbons production

Biomass pyrolysis is a promising method to produce renewable energy, which can contribute to the realization of carbon neutrality. However, high oxygen content and complex composition hinder the utilization of bio-oil produced by biomass pyrolysis. A new technology, two-step fast pyrolysis of torrefied biomass derived from corncobs and waste cooking oil under CO₂ atmosphere, was studied to produce hydrocarbons-rich bio-oil. Results showed that two-step pyrolysis was beneficial to the initial separation of hydrocarbons and oxygen-laden compounds. And the synergy between the torrefied corncobs and waste cooking oil occurred primarily in the second step of the two-step pyrolysis. Application of CO₂ in the first step significantly decreased the total peak area of condensable organic compounds, but increased the relative content of hydrocarbons. No matter what atmosphere was used in the first step, the relative content of hydrocarbons during the application of CO₂ in the second step was lower. Using a CO₂ atmosphere in the first step gave better results, while using N₂ in the second step tended to maximize the hydrocarbons content. Combined with CO₂-assisted pyrolysis and stepwise pyrolysis, this paper provides a new idea for the thermal conversion of corncobs and waste cooking oil, to produce hydrocarbons.