In-situ catalytic pyrolysis of pine powder by ZnCl2 to bio-oil under mild conditions and application of biochar

Fast pyrolysis of biomass is an effective way for biomass conversion and utilization. However, the pyrolysis temperature is usually high because it is a non-catalytic process, resulting in the complicated composition of bio-oil and difficulty to control. Aiming to explore in-situ catalysis in this paper, the fast pyrolysis of lignin, cellulose, corncob and pine wood powder was studied using ZnCl₂ as the catalyst. The activation energies of non-catalytic pyrolysis and catalytic pyrolysis were obtained based on kinetic fitting of their thermal gravimetric curves. The variation in pyrolysis oil composition was analyzed. It was found that ZnCl₂ in situ catalysis could not only significantly reduce the pyrolysis temperature, but also simplify the resultant bio-oil composition. Even under pyrolysis temperature as low as 350 °C, fast pyrolysis of pine wood powder could achieve a yield of 47% of bio-oil, which was predominantly composed of the derivatives of cellulose and hemicellulose. ZnCl₂ in situ catalysis could significantly decrease the activation energy of cellulose cracking from 304.78 to 112.46 kJ/mol, but has little effect on that of lignin. The carbon residue from ZnCl₂-catalyzed pyrolysis was further carbonized at 600 °C, affording activated carbon with adsorption capacity of phenol up to 165 mg/g. The research work provides guidance and reference for the development of in-situ catalytic pyrolysis technology with high efficiency.