Study on free radical mechanism and experimental verification in biomass hydropyrolysis conversion to liquid fuels

For the biomass hydropyrolysis vapor upgrading (HPVU) route to be widely adopted, comprehensive and indepth research on the free radical mechanism involved and the catalysts' performance is essential. Nine kinds of doped catalysts based on Al2O3-TiO2-SiO2(ATS) as composite supports with different Co, Ni and Mo metal loadings were prepared. Changes in the content of free radicals during the pyrolysis of poplar wood under different sources of hydrogen have been observed by the use of electron paramagnetic resonance. The doped catalysts with high conversion efficiency and carbon deposition resistance were screened out. To validate the findings, product analysis and experimental verification under three different poplar pyrolysis routes(i.e., catalytic hydropyrolysis, hydropyrolysis vapor upgrading, and catalytic hydropyrolysis vapor upgrading) were conducted using a long-term continuous lab-scale HPVU system under different pressures. The study reported a carbon deposition of only 1.56 wt% on the catalyst,and the highest yield of C4 + hydrocarbons achieved was 23.81 wt%daf. Based on the observations, the evolution mechanism in the hydrogenation conversion of biomass to liquid fuels was analyzed.