Comparative study on thermal cracking behaviors and kinetics of two typical lignocellulosic biomass pyrolysis oils

To improve the utilization efficiency of biomass pyrolysis oil, the pyrolysis characteristics of biomass pyrolysis oil in the process of transformation were explored, so as to further expand the utilization ways of biomass pyrolysis oil, two kinds of lignocellulosic biomass pyrolysis oils of rice husk and sawdust were selected as the materials, and the cracking behaviors of these two pyrolysis oils were investigated by TG. The Friedman, FWO, and distributed activation energy model (DAEM) methods were used to calculate the overall reaction and kinetic parameters of two virtual components. The results showed that the content difference between light components and heavy components of two pyrolysis oils resulted in different cracking behaviors. The maximum thermogravimetric rate corresponds to temperature and the end temperature of sawdust pyrolysis oil weight-loss reaction was higher than that of rice husk. The activation energy calculated by Friedman and FWO methods was 89.92 and 90.30 kJ/mol for rice husk pyrolysis oil, and 145.98 and 138.44 kJ/mol for sawdust pyrolysis oil, respectively. Two pyrolysis oils were separated into light and heavy components by DAEM. The calculated activation energy of light components of rice husk and sawdust pyrolysis oils (79.03 and 85.00 kJ/mol) was lower than that of heavy components (158.56 and 160.00 kJ/mol). Synergistic effect between light and heavy component existed in the cracking process, and the light component reduced the cracking activation energy of biomass pyrolysis oil. The comprehensive use of the two kinetic calculation methods was conducive to the formation of a more comprehensive understanding of the pyrolysis reaction of bio-oil.