Characteristic analysis and kinetics description for biochar-based catalysts coking during the biomass catalytic pyrolysis

[Display omitted] •Coke formation characteristics of biochar-based catalysts were systematically investigated.•Development of a MMCGM for characterizing coke on biochar-based catalysts at low temperatures.•Based on the mechanism and experimental data, the carbon particle stacking model was established. Coke formation is one of the major obstacles in the development of catalytic pyrolysis of biomass. The experiments were carried out on poplar wood chips using the biochar-based catalysts (poplar biochar: ZSM-5 = 1:2) to study the coke formation characteristics of biochar-based catalysts and to develop the kinetic models of coke formation. It is shown that the high temperature and long reaction time promoted the conversion of carbon from amorphous coke to graphitized coke. The higher the degree of graphitization of the coke, the higher the combustion temperature and the richer the cyclized structure. Activated coke and neutral coke were gradually converted to inert coke per unit mass of catalyst. Based on the experimental data, combined AIC evaluation system, it is found that the MMCGM (monolayer-multilayer coke growth model) can only describe the coke formation at low temperature well. Therefore, the kinetic model of carbon particle stacking model was established. This model can well describe the coke formation process on biochar-based catalysts. This study is expected to provide a guide for understanding the characteristics of catalyst coke formation and optimizing pyrolysis conditions and reactors.