Pyrolysis characteristics of Camellia oleifera seeds residue in different heating regimes: Products, kinetics, and mechanism

The mechanisms, kinetics, and product evaluations of Camellia oleifera seeds residue (COSR) pyrolysis were studied using TGA-FTIR-MS, Py-GC/MS, and a fixed-bed reactor. The pyrolysis process could be divided into primary devolatilization (PDVL) and biochar refractory (BCRF) stages with low and high activation energies, respectively. The gases of CO2, H2, CH4, and H2O(g) were generated in the overall process of pyrolysis. The increase in pyrolysis temperature led to cracking of bio-oil components, especially the fatty acids (FA) and reduced bio-oil yield. The highest bio-oil yield (47.81 wt%) was obtained at 773 K. The biochar refractory stage was characterized by slow depolymerization, dehydrogenation, and deoxygenation reactions to generate more aromatic, alkynes containing compounds, and groups of -CH3, -CH2-, and -CH-. Due to the low reactivity in the biochar refractory stage, the reaction-order of pyrolysis was high (n = 5.2) when kinetic was studied by single-step reaction. In the independent pyrolysis of components model, decompositions of the 1st and 2nd components occurred in the primary devolatilization stage. Whereas, the decomposition of 3rd component corresponded to BCRF stage with similar reaction-order (n = 4.74–5.83) of model-free procedure.