Thermal behavior and kinetic study on the co-pyrolysis of biomass with polymer waste

The intrinsic smaller hydrogen to carbon (H/C) ratio for lignocellulosic biomass significantly affects the yield and production of target products. Co-pyrolyzing of biomass with hydrogen-rich chemicals or raw materials offers an alternative pathway to improve the H/C ratio of feedstock and thus upgrade the bio-oils. In this work, the co-pyrolysis of rice husk (RH) with epoxy resin (ER) was attempted, and its kinetic was comprehensively studied using the model-free and model-fitting methods. The co-pyrolysis mechanism and kinetic compensation effects were probed as well. The thermogravimetric analysis indicated that the decomposition of RH-ER blend with a weight ratio of 1:1 can be divided into three stages with heating temperatures of 27–270, 270–500, and 500–850 °C and corresponding mass loss of 6.86, 49.30, and 5.60%, respectively. For the model-free models applied, the activation energies (Ea) displayed an uptrend in the degree of conversion (α) range of 0.05–0.2 and a downtrend in α range of 0.2–0.6. Comparing the six methods, the Ea values from Friedman method was significantly larger than those from other models. The Flynn–Wall–Ozawa (FWO) method was more reliable with higher correlation coefficients. The obtained Ea values gradually increased from 65.06 to 159.55 kJ/mol (0.05 ≤ α ≤ 0.20) and then decreased to 38.32 kJ/mol (0.2 < α ≤ 0.60). The Ea values calculated based on three-dimensional diffusion (Jander equation) was comparable to that from the FWO method and could be responsible for the co-pyrolysis mechanism for RH-ER blend. An excellent linear relationship lnA = 0.2058Ea − 2.63095 can be observed, indicating that the compensation effect existed between the Ea and lnA during RH and ER co-pyrolysis. The pre-exponential factor (A) was determined as 2.9E8 min−1 using the average Ea value of 107.48 kJ/mol. Through this study, it is expected to promote the collaborative disposal of multisource solid waste.