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 degrees 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 (alpha) range of 0.05-0.2 and a downtrend in alpha 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 <= alpha <= 0.20) and then decreased to 38.32 kJ/mol (0.2 < alpha <= 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.