A novel strategy for rapid identification of pyrolytic synergy and prediction of product yield: Insight into co-pyrolysis of xylan and polyethylene

The distributions of biomass and plastic co-pyrolysis products are complicated by abundant component combinations, pyrolysis conditions, and synergies. Herein, the hierarchical clustering analysis (HCA) and response surface methodology (RSM) were used to rapidly determine synergies and predict product yields of xylan and polyethylene (PE) co-pyrolysis at 500–700 °C. The results showed that co-pyrolysis promoted liquid production and suppressed solid and char formation. Pyrolytic interactions improved the decomposition of the PE-derived wax, resulting in 1.5–1.9- and 1.7–2.1-fold higher yields of heavy gas oil and C≥26 hydrocarbons compared to the theoretical values. HCA classified pyrolyzates with similar synergy into the same cluster, which reflected the suppressed carbonyl compound production, enhanced furfural and phenols yields at 700 °C, and greater C17–C30 hydrocarbon production. The quadratic model of RSM predicted the yields of gas, CO, C3Hn, C4Hn, liquid, ethanol, acetaldehyde, hydrocarbon oil, gasoline, solid, and char influenced by synergies. Owing to complex interactions, the cubic model fitted the CH4 and C2H4 yields. The linear model described the CO2 yield without synergy. This work illustrates the utility of combining RSM and HCA to predict product distributions of various waste co-treatment processes.