Co-Pyrolysis of Waste Tires and Beech Sawdust: Comprehensive Analysis of Thermal Behavior, Synergistic Effect, and Interaction Mechanisms

Against the backdrop of the global search for alternatives to fossil fuels, waste tires have attracted attention as a significant resource due to their enormous production volume and considerable energy potential. However, the application of tar derived from waste tires alone is limited by its poor stability and other deficiencies. This study systematically investigates the co-pyrolysis behavior and synergistic mechanisms of waste tires and beech sawdust at various blending ratios. Thermogravimetric analysis indicates that the addition of beech sawdust reduces the decomposition temperature of the blend and induces a synergistic effect that promotes waste tire pyrolysis within the temperature range of 384–440 °C. Pyrolysis experiments results show that tar yield of the blends reached 64.45 wt.%, while the char yield decreased from 40.67 wt.% to 24.83 wt.%. Also, the presence of beech sawdust synergistically enhanced the formation of aromatic hydrocarbons in the tar of waste tires, with the total yield of aromatics increasing synergistically by up to 54.8%. Specifically, the yields of stable alkylbenzenes such as toluene and xylene were consistently promoted, whereas the yields of unsaturated aromatics such as allylbenzene and 2,4-dimethylstyrene were enhanced at low beech sawdust ratios but suppressed at higher ratios. Based on these findings, the interaction mechanisms underlying the co-pyrolysis process were elucidated, providing theoretical guidance for the high-value utilization of waste tires.