Hydrogen-Rich Syngas Production and Mechanism via Staged Pyrolysis-Chemical Looping Gasification of Waste Plastics Based on LaFeO₃

In the process of waste resource utilization for the goal of “double carbon”, waste plastic gasification syngas has become the focus of emerging technologies due to its rich hydrocarbon characteristics and negative carbon potential. Compared with the carbon resource dissipation and secondary pollution caused by traditional incineration or landfill, gasification technology converts polyolefin waste into high-purity syngas, which has the advantages of low pollution, high economic benefits and strong flexibility. It provides a key path for high-value utilization of waste and green hydrogen co-production, and has a significant effect in realizing resource recycling and reducing environmental pollution.To address challenges such as inadequate syngas quality and catalyst deactivation in conventional gasification processes, a staged chemical looping gasification （SCLG） process is proposed. A typical perovskite-type LaFeO₃ oxygen carrier, synthesized via the sol-gel method, is employed in gasification experiments using polypropylene in a fixed-bed reaction system. The influence of pyrolysis temperature, gasification temperature, and the mass ratio of LaFeO₃（OC） to polypropylene （PP） on the gasification performance of the LaFeO₃ oxygen carrier is systematically investigated. In this process, the feedstock and oxygen carrier are physically separated, thereby effectively avoiding issues of catalyst contamination by solid residues, char, and tar that are commonly encountered in single-stage gasification. Furthermore, the staged reaction mechanism fully utilizes the partial oxidation capacity of the oxygen carrier and the catalytic cracking ability of the reduced metal, leading to a notable improvement in both the yield and quality of syngas. Results indicate that the pyrolysis temperature exerts limited influence on gasification performance, whereas appropriately elevated gasification temperatures are found to significantly enhance the process. An optimal m（OC）∶m（PP） ratio is identified to effectively balance the two-step reactions of oxidative reforming and catalytic cracking, resulting in improved gasification outcomes. Under conditions of a pyrolysis temperature of 600 ℃, a gasification temperature of 850 ℃, and an m（OC）∶m（PP） ratio of 1∶1, the optimal gasification performance is achieved: a syngas yield of 143 mmol/g, a carbon conversion rate of 82%, CO selectivity of 80%, and satisfactory cycling stability are obtained. Guidance is provided for the scaling of efficient and stable gasification technology and the resource utilization of waste plastics.