Sulfur Speciation and Pyrolysis Behavior of Petroleum Cokes with Different Sulfur Levels from Xinjiang

Abstract Petroleum cokes from Xinjiang, China, exhibit significant differences in sulfur content; however, systematic studies on sulfur speciation and pyrolysis behavior across different sulfur levels remain scarce. Herein, three typical industrial petroleum cokes—low-sulfur (Wushihua (WSH), 0.295 wt %), medium-sulfur (Balian (BL), 3.356 wt %), and high-sulfur (Tahua (TH), 4.129 wt %)—were comprehensively characterized using XRD, Raman spectroscopy, XPS, FTIR, SEM–EDS, and TG/DTG. All cokes possess a disordered microcrystalline carbon structure (graphitization degree g ≈ 0). Raman analysis revealed that BL has the highest total defect density (IDall/IG = 5.895), while TH contains the most amorphous carbon (ID3/IG = 2.129). According to XPS quantification, sulfur in WSH exists mainly as highly reactive thiol sulfur (77.07%) and sulfone sulfur, without thiophenic sulfur; BL and TH contain considerable thiophenic sulfur (32.93 and 40.46%) and inorganic sulfur. Notably, WSH, with the lowest total sulfur content, reaches its maximum weight loss rate at 541°C, earlier than BL (610°C) and TH (620°C), indicating that pyrolysis reactivity is governed by the relative proportion of active thiol to stable thiophenic sulfur rather than the total sulfur content. This study provides important theoretical insights and practical value for the clean and high-value utilization of petroleum coke in Xinjiang and the development of targeted downstream desulfurization processes.