Analysis of the Composition and Thermogravimetric Kinetics of Vacuum Residue from Karamay

Abstract

Vacuum residue (VR) is one of the more difficult heavy fractions to process in petroleum refining, and the development of clean utilization technologies for vacuum residue has become a major research focus in the petrochemical industry. This paper discusses the compositional and structural characteristics of vacuum residue from Karamay (KVR) using methods such as ultimate analysis, FTIR, and TG-DTG. The thermal gravimetric kinetics analysis was conducted based on TG-DTG curves at different heating rates. Ultimate analysis revealed that KVR has a high H/C atomic ratio (1.84), and combined with the strong peaks at 2920 cm−1 and 2850 cm−1 in its infrared spectrum, it indicates that KVR is mainly composed of aliphatic compounds, with aromatic compounds being relatively few. High-temperature simulated distillation showed that KVR had a broad boiling-range distribution, with the temperature corresponding to a cumulative recovery of 86.4% exceeding 720 °C, indicating the presence of a certain proportion of ultra-high-boiling components in KVR. The Coats–Redfern kinetic model shows significant variations in activation energy (Ea) at different temperature ranges and reaction orders. Kinetic studies using non-model methods show smaller differences in Ea derived from four different non-model methods. Overall, KVR’s pyrolysis process is complex, with Ea ranging between 100 and 300 kJ/mol.