Kinetic Modeling of Gas Generation in Residue Hydrocracking: A Conversion-Based Approach

In residue hydrocracking, gaseous products (especially methane and ethane) play a significant role in resource allocation and catalyst evaluation. However, current lumped kinetic models for gas formation require numerous parameters and typically exhibit low precision. Here, a simple and relatively independent gas kinetic model was developed for the first time that correlated with residue conversion rates. This newly developed gas model possessed a mean absolute percentage error of 4.5% and was independent of both the reaction temperature (400–420 °C) and time. Subsequently, a dual-pathway kinetic model with different gas generation pathways was further developed. A dual-pathway kinetic model with a mean absolute percentage error of 2.6% could accurately calculate the gas content from both direct and indirect residue cracking. For example, 70.45% of the gas was produced from indirect residue cracking at a residue conversion rate of 75%. Then, the dual-pathway model was applied to effectively distinguish the activity and selectivity of catalysts based solely on the total gas catalysts, although there was a minimal difference (<0.11%) between the two kinds of catalysts. The results revealed that the molybdenum-based catalyst (MoO3/Al2O3) exhibited excellent performance in the direct cracking pathway. Overall, the newly developed model enhances the understanding of gas generation and offers guidance for the catalyst evaluation.