Comparison of conventional and simplified heterogeneous modeling frameworks for simulation of sulfur poisoning in methane reforming catalyst

Abstract

Hydrogen production from methane and carbon dioxide offers a promising route to add value and mitigate climate change. These gases often contain hydrogen sulfide, a well-known catalyst poison, driving the development of sulfur-tolerant catalysts. However, sulfur poisoning has received limited attention in fixed-bed reactor modeling. In this study, two modeling frameworks—simplified and conventional heterogeneous—are developed and compared. The conventional model explicitly accounts for reaction and heat and mass transfer within the catalyst pellet, while the simplified model represents these effects using a catalyst effectiveness factor. Both models are discretized using the finite volume method and programmed in MATLAB, with predictions validated against experimental data from the literature. Kinetic modeling identifies activation energy corrections of 24.4 $kJ/mol$ and 27.0 $kJ/mol$ for the simplified and conventional models, respectively. Transport limitations appear above 1173 $K$. The order of deactivation was determined to be $n=1.0$, with an average absolute error of 27.2% and 26.2% for methane conversion predictions in simplified and conventional models, respectively, contrasting the more commonly assumed $n=3.0$. Under industrial conditions, both models performed similarly when unpoisoned. However, the conventional model showed an increase in catalyst effectiveness as poisoning occurred, reflecting the slower reaction kinetics relative to mass transport. When the effectiveness in the simplified model was adjusted to match the conventional model, their results realigned. While conventional modeling is more robust, it has a higher computational cost. Simplified modeling remains desirable for assessing catalyst poisoning, but further research is needed to determine how it can account for changes in catalyst effectiveness during poisoning.