Sulfur Impact on Methane Steam Reforming over the Stoichiometric Natural Gas Three-Way Catalyst 2024-01-2633
The steam reforming of CH4 plays a crucial role in the high-temperature activity of natural gas three-way catalysts. Despite existing reports on sulfur inhibition in CH4 steam reforming, there is a limited understanding of sulfur storage and removal dynamics under various lambda conditions. In this study, we utilize a 4-Mode sulfur testing approach to elucidate the dynamics of sulfur storage and removal and their impact on three-way catalyst performance. We also investigate the influence of sulfur on CH4 steam reforming by analyzing CH4 conversions under dithering, rich, and lean reactor conditions. In the 4-Mode sulfur test, saturating the TWC with sulfur at low temperatures emerges as the primary cause of significant three-way catalyst performance degradation. After undergoing a deSOx treatment at 600 °C, NOx conversions were fully restored, while CH4 conversions did not fully recover. Experimental data under fixed lambda conditions reveal that sulfur stored on the catalyst leads to reduced CH4 conversions by steam reforming at high temperatures under rich conditions. In contrast, CH4 conversions by oxidation at high temperatures under lean conditions remain consistent, indicating a greater impact of sulfur on CH4 steam reforming. Analysis using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) shows the potential for sulfur-induced deterioration of active sites and oxygen storage capacity, resulting in the formation of carbonaceous species on the catalyst surface.
