Synergistic Desulfurization Performance of Industrial Waste Red Mud: A Comprehensive Experimental and Computational Study for COS Removal and CO(g) Production

The desulfurization process is crucial to produce high-purity hydrogen from natural gas because the gas contains sulfur compounds, which triggers the corrosion of tanks and pipes, and deactivates hydrogen fuel cell catalysts. This study evaluated experimentally and computationally the desulfurization performance of industrial waste red mud. The experimental results show that red mud has an outstanding performance in COS desulfurization, in which the sulfur capacity was larger than that for Fe2O3 by 146-156 %. The experimentally observed high performance originated from the synergetic effects between the main active phase of Fe2O3 and another element (Ti). Interestingly, the red mud provides the catalytic behavior producing CO(g) with deposited solid sulfur during the desulfurization reaction. Computational analysis proposed that the Ca/Fe2O3 phase plays a critical role in the catalytic behavior of COS decomposition. Adsorbed CO and S weakly bind on the Ca/Fe2O3 surface compared to the other phases. Based on the results, red mud has a strong potential to be a desulfurization absorber and COS decomposition catalyst. In addition, these findings provided initial insights into the development of the new low-cost sulfur absorber (Ti substituted Fe2O3) and COS decomposition catalyst (Ca substituted Fe2O3), producing the value-added product of CO(g) from COS(g).