(6c) Investigating Metal–Support Combinations for Catalytic Activity and Sulfur Tolerance in the Water-Gas Shift Reaction

Hydrogen production from syngas derived through coal or heavy oil gasification is often compromised by the presence of sulfur compounds, primarily hydrogen sulfide (H₂S). These contaminants poison conventional water-gas shift reaction (WGSR) catalysts, severely reducing their effectiveness. The WGSR, essential for increasing H₂ yield by converting CO and H₂O to CO₂ and H₂, typically requires upstream desulfurization, which increases operational complexity and cost. To address this, sulfur-tolerant WGSR catalysts are being developed to eliminate or bypass this desulfurization step, enabling more efficient and economical processing. Sulfur tolerance in WGSR catalysts is determined largely by the nature of the active metal and the physicochemical characteristics of the support, including reducibility, oxygen mobility, and surface basicity. This study investigates how the interaction between metal types and support materials influences both catalytic activity and sulfur resistance under WGSR conditions.

The performance of WGSR catalysts in sulfur-contaminated environments is heavily influenced by both the active metal and the support. Pt/Ce-Zr mixed oxides displayed high initial activity, limited reversible deactivation, and strong oxygen mobility, making them effective for sour WGSR applications. However, Pt/Nb₂O₅ was the standout catalyst, maintaining activity even at high sulfur levels (1000 ppm H₂S), due to its intrinsic sulfur tolerance and support stability. Nb₂O₅ also proved beneficial as a support for Au and CuO-ZnO systems but was ineffective with Cu alone, highlighting the importance of metal-support compatibility. CuO-ZnO/HAP catalysts showed better sulfur resistance and slower deactivation than their Al₂O₃-supported counterparts, pointing to HAP as a promising support for enhancing the durability of Cu-based systems. These findings suggest that with proper design—particularly using Nb₂O₅ or Ce-Zr oxides as supports—it is feasible to develop sulfur-tolerant WGSR catalysts that could eliminate the need for costly desulfurization units in hydrogen production from contaminated feedstocks.