Utilization of steelwork off-gases through methanol synthesis: Sulfur-induced dynamic migration of ZnOx over industrial Cu/ZnO/Al2O3 catalyst and the poisoning mechanism.

The reduction of carbon emissions in the steel industry is a significant challenge, and utilizing CO2 from carbon intensive steel industry off-gases for methanol production is a promising strategy for decarbonization. However, steelwork off-gases typically contain various impurities, including H2S, which can deactivate commercial methanol synthesis catalysts, Cu/ZnO/Al2O3 (CZA). Reverse water-gas shift (RWGS) reaction is the predominant side reaction in CO2 hydrogenation to methanol which can occur at ambient pressure, enabling the decouple of RWGS from methanol production at high pressure. Then, a series of activated CZA catalysts has been in-situ pretreated in 400 ppm H2S/Ar at 250 ℃ and tested for both RWGS reaction at ambient pressure and CO2 hydrogenation to methanol at high pressure. An innovative decoupling strategy was employed to isolate the RWGS reaction from the methanol synthesis process, enabling the investigation of the evolution of active site structures and the poisoning mechanism through elemental analysis, X-ray Diffraction, X-ray Photoelectron Spectroscopy, Fourier Transform Infrared Spectroscopy, Temperature Programmed Reduction and CO2 Temperature Programmed Desorption. The results indicate that there are different dynamic migration behaviors of ZnOx in the two reaction systems, leading to different poisoning mechanisms. These interesting findings are beneficial to develop sulfur resistant and durable highly efficient catalysts for CO2 hydrogenation to methanol, promoting the carbon emission reduction in steel industry.