Migration and Rearrangement of Fe-Zn Species in the Preparation of Fe-Zn Bimetallic Catalysts and Their Effects on the Hydrodesulfurization Reactivity

Bimetallic chemistry and structural arrangements are effective ways to improve catalytic activity. The Fe-Zn bimetallic catalysts were prepared by urea addition, and their effects on the hydrodesulfurization (HDS) reactivity of dibenzothiophene were investigated. It indicated that the addition of urea changed the bimetallic distribution, resulting in a significant increase in the Fe/Zn atomic ratio on the catalyst surface, which not only promoted the electron donating ability of Zn to Fe but also weakened the interaction between the metal and support. As a result, the sulfidation degree and the FeZnS active phase content in the urea-modified catalyst increased through bimetallic migration and rearrangement during the activation process. This resulted in an enhanced HDS activity by up to 50%, and the rate constant kHDS increased by 3.15 times versus the urea-free catalyst at 613 K. Moreover, it shows that the urea-modified Fe-Zn bimetallic catalysts enhanced the hydrogenation pathway significantly.