Interfacial engineering of MnO2/Al2O3 catalyst for unique sulfur-promoted benzene oxidation at mild temperatures.

Catalyst deactivation by sulfur poisoning remains a critical barrier to widespread industrial application. In this study, MnO2/Al2O3 catalyst was prepared via a simple wet impregnation and in situ redox method. The abundant surface hydroxyl groups of Al2O3 facilitate the formation of Mn-O-Al bonds, creating an intimately contacted Mn-Al interface. Experimental and theoretical calculations reveal that the MnO2/Al2O3 catalyst with an engineered interface exhibits enhanced sulfur resistance and sulfur-promoted activity for benzene oxidation compared to pure MnO2. Interface structure alters the site of sulfur action, and the enhanced sulfur resistance is attributed to the preferential capture of SO2 by interfacial oxygen, forming interfacial sulfates that protect the Mn active sites. The sulfur promotion originates from the formation of Mn-O-(SO3)-Al interfacial structure with abundant defects. Interfacial electron transfer facilitates the formation of high-valent Mn4+ and electrophilic O- species. Meanwhile, the interfacial sulfates act as strong acid sites that adsorb and attack benzene to promote ring-opening. Interface defects induce the formation of oxygen vacancies, which synergistically activate gas-phase oxygen and drive the deep oxidation of benzene. This work provides new insights into the design of sulfur-resistant catalysts.