Significant Enhanced SO2 Resistance of Pt/SiO2 Catalysts by Building the Ultrathin Metal Oxide Shell for Benzene Catalytic Combustion

A noble metal catalyst shows excellent low-temperature oxidation activity in the catalytic combustion of benzene but has the problem of SO₂ poisoning. We all know that SO₂ easily competes with the reactant molecules for adsorption of the active site and has electronic effects on the active site to deactivate the catalyst. Therefore, the sulfur resistance of catalysts is the key problem to be solved in the process of catalytic combustion of benzene. Herein, the Pt/SiO₂ catalyst with an ordered mesoporous structure was prepared by a one-step hydrothermal method, and MgO, ZnO, and MnO_x were, respectively, coated on the surface of Pt/SiO₂ as ultrathin shells to improve the sulfur resistance of Pt/SiO₂. We observed that the sulfur resistance of the Pt/SiO₂ catalyst was significantly improved due to the protective effect of the metal oxide shell. By comparing the three core-shell catalysts, it was found that the Pt/SiO₂@MnO_x catalyst coated with a MnO_x shell had the best performance. The reason was that the MnO_x shell not only protected the Pt active site but also had a good electron transfer effect on the core Pt, so it could effectively avoid the rapid adsorption poisoning of SO₂ on the active Pt⁰ site. In addition, it was verified that the excellent redispersion of MnO_x species in a SO₂ atmosphere could increase the low-temperature oxidation activity of the Pt/SiO₂@MnO_x catalyst. Meanwhile, in situ DRIFT results also confirmed that the MnO_x shell could significantly promote the oxidation of benzene molecules in the SO₂ atmosphere.