Non-vanadium-based catalysts with high SO2 tolerance are still interesting in selective catalytic reduction of NO by NH3 (NH3-SCR) and SO2 adsorption is the foremost step for the deactivation of catalysts. In order to alleviate the adsorption of SO2, we fabricated a series of rhenium (Re; without stable sulfate) supported TiO2 catalysts and studied their SO2 tolerance for the first time. Owing to suitable surface acidity and reducibility, ReOx/TiO2 catalysts exhibited satisfactory activity in a wide temperature range of 250–350 °C. As expected, experimental results and DFT calculations indicated that SO2 adsorption on ReOx/TiO2 catalysts was rather weak, thus the catalysts performed excellent SO2 tolerance in the NH3-SCR reaction. Moreover, in situ DRIFTS indicated that the NH3-SCR reaction on ReOx/TiO2 catalysts followed the Eley–Rideal mechanism and SO2 had little effect on the reaction mechanism. Our findings should provide new insights into the development of SCR catalysts with high SO2 tolerance.
Guang Gao,Zelun Zhao,Jia Wang,Yongjie Xi,Peng Sun,Fuwei Li
ABSTRACT Engineering the surface microenvironment by tuning the binary interactions between a supported metal with a secondary metal oxide (MO x ) or support has been a common method for improving the catalytic performance of supported metal catalysts. However, few studies have investigated the ternary interactions among the metal, MO x , and support. Here, we report for the first time the formation of metal-MO x -support interaction (MMSI) in reducible TiO 2 -supported PtReO x catalysts, affording 87% yield and 100% ee in the tandem hydrogenation of an aqueous chiral cyclohexane-1,2-dicarboxylic acid into the corresponding diol; the catalytic activity is eight times higher than that obtained with non-reducible support counterparts in the same reaction via traditional batch synthesis with multiple steps and unfriendly reagents. Detailed experimental and computational studies suggest that the TiO 2 crystalline phase-dependent density of the oxygen vacancies induces different Pt-ReO x -TiO 2 interactions, which dominate the electron transfer therein and tune the adsorption strength of the carbonyl moiety of the substrate/intermediate, thus promoting the hydrogenation activity and selectivity. In addition, the strong MMSI endows the optimal rutile TiO 2 supported PtReO x catalyst with an outstanding lifetime of 400 h in a fixed-bed reactor under acidic aqueous conditions and ensures efficient applications in the selective hydrogenation of aliphatic dicarboxylic acids and functional carboxylic acids. This work provides a promising strategy for the development of efficient and stable supported catalysts for the selective hydrogenation of diverse C–O and C=O bonds.
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