In-situ One-Pot Synthesis of Ti/Cu-SSZ-13 Catalysts with Highly Efficient NH3-SCR Catalytic Performance as Well as Superior H2O/SO2 Tolerability

Abstract

Series of Ti/Cu-SSZ-13 zeolite catalysts with variable Ti content were prepared via convenient in-situ one-pot synthesizing strategy. Systematic evaluations of the NH₃-SCR catalytic performance over the obtained catalysts were conducted. Results show that Ti/Cu-SSZ-13 with appropriate Ti content (in the current work Ti_0.81/Cu_2.15-SSZ-13) could serve as capable candidate for NH₃-SCR application, as it exhibits highly efficient catalytic activity with expanded operation temperature window width from 140 to 540 °C, nearly 100% N₂ selectivity, as well as superior tolerability against water vapor and SO₂. Further structural/physicochemical characterizations demonstrate that the obtained Ti/Cu-SSZ-13 catalysts possess well-crystallized characteristic chabazite (CHA) structure. Isolated Cu²⁺ and monomeric Ti⁴⁺ are recognized as the primary active species, as the former mainly contributes to SCR reaction at low temperatures, while the latter are conducive for improving the high temperature SCR activity. Ti over doping would result in partial destruction of the zeolite structure, occupation of Cu²⁺ cation sites and formation of surface aggregated TiO_x, thus leading to unsatisfactory NH₃-SCR performances. Moreover, formation of agglomerated CuO_x species during hydrothermal ageing and blockage of surface active sites by sulfate species formed during SO₂ pretreatment are considered responsible for activity deterioration in the tolerability tests.