To address the problem of poor low-temperature activity of molecular sieve catalysts,Cu-SAPO-34 catalysts with different Cu loadings were synthesized in situ by a one-pot method,and the effects of catalyst surface properties,Cu species distribution and species on the low-temperature activity of Cu-SAPO-34 were analyzed.Furthermore,the reaction mechanism of NH3 selective catalytic reduction of NOx(NH3-SCR)were investigated.The results show that in situ synthesis is beneficial to SAPO-34 framework stabilization,and the appropriate amount of Cu can make the prepared catalysts to possess a multi-level pore structure dominated by micropores,which is beneficial to SCR reaction.The abundant ZCuOH sites and stable acid sites give the 0.2 Cu-SAPO-34 catalyst excellent low-temperature SCR activity.After mechanistic analysis,SCR reactions over 0.2 Cu-SAPO-34 catalysts both followed the Eley-Rideal and Langmuir-Hinshelwood reaction mechanisms,and the Eley-Rideal mechanism is dominant at low temperatures.
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