Effect of metal complexing on Cu-Mn/SAPO-34 catalysts for selective catalytic reduction of NO with NH3

A bimetallic Cu-Mn/SAPO-34 catalyst was synthesized through a one-step hydrothermal process, using coppertetraethylenepentamine (Cu-TEPA) and manganese-diethylenetriamine (Mn-EDTA) as co-templates. The co- templates could effectively disperse and stabilize active metal components compared to conventional CuTEPA. The effect of EDTA content on ammonia selective catalytic reduction (NH3-SCR) performance was investigated, revealing that CMS-2, with a Mn/EDTA ratio of 2, achieved a NOx conversion efficiency of 90 % within a broad temperature window of 150-400 degrees C at a GHSV of 20,000 h-1 . CMS-2 also exhibited superior H2O/ SO2 resistance compared to the CMS catalyst prepared using Cu-TEPA as a template, maintaining over 95 % NOx conversion after exposure to 100 ppm SO2 for 6 h or 5 vol% H2O for 2 h at 200 degrees C. The physicochemical properties of the catalysts were characterized using XRD, N2 adsorption-desorption, SEM, XPS, NH3-TPD, H2- TPR, and kinetic tests. CMS-2 exhibited a high specific surface area (705 m2 g-1) and inter-crystal mesopores, enhancing reactant accessibility. XPS and H2-TPR revealed abundant active sites (Cu 0.51 at%, Mn 0.91 at%) and excellent redox properties (H2 consumption: 11.51 mL g-1). NH3-TPD confirmed strong NH3 adsorption and activation capabilities, with low-temperature (200-300 degrees C, 9.40 mL g-1) and total adsorption (19.26 mL g-1). These properties collectively contribute to the enhanced catalytic performance of CMS-2.