Cu SAPO 34 One Pot Hydrothermal Preparation Method for Particular Copper Configuration

Abstract

Two different routes of synthesis were followed in order to compare the surface properties of two Cu-SAPO-34 catalysts. The direct copper incorporation during the hydrothermal synthesis, compared to the conventional impregnation method, allowed us to study the impact of active centers location on the catalytic activity during both the selective catalytic reduction of NOx by NH3 and the NH3 oxidation. X-ray diffraction, ex-situ diffuse reflectance infrared spectroscopy and X-ray photoelectron spectroscopy analysis were performed to know the copper location and its state for each catalysts. A unique location of the copper oxide at the surface of the synthesized catalyst was observed when the hydrothermal process was used. For similar Cu contents in the catalysts, different catalytic behaviors during the selective catalytic reduction of NOx by NH3 and during the NH3 oxidation were observed as a consequence of the specific activity of the copper clusters. Indeed, some cations in exchanged position were detected when the impregnation method was used, allowing high SCR performance at low temperature. On the other hand, the small copper clusters at the surface and the exchanged cations exhibited a certain NH3 oxidation at low temperature, hindering DeNOx activity. Catalyst with mainly large copper clusters and no appreciable occurrence of exchanged Cu2+ present in a range of temperatures, limited NH3 oxidation and high SCR performance.