The effect of various templates on the NH3-SCR activities over Cu/SAPO-34 catalysts

Abstract The influence of various acid properties on the NH 3 -SCR activities was studied over four Cu/SAPO-34 catalysts, and these SAPO-34 supports were synthesized by various templates to generate diverse Si coordination structures. The XRD, SEM, NMR, NH 3 -TPD, NH 3 oxidation and kinetic tests were used to characterize the Si coordination structures in SAPO-34 supports and their roles on the NH 3 -SCR activities. The 29 Si NMR and NH 3 -TPD results showed that the template affected the Si coordination structures in SAPO-34 supports, and Si coordination structures further adjusted the acid properties and the Cu species distribution in Cu/SAPO-34 catalysts. The four Cu/SAPO-34 catalysts performed different NO conversions during 120–600 °C though they contained the similar Cu loading by ion-exchange method. During the low temperature range, the kinetic results proved that various Si coordination structures did not affect the apparent activation energy (Ea) of NH 3 -SCR. But it was found that the acid densities were related to the NO conversions. In addition, the NH 3 oxidation and NH 3 -SCR were competing reactions during the high temperature range, and the former one decreased the NO conversions in NH 3 -SCR for the competition of NH 3 consumption. The strong acid sites could inhibit the NH 3 conversions in NH 3 oxidation, and it is found that the different Si coordination structures influenced the apparent activation energy (Ea) of NH 3 oxidation over Cu/SAPO-34 catalysts. It was likely that the adsorbed NH 3 species on the Bronsted acid sites showed more active in NH 3 -SCR than NH 3 oxidation. Finally, the influence of various acid properties on NH 3 -SCR activities and the NH 3 oxidation was concluded.