Insights into the impact of lanthanum on hydrothermal-induced migration and transformation of copper species in Cu/SAPO-34 catalyst for NH3-SCR

Abstract

During the high-temperature hydrothermal aging process, the tolerance of the zeolite structure and the stability of the active Cu2+ ions directly determined the denitration (deNOx) performance of the copper-based zeolite catalysts in automobile exhaust treatment. Herein, we displayed the hydrothermal aging stability of La-free and La-doped Cu/SAPO-34 catalysts at variant temperatures (650, 750 and 850 °C). A series of characterization results signified that the addition of La into SAPO-34 framework by ion exchange method had obvious contribution to hold back the collapse of SAPO-34 structure and transformation of isolated Cu2+ ions. Different from Cu/SAPO-34 catalyst, Cu/La-SAPO-34 catalyst was more prone to maintain its superior catalytic activity after hydrothermal aging at 750 °C, which possessed great application potential. In addition, NH3-TPD and DRIFT spectra shed light on the variation of surface acidity over two kinds of catalysts inducing by hydrothermal treatment. It could be discovered that doping of La provided moderate surface acidity and excellent hydrothermal stability for Cu/SAPO-34 even up to 750 °C, which was in favor of the NH3-SCR reaction.