Improved hydrothermal stability of Cu-SSZ-13 by SAPO-34 modification: Framework stability and inter-particle migration

Abstract

Cu-SSZ-13 catalysts face a challenge of more severe hydrothermal aging from the regeneration of upstream diesel particulate filter (DPF) or in-situ regeneration of SCR on filter (SCRF). Herein, a typical Cu-SSZ-13 was modified by mixing with low proportions of SAPO-34 (3–30 wt%) via ball milling, and the obtained catalysts were hydrothermally aged at 800 °C for 16 h. The reservation and evolution of isolated Cu2+ ions and CHA framework were revealed by scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), magic angle spinning nuclear magnetic resonance (MAS NMR), electron paramagnetic resonance (EPR), ultraviolet–visible (UV–Vis) absorption spectroscopy, and in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Compared to the aged Cu-SSZ-13, the dealumination of zeolite framework was suppressed over the co-aged composite, in which more Cu2+ and strong Brønsted acid sites were reserved. Importantly, it is attributed to inter-particle migration of extra-framework P of SAPO-34 into the defects of SSZ-13 produced new P-O-Al bonds. Additionally, SAPO-34 provided accommodation for some detached copper of Cu-SSZ-13 at the interface and reactivated them as Cu2+ active sites instead of the formation of harmful CuO-like and inert CuAl2O4-like species.