A series of CuII−SSZ−13 catalysts are prepared by in-situ hydrothermal method using different copper precursors (CuII(NO3)2, CuIISO4, CuIICl2) for selective catalytic reduction of NO by NH3 in a simulated diesel vehicle exhaust. The catalysts were characterized by X−ray diffraction (XRD), scanning electron microscope (SEM), X−ray photoelectron spectroscopy (XPS), N2 adsorption-desorption, hydrogen-temperature-programmed reduction (H2−TPR), ammonia temperature-programmed desorption (NH3−TPD), and 27Al and 29Si solid state Nuclear Magnetic Resonance (NMR). The CuII−SSZ−13 catalyst prepared by CuII(NO3)2 shows excellent catalytic activity and hydrothermal stability. The NO conversion of CuII−SSZ−13 catalyst prepared by CuII(NO3)2 reaches 90% at 180 °C and can remain above 90% at a wide temperature range of 180–700 °C. After aging treatment at 800 °C for 20 h, the CuII−SSZ−13 catalyst prepared by CuII(NO3)2 still exhibits above 90% NO conversion under a temperature range of 240–600 °C. The distribution of Cu species and the Si/Al ratios in the framework of the synthesized CuII−SSZ−13 catalysts, which determine the catalytic activity and the hydrothermal stability of the catalysts, are dependent on the adsorption capacity of anions to the cation during the crystallization process due to the so called Hofmeister anion effects, the NO3− ion has the strongest adsorption capacity among the three kinds of anions (NO3−, Cl−, and SO42−), followed by Cl– and SO42– ions. Therefore, the CuII−SSZ−13 catalyst prepared by CuII(NO3)2 possess the best catalytic ability and hydrothermal stability.
Thermal and hydrothermal stability of pure and silica-doped mesoporous aluminas