A series of Cu^II−SSZ−13 catalysts are prepared by in-situ hydrothermal method using different copper precursors (Cu^II(NO₃)₂, Cu^IISO₄, Cu^IICl₂) 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 Cu^II−SSZ−13 catalyst prepared by Cu^II(NO₃)₂ shows excellent catalytic activity and hydrothermal stability. The NO conversion of Cu^II−SSZ−13 catalyst prepared by Cu^II(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 Cu^II−SSZ−13 catalyst prepared by Cu^II(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 Cu^II−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 SO₄^2– ions. Therefore, the Cu^II−SSZ−13 catalyst prepared by Cu^II(NO₃)₂ possess the best catalytic ability and hydrothermal stability.

Noble metals have become a research hotspot for the oxidation of light alkanes due to their low ignition temperature and easy activation of C-H; however, sintering and a high price limit their industrial applications. The preparation of effective and low-noble-metal catalysts still presents profound challenges. Herein, we describe how a Ru@CoMn₂O₄ spinel catalyst was synthesized via Ru in situ doping to promote the activity of propane oxidation. Ru@CoMn₂O₄ exhibited much higher catalytic activity than CoMn₂O₄, achieving 90% propane conversion at 217 °C. H₂-TPR, O₂-TPD, and XPS were used to evaluate the catalyst adsorption/lattice oxygen activity and the adsorption and catalytic oxidation capacity of propane. It could be concluded that Ru promoted synergistic interactions between cobalt and manganese, leading to electron transfer from the highly electronegative Ru to Co²⁺ and Mn³⁺. Compared with CoMn₂O₄, 0.1% Ru@CoMn₂O₄, with a higher quantity of lattice oxygen and oxygen mobility, possessed a stronger capability of reducibility, which was the main reason for the significant increase in the activity of Ru@CoMn₂O₄. In addition, intermediates of the reaction between adsorbed propane and lattice oxygen on the catalyst were monitored by in situ DRIFTS. This work highlights a new strategy for the design of a low-noble-metal catalyst for the efficient oxidation of propane.

To reveal the role of SO₃ poisoning in Cu/SSZ-13 NH₃-SCR catalysts, fresh and sulfated Cu/SSZ-13 catalysts were prepared in the presence or absence of SO₃ flux. The deactivation mechanism is probed by the changes of structural, copper species, and selective catalytic reduction (SCR) activity. The variations concentrate on the changes of copper species as the Chabazite (CHA) framework of Cu/SSZ-13 catalysts could keep intact at high ratios of SO₃/SO_x. The thermal gravimetric analyzer (TGA) results reveal that the copper sulfate formed during sulfation and the amounts of sulfate species increased with an increase in the SO₃/SO_x ratio. In contrast to the changing trend of copper sulfate, temperature program reduction (H₂-TPR), and electron paramagnetic resonance (EPR) results manifest that, since the number of active copper ions declines with an increase of the SO_3/SO_x ratio, the active sites transform to these inactive species during sulfation. Due to the combination of NH₃-SCR activity and the kinetic tests, it is shown that the decreased number of active sites is responsible for the declined SCR activity at low temperature. As Cu/SSZ-13 catalysts show excellent acid-resistance ability, our study reveals that the Cu/SSZ-13 catalyst is a good candidate for NO_x elimination, especially when SO₃ exists.