The stable phase equilibrium data of the K + , Mg 2+ //Cl − , SO 4 2− + H 2 O quaternary interaction system and its four ternary subsystems KCl

To reveal the role of impregnated sodium (Na) ions in Cu/SSZ-13 catalysts, Cu/SSZ-13 catalysts with four Na-loading contents were prepared using an incipient wetness impregnation method and hydrothermally treated at 600 • C for 16 h. The physicochemical property and selective catalytic reduction (SCR) activity of these catalysts were studied to probe the deactivation mechanism. The impregnated Na exists as Na + on catalysts and results in the loss of both Brönsted acid sites and Cu 2+ ions. Moreover, the high loading of Na ions destroy the framework structure of Cu/SSZ-13 and forms new phases (SiO 2 /NaSiO 3 and amorphous species) when Na loading was higher than 1.0 mmol/g. The decreased Cu 2+ ions finally transformed into Cu x O, CuO, and CuAlO x species. The inferior SCR activity of Na impregnated catalysts was mainly due to the reduced contents of Cu 2+ ions at kinetic temperature region. The reduction in the amount of acid sites and Cu 2+ ions, as well as copper oxide species (Cu x O and CuO) formation, led to low SCR performance at high temperature. Our study also revealed that the existing problem of the Na ions' effect should be well-considered, especially at high hydrothermal aging when diesel particulate filter (DPF) is applied in upstream of the SCR applications.Catalysts 2018, 8, 593 2 of 15 (>0.5%) mainly due to the decreased amount of isolated Cu 2+ formed CuO x clusters. Wang et al. [10] further found that alkali decreased the number of Brönsted acid sites and NH 3 coverage, and would decrease the SCR reaction rate. In our previous study [11], the different contents of Na impact on Cu/SAPO-34 were also studied. Except for the decrease of active sites and acidity, the results also showed the framework of Cu/SAPO-34 damaged and CuAlO x species formed at a high content of sodium (>0.8%), and all these factors hindered the SCR activity.In recent years, some studies have also considered the Na ions' effect on Cu/SSZ-13 catalysts, but most of them focused on co-cation Na ions. Gao et al. [12] investigated the effects of co-cation Na on Cu/SSZ-13 catalyst. They found ≈1.78% Na promoted SCR performance at low temperatures and helped to improve the hydrothermal stability of Cu/SSZ-13 because Na ions modified the redox of active sites and protected the framework of CHA structure. Zhao et al. [13] found a high amount of co-cation Na ions decreased the hydrothermal stability of Al-rich Cu/SSZ-13 at 750 • C for 5 h because the excess amount of Na ions weakened the interaction between Cu ions and the zeolitic framework and formed Cu x O species. Xie et al. [14] found one-pot-synthesized Cu/SSZ-13 with higher co-cation Na contents showed poorer hydrothermal stability at 750 • C for 16 h, which was attributed to Cu species with poor stability and CHA structure deterioration. Even though some achievements have been made on co-cation Na, the conclusion could not be applied in real-world applications because co-cation Na ions have already existed before Cu exchange and could not represent the deposition of Na in the ...

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The oxidative absorption of nitric oxide (NO) by sodium persulfate (Na2S2O8) coupled with Fe2+, Fe3O4, and H2O2 was investigated in a bubble column reactor. Moreover, the effect of temperature on NO removal has been studied. At high temperatures, Fe2+ and Fe3O4 could effectively activate persulfate to form sulfate radicals, leading to high removal efficiency of NO. About 62% and 86% of NO were removed at 75 and 90°C, respectively. Also, the optimum Fe2+ concentration for 0.2 mol L−1 persulfate was 1.0 mmol L−1 at 75°C, under which the removal efficiency of NO was observed to be 89%. However, beyond 1.0 mmol L−1 Fe2+, the increase in Fe2+concentration was unfavorable to NO removal due to the scavenging of radicals by the excess Fe2+. Additionally, the presence of 2.85 mmol L−1 Fe3O4 increased the NO removal efficiency by 11% compared to that obtained in the absence of Fe3O4. It was proposed that activation ability of Fe3O4 to persulfate was attributed to Fe2+ on the Fe3O4 surface. Moreover, the addition of H2O2 led to the increase of the NO removal for some time, but followed by a drop because of the depletion of H2O2. It was suggested that H2O2 served as an oxidant rather than an activator of persulfate. © 2014 American Institute of Chemical Engineers Environ Prog, 2014 © 2014 American Institute of Chemical Engineers Environ Prog, 34: 117–124, 2015