Search

NO conversion using dielectric barrier discharge (DBD) plasma with different catalysts was investigated. Cu/TiO2, Cu/Al2O3, Cu/ZSM-5, Cu/CNTs and Cu/AC catalysts were prepared by incipient wetness impregnation with 4 wt% Cu loaded. BET, SEM, XRD, XPS, H2-TPR, NH3-TPD were used to measure and evaluate various catalysts. Compared with the plasma only process, the combination of plasma with different catalysts significant improved the NO conversion rate. The highest NO conversion rate of 76% could be achieved with Cu/ZSM-5 catalyst at the energy density of 184 J/L. The results indicate that Cu species over the support ZSM-5 can produce high concentrations of CuO, largest specific surface area, largest amounts of acidity and lowest reduction temperature (209 °C), these factors conducive to plasma-catalyst reaction. Besides, Cu/TiO2 and Cu/Al2O3 catalysts exhibited excellent NO conversion at the low energy density because of the low thermal stability. After plasma-catalyst reaction, the reducibility of CuO and Cu2O over supports decreased and the peak position of acid sites shifted to lower temperature. [ABSTRACT FROM AUTHOR]

A series of Cu-Fe catalysts with fixed metal content and variable ratios of ZSM-5 and CNTs were used to investigate NO removal in a plasma-catalyst system at low temperature. The catalysts were characterized by BET, XRD, TGA, XPS, H 2 -TPR and NH 3 -TPD. The results showed that the catalyst promoted the NO conversion rate from only plasma system, and 1Z3C catalyst exhibited the best NO conversion rate of 86.1% at 191.5 J/L. Composite support promoted the catalytic activity at low temperature, and greatly improved the Cu 2+ and Fe 3+ concentration on the 1Z3C catalyst, both Cu 2+ and Fe 3+ contributed greatly to catalytic reaction of NO conversion. Chemisorbed oxygen also acted as activated sites for NO conversion. When the input energy was 75 J/L, the NO conversion rate decreased from 70% to 41% with adding 500 ppm SO 2 , which decreased with increasing SO 2 concentration, while generation rate of SO 3 was less than 0.2% in the combination system. In the presence of SO 2 , copper sulfate species, ferric sulfate species and ammonium sulfates generated on the surface of catalyst, which consumed Lewis acid sites and blocked the active sites, decreasing NO conversion rate. [ABSTRACT FROM AUTHOR]

A series of CuCe catalysts were prepared by an incipient-wetness impregnation method for selective catalytic reduction of NO in combination with dielectric barrier discharge plasma. The effect of the Cu/Ce mass ratio on NO and NO x (NO + NO 2 ) removal efficiency has been studied as a function of energy density at ambient temperature. The catalyst samples were characterised by BET, XRD, XPS, H 2 -TPR and NH 3 -TPD. The results indicated that catalyst addition enhances NO and NO x removal based on only the plasma process. The CuCe catalysts exhibited higher reduction performance compared with the 4 wt.% Cu or 4 wt.% Ce catalysts, and the catalyst with 4 wt.% Cu and 4 wt.% Ce showed the best reduction performance with the highest NO and NO x removal efficiencies of 90.7% and 80.1%, respectively, at an energy density of 367 J/L. The interactions between Cu and Ce increase oxygen migration to form oxygen vacancies, which facilitates the oxidation of NO to NO 2 , and NO 2 favours NO removal via a fast selective catalytic reduction reaction at low temperature. In addition, the CuCe catalysts exhibited low thermal stability, thereby facilitating the catalytic reduction of NO at ambient temperature. [ABSTRACT FROM AUTHOR]

Mercury is harmful to the human body and to the ecological environment. Mercury emission from coal-fired power plants is one of the main sources of anthropogenic mercury emissions. Adsorbents and catalysts are popular materials developed to capture mercury from flue gas. Sulphur oxides (SO 2 , SO 3) are the main components of flue gas; their concentration is more than 3 orders of magnitude higher than that of mercury. Sulphur oxides have a significant effect on mercury adsorption and catalytic processes. However, the effect mechanisms of sulphur oxides on mercury removal by adsorbents/catalysts are not uniform. In this review, the effects of SO 2 and SO 3 on the mercury removal process by adsorbents/catalysts are provided separately, and the suggested influence mechanisms are also summarized. SO 2 has a two-sided effect on the performance of mercury removal by adsorbents and catalysts. Oxidation and activated adjacent sites are considered to be the main reasons for the promotion effect of SO 2. Competitive adsorption, active consumption and sulphate deposition are the main reasons for inhibition of mercury removal by SO 2. O 2 , H 2 O, SO 2 concentration and temperature have an impact on the effect of SO 2 on mercury removal. SO 3 can enhance the mercury removal efficiency of metal oxides-containing materials by increasing mercury oxidation rate. This review aims to promote a basic understanding of the effect of sulphur oxides on the mercury removal process and outline the future research direction of sorbents/catalysts for mercury removal, thereby advancing the research, development and application of materials with high sulphur resistance ability and removal efficiency. Image 1 • The promotion effect of SO 2 is achieved by oxidation and adjacent sites activation. • Inhibition reasons: competitive adsorption, activity consumption, sulphate deposition. • SO 3 can enhance mercury removal efficiency of metal oxide supported material. • Gas components and temperature influence the effect of SO 2 on mercury removal. • Sulphur-resistant and magnetic metals enhance the practicality of adsorbents/catalysts. [ABSTRACT FROM AUTHOR]

• SO 2 inhibited the Hg0 removal, while SO 3 promoted the Hg0 removal. • SO 3 was more easily adsorbed on the surface of the catalyst compared with SO 2. • The adsorbed SO 3 served as a new active site for Hg0 removal. • SO 3 adsorption was promoted at high temperature, improving Hg0 removal. The Cu/ZSM-5 was used to study the effects of SO 3 on mercury removal. The addition of SO 2 decreased the Hg0 removal efficiency but the efficiency increased from 82% to 95% after 21 ppm SO 3 was introduced at 200 °C. The inhibition effect of SO 2 on mercury removal was weakened at 400 °C and the promotion effect of SO 3 on mercury removal was enhanced significantly. HgSO 4 was the main mercury species formed on the catalyst in the presence of SO 3. The in-situ FTIR results showed a large number of S-related peaks were generated on the surface of the catalyst with SO x (SO 2 and SO 3). The peak of adsorbed SO 2 weakened when SO 2 and SO 3 coexisted in the reaction atmosphere. This is due to the SO 3 inhibiting the adsorption of SO 2. The peak of adsorbed SO 3 was the most obvious and was then gradually consumed after Hg0 introduced. Meanwhile, the peak of sulphate appeared on the surface of the catalyst. This indicated SO 3 preferentially adsorbed on the catalyst to form active sites for oxidizing Hg0 to HgSO 4. The adsorption of SO 3 on the catalyst was promoted at 400 °C, compared with 200 °C, which directly contributed to the enhancement of Hg0 removal. [ABSTRACT FROM AUTHOR]