Search

The mercury removal capacity of biochar can be improved by plasma modification and the functional group is an important factor affecting the mercury removal. This paper examines factors such as discharge voltages, gas flow rates, chlorine concentrations and discharge times that may affect functional groups on the surface of biochar. The mercury removal performance of the tobacco stem biochar prepared under different Cl2 plasma modification conditions was investigated using a fixed bed reactor. The number of C–Cl bonds and carboxyl increased after modification and decreased in mercury removal. Longer discharge times can destroy the biochar surface and possibly cause a decrease in the number of active sites. Increasing the discharge voltage promotes the formation of C–Cl bonds and carboxyl groups. Excessive gas flow rates cause active chlorine to be carried out of the reactor quickly which reduces the formation of C–Cl. The amount of C–Cl bonds increases with increased chlorine concentration. In the modified biochar, C–Cl and carboxyl take part in the adsorption of mercury to form HgCl2 and HgO, while the unmodified biochar is mainly physically adsorbed Hg0. C–Cl is the main functional group participated in mercury removal and the carboxyl is a secondary functional group. The proportion of HgCl2 is at least 68.2% in the used modified biochar. Under optimum conditions, the initial mercury removal efficiency of modified tobacco biochar was 99.1%, and the efficiency was still 79.1% after 100 min. [ABSTRACT FROM AUTHOR]

A series of MnOx-CeO2/ZSM-5 catalysts with different Ce loadings were prepared through the impregnation method and characterized by BET, XRD, SEM, H2-TPR, and XPS. The performances of selective catalytic reduction (SCR) of NO/NO2 with NH3 and NO oxidation over MnOx-CeO2/ZSM-5 catalysts were investigated. The result showed that the MnOx dispersions, redox abilities and proportions of Mn4+ of catalysts were enhanced by the doping of CeO2. However, the excessive Ce loadings led to the accumulation of active components on the catalyst surface. The sample with Ce/Mn molar ratio of 0.39 exhibited the best SCR performance, the NOx conversion achieved 95.4% at 150 °C, and maintained higher than 95% in a wide operating temperature range (150-350 °C). MnOx-CeO2/ZSM-5 also exhibited considerable catalytic performance of NO oxidation, the maximum conversion of NO achieved 56.5% at 350 °C. [ABSTRACT FROM AUTHOR]

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]

The dielectric barrier discharge synergy with 10 wt% MnO/TiO-MWCNTs was investigated with different proportions of support materials. All as-prepared catalysts were analyzed by BET, ICP-AES, SEM, XRD, XPS, Raman spectroscopy and H-TPR. The MnO/TiO-MWCNT (1:4) catalysts exhibited the best catalytic activity with NO removal efficiency of 72.4% at the discharge power of 45 W when temperature was ambient. This was a result of the extremely dominant phase of MnO (76.21%), the high concentration of lattice oxygen (74.92%) and the good dispersion of manganese oxides on the surface of the catalysts, as proven by the characterization methods used in this study. Our XPS and ICP-AES analysis illustrated that manganese oxide particles could be decorated on the internal channels of MWCNTs, which was found to be abundant with the increasing MWCNTs and exhibited better ability to adsorb NO and supply oxygen. According to the sulfur poisoning experiment, a small amount of SO (the concentrations of SO and NH were 1000 and 500 ppm, respectively) could facilitate the SCR catalytic performance by generating sulfate species on the surface of the carbon, which was regarded as a Brønsted acid site on the surface of the catalyst. [ABSTRACT FROM AUTHOR]

Manganese-copper bimetal oxide catalysts supported on ZSM5 and acid-treated multi-walled carbon nanotubes (MWCNTs) were produced by incipient wetness impregnation for selective catalytic reduction of NO with dielectric barrier discharge plasma. Plasma can activate molecules even at ambient temperature, generating active oxygen species such as O, O, and HO radicals, which can oxidize NO to NO effectively. The SCR activity of Mn-Cu/MWCNTs was studied and compared to that of the Mn-Cu/ZSM5. The obtained samples were characterized by XRD, SEM, TEM, ICP, H-TPR, Raman spectroscopy, and XPS. The results show that Mn -Cu/MWCNTs catalyst possesses NO removal activity superior to that of the Mn -Cu/ZSM5 catalyst. MWCNTs-based catalyst attains NO removal efficiency of 88% at 480 J/L, while the ZSM5-supported catalyst achieves NO removal efficiency of 82% at the same energy density. The oxygen content increased from 3.33 to 19.07% on the nanotube surface after introducing Mn and Cu, which almost remained unchanged on ZSM5. The oxygen-containing functionalities are important for NO adsorption and removal. Moreover, the characterization revealed that CuO is the main phase of copper oxide, but copper dispersion decreases on Mn -Cu/ZSM5 surface because of the formation of copper dimer species. The manganese is well-dispersed on the catalysts, MnO and MnO contents of Mn -Cu/MWCNTs are larger than that of Mn -Cu/ZSM5, MnO is the predominant phase of manganese oxide. [ABSTRACT FROM AUTHOR]