Wei Li,Rui-tang Guo,Shu-xian Wang,Wei-guo Pan,Qi-lin Chen,Ming-yuan Li,Peng Sun,Shu-ming Liu
Heavy metals (such as Zn and Pb) have a deactivation effect on the catalyst for selective catalytic reduction of NO with NH 3 . In this study, it was found that the modification of Mn/TiO 2 catalyst by Nb could greatly enhance its Zn resistance. From the characterization results of BET, XRD, H 2 -TPR, NH 3 -TPD, it may be concluded that the introduction of Nb into Mn/TiO 2 catalyst would lead to its lower crystallinity , more acid sites and higher concentrations of Mn 4 + and surface chemisorbed oxygen. The results of in situ DRIFT study reveal that the NH 3 -SCR reactions over Mn/TiO 2 and Mn-Nb/TiO 2 all obey both the Langmuir-Hinshelwood mechanism and the Eley–Rideal mechanism, and the doping of Nb on Mn/TiO 2 catalyst could promote the adsorption of NH 3 and NOx species on it. All these features make a contribution to the high SCR activity and good Zn resistance of Mn-Nb/TiO 2 catalyst.
Plasma-assisted catalytic oxidation of chlorinated volatile organic compounds (CVOCs) over Co-Mn/TiO 2 catalyst was performed in a dielectric barrier discharge (DBD) reactor having two segmented electrodes. The combination of DBD reactor with segmented electrodes and Co-Mn/TiO 2 catalyst remarkably enhanced the removal efficiency of chlorobenzene (CB) and selectivity of CO 2 . The segmented discharge reactor with Co-Mn/TiO 2 catalyst presented the best performance with 96.3 % of removal efficiency and 69.0 % of CO 2 selectivity at discharge voltage of 17 kV compared with the traditional plasma-only and other plasma-catalytic reactors. Results from discharge characteristics analysis showed that the addition of segmented electrodes and the catalysts could improve the plasma characteristics and greatly boost the specific energy density (SED) at the same voltage, resulting in the generation of more high-energy electrons and chemical active species which favor the oxidation of CB. Although the segmented electrodes facilitated the generation of O 3 , the Co-Mn/TiO 2 catalyst boosted the decomposition of O 3 to generate active oxygen species (O* and O 2 ). The synergistic effect of introducing segmented electrodes and the Co-Mn/TiO 2 catalyst into the DBD reactor at alternate voltages of 13 and 15 kV could promote the deep oxidation of intermediate products thereby bringing less effects on the catalyst surface, leading to a stable and high performance in CB removal. Furthermore, a plausible decomposition mechanism of CB destruction in the DBD reactor having segmented electrode over Co-Mn/TiO 2 catalyst was proposed according to the identification of gaseous intermediates based on GC-MS analysis.
A series of Mn/TiO 2 catalysts were prepared by ultrasonic spray pyrolysis (USP) method for selective catalytic reduction (SCR) of NOx from flue gas at low temperatures. The highest activity of Mn/TiO 2 was obtained with a Mn/Ti ratio of 0.5. When Fe was doped into Mn(0.5)/TiO 2 , the NOx conversion rate on Fe(0.05)-Mn(0.5)/TiO 2 was increased by approximately 10 % at 120–180 °C. The samples were characterized by XRD , SEM , H 2 -TPR, and N 2 adsorption analyses. Results revealed that Mn(0.5)/TiO 2 with Mn/Ti ratio of 0.5 presented the lowest crystallinity , the highest surface area, and the highest redox ability. Although the surface area was significantly decreased by Fe doping, it also reduced the crystallinity and crystal size of the catalysts, thereby increasing the O concentration on the surface of catalyst. Moreover, Fe(0.05)-Mn(0.5)/TiO 2 displayed a higher redox ability than the other catalysts. At 120–240 °C, the activation energy decreased from 27.65 kJ/mol on Mn(0.5)/TiO 2 to 14.46 kJ/mol on Fe(0.05)-Mn(0.5)/TiO 2 , thereby facilitating the activation of the reaction on Fe(0.05)-Mn(0.5)/TiO 2 . Despite that the NO and NH 3 adsorptions were lower on Fe(0.05)-Mn(0.5)/TiO 2 than on Mn(0.5)/TiO 2 , the intermediates on Fe(0.05)-Mn(0.5)/TiO 2 , particularly nitrates, were easily activated to participate in the reaction, leading to increasing catalytic activity.
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