Effects of support acidity on the reaction mechanisms of selective catalytic reduction of NO by CH4 in excess oxygen |
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Authors: | Shicheng Xu Junhua Li Dong Yang and Jiming Hao |
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Institution: | (1) Department of Environmental Science and Engineering, Tsinghua University, Beijing, 100084, China |
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Abstract: | The reaction mechanisms of selective catalytic reduction (SCR) of nitric oxide (NO) by methane (CH4) over solid superacid-based catalysts were proposed and testified by DRIFTS studies on transient reaction as well as by kinetic
models. Catalysts derived from different supports would lead to different reaction pathways, and the acidity of solid superacid
played an important role in determining the reaction mechanisms and the catalytic activities. Higher ratios of Br?nsted acid
sites to Lewis acid sites would lead to stronger oxidation of methane and then could facilitate the step of methane activation.
Strong Br?nsted acid sites would not necessarily lead to better catalytic performance, however, since the active surface NOy species and the corresponding reaction routes were determined by the overall acidity strength of the support. The reaction
routes where NO2 moiety was engaged as an important intermediate involved moderate oxidation of methane, the rate of which could determine
the overall activity. The reaction involving NO moiety was likely to be determined by the step of reduction of NO. Therefore,
to enhance the SCR activity of solid superacid catalysts, reactions between appropriate couples of active NOy species and activated hydrocarbon intermediates should be realized by modification of the support acidity. |
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Keywords: | selective catalytic reduction (SCR) nitric oxide (NO) methane support acidity Br?nsted acid sites NOy species |
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