In/HZSM-5催化剂上CH4选择还原NO机理研究

考察了CH⁴+O₂,NO+CH₄(+O₂)与NO₂+CH₄(+O₂)反应体系中CH₄的转化活性.结果表明,浸渍法制备的In/HZSM₅催化剂上CH₄选择还原NO过程中,NO₂的形成起到了活化甲烷的作用.根据NO和NO₂在In/HZSM₅与HZSM₅样品上的TPD及IR研究结果,认为在载体HZSM₅的酸性位及In/HZSM₅催化剂的活性中心In位上均可形成NO₂,NO₂与CH₄的反应在In位上进行.

Mechanismic Studies on the Selective Reduction of NO by CH4 over an In/HZSN-5 Catalyst

CH_4 oxidations in CH_4+O_2, NO+CH_4(+O_2) and NO_2+CH_4(+O_2) reaction systems over the catalyst of indium impregnated on HZSM-5(In/HZSM-5) were studied. The efficacies of O_2, NO and NO_2 for CH_4 oxidation were evaluated. The dramatically different conversions of CH_4 in these different reaction systems suggested that NO_2 played a key role in CH_4 conversion. TPD studies of CH_4, O_2, NO and NO_2 on HZSM-5 and In/HZSM-5 were also investigated. It was found that only NO_x could absorb on the samples and the chemisorbed amount of NO_2 was much larger than that of NO. This illustrated that the absorbed NO_2 species were very important in the CH_4-SCR process. Our TPD results and IR results from the literatures both indicated that not only the acid sites but also the In sites in the In/HZSM-5 catalyst facilitated the formation of NO_2. Moreover, the reaction between NO_2 and CH_4 took place on the In sites.