【摘要】 考察了没有固体催化剂时NOx 对甲烷气相氧化的催化作用 ,并用原位红外光谱研究了CH4 O2 NOx 体系随温度的变化 .实验结果表明 ,NOx 对甲烷气相氧化有很高的催化活性 .在 2 0 %CH4 10 %O2 体系中加入 0 0 5 %～ 0 2 %的NO后 ,反应温度可降低 2 0 0～ 3 0 0℃ ,在 65 0～ 70 0℃下反应时 ,CH4 转化率和CO选择性可分别达到 3 8%和 90 % ,产物中的n(H2 ) /n(CO)比为 0 4～ 0 7.反应产物中可观察到有甲醛、甲醇和乙烯等 ,通过改变反应条件可以控制各组分的相对浓度更多还原

【Abstract】 Catalytic conversion and catalytic combustion of CH₄ have received extensive attention because of their potential to synthesize useful chemicals and to reduce pollutant emissions. Both the processes require activation of CH₄, which has been mostly achieved over solid catalysts to date. In the catalytic conversion of CH₄, the promotional effects of NO_x on CH₄ oxidation were reported by some researchers, but the role that NO_x may play in CH₄ activation and the importance of this gas-phase reaction have not received more attention. This work investigated the catalytic effect of NO_x on partial oxidation of CH₄ in the absence of solid catalyst. The product distribution was studied by in-situ FT-IR under different reaction conditions. The results showed that the addition of a small amount of NO into 20%CH₄-10%O₂ system decreased the reaction temperature by 200～300 ℃. At 650～700 ℃, the CH₄ conversion and CO selectivity were 38% and 90%, respectively, and n（H₂）/ n（CO）=0.4～0.7. The optimum conditions for CO formation were n（CH₄）/ n（O₂）=2 and low flow rate. Some reducible substances, such as HCHO, CH₃OH and C₂H₄, were also observed in the products. The HCHO was formed at 460 ℃, then CO （480 ℃）, CH₃OH （500 ℃）, and C₂H₄ （540 ℃） were formed. Low temperature favours the formation of HCHO and CH₃OH, while high temperature favours C₂H₄. Under strong oxidizing conditions （ n（O₂）/ n（CH₄）=5）, NO_x also exhibits considerable catalytic activity and selectivity for CH₄ conversion to CO. For 0.4%CH₄-2%O₂ system, the temperature for CH₄ activation is higher than 800 ℃ in the absence of NO_x. In the presence of NO_x, however, the activation temperature is reduced to below 570 ℃. The addition of 0.06%NO results in the increase of CO yield from 25% to 68%. It was shown that no reaction was observed for CH₄-NO_x system （without O₂） under the reaction conditions, indicating that the NO₂ formation is a prerequisite for CH₄ activation. Also, no decrease of NO/NO₂ concentration was observed up to 950 ℃, indicating that NO_x cannot be reduced by CH₄ in the absence of solid catalyst. Both CH₄ conversion and CO yield reached a maximum when φ（NO）=0.04%～0.06%, while the highest TOF （turnover frequency） of 40 s -1 was obtained when φ（NO）=0.01%.更多还原