对于lA0.2bA0.8-XCAX（O，CO3）其中X＝0.0、0.2、0.4、0.6氧化物在973k及甲烷氧化偶联（OCM）条件下，无CA2＋的样品可用表面bACO3和（lAO）2CO3的rAMAn谱及810CM-1附近的O2-2特征峰来表征；含CA2＋的样品，则表现了混合碳酸盐（CA，bA）CO3的特征，还有位于1135CM-1（W）和810CM-1（W）的O-2、O2-2瞬时态氧物种；973~1053k发现OCM反应活性随温度和CA2＋含量而增加，C2烃选择性也随OCM反应温度增大；1053k时，CA2＋含量的增加，C2烃选择性略有下降，这些结果指出O-2是OCM反应的活性氧物种，它在较高温度下与CH4作用，且具有较好的C2烃选择性和较大的反应活化能。For a series of La-Ba-Ca-(O,CO 3) catalysts under methane-oxidative-coupling conditions at 973K,the Ca-Free sample was characterized by Raman bands due to surFace carbonates of BaCO 3 and (LaO) 2(O,CO 3) phases,and a weak and broad band around 810cm -1 ,probably due to O 2- 2;the Ca-containing samples showed Raman bands of surFace carbonates associated with (Ba,Ca)CO 3 phase and minor amount of BaCO 3 phase (but not with lanthania phase),and active-oxygen bands at 1135cm -1 (w) and 810cm -1 (w,br) attributed to O - 2 and O 2- 2 transient species,respectively.At 973～1053K,the activities of all the samples were Found to increase with increasing OCM temperature and with increasing calcium contents.The C 2-selectivities increased with increasing temperature For all the samples,and increased with increasing calcium contents at 973K,but decreased slightly with increasing calcium contents at 1053K.These results strongly indicate that O - 2 might be an active oxgen-species reacting with CH 4 with higher C 2-selectivity and higher activation energy,becoming suFFiciently active only at higher temperature.国家自然科学基
