硅藻土负载H6PMo9V2Nb1O40催化剂上乙烷氧化制乙酸和乙醛的反应性能

采用浸渍法制备了硅藻土负载的杂多化合物催化剂PMo9V2Nb1/K，利用TPR、IR、TPD和微反技术研究了催化剂的表面酸性、乙烷化学吸附和氧化反应性能。结果表明，含铌的PMo9V2Nb1/K催化剂仍保持着Keggin形杂多酸的化学构造，晶格氧的活泼性明显提高，B酸强度和酸量均有所降低；乙烷分子主要通过H原子吸附在Lewis碱位V—O—Mo和Nb—O—Mo的桥氧上，吸附在Nb—O—Mo桥氧上的乙烷易发生解离吸附，并与邻近的表面氧发生反应生成乙酸或乙醛；在240 ℃，0.4 MPa和2 000 h-1下，乙烷的摩尔转化率为22.5%，产物乙酸和乙醛的总选择性达90.8%。

Selective oxidation of ethane to acetic acid and acetaldehyde on kieselguhr supported H6PMo9V2Nb1O40 catalyst

The heteropoly acid complex H6PMo9V2Nb1O40 was prepared by the method of common acidification. Kieselguhr supported heteropoly compounds PMo9V2Nb1/K was prepared by the isovolumic impregnation. Its reducibility and acidity and the chemisorption and reactivity for C2H6 oxidation were characterized by IR, H２-TPR, NH３-TPD and microreactor techniques. The results showed that the catalyst PMo9V2Nb1/K still keeps the original Keggin structure like H6PMo9V2Nb1O40, but the activity of the crystal oxygen increased obviously and the strength and amount of the Br ö nsted acidity decreased in some degree. The hydrogen in C2H6 can be adsorbed on the surface oxygen sites in Nb—O—Mo or V—O—Mo bonds of the catalyst to form a molecular adsorption state. With the temperature rising, the C—H bond in the adsorbed C2H6 on the bridge oxygen of Nb—O—Mo bond would be broken to form dissociative adsorption states, then react with the surface oxygen to form the target products. Under the optimal conditions of 240 ℃, 0.4 MPa and space velocity 2 000 h-1, the conversion of ethane reached 22.5%, with the selectivity of 90.8% to acetic acid and acetaldehyde. The support of heteropoly compounds PMo9V2Nb1 on kieselguhr improved remarkably the conversion of ethane.