碱金属修饰的MoVTeO_x/SiO_2上异丁烷选择氧化制MAL反应研究

Effect of Alkali Metal Doping on the Performance of Silica-supported MoVTeO_x Catalysts for Selective Oxidation of Isobutane to Methacrolein

采用常规浸渍法制备了相同含量碱金属(Li、Na、K和Cs)修饰的负载型MoV0.8Te0.23MmOx/SiO2催化剂,在对催化剂进行异丁烷选择氧化制甲基丙烯醛(MAL)反应性能评价的基础上,采用BET、XRD、Raman和H2-TPR等表征技术分别考察了催化剂的比表面积、相结构、表面氧物种和可还原性等,并将实验结果与催化剂的性能进行了关联。研究表明:在反应温度为420℃时,Cs与Mo摩尔比为0.2的催化剂上MAL的收率最高;经Cs修饰的3%MoV0.8Te0.23Ox/SiO2催化剂中出现了晶相TeO2物种,在反应过程中,TeO2中的Te-O活性位被还原后能快速得到体相晶格氧的补充,从而促进晶格氧的传递。

Based on 3% MoV0.8Te0.23Ox /SiO2 catalyst,effect of alkali metal（Li,Na,k,Cs） doping on its catalytic performance was investigated.Alkali-free and alkali-doped MoV0.8Te0.23Ox /SiO2 catalysts were characterized by BET,XRD,Raman and H2-TPR.In addition,the relationship between characterization results and catalytic performance was also studied.The results show that the highest MAL yield can be obtained on the catalyst with Cs/Mo molar ratio of 0.2 at the reaction temperature of 420 ℃.The enhanced catalytic performance in the selective oxidation of isobutane to MAL on the Cs-doped catalyst seems to be related to the crystalline TeO2 species appearing on the catalyst,the Te-O active site of which can be supplied with bulk lattice oxygen fast after reduction,which can promote the delivering of lattice oxygen.