焙烧温度对钼锡催化剂结构和二甲醚氧化性能的影响

Effect of calcination temperature on the structure and performance of molybdenum-tin catalyst for DME oxidation

采用水热法制备了Mo/Sn物质的量比为1∶2的Mo1Sn2催化剂,通过改变焙烧温度(400−700℃),调控了钼锡催化剂的结构,并研究了催化剂结构变化对二甲醚(DME)选择氧化制甲酸甲酯(MF)性能的影响。发现400℃焙烧的Mo1Sn2催化剂具有良好的催化氧化二甲醚生成甲酸甲酯的性能,在110℃、常压条件下,DME转化率为9.2%,MF选择性可达86.9%,并且无CO_(x)生成。采用XRD、Raman、XPS、TPD、H_(2)-TPR和in-situ FT-IR等表征手段对催化剂的结构和表面性质进行了系统研究。结果表明,低温焙烧更利于钼锡催化剂表面形成更多的MoO_(x)结构和Mo^(5+)物种,由此引起的催化剂的酸性、氧化还原性的增强和中强碱性位的增多可明显促进催化剂活性的增强和甲酸甲酯的生成。

The Mo1Sn2 catalysts with a Mo/Sn molar ratio of 1∶2 were prepared by the hydrothermal method,and their structure was regulated by changing the calcination temperature(400–700℃).The effect of the structural transformation of catalysts on the performance of selective oxidation of dimethyl ether(DME)to methyl formate(MF)was studied.It was found that the Mo1Sn2 catalyst calcined at 400℃exhibited good performance in the oxidation of DME to methyl formate,showing a DME conversion of 9.2%and the MF selectivity of 86.9%at 110℃and under atmospheric pressure without the generation of CO_(x).The catalysts were systematically characterized by XRD,Raman,XPS,TPD,H_(2)-TPR and in-situ FT-IR.The results showed that the low-temperature calcination was favorable for the formation of MoO_(x)structure and more Mo^(5+) species on the catalyst surface,resulting in the enhanced acidity and redox ability of the catalyst,and the increase of medium to strong basic sites on the catalysts.In such case,the activity and methyl formate production of the catalyst were significantly promoted.