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采用原子层沉积法(ALD)法制备出一系列不同WO3含量的WO3/HMS催化剂,通过电感耦合等离子体质谱(ICP-MS)、X射线衍射(XRD)、BET表征、透射电镜(TEM)等技术对制备的催化剂进行了详细表征,在以双氧水为氧化剂的环氧油酸甲酯(MES)氧化裂解制壬醛酸甲酯(MAA)反应中考察了催化剂性能,并与以SBA-15和MCM-41为载体的催化剂进行了比较。表征结果证实,对于载体HMS,WO3含量小于5%时钨物种能均匀地分散在HMS的孔道中,而采用SBA-15和MCM-41为载体时,以WO35%(wt)的比例制备时,WO3的实际含量明显低于5%(wt),并且钨物种出现了团聚现象。反应结果表明,以HMS为载体,WO3含量小于5%(wt)的WO3/HMS表现出较好的选择性,MAA的产率可达80%以上;溶剂对反应选择性影响较大,以t-BuOH和二氧六环作为溶剂有利于反应进行;随着反应温度的升高,MES的转化率明显提高。另外,催化剂2-WO3/HMS重复使用3次后催化活性仍能基本保持。
A series of WO3 / HMS catalysts with different amounts of WO3 were prepared by atomic layer deposition (ALD) and characterized by inductively coupled plasma mass spectrometry (ICP-MS), X-ray diffraction (XRD), BET characterization, transmission electron microscopy The catalyst was characterized in detail. The catalyst performance was investigated in the oxidative cleavage of methyl-oxalate (MAA) with methyl oxalate (MES) as oxidant. MCM-41 as a carrier of the catalyst were compared. The characterization results showed that the tungsten species could be uniformly dispersed in the pores of HMS when the WO3 content was less than 5% for the carrier HMS, and when prepared using the SBA-15 and MCM-41 as the carrier in the proportion of 35% by weight, The actual WO3 content is significantly below 5% (wt), and the tungsten species are agglomerated. The results showed that WO3 / HMS with WO3 content less than 5% (wt) showed better selectivity with HMS as support, and the yield of MAA was more than 80%. The effect of solvent on the reaction selectivity was great. -BuOH and dioxane as a solvent to facilitate the reaction; with the increase of the reaction temperature, the conversion of MES significantly increased. In addition, the catalytic activity can still be basically maintained after the catalyst 2-WO3 / HMS is repeatedly used three times.