【作者】 胡盼静；

【导师】 罗孟飞；

【作者基本信息】 浙江师范大学 ， 物理化学， 2011， 硕士

【摘要】 挥发性有机化合物(VOCs)、甲烷和CO的催化燃烧是减少污染物排放的主要途径。其中甲烷、CO氧化也是评价催化剂氧化性能的模型反应,也是当前环境催化领域非常值得关注的课题。本论文采用浸渍法制备了一系列的Ir/ZrO2、Ir/CeO2催化剂和OMS-2负载过渡金属氧化物Co、Cu、Fe催化剂,分别用于CH4、CO和VOCs的氧化消除,主要研究结果如下：1.Ir/ZrO2催化剂的CH4催化燃烧性能采用沉淀法制备了Zr02载体,利用浸渍法制备了不同Ir负载量的Ir/ZrO2催化剂,并考察了催化剂的CH4催化燃烧性能。采用XRD、Raman、XPS、H2-TPR等技术对催化剂的结构和Ir物种的存在形式进行了表征。结果表明,Ir/ZrO2催化剂中Ir是以IrO2形式存在的,Ir/ZrO2催化剂的CH4燃烧表观活性随着Ir负载量的增加而提高,并且催化剂表现出较高的催化活性和良好的反应稳定性。在低Ir负载量(≤1%)时,CH4燃烧的TOF随着Ir粒子的增大而提高；然而高Ir负载量(≥1%)时,TOF随着Ir粒子的增大保持不变。2.Ir/CeO2催化剂对CO的催化氧化采用浸渍法制备了Ir/CeO2催化剂,考察了催化剂对CO的氧化活性。实验结果发现随着Ir负载量的增加,Ir/CeO2催化剂的CO氧化活性先上升后下降,当Ir的负载量为1%时,催化剂的活性最高。Ir/CeO2催化剂中Ir以IrO2的形式存在,当低负载量(≤1%)时以高分散形式存在；高负载量(>1%)时以晶相IrO2的形式存在。随着Ir负载量增加,Ir粒子逐渐变大,反应比速率和反应转换频率(TOF)逐渐下降,表明小粒子上具有更高的CO反应活性。同时也发现金属态Ir催化剂的CO氧化活性高于氧化态IrOx催化剂。3.OMS-2分子筛负载Co、Cu、Fe氧化物催化剂的VOCs氧化性能以KMnO4和MnSO4为前躯体,采用回流法合成了氧化锰八面体分子筛(OMS-2)。以OMS-2为载体采用浸渍法制备了Co/OMS-2、Cu/OMS-2和Fe/OMS-2催化剂,考察了催化剂对甲苯和乙酸乙酯的催化燃烧性能。扫描电镜(SEM)、X射线粉末衍射(XRD)表征表明合成的OMS-2分子筛为纳米棒状,且具有典型的cryptomelane结构。氢气程序升温还原(H2-TPR)实验结果表明OMS-2负载金属氧化物具有较低的还原温度。活性测试结果表明催化剂对乙酸乙酯的氧化活性明显高于对甲苯的氧化活性。添加少量的Co、Cu和Fe氧化物(1-2%)有利于提高OMS-2对甲苯和乙酸乙酯的催化燃烧活性,然而过多的负载量,造成OMS-2载体表面的覆盖使得活性反而下降。催化剂的活性顺序为Fe/OMS-2> Cu/OMS-2> Co/OMS-2> OMS-2。在Fel/OMS-2催化剂上乙酸乙酯和甲苯完全氧化温度分别为175℃和220℃。更多还原

【Abstract】 Catalytic combustion of volatile organic compounds (VOCs), CH4 and CO is the main way for reducing emissions of pollutants. CH4 and CO oxidation are widely studied to evaluate catalytic performances of catalysts. In this work, Ir/ZrO2, Ir/CeO2 and a series of Co, Cu and Fe oxide catalysts supported on OMS-2 were prepared using an impregnation method. These catalysts were tested for oxidation of CH4, CO and VOCs. The detailed results are as follows:1. Catalytic combustion of methane over Ir/ZrO2 catalystsZrO2 supports were prepared by precipitation method, and a series of Ir/ZrO2 catalysts were prepared by an impregnation method and their catalytic performance for CH4 catalytic combustion were tested. The catalyst structure and Ir species in the catalyst were characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and H2 temperature programmed reaction (H2-TPR) techniques. The results showed that Ir existed in the form of IrO2 in the Ir/ZrO2 catalysts. The apparent activity of Ir/ZrO2 catalysts for CH4 combustion increased with Ir loading, and the catalysts showed high activities as well as good stability. With low Ir loading (≤1%), turnover frequency (TOF) for CH4 combustion increased with Ir particle size, however, it remained constant with high Ir loading (≥1%).2. Ir/CeO2 catalysts for CO catalytic oxidationA series of Ir/CeO2 catalysts were prepared by an impregnation method, and they were tested for CO oxidation. It was found that the activity of Ir/CeO2 catalysts for CO catalytic oxidation rose first and then declined with Ir loading. The catalysts showed the highest activity when Ir content is 1%. Ir existed in the form of IrO2 in the Ir/CeO2 catalysts. IrO2 was high dispersed with low Ir loading (≤1%), and existed as crystalline phase with high Ir loading (>1%). Ir particle size increased gradually with Ir loading, but specific rate and turnover frequency (TOF) declined gradually. It indicated that the catalyst with small particle size had a higher CO reactivity. It was also found that for CO oxidation, the activity of Ir catalyst with metal state was higher than that of with oxidation state.3. Oxidation of volatile organic compounds (VOCs) over manganese oxide octahedral molecular sieves (OMS-2) supported Co, Cu and Fe oxide catalystsA manganese oxide octahedral molecular sieve (OMS-2) was synthesized using KMnO4 and MnS04 as precursors by a reflux method. Co/OMS-2, Cu/OMS-2 and Fe/OMS-2 catalysts were prepared using a impregnation method and tested for catalytic combustion of toluene and ethyl acetate. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) results showed that the synthesized OMS-2 molecular sieves were nano-rods, with the cryptomelane-type structure. Hydrogen temperature program reduction (H2-TPR) results indicated that the supported Co, Cu and Fe oxide catalysts have lower reduction temperatures. The activity test results showed that the catalytic activity of the catalysts for ethyl acetate was much higher than that for toluene. The addition of a small amount of Co, Cu and Fe oxides (1-2%) to OMS-2 was favorable for the catalytic combustion of ethyl acetate and toluene. However, due to excessive loading, the surface of OMS-2 was covered and the catalytic activity decreased. The activity order of the catalysts was Fe/OMS-2> Cu/OMS-2> Co/OMS-2> OMS-2. The highest activity was obtained over Fel/OMS-2 catalyst, with a complete oxidation of ethyl acetate and toluene at 175℃and 220℃respectively.更多还原