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题名	纳米氧化物催化二氧化碳氧化乙烷脱氢制乙烯的绿色过程
作者	邓双
学位类别	博士
答辩日期	2004
授予单位	中国科学院过程工程研究所
授予地点	中国科学院过程工程研究所
导师	张懿
关键词	纳米复合催化剂 乙烷 氧化脱氢
其他题名	Green Process of Oxidative Dehydrogenation of Ethane with Carbon dioxide to Ethylene over Nano-oxide Catalysts
学位专业	化学工艺
中文摘要	二氧化碳氧化乙烷脱氢制乙烯工艺是一个具有环境和资源替代式经济双重效益的绿色过程。采用CO2作为温和氧化剂参与反应，不仅可以提高乙烯选择性；还可以减少温室气体CO2排放，实现碳资源转化利用；并且可以充分利用天然气、油田气等非石油资源。该工艺工业化的关键是开发低温、高活性和高选择性的催化剂体系，纳米材料由于其高比表面能、高表面缺陷等特性，可用做高活性催化材料。本论文从纳米催化剂的制备方法入手，采用XRD、TPR、TPD、XPS和物理吸附等表征手段，对催化剂结构、表面性质和催化性能进行了系统的分析和研究，旨在研制出高活性和高稳定性的纳米催化剂，并对失活原因和催化反应机理进行了探讨。本论文首次采用溶胶一凝胶与共沸蒸馏法祸合技术制备纳米Cr2O3，考察了纳米Cr2O3催化剂上CO2氧化乙烷脱氢制乙烯反应性能及其物化性质。首次发现纳米Cr2O3的FT-IR谱出现蓝移，且在651.8cm-1处伸缩振动峰强度增强的现象。H2-TPR表征结果表明，纳米Cr2O3催化剂表面Cr的起始还原温度比常规Cr2O3催化剂降低。纳米Cr2O3催化剂上乙烷和CO2转化率均明显高于常规Cr2O3催化剂，而乙烯选择性降低。为了提高纳米Cr2O3催化剂上乙烯选择性，本论文又采用共沉淀与共沸蒸馏法祸合技术制备了纳米Cr2O3／Al2O3、Cr2O3／ZrO2和Cr2O3／MgO复合催化剂，并系统考察了复合成分对催化剂结构、表面性质以及催化性能的影响，通过研究三者之间的关系，揭示出影响催化剂性能的主要因素是催化剂表面Cr物种的还原性、Cr6＋／Cr3＋比值以及表面氧物种。研究了Ni、Fe、Mn和Co等助剂分别对纳米CrZO3／A12O3、Cr2O3／ZrO2和Cr2O3／MgO复合催化剂结构、表面性质和催化性能的影响。结果表明，助剂降低了纳米Cr2O3系列复合催化剂表面cr物种的还原性，改变了催化剂表面的Cr6＋／Cr3+比值。催化剂表面的晶格氧O2-，吸附CO2中的氧以及吸附氧Oad（O-、O22-）在CO2氧化乙烷脱氢制 乙烯的反应中都起着非常重要的作用。只有催化剂表面这三种氧物种的比例合适，才能在CoZ氧化乙烷脱氢制乙烯反应中表现出好的催化效果。并且催化剂表面酸碱性对催化剂催化性能的影响比较显著，催化剂表面超强酸和超强碱中心不利于提高乙烷和CO2转化率，而弱酸中心和中强碱中心有利于乙烷活化。并筛选出了一种在较低温度下（650℃）具有良好催化性能的Fe-Cr／ZrO2纳米复合催化剂，其乙烯产率可达50.05％。催化剂性能与催化剂的制备方法和工艺条件息息相关，因此进一步考察了原料、焙烧温度、pH值、焙烧时间以及制备方法等对Fe-Cr／ZrO2纳米复合催化剂性能的影响，为开发更高效的纳米催化剂提供有力依据。研究发现，催化剂表面微量Cl可以提高催化剂的乙烯选择性：且催化剂的晶相结构也影响催化剂的乙烯选择性。采用纳米氧化物载体浸渍法制备的Cr／Fe-ZrO2-FS纳米复合催化剂虽然其乙烯产率比采用共沉淀一共沸蒸馏祸合法制备的Cr-Fe／ZrO2纳米复合催化剂降低，但其稳定性显著提高。通过分析反应前后纳米复合催化剂性能及物化性质的差异，表明催化剂失活的主要原因是表面积炭。并在以上研究基础上提出了可能的催化反应机理，认为Fe-Cr／ZrO2纳米复合催化剂是双功能催化剂，反应物在催化剂表面不同的活性中心活化，通过“协合作用”催化CO2氧化乙烷脱氢制乙烯反应。
英文摘要	Oxidative dehydrogenation of ethane (ODE) with carbon dioxide to ethylene is one of promising routes for the conversion of ethane to highly value chemicals. Carbon dioxide as a mild oxidant could participate in the dehydrogenation of ethane and increase the conversion of ethane and the yield of ethylene. In this paper, the nano-sized Cr2C>3 were prepared by Sol-Gel method coupling with azeotropic distillation method. The obtained nano-powders were characterized by BET, XRD, TEM, FT-IR and XPS techniques. FT-IR spectra revealed an unreported phenomenon that the absorption of Cr-0 bond in Cr2O3 nano-powders was blue shift and the intensity of the absorption of Cr-0 bond (658cm"1) increased. The mechanism of red shift and blue shift in nano-powders of oxides was discussed, and it was concluded that the crystal structure of nano-powders of oxides influences their infrared spectra. H2-TPR patterns indicated that the reducibility of chromium species over nano-sized Cr2O3 catalyst increased. The nano-Cr2O3 catalyst exhibits much higher ethane and CO2 conversion but lower ethylene selectivity than those of normal Cr2O3 catalyst. In order to improve ethylene selectivity over nano-Cr2O3 catalyst, the nano-sized Cr2O3/Al2O3j CtjO^IZxOi and C^Oa/MgO composites as novel catalysts for the oxidative dehydrogenation of ethane to ethylene with carbon dioxide have been studied. Similar to the preparation of nano-Cr2O3 catalyst, the nano-sized composite catalysts were prepared by co-precipitation coupling with azeotropic distillation method. The result showed the catalytic activity varies with the nature of composites. Characterization indicated that the reducibility, Cr6+/Cr3+ ratio and oxygen species of these nano-particle catalysts determine the catalytic activity in the oxidative dehydrogenation of ethane with CO2. The effect of Fe, Mn, Co, and Ni modifier on the catalytic activity of the nano-sized Cr2O3/Al2O3j Cr2O3/ZrO2 and C^CVMgO composite catalysts was investigated. The modifier decreases the reducibility of chromium species over modified nano-sized composite catalysts. The adsorbed oxygen species (Oad), oxygen species in adsorbed CO2 and lattices oxygen (O2') species all play important roles in oxidative dehydrogenation of ethane with CO2 to ethylene. The catalysts can exhibit good catalytic reaction activity if the proportion of these three oxygen species over catalyst is proper. The base and acid properties of these nano-sized composite catalysts markedly affect the catalytic performance. The superacidic and superbasic sites respectively aren't favor to improve ethane and CO2 conversion, but the week acid and moderate strength basic sites favor activating of ethane. Nano-sized Fe-Cr/ZrO2 catalyst exhibits an excellent performance in this reaction, and it can produce 50.05% ethylene yield at 650 °C. In this study, the effects of pH of precipitation solution, the precursors, the calcination temperature, washing and other preparation factors on the catalytic performance of nano-sized Fe-Cr/ZrO2 catalyst were also investigated. It was found that Cl over catalyst surface could improve ethylene selectivity, and the crystalline structure of catalyst also affects the ethylene selectivity. Nano-sized Cr/Fe-ZrCVFS catalyst was prepared by impreganating nano-Fe/ZrCh composite with an aqueous solution of Cr(NO3)3.9H2O, and its stability is much better than nano-sized Fe-Cr/ZrC>2 catalyst which was prepared by co-precipitation coupling with azeotropic distillation method. Nano-sized Cr/Fe-ZrO2-FS catalyst showed a much lower deactivation rate. The catalyst deactivation was investigated by characterizing the fresh and used catalysts, and found that carbon deposition is the main reason of catalyst deactivation. Based on the above research, the possible catalytic mechanism for the ethane dehydrogenation by CO2 over nano-sized Fe-Cr/ZrCh catalyst was proposed. The nano-sized Fe-Cr/ZrC^ catalyst is bi-functional catalyst in the oxidative dehydrogenation of ethane with CO2. The activating sites over catalysts surface play different roles, and these sites co-operate to perform the catalytic process.
语种	中文
公开日期	2013-09-16
页码	137
内容类型	学位论文
源URL	[http://ir.ipe.ac.cn/handle/122111/1412]
专题	过程工程研究所_研究所（批量导入）
推荐引用方式 GB/T 7714	邓双. 纳米氧化物催化二氧化碳氧化乙烷脱氢制乙烯的绿色过程[D]. 中国科学院过程工程研究所. 中国科学院过程工程研究所. 2004.

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