【作者】 李哲；

【导师】 程铁欣； 周广栋；

【作者基本信息】 吉林大学 ， 物理化学， 2014， 博士

【摘要】 乙烷氧氯化制氯乙烯是全世界广泛研究的具有广阔市场前景和环境和谐的新型工艺。本文通过氧化镁改性氧化铝载体制备了负载型CuCl2基催化剂，并利用稀土元素作为催化助剂对催化剂进行改性，采用XRD、BET、H2-TPR、NH3-TPD、SEM、TEM、ICP、UV-Vis和XPS等方法对改性后催化剂的物化性质、表面酸性及氧化还原性质进行了表征，而且通过催化反应评价考察了稀土元素助剂改性催化剂对乙烷氧氯化反应催化性能的影响。考察了Pr助剂含量对催化剂结构、表面酸性、氧化还原性质和乙烷氧氯化活性的作用，结果表明Pr助剂减弱了CuCl2与MgO-γ-Al2O3之间的相互作用，使表面Cu物种含量增加，电子由Pr助剂转移到活性组分Cu物种上，Pr助剂加速了Cu(Ⅱ)→Cu(Ⅰ)→Cu(Ⅱ)氧化还原反应的进行,同时，Pr助剂使Cu物种粒径变小，促进了Cu物种在催化剂表面的分散。Y助剂改性CuCl2基催化剂表面存在了较多的氧物种，有利于催化反应中的CuI→CuII转化，促进了Cl2中间产物的生成；Y助剂的添加有效调节催化剂表面酸中心性质，减弱了酸强度，产生比较多弱酸活性中心，减少了积碳在反应中的形成，经过120小时活性测试后，乙烷转化率维持在93.8%以上，氯乙烯选择性仍然大于43.0%。采用水热法合成了稀土元素（La、Ce、Pr）改性的TiO2载体，稀土元素La，Ce，Pr半径远远大于Ti4+半径，吸附在TiO2载体的外表面，抑制了TiO2粒度进一步的增长，使得TiO2粒径变小；稀土元素La，Ce，Pr改性TiO2载体与未改性TiO2载体相比，比表面积显著增大，稀土元素La，Ce，Pr改性TiO2载体负载CuCl2和KCl催化剂表面氧化还原性质与未改性TiO2载体相比，加快了CuII→CuI→CuII氧化还原过程，促进了Cu活性物种的还原，提高了乙烷氧氯化反应活性。更多还原

【Abstract】 Vinyl chloride monomer (VCM) is an important monomer in the manufacture ofpolyvinyl chloride (PVC). Nowadays, VCM is commercially produced by threeprocesses: acetylene process, ethylene oxychlorination and ethane oxychlorination.Acetylene process of production of vinyl chloride involves reacting hydrogen chlorideand acetylene in the presence of a mercuric chloride catalyst. The method has beenoutdated all over the world for the high energy consumption and serious environmentpollution, it is yet predominant in China. The ethylene oxychlorination processincludes the cracking of ethylene dichloride (EDC) and the direct chlorination ofethylene or oxychlorination of ethylene with oxygen and hydrogen chloride. Ethyleneoxychlorination process is the principal way to produce vinyl chloride all over theworld. But the expense of ethylene as the raw material is usually high due to thedecrease in storage of petroleum. Furthermore, the technique of the process iscomplicated. The oxychlorination reaction of ethane is a promising and economicroute to produce vinyl chloride, because ethane as a raw material is much cheaper andwidely distributed. Many foreign institution have made great efforts to researchproduction of vinyl chloride by ethane oxychlorination process. By contrast there hasbeen little report about this technology in our country. Therefore, Study of preparationof vinyl chloride by ethane oxychlorination process is of great scientific value. Ethaneoxychlorination process includes two independent catalytic reactions: the oxidation ofHCl with the copper based catalysts and dehydrochlorination of dichlroethanedepended on the surface nature of the catalyst. Many kinds of catalysts have beeninvestigated for the reaction.In this work, a series of rare earth element modified copper-base catalysts wereprepared by conventional impregnation method and the catalytic activity for ethaneoxychlorination reaction was also investigated. The catalysts were characterized bymeans of XRD, BET, H2-TPR, NH3-TPD, SEM, TEM, ICP, UV-Vis and XPS to discuss the structure, surface acidity, redox properties of the catalysts and the catalyticperformance. The main experimental results and conclusions are as follows:1. Ethane oxychlorination over Pr modified CuCl2-KCl/MgO-γ-Al2O3catalystPr modified CuCl2-KCl/MgO-γ-Al2O3catalysts were prepared by animpregnation method and the influence of Pr additive content on the structure surfaceacidity, redox properties of the catalysts and catalytic performance of ethaneoxychlorination was investigated. It was found that the Cu species must be anamorphous phase, or in the form of nanoclusters, which cannot be detected by XRD.Addition of Pr decreased the interaction between active species CuCl2and γ-Al2O3and made the active species more dispersed. The experiment results showed theelectronic transformation from Pr to Cu species, which accelerated the conversion ofredox couple (Cu+/Cu2+). The latter will promote the conversion of C2H6andselectivity to C2H3Cl. More amorphous CuCl2species were present on the surface ofsupport due to the presence of Pr species in the samples. At the same time, theaddition of Pr can reduce the particle sizes of the copper species and improve thedispersion in the catalysts. The ethane conversion and selectivity of vinyl chloridereached97.5%and52.0%respectively for Pr6O11-CuCl2-KCl/MgO-γ-Al2O3catalystwhile praseodymium content was5wt%with the reaction condition: T=500℃，GHSV＝3200h-1and VC2H6/VHCl/Vair=1/2/5.2. Y2O3modified CuCl2catalyst for Ethane OxychlorinationA series of Y2O3promoter modified CuCl2-based catalysts were prepared by theincipient impregnation method. Effect of Y2O3promoter on the structure, redoxproperties, acidity as well as catalytic performance of CuCl2-based catalyst for ethaneoxychlorination was discussed. With modification by Y2O3promoter, there were moresurface oxygen species on the surface of CuCl2-based catalysts, which increased theselectivity of the vinyl chloride. The Y2O3promoter adjusted surface acidity andincreased weak acid sites of the support, which contributed to decrease the amount ofdeposited coke. Y2O3promoter modified Pr-Cu/Yxcatalysts showed the better activityand stability than the unmodified ones. The ethane conversion and the selectivity ofvinyl chloride and ethylene were98.5%,55.8%and34.7%, respectively. Moreoverthe catalytic activity for Pr-Cu/Y3catalysts was still high after120h reaction, theconversion of ethane and selectivity of vinyl chloride was more than93.8%and43.0%, respectively. 3. Study of the nature of Cu-based catalysts supported on rare earth element(La, Ce, Pr) modified TiO2supportThe different TiO2support were prepared using hydrothermal treatment method.The structure and physico-chemical properties of the rare earth element La, Ce, Pr,motified TiO2support were searched by BET, XPS, XRD, SEM, NH3-TPD andH2-TPR. Furthermore, the catalytic activity of La, Ce, Pr, motified TiO2supportedCuCl2and KCl catalysts were evaluated. It was found that the addition of La, Ce andPr promoter to TiO2support increased the surface area and reduced the particle size ofthe support. Because the radius of La, Ce and Pr atom was much bigger than that of Tiatom, La, Ce and Pr additives were adsorbed on the external surface of the supportand inhibited the growth of the crystallite size. The SEM result indicated that thereexisted a great deal of pore, which improved the dispersion of the active species. TheLa, Ce and Pr promoter decreased the reduction temperature of CuCl2-based catalystsuppored on TiO2support, which accelerated the reduction-oxidation step forCuII→CuI→CuIIand was responsible for the excellent catalytic performance. The La,Ce and Pr species modified TiO2support showed that the number of strong acid sitesdecreased and that of weak acid sites increased, which increased of the catalyticactivity for ethane oxychlorination.更多还原