【作者】 刘永梅；

【导师】 范康年；

【作者基本信息】 复旦大学 ， 物理化学， 2004， 博士

【摘要】 丙烷氧化脱氢制丙烯纳米催化剂的制备、表征及应用 丙烯作为重要的石油化工中间体，其需求量日益增长，因此开展由资源丰富的丙烷转化为的丙烯的研究意义非凡。目前工业丙烯主要来自炼油厂流化床裂解和乙烯裂解，其收率均比较低，难以满足增长的需求；而丙烷无氧条件下直接脱氢制丙烯的反应由于反应温度高、能耗大、催化剂易结焦失活等原因，使其在工业生产中受到很大限制。近年来人们开始尝试临氧条件下丙烷氧化脱氢制丙烯，期望用较低温度下的放热反应替代高温下的吸热反应，从而降低反应能耗，为今后的工业化创造条件。然而经过数十年的努力，仍没有能够工业化的催化剂问世，文献和专利报道的丙烷氧化脱氢反应的收率水平比较低，开发新催化材料用于丙烷氧化脱氢反应势在必行。近年来，由于含铈复合氧化物新材料具有独特的氧化还原性能及储放氧能力备受科学工作者的关注，为开发具有低温活性的丙烷氧化脱氢制丙烯催化剂提供了可能。另一方面，具有规整孔道结构和较窄孔径分布的介孔分子筛作为性质优良的催化载体引起催化界的广泛关注，特别是以SBA-15为代表的新一代介孔材料，具有单一的孔径分布、较大的孔径、规则的孔道和较厚的孔壁，使其热稳定性和水热稳定性都有很大的提高，有望作为丙烷氧化脱氢制丙烯高效催化剂的新型载体。 一般认为丙烷氧化脱氢反应机理有两类，一类是氧化还原反应机理，另一类是自由基反应机理。对前一类反应，选择了具有低温催化活性的含铈复合氧化物新材料和较为经典的钒氧化物催化剂作为研究对象，后一类反应选择了能够引发自由基反应的硼氧化物催化剂。通过催化剂的制备、表征及其反应活性的测试，对各类催化剂上丙烷氧化脱氢的反应本质进行了不同程度的探讨。论文主要研究内容如下： 一、纳米Ce-Ni-O复合氧化物催化剂的制备、表征及其在丙烷氧化脱氢反应中的应用 用草酸盐胶态共沉淀法制备了不同Ce／Ni摩尔比的Ce_mNi_nO系列催化剂（Ce_mNi_nO-OG），还用其他方法制备了相同Ce／Ni摩尔比的CeNi₂O参比催化麦{互丈学麟全学夕老戈沪戈满萝剂。扫描电镜表征发现CeNiZO一OG由大小均一的小“面包圈”组成，而CeNiZO一OC（水相共沉淀法制备样品）却不太均匀;高分辨透射电镜结果表明，CeNiZO一OG的小“面包圈”是由大小均一的CeOZ、Nio复合氧化物纳米粒子组成，而CeNiZO一OC是由独立的CeOZ、NIO组成。XRD、Laser Raman、HZ-TPR、XPS等表征手段研究发现:（l）CemNino样品中有三种镍物种存在一团聚的Nio颗粒、高度分散在CeO:表面的Nio颗粒及进入CeOZ晶格形成固融体的Ni2+。（2） ce加i摩尔比的变化对晶态Nio及分散Nio的颗粒大小、还原能力有影响，但对进入ceoZ晶格形成固融体的Ni2+影响不大。（3）焙烧温度对催化剂的性能有一定的影响，焙烧温度越低，催化剂的比表面越大，表面颗粒分散度越高，晶体的晶化程度越低，还原温度越低，更易形成固融体。（4）不同制备方法对催化剂的性能影响较大，其中浸渍法制备的催化剂中，饰与镍之间的相互作用较弱，镍包裹在CeO:的表面，催化剂表面基本上检测不到CeOZ的信号;而KOH作沉淀剂制备的催化剂表面，表面吸附活性氧物种相对较少。 用连续微反装置考察CemNinO系列催化剂活性结果表明，在200一300“C的低温范围内，CemNinO系列催化剂具有良好的催化活性，其中CeNiZO一OG催化剂在275“C、v（C3Hs）/V（02）=0.7、空速5.5L/（g·h）的条件下，丙烷转化率为12.8%时，丙烯选择性高达82.7%。不同方法制备的催化剂在相同反应条件下，草酸盐胶态共沉淀法制备的催化剂活性最好。此外，对反应条件考察结果表明:催化剂的最佳焙烧温度范围为500一600“C，反应温度是250一300“C，V（C3Hs）那（02）=0.7一l，空速5.5U（g·h），Ce加i摩尔比为l一0.25。 原位红外漫反射研究结果表明，在纯Nio、Ceo:上丙烷氧化脱氢反应过程中没有检测到吸附态C二C的信号，而在CemNinO催化剂上检测到了该信号，因此可以认为饰镍相互作用固融体是该反应的活性位，并提出了丙烷在CemNinO催化剂上经由烯丙基生成丙烯的分子反应机理。二、V一SBA一巧系列催化剂的制备、表征及在丙烷氧化脱氢反应中的应用 以介孔分子筛SBA一巧为载体采用浸渍法、吸附法、机械混合法制备了各种钒负载量的V一SBA一15催化剂，同时制备了2.8V一MCM一41和2.8V一510:等参比催化剂。XRD、TEM、SEM等结果表明所制备的SBA一15具有典型的六方孔结构及规整的孔道，而且钒的引入并没有破坏SBA一15的孔结构，但机械混合法引入的钒不能很好的分散在SBA一15表面。不同载体相同钒负载量催化剂上，钒分散程度也不相同。夏旦丈学麟士学世论戈 红外漫反射结果表明，浸渍法制备的V一SBA一15系列催化剂（V一SBA一15-imP）上，随着钒负载量增加，SBA一15表面的硅轻基逐步被中和，形成Si一。一v的共价键结构。NH3一TPD和Py一FT一IR表征结果表明，v一SBA一15一imp表面具有较弱的酸性中心，其强度比V一MCM一41及V一5102表面的酸性弱，钒的引入在催化剂表面形成了新的L酸中心和B酸中心，且随着钒负载量增加，催化剂表面的酸量增加?更多还原

【Abstract】 The research drive to develop an oxidation dehydrogenation (ODH) process for propane comes from the facts that the chemical industry depends heavily on the propene and other alkenes feedstock. The major source of propene currently is steam cracking and FCC, the steam cracking maximizes ethene yield and in the FCC plant propene is produced as a by-product, so propene production from these sources will barely match the consumption. Thermal dehydrogenation suffers from several drawbacks, such as thermodynamics limited, rapid coking and high reaction temperature, from the industrial standpoint. ODH can be a viable route for production alkenes as the presence of oxygen counteracts the thermodynamic limitation and prevent coking. While this has been recognized for a long time, an industrially applicable process has not been developed, because secondary oxidation of alkanes to carbon oxides is very significant on most materials. Thus the yield of alkenes remained under 30%, far from satisfactory for commercial application. So it is necessary to develop other new efficient catalysis materials for the ODH of propane. Recently considerable interest has been focused on the catalytic properties of the mixed oxide materials containing cerium due to their improved redox properties and their ability to store and release oxygen under the reaction conditions, which is related to the occurrence of bulk reduction at a moderate temperature. So it is possible to prepare catalyst with high performance under lower temperature for the ODH of propane for propene. Besides the nanocomposite materials, the potential applications porous solid of ordered mesoporous silica with pore walls of uniform width in the range 1-5 nm and controlled uniform pore diameters in the range 2.5-25 nm as periodic hosts for the preparation of mesoporous catalysts with chemically functionalized surfaces have been widely investigated in the past decade. SB A- 15 is a newly discovered mesoporous silica molecular sieve with larger pore diameters, tunable uniform hexagonal channels and thick framework walls, which improve itsAbstractthermal stability, so it is a promising new type of porous support for fabrication the catalyst for ODH of propane.Generally, there are two commonly accepted reaction mechanisms for describing the molecular process of the ODH of propane. One is the redox mechanism and the other is the radical mechanism. For the former reaction mechanism, we have investigated the mixed oxides containing cerium with high performance under lower temperature as well as the vanadium-based catalysts. For the radical mechanism, the boron oxide-based catalysts were studied. Through the preparation, characterization and activity test, we have systematically investigated the reaction nature of the ODH propane over different catalysts.1 . Preparation, Characterization of Ce-Ni-O Mixed Oxide Catalysts and Application in the Oxidative Dehydrogenation of PropaneCewNinO catalysts (m/n denotes the molar ratio of Ce to Ni) with well-defined doughnut-like macrostructures, were prepared by alcoholic coprecipitation of oxalate precursor. For comparison, the pure CeO2 and NiO were prepared by the same method, the reference samples denoted as CemNiwO-OC, CeOTNinO-KC and CeOTNinO-imp were prepared by aqueous oxalate coprecipitation, KOH coprecipitation and conventional wet-impregnation methods, respectively. The SEM image reveals that the CehfoO-OG sample consists of well-defined doughnut-like macrostructures with uniform size of ca. 14 um, which is totally different from the ones prepared by other techniques. The TEM result reveal that there are strong interaction between cerim and ruckle in the CeNi2O-OG, but there are much weaker interaction between cerim and nickle in the CeNi2O-OC, which is consited of single NiO and CeOi. On the other hand, the combined XRD, Laser-Raman, H2-TPR and XPS results reveal that: (1) There are three types nickle phase in the CemNinO-OG samples- aggregated NiO on the support CeO2, high dispersed NiO with strong interaction with CeO2更多还原