【作者】 王君；

【导师】 张密林；

【作者基本信息】 哈尔滨工程大学 ， 材料学， 2007， 博士

【摘要】 烃类的催化裂化，烯烃的异构化，芳烃和烯烃的烷基化反应，烯烃和二烯烃的低聚、共聚和高聚，酯化及水解等反应是目前催化领域研究的热点。长期以来，科研工作者致力于通过开发新型的固体超强酸来代替目前工业上主要采用的液体酸。近年来，人们借助迅速发展的纳米技术，合成了纳米固体超强酸。纳米粒子具有大的比表面积和比表面自由能，大大提高了固体超强酸的催化活性，但纳米固体超强酸催化剂在液相催化体系中易团聚，分离和回收困难，在气固催化体系中，会造成床层阻力增大。因此，研究和开发一种易于分离和回收，同时又具有较高催化活性的新型纳米固体酸催化剂，具有重要的理论和实际意义。本论文系统地总结、综述了固体酸的分类以及氧化物固体酸的形成机理。采用化学共沉淀法合成具有较高磁响应性和悬浮稳定性的磁性基质，通过将磁性基质与固体酸氧化物复合，首次合成了既具有磁性又具有较高酸强度的ZrO₂基三元复合氧化物磁性纳米固体超强酸催化剂。以ZrO₂为固体酸催化剂的主活性组分和载体，通过掺杂其它氧化物来改进单组分二氧化锆作为固体酸热稳定性差、比表面小的缺陷。在高温焙烧过程中，多组分复相金属氧化物催化剂的各组分发生了氧物种在物相之间的迁移，导致多组分复合氧化物各个物种之间的协同作用，高温焙烧过程中延迟了主活性组分ZrO₂的晶化温度，有效抑制了ZrO₂晶体颗粒的长大，抑制了四方晶相ZrO₂（t）向单斜晶相ZrO₂（m）的转变，增强了催化剂的稳定性，增加了酸中心密度和酸强度，形成比单组分体系多得多的活性中心。Fe₃O₄磁性基质的引入赋予固体超强酸以顺磁性，在产物的分离、洗涤和回收过程中，引入了磁分离技术。与离心、抽滤等传统分离方法相比，具有省时、简捷、耗能低等优点。设计并合成了SO₄^2-／ZrO₂／Fe₃O₄／Al₂O₃、SO₄^2-／ZrO₂／Fe₃O₄／TiO₂、SO₄^2-／ZrO₂／Fe₃O₄／B₂O₃、SO₄^2-／ZrO₂／Fe₃O₄／WO₃四种不同系列的SO₄^2-促进型三元复合氧化物磁性纳米固体超强酸催化剂。利用XRD、IR、TG-DSC、TEM、HRTEM、SEM、NH₃-TPD、Mossbauer、VSM以及N₂吸附-脱附等综合实验手段，系统考察了Fe₃O₄、Al₂O₃、B₂O₃、TiO₂、WO₃等氧化物的引入对固体酸催化剂粒子大小、磁学性能、晶体结构、表面酸性、孔径分布、比表面积等变化规律的影响。研究和探讨了磁性基质负载量、氧化物的掺杂量及焙烧温度等因素对ZrO₂晶化温度和晶型转变温度的影响。磁性基质的引入及B₂O₃、WO₃、Al₂O₃、TiO₂等氧化物的掺杂稳定了介稳态的ZrO₂（t）。Al₂O₃、TiO₂、WO₃等粒子高度分散在ZrO₂中，在烧结过程中有效地阻碍了扩散传质的进行以及晶界的移动，抑制ZrO₂晶体的生长，细化了晶粒，降低了ZrO₂（t）的晶相转变温度。样品的HRTEM显示，氧化物的掺杂可以有效的抑制ZrO₂（t）向ZrO₂（m）晶相的转化，使晶体按ZrO₂（t）的（101）晶面取向生长，晶面间距为d（101）=0.29 nm。本文以酯化反应作为磁性复合氧化物固体酸催化剂的探针反应，对磁场对酯化反应的影响机理作了初步探讨研究，取得了一些重要的实验结果和创新性成果，为深入研究磁性催化剂的磁化学反应机制提供了实验参考，并为开发环境友好的新型双功能催化材料提供了参考依据。更多还原

【Abstract】 In present, catalytic cracking of hydrocarbon, isomerization of olefins, alkylation of aromatic hydrocarbon and olefins, polymerization of olefins and diolefine, esterification and hydrolysis have attracted much attention in the field of catalysis. In the past decades, great effort have been made in developing novel solid superacid instead of liquid acid which has been mostly used in industrial applications. Recently, nano-scale solid superacid has been synthesized by rapid developing nanotechnology. These nano-scale particles with high specific surface area and large free energy can greatly improve the catalytic activity of solid superacid. However, the difficulties of separating and reclaiming in the liquid phase reaction and the large mass transfer resistance in the gas phase reaction of these catalysts have greatly limited their application. Therefore, it is essential to design a novel nano-scale solid acid catalyst with the advantages of high catalytic activity and ease of separation and recovery.In this dissertation, classification and formation mechanics of solid acid has been reviewed. Magnetic substrates with high magnetism and suspension stability were prepared by chemical co-precipitation process. In addition, a novel zirconium based ternary-oxide solid acid catalyst with high magnetism and acidity was prepared by assembling of as-made magnetic substrates and solid acid for the first time. The drawbacks of low thermal stability and low specific surface area for zirconia have been improved by doping other oxide. Multi-component heterogeneous metal oxide catalyst migrated during different phases under high heat treatment, which lead to the coordination of multi-component oxide in the phase. As a result, the crystallization temperature of zirconia has been delayed greatly, which markedly inhibited the growth of crystal particle and phase transformation from tetragonal zircoina to monoclinic zirconia. Furthermore, the thermal stability, acid amount and intensity, the number of active centers have been also increased as well. The introduction of Fe₃O₄ magnetic substrate endowed solid superacid with supermagnetism, which can be easily separated and recovered in comparison with the traditional solid acid catalysts.In this work, four magnetic solid acid catalysts includingSO₄^2-/ZrO₂/Fe₃O₄/Al₂O₃, SO₄^2-/ZrO₂/Fe₃O₄/TiO₂, SO₄^2-/ZrO₂/Fe₃O₄/B₂O₃,SO₄^2-/ZrO₂/Fe₃O₄/WO₃ have been prepared. The structure, morphology, textural, and magnetic properties of the catalysts were systematically characterized by XRD, FT-IR, TG-DSC, TEM, SEM, NH₃-TPD, Mossbauer spectra, VSM and N₂ adsorption/desorption techniques. Influence of magnetic substrate, doped amount of oxide and calcination temperature on crystalline temperature and crystal transformation temperature have been investigated. The results indicated that the introduction of magnetic substrate and oxides such as B₂O₃, WO₃, Al₂O₃ and TiO₂ markedly improved the thermal stability of tetragonal zirconia resulting from the uniform distribution of the doped oxide throughout the matrix of the zirconia. Because of the existence of Fe₃O₄ particles, magnetic solid acid catalyst shows the characteristics of superparamagnetism, and the easy-axis of samples are perpendicular to magnetic field. In addition, the HRTEM showed that the tropism of the crystal plane is （101） of tetragonal zirconia, and the interplanar spacing is d（101） = 0.29 nm.The effect of magnetic field on the mechanism of esterification was investigated by esterification which was used as probe reaction for magnetic solid acid catalysts. And some important experiment results and creative achievements have been obtained, which can provide the reference for further study of magnetism chemistry mechanics and for developing novel environmental friendly catalytic materials with double functions.更多还原