【作者】 马晶；

【导师】 强亮生；

【作者基本信息】 哈尔滨工业大学 ， 化学工程与技术， 2011， 博士

【摘要】 介孔分子筛具有较大的比表面积、孔径均一且表面易官能团化等一系列特点,这些特性使得其在光学、电磁学和生物医学等领域展现了非常诱人的应用前景。目前,介孔分子筛的发展重点是在催化方面的应用。选择合适的修饰剂和适宜的方法,对介孔分子筛进行功能化修饰是提高其催化性能的有效方法。通过对不同方法制备催化剂的结构分析和催化性能测试,不仅可以对催化剂的制备条件进行优化,还可以进一步获得催化性能与其结构和制备方法相关联的信息,从而为设计和制备高性能催化剂提供新的方法。本研究旨在利用改进的后嫁接法对SBA-15与SBA-16介孔分子筛进行功能化修饰,以引入酸性中心和氧化中心。在合成过程中,解决SBA-15与SBA-16在酸性条件下Al不易进入分子筛骨架和TiO₂前驱物在过滤洗涤过程中易流失等问题,制备Al/SBA-15、Al/SBA-16、TiO₂/SBA-16和Bi-TiO₂/SBA-15四种功能化修饰的介孔分子筛,并研究其在催化苯酚叔丁醇烷基化和降解有机染料罗丹明B（RhB）的反应机理。以SBA-15为载体,利用改进的直接法和后嫁接法合成了高度有序的Al/SBA-15。对样品的结构分析表明:合成方法对Al/SBA-15的形貌和酸性有较大影响。直接法合成的Al/SBA-15经过水热处理,Al取代Si进入SBA-15的骨架中,使得Al/SBA-15的孔径、孔容增大;而后嫁接法合成的Al/SBA-15,一部分Al负载于SBA-15的内表面使得孔径、孔容减小。Al/SBA-15的酸性测试结果表明:后嫁接法合成的Al/SBA-15具有更多的B酸和L酸性中心。参照Al负载SBA-15的合成方法及催化效果,以SBA-16为载体,采用后嫁接法合成了Al/SBA-16。测试表明:Al/SBA-16仍具有高度有序的三维孔道结构和中等酸强度。在Al/SBA-15（16）中,Al的修饰增强了Si与Al的相互作用,调变了SBA-15（16）的酸量。同时,Al的引入还调控了SBA-15（16）的孔道结构,使得孔径、孔容和比表面积发生变化。以苯酚叔丁醇烷基化为反应探针,研究了Al/SBA-15（16）的催化活性和重复利用率。研究表明:当催化剂用量为0.05g,叔丁醇与苯酚的物质的量配比为5时,在190℃下反应7h,苯酚的转化率和2,4-二叔丁基苯酚的选择性均达到最佳。结合苯酚与叔丁醇在Al/SBA-15（16）孔道内的吸附能和苯酚叔丁醇烷基化反应的活化能,探讨了Al/SBA-15与Al/SBA-16催化烷基化反应的机理。利用孔道内水解的方法合成了TiO₂/SBA-16。采用XRD、N2吸附-脱附、UV-vis和TEM等手段对样品进行了测试表征。结果表明,TiO₂/SBA-16仍然保持了SBA-16的介孔结构;SBA-16的三维孔道结构对TiO₂纳米粒子的生长起到很好的限制作用,TiO₂的粒径被限制在5nm以下。TiO₂/SBA-16的光催化活性优于传统后嫁接法合成的TiO₂/SBA-16和工业上使用的纯TiO₂纳米颗粒。Laungmuir-Hinshelwood（L-H）动力学模型研究表明,在合成TiO₂/SBA-16中存在最佳Ti/Si配比。当Ti/Si配比过小时,TiO₂颗粒被大量的SBA-16包裹,导致其无法与反应物分子充分接触,失去小尺寸效应;当Ti/Si配比过大时,TiO₂可能会造成某个方向孔道的堵塞,阻碍RhB与TiO₂的接触,导致催化效果减弱。以SBA-15为载体,Bi（NO₃）₃·5H₂O和C₁₆H₃₆O₄Ti为无机前驱体,利用二步法设计合成了Bi-TiO₂/SBA-15。通过XRD、XPS和TEM等测试技术对合成的样品进行了表征,结果表明:负载后样品仍保持SBA-15原有介孔结构,且Bi₂O₃和TiO₂均匀地负载于SBA-15的孔道内。通过DFT方法,对TiO₂和Bi-TiO₂的能带结构进行了计算,并以此为依据,分析了Bi-TiO₂/SBA-15光催化性能提高的原因。在SBA-15和Bi-TiO₂的协同作用下,Bi-TiO₂/SBA-15在紫外光和可见光下,都具有极高的光催化活性,其原因是:首先SBA-15较大的比表面积和发达的孔结构,既提供了高浓度反应条件,也增加了光生空穴和自由基与被吸附的RhB分子碰撞概率。另外Bi-TiO₂的带隙宽度（1.85eV）小于TiO₂带隙宽度（3.2eV）,这使光生导带电子能够从Bi注入到TiO₂的导带上,产生有效地电荷分离,从而提高光催化效率。更多还原

【Abstract】 Mesoporous materials have attracted considerable attention in the region of optics, electromagnetic and biomedicine due to high surface area, uniform pore size and easily functionalized surface. The research on mesoporous materials is currently changing to the exploitation of their application in catalysis. By choosing appropriate precursors and preparation methods, the functional modification of mesoporous materials has played significant roles in improving the performance of catalytic ability. Combining compositional analysis, structural characterization and catalytic tests, the correlation between structural characteristics and catalytic performance can be performed and the design and preparation of a highly effective catalyst can be optimized, which can provide new insights into the preparation of catalysts.SBA-15 and SBA-16 is a new type of mesoporous silica molecular sieves with uniform hexagonal and 3D channels.The introduction of metal ions in the framework of SBA-15 and SBA-16 is one of the important approaches for its catalytic applications. Nevertheless, it is difficult to directly incorporate metal atom into the framework because SBA-15 and SBA-16 have been generally synthesized under acidic hydrothermal condition that easily induce the dissociation of the M-O-Si bonds. In this paper, SBA-15 and SBA-16 as a matrix, its functional materials （Al/SBA-15、Al/SBA-16、TiO₂/SBA-16、Bi-TiO₂/SBA-15） were synthesized successfully and their catalytic performance in the tert-butylation of phenol and photodegradationRhB are also studied.Two different aluminum-containing mesoporous Al/SBA-15 were prepared by post-synthesis method and direct synthesis method. The results show that Al/SBA-15（DS） possessed higher BET surface area and larger pore volume. The acidic properties were investigated by NH3-TPD and Py-IR. The different synthesis method leads to distinct coordination of Al and intensity of acidity. These results indicated that Al/SBA-15（PG） has more activity ability than the corresponding one synthesized by direct method since they contain more Lewis acid sites and Br?nsted acid sites. Al-containing SBA-16 was prepared by post- -grafting synthesis method. The results indicated that the materials possess 3D caged-like mesostructure and Al was successfully incorporated into the SBA-16 framework. Al/SBA-16 has middle activity ability.The modification of Al controlled the acidity of Al/SBA-15（16） effectively. The interaction betweenSiandAl enhanced the acid content of Al/SBA-15（16）. Meanwhile, the modification of Al has also modified the pore structures of SBA- 15（16）.In the tert-butylation of phenol, the catalytic activity and reusability of Al/SBA-15（16） were studied. It was found that the highest activity result was obtained under reaction condition: 0.05g Al/SBA-15（16） as catalyst, n（TBA）: n（phenol）=5, WHSV=2.5h-1, reaction temperature at 190℃, time for 7h. The catalyst preserved almost their initial catalytic activity after five reuses. The adsorbed energy of phenol and TAB in the channels was calculated by the DFT method. Finally, the alkylation mechanics on Al/SBA-15 and Al/SBA-16 were discussed, respectively.TiO₂/SBA-16 was synthesized by internal hydrolysis method. The results indicated that SBA-16 retained the 3D caged-like mesostructure while TiO₂ located almost inside the mesoporous channels in form of small crystals with anatase structure.and the size of TiO₂ was limited under 5nm. The high specific surface area and pore volume for TiO₂/SBA-16 with 3D mesostructure were prone to have high adsorption capability and easier diffusion to the photo-oxidative. TiO₂ dispersed in form of small crystals with anatase structure and its size was limited by the channel of SBA-16, which could provide more photo-oxidative sites due to quantum effect, leading to improvement of its photocatalytic activity. L-H kinetics model was indicated that an optimal amount of TiO₂ loading is crucial for the photocatalyst. When the loading is too high, TiO₂would gather into larger particles and block the mesopores of SBA-16, leading to decrease of photocatalytic activity. On the contrary, if the loading is too small, the photoactive sites are relatively low, which leads to the increase of average distance from the photoactive sites to the adsorption sites.Bi-TiO₂/SBA-15 was synthesized by two steps synthesis. The high specific surface area and ordered mesoporous channels of SBA-15 are prone to have high adsorption capability and easier photo-oxidative diffusion sites for RhB.The band structure and total density of states of TiO₂ and Bi-TiO₂ were calculated in order to study their electronic structures by the DFT method. It was found that the Bi-TiO₂ in modified SBA-15 catalysts was active centers and the doping of Bi can enhance the photoinduced degradation very significantly. In this system, the electron-hole pairs induced by light irradiation transfer easier and a smaller band gap was also observed for Bi-TiO₂ （from 3.2eV to 1.85eV）. This demonstrated that after integration, the electron and hole was separated efficiently, which has played a key role in enhancing the photoactivity.更多还原