Preparation, Characterisation And Catalytic Properties Of A1-SBA-15 Mesoporous Materials

Mesoporous materials have significant potential applications in multifarious areas such as adsorption, separation, catalysis, drug delivery, photonic, electronic devices and other fields, due to their large surface areas and pore volumes, controlled pore sizes, and very narrow pore size distributions. However, pure siliceous mesostructured materials lack active sites and exhibite relatively low hydrothermal stability, which hinders their applications. Hence, the incorporation of heteroatoms into the siliceous material is one of the important approaches to improve their activities. To date, many researchers have focused on Al-containing mesoporous molecular sieves, such as Al-MCM-41 or Al-SBA-15, which possess acidic sites and reasonably good hydrothermal stability. Compared to Al-MCM-41 mesoporous materials, Al-SBA-15, which is more easily synthesized, has larger diameter, thicker pore walls and better hydrothermal stability. It is especially suitable for the catalytic reaction of large molecules reactants.On the other hand, benzene styrene phenolic compounds are important intermediate for organic synthesis with epoxyethane, aminosulfonic acid and other substances in the reaction to generate a series of compounds. These products are widely used in chemical, pesticide and other fields. As we all know, Al-SBA-15 may exhibite good catalytic properties in the Friedel-Crafts alkylation reaction. Therefore, the study of Friedel-Crafts alkylation over Al-SBA-15 mesoporous catalysts has important practical significance and academic value.In this thesis, a series of Al-SBA-15 mesoporous catalysts were directly synthesized via hydrothermal method using Pluronic P123 triblock polymer (EO20PO70EO20, Mav=5800, Aldrich) as structure-directing reagent. tetraethoxysilane, aluminum isopropoxide and aluminumchloride were used as the silicon and aluminum sources, respectively. The synthesized materials were characterized by using N2 adsorption-desorption, powder X-ray diffraction patterns (XRD), scan electronic microscopy (SEM), transmission electronic microscopy (TEM), fourier transform-infrared spectroscopy (FT-IR), ammonia temperature-programmed desorption (NH3-TPD), inductive coupled plasma atomic emission (ICP), and pyridine infrared spectroscopy (Py-IR). Meanwhile, the catalytic performance of the obtained Al-SBA-15 materials was investigated through Friedel-Crafts alkylation of 2, 4-ditert-butyl-phenol and cinnamyl alcoholby. The primary conclusions were as follows:1. When the Al-SBA-15 mesoporous materials was synthesized with aluminum isopropoxide as the aluminum source, the sample with nSi/nAl=40 crystallized at 110℃for two days exhibited better crystalline structure and catalytic properties than the others.2. When the Al-SBA-15 mesoporous materials was synthesized with aluminumchloride as the aluminum source, the sample with nSi/nAl=50 crystallized at 110℃for two days exhibited better crystalline structure than the others. While the sample with nSi/nAl=40 exhibited the best catalytic properties.3. Comparing the structure and catalytic activity between the two kinds of Al-SBA-15 samples synthesized with different aluminum source, it was found that the mesoporous materials exhibited good catalytic properties with aluminum isopropoxide as aluminum source. While the samples has good crystalline and meso-structure with aluminumchloride as aluminum source. This may be due to that the matched hydrolysis rate of silicon and aluminum source is important to achieve highly ordered samples. In addition, the acidity of the reaction solution is a key factor for the successful incorporation of aluminum atoms into the mesoporous materials.