Synthesis Of Large Pore SBA-15 Mesoporous Molecular Sieve

Mesoporous molecular sieve as a catalyst, adsorbent, as well as nonlinear optical materials, nano-electronic conductors, nano-composite materials based on cutting-edge material used is reflected in the three aspects of its pore structure, pore size and pore volume. Therefore, pore size, pore shape, topology of the mesoporous molecular sieve is very interested in chemists at home and abroad. The modulation of pore size is one of the most enthusiastic what they study.Mesoporous SBA-15 has aroused more and more people's attention as a high surface area and adjusted pore size in just the past ten years.For the SBA-15 molecular sieve, the researchers are concerned with the question of how prepared SBA-15 molecular sieve with a large pore size, ordered highly and large surface area. Increasing pore size of molecular sieve SBA-15 not only can make biological macromolecules, metal oxides and metal clusters and other large volume of functional groups to extend into the pore selectively, and make the reactants and solvent molecules to spread in the channels more easily, but also can achieve molecular-level screening at a wider range. It realize its value betterly.Large pore SBA-15 mesoporous molecular sieve has a very good value in the molecular adsorption, separation and macromolecular enzyme immobilization and catalytic converter.In this study, molecular sieve SBA-15 with large pore was synthesized by double template method and two-step sol - gel method based on the previous synthesis of SBA-15 molecular sieve, while the ratio of reactants and the different crystal temperature and calcined temperature was investigated on the impact of pore size. The synthetic samples were characterized by X-ray powder diffraction (XRD), nitrogen adsorption, transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FT-IR). The main results and conclusions are as follows:First,SBA-15 molecular sieves is prepared by using three-block copolymer PEO20-PPO70-PEO20 (P123) as a single template,TEOS as silicon source under acidic conditions. XRD and TEM analysis results showed that SBA-15 sample is two-dimensional (p6mm) hexagonal mesoporous structure. Nitrogen adsorption analysis showed that pore size of mesoporous SBA-15 is 7.789nm and pore volume is 1.287cm3g^-1 and surface area is 878.2m2g^-1. This experiment will serve as a comparative experiment in the use of follow-up study.Second, Large pore SBA-15 mesoporous molecular sieve is prepared by using the double template method (P123 and F127), while the ratio of reactants and different crystal temperature and calcined temperature is investigated on the impact of pore size. It find that the best template ratio is n (F127): n (P123) = 0.0065 through the experiments.Ordered SBA-15 sample is prepared when the crystal temperature is 110℃and the calcined temperature is 550℃. Calcined temperature can not be expanded pore size. Pore size SBA-15 mesoporous molecular sieve using double template method is about 10nm and the pore volume is increased, but the surface area is decreased slightly to compare with synthesized samples using a single template.So double template method can expand pore size of the SBA-15 molecular sieve effectively.Third, large pore of the SBA-15 molecular sieve is prepared by using two-step sol - gel method, while the addition of xylene and ammonia is investigated on the impact of pore size. when the amount of raw material Ratio is 1.0 TEOS: 0.01 P123: 5.88 HCl: 136 H2O: 0.03 (xylene): 0.5 (ammonia), average pore size of synthesized samples is 9.498nm,but surface area and pore volume decreased slightly.Finally, the SBA-15 molecular sieve was synthesized by adding assisted agent, while the ratio of reactants and different crystal temperature was investigated on the impact of pore size. When the crystal temperature is 110℃and the amount of raw material ratio is 1.0 TEOS: 0.01 P123: 5.88 HCl: 136 H₂O: 0.06 (ethylenediamine), order samples is synthesized, but pore size of synthesized samples not expanded to compare with synthesized samples using a single template,and pore volume and surface area decreased slightly.It show that double template method (P123 and F127) can not only expand pore size of the sample SBA-15 molecular sieve but also increase pore volume through a lot of experiments. Pore size of SBA-15 molecular sieve can also expand through two-step sol - gel method ,but the order of sample decreased slightly. And pore size of the sample is not increased by adding assisted agent.