Studies On Synthesis, Characterzation And Catalyst Application Of Orderly Mesoporous Molecular Sieves

The paper reviewed the evolution and classification of the mesoporous materials and their synthesis methods, their formation mechanisms, as well as their physicochemical properties and their application. This paper thesis emphasized on the preparation and characterization of bimodal mesoporous silica molecule sieves and Ag/SBA-15 materials, and the catalytic activity of the Ag/SBA-15 were test by CO oxidation and the three-component coupling reaction of aldehyde, amine and alkyne.The MCM-48 mesoporous molecular sieves was synthesised using aqueous ammonia as catalyst without hydrothermal treatment. This experiment can be processed in short time with high yield(97%), and the method can be used in industrialisation.A convenient preparation of ordered bimodal mesoporous silica nanoparticles has been achieved by mild-temperature post-synthesis hydrothermal treatment of the as-synthesized MCM-48 mesoporous materials in H2O2 solution. After hydrothermal treatment at 100℃for some time, the channel from the cubic structure turned to wormhole-like bimodal mesoporous stucture. Interestingly, the BJH model analysis of this material provides one narrow peak centered at 2.5 nm in the pore size distribution and another broader peak in the region of 3–5 nm with an evident maximum at 3.6 nm, showing a dual mesoporous distribution. The organic templates were removed from the materials in the progress of the hydrothermal treatment. XRD, TEM, FT-IR, TG and nitrogen sorption were used to characterize the obtained bimodal mesoporous silica sample.Ag/SBA–15 catalysts have been prepared by means of in situ reduction methods using hexamethylenetetramine and formaldehyde as reducing agents, respectively, and characterized by N2 adsorption/desorption, XRD, TEM and XPS. Presence of nanoparticles of silver in SBA–15 were confirmed by high angle X-ray diffraction data (peaks between 2θ= 10–80o) and XPS, and transmission electron microscopy confirmed the diameter of the nanoparticles. The content of the silver in the Ag/SBA-15 was detected by ICP-AES. When hexamethylenetetramine was used as reducing agent, uniform Ag nanoparticles inside the channels were formed, and diameter of nanoparticles is found to be ~ 6.0 nm which is coincident with channel diameter of SBA–15. The catalysts were subjected to CO oxidation in a flow reactor at atmospheric pressure and temperatures up to 300°C. Studies revealed that catalysts prepared with different reducing agents strongly influence their catalytic and stability performance in the CO oxidation, what prepared with hexamethylenetetramine as mild reducing reagent shows a certain low temperature catalytic activity.A series of Ag/SBA15-n catalysts were synthesized with different amount of AgNO3 reduced by hexamethylenetetramine(HMT). These catalysts were employed to multi component A3 coupling reaction of aldehyde, amine and alkyne. The results showed the reaction had a high efficiency with silver content of 7wt.% in glycol. The catalysts could repeat for many times and the samples were characterized by 1H NMR.