Synthesis, Characterization And Catalytic Properties Of Mesoporous Titanosilicates

As an important inorganic material, molecular sieve plays an important role inmany scientific fields, such as ion exchange, adsorption and separation, host-guestchemistry, etc. So a lot of scientists are engaging themselves in researching thesynthesis of molecular sieves. After decades of years'hard work, a large number ofmicroporous or mesoporous materials with novel structures and functions aredeveloped. The research on the microporous materials were covered half a century,their applied aspects are developed stably. The next important research area is in themolecular biology, medication, photo electricity, etc. Microporous materials hasmore than 40 years history as the catalysts, some molecular sieves were alreadyapplied in the petrol-chemistry and fine chemistry, such as Y, ZSM-5, TS-1, etc.The discovery and application of microporous titanosilicate(TS-1) had animportant progress in the catalytic oxidation recent 20 years. Many scientists puttheir interests in the liquid oxidation reactions with mixed atom microporousmaterials. However, there is a fatal shortcoming about catalyst TS-1, its porediameter is too small(about 6 ?) to let bigger molecular react with activity centersthrough the pore. What's more, the oxidation of big molecular is popular in finechemistry and medication chemistry. In the area of photo catalysis, the mesoporoustitanosilicates with bigger pore diameters have better reaction abilities, they showbetter catalytic effects in the treating of polluted waters compared with traditionalmicroporous materials. So the researches on the synthesis of mesosturcturedtitanosilicates with large pore diameter are always in the progress.As we all know, mesoporous molecular sieves have been obtained by means ofthe corporative interaction between inorganic precursors and supramolecularsurfactants. They have large pore size(2-50nm), large surface area and narrow poresize distribution. The circumstance in the synthesis of inorganic precursor is usuallyin basic condition, so, in the course of interation between precursor and surfactants,if the basic condition could be continued, it is benefit to the formation of orderstructure in microporous materials, and then form the well ordered mesostructuredmaterial by the supramolecular surfactants. In this paper, we use this method,preforming inorganic precursor with microstructured molecular sieve, then mixed itwith surfactant CTAB, the well ordered mesostructured titanosilicate can besynthesized in the basic condition. And then TS-1 precursors were loaded and highlydispersed on the surface of mesoporous materials MCM-41 and SBA-15, the samplesretain the mesopores channels and characteristic structure of microporous TS-1.Catalytic results show that these materials are more active than conventionalmesoporous Ti-MCM-41 and Ti-SBA-15.First of all, the mesotructured aluminosilicate were synthesized by means ofStructure Directing Agent method(SDA), there were some differences in the samplesof different Si/Al, improving the concentration of Al species, the order structure offrame work will be destroyed. However, Al species played an important role incatalysis of the sample, so we should experiment the lower Si/Al but not destroy theordered structure. The higher temperature will not be benefit to the order frame work,so we synthesize the sample in 373K. The aging time of SDA is the most importantcourse in the synthesis, we use 4 hours to age the SDA. Compare the XRD patternsof MCM-41,SBA-15å’ŒSi-MAS(Si/Al=20) after treated in the boiling water for 48hours, the sample of Si-MAS has similar hydrothermal stability with SBA-15, afterthe boiling water treating it retain the mesostucture. IR pattern shows there arefundamental structure and secondary structure unit of microporous molecular sievein the frame work of Si-MAS. With the same synthesis method, we prepared the mesostructured Ti-MAScontaining Ti species. Leading the Ti atom to the frame work of mesoporousmaterials to let it has fine catalytic ability and large pore size. The mesoporousstructure could be confirmed by XRD pattern. We choose Si/Ti=60 as the best scale.IR pattern also shows there are fundamental structure and secondary structure unit ofmicroporous molecular sieve in the frame work of Ti-MAS. UV-Vis spectra is thecommon tool for the conformation of Ti species'cooperation condition in themolecular sieve frame work, only Ti species with four-cooperation has fine catalyticability. Our sample synthesized in the condition of 373K and Si/Ti=60 gives anobvious absorb peak about 210nm in the UV-Vis pattern, it shows the Ti species offrame work are mostly in four cooperation, implies that the sample has well catalyticproperty. In the reaction of photocatalysis of RhB, Ti-MAS could degrade the red dyein the visible light whose wavelength are above 470nm. The photodegradation abilityshowed by Ti-MAS was higher than traditional microporous molecular sieve TS-1.TS-1 precursors were loaded and highly dispersed on the surface of mesoporousmaterials MCM-41 and SBA-15, and these samples are characterized by infrared,UV-Visible and other techniques. These results suggest that the samples retain themesopores channels and characteristic structure of microporous TS-1. Catalytic...