Synthesis,Characterization And Catalytic Properties In Selective Oxidation Of Titanosililcates

Titaniumsilicalite zeolites including Ti atoms in the framework is a new kind of zeolites catalysts developed in 1980s. It was found that TS-1 has unique catalytic properties in selectivity oxidation of many organic compounds with hydrogen peroxide as oxidant, under ambient conditions without harmful waste. This kind of zeolites have been attracting more attentions because its environment-friendly selectivity oxidation catalytic properties. By traditional methods, TS-1 was synthesized using alkali-free TPAOH as the templates at severe conditions and high cost, which makes the industrial application of TS-1 difficult. The cheaper system has been developing quickly with TPABr as the templates. However, some disadvantages were brought by the cheaper system because of the different synthesizing conditions, such as longer crystallizing time and lager crystalline sizes, which also became the handicap in the industrial application of TS-1.This dissertation was addressed on the research of titanosilicates catalytic materials. A route of synthesizing TS-1 was proposed using titanium tetrachloride(TiCl4)/(TiCl4+TBOT) as Ti source in the cheaper system. The acidity of TS-1 was studied by NMR and UV-Vis techniques. The synthesis, physicochemical properties and the active sites of TS/Ti02 were studied. From the above research, the following results have been obtained.1) Synthesis of TS-1 with titanium tetrachloride as Ti-sourceTitanium tetrachloride solved in different alcohol was used to synthesize TS-1 as Ti source. The molecular sizes of the solvents have obvious effect on the crystallization and physicochemical properties of TS-1 products. Because titanium tetrachloride reacted strongly with H2O to form Ti-OH when it was added to the gel directly, further polymerization happened among those species to form (-Ti-O-)n, which obstructed the incorporation of Ti atoms. After TiCl4 was added into alcohol, partial HC1 was released from TiCl4 and the rate of hydrolysis and polymerization decreases to the level matching that of SiO2 It indicates that the ability to adjusting the hydrolysis properties of Ti source decreases as following: iso-propanol ) ethanol ) methanol. Iso-propanol is more suitable using as the solvent, which improves the inclusion of Ti atoms in the framework. TS-1 has most excellent catalytic activitywith titanium tetrachloride solved in iso-propanol as the titanium source.TS-1 was also synthesized using the mixture of TBOT and TiCl4 as the Ti source. The samples have higher crystallinity and more framework titanium, also have more excellent performance in the oxidation of propylene with hydrogen peroxide, compared with those of the zeolites synthesized by TBOT or TiCl4 individually. Replacement of alkoxy groups by chlorine decreases the association degree of titanium alkoxides and prevents the preferential segregation of titanium and silicon, which improves the inserting of titanium into the framework of silicalite-1.In TPABr-TiCl4 system, no Anatase TiO2 was produced in zeolite samples, which is difficult to avoid by the traditional method. However, extraframework titanium species were formed which have a broad absorption peak in the range of 240~270nm. The amount of ammonia can be changed in a large range and has marked effect on the crystalline size.2) Rapid synthesis of TS-1 and synthesis of TS-1 with small crystalline sizesTS-1 was synthesized with TPABr as the templates, titanium tetrachloride as Ti source, colloidal silica as Si source and ethylamine as the base. The samples were studied by UV-Vis, 13C CP/MAS NMR, 29Si MAS NMR and 'H-29Si CP/MAS NMR spectra. It has been shown that TS-1 can be synthesized rapidly in 24 hours. The NMR results showed that TPABr served as templating agent and ethylamine can not take the role of template in this system. The results of UV-Vis show that there is no structure of -Si-O-Ti-O-Si- formed in the gel of synthesizing zeolites. After the hydrolysis of Ti source, TiOx species were produced. During the crystallizing period, TiOx species were di...