Synthesis Of TS-1 From Inorganic Reactant System And Its Catalytic Properties For Allyl Chloride Epoxidation

Since it was first successful synthesis by EniChem in 1983,titanium silicalite-1(TS-1)has attracted much research attention for its remarkable catalytic properties to the selective oxidation using H2O2 as green oxidant,such as aromatic hydroxylation,oxidation of alcohols and alkanes,ammoximation of ketone and epoxidation of alkenes.Originally,TS-1 zeolite was synthesized from organic reactant system by using tetraethyl orthosilicalite(TEOS)and tetraethyl orthotitanate(TEOT)as the silicon and titanium resource,respectively,and using large amount of tetrapropylammonium hydroxide(TPAOH)as the template.However,these organic materials such as TPAOH and TEOS are expensive;the ethanol formed from the hydrolysis of TEOS is required a troublesome step of eliminating;the TS-1 is too small(100-200 nm)to separate from the mother liquid or the reaction solution.Therefore,the preparation cost of TS-1 is high and its further commercial applications are delayed.TS-1 is still belongs to the category of micropore and its pore is constrictive,so it also has the TS-1 steric hindrance,so TS-1 can't be used in the reaction of macromolecule materials reaction now.However,the discovery of Ti-containing ordered mesoporous materials have weak stability and low oxidation performance due to the amorphous nature of their walls.TS-1 has a good thermal stability and it is significant to develop the hierarchical TS-1.In our study,TS-1 has been synthesized from inorganic reactant system using TPABr and base as the templating agent.The effects of preparation parameters,such as titanium sources,base sources,SiO2/TiO2,TPABr/SiO2,base/SiO2,seed amout,gelatinization temperature,crystallization temperature and time,the concentration of sulfate ion and bromide on the physicochemical and catalytic properties of TS-1 were investigated in detail.The TS-1 samples were characterized by XRD,FT-IR,UV-vis,SEM and ICP-AES,and the catalytic performance of TS-1 was evaluated in the epoxidation of allyl chloride.The synthesis raw materials and conditions had a great influence on the properties of TS-1.The optimum titanium source and base source is Ti(SO4)2 and ammonia;the optimum synthesis conditions for the present system should employ a gel composition of SiO2/TiO2/NH3/TPABr/H2O = 1:0.022:2.5:0.15:35 under 298 K,and carry out the crystallization at 443 K for 3 days,the addition of seed in the synthesis gel played an important role in the crystallization of TS-1.Moreover,the the concentration of sulfate ion and bromide had a great influence on the crystallization rate,crystal size and the amount of framework Ti.The TS-1 prepared from inorganic reactant system has a characteristic of low cost,operation simplicity,big size and easy to separation.The TS-1 also prepared from this system showed a higher catalytic performance for the epoxidation of allyl chloride with H2O2,and even compared with TS-1 prepared by classic method,the catalytic activity of TS-1 synthesized from Ti(SO4)2 was not low.The stability and reusability of TS-1 synthesized from inorganic reactant system were also excellent,the MFI structure of TS-1 had no obvious change after nine-times regeneration,and the catalytic performance of TS-1 was still fine.Finally,we synthesized micro-mesoporous TS-1 using the sucrose as soft template,and the existence of mesoporous was proved by the N2 adsorption.Compared with conventional TS-1,the hierarchical TS-1 showed a higher catalytic property,because the existence of mesoporous can help the diffusion in the reaction.