Postsynthesis And Catalytic Properties Of MWW And MSE-type Titanosilicates

As highly efficient speciality catalysts,zeolites have been widely applied to the catalytic processes in refining and petroleum industry.In this thesis,two titanosilicates with MWW and MSE topologies have been postsynthsized by inserting Ti4+ ions into the zeolite framework.The catalytic oxidation properties of these catalysts were also investigated.A greener route was designed to synthesize B-MWW precursor under reduced amounts of piperidine and boric acid condition through the introduction of Na+ ions as mineralizer.Then,Ti-MWW zeolite was postsynthesized by acid treatment of B-MWW and subsequently solid-liquid treatment with H2TiF6 aqueous solution.Ti4+ions were tetrahedrally incorporated into MWW zeolite,yielding catalytically active Ti-MWW zeolite in the liquid-phase epoxidation of n-hexene.A postsynthetic method including acid-treatment and gas-phase Ti insertion was performed to prepare Ti-MCM-68(MSE)zeolite,making full use of the large 12R pores.The MCM-68 framework was well-preserved during the post-treatments and Ti4+ ions were tetrahedrally incorporated.No extraframework Ti species or TiO2 was observed.The obtained Ti-MCM-68 showed good activity and selectivity in the oxidation of linear and cyclic alkene and the ammoximation of cyclohexanone.Moreover,a seed-assisted method was developed to synthesize MCM-68 zeolite without using any organic structure-directing agent(OSDA).The traditional synthesis method of MCM-68 possesses many disadvantages,such as complex synthesis of OSDA,long crystallization time,etc.The effects of gel composition,crystallization condition as well as the type of seed were investigated.The introduction of active seed effectively inhibited the crystallization of impurity and also enhance the yield of MCM-68,making this seed-assisted method an effcient approach to prepare MCM-68 zeolite.