MWW type titanosilicate, Ti-MWW, has been synthesized by the dry-gel conversion (DGC) method, and its physicochemical properties and catalytic performance in the liquid-phase epoxidation of alkene have been compared with that of hydrothermally synthesized (HTS) Ti-MWW. The roles in the crystallization of silica source, alkali cation, cyclic amine as a structure-directing agent (SDA), and boric acid structure-supporting agent have been investigated. The crystallization of Ti-MWW did not occur for the dry gels free of boric acid, but was feasible at a Si/B molar ratio as high as 12 in marked contrast to the ratio of 0.75 required in the hydrothermal synthesis. The sodium as a mineralization agent was not necessary and on the contrary inhibited the crystallization particularly at a high content. The seeding technique using deboronatedMWWeffectively accelerated the crystallization speed and reduced the amount of boric acid required. As-synthesized Ti-MWW-DGC lamellar precursors contained both tetrahedral and octahedral species but the latter was selectively removed by acid treatment. Ti-MWW-DGC catalysts showed lower intrinsic activity than Ti-MWW-HTS in the epoxidation of hex-1-ene with hydrogen peroxide probably because the crystal size of the former was 10-20 times as large as that of the latter and then imposed significant diffusion problems for both the substrates and the products.

A new titanosilicate, named Del-Ti-MWW, has been prepared by delaminating the lamellar precursor of Ti-MWW, which is postsynthesized from highly deboronated MWW zeolite with the assistance of cyclic amine. The amount of organic base used for supporting surfactant in swelling the layered structure should be controlled carefully to delaminate efficiently without the collapse of the structure. Ultrasound treatment is demonstrated to delaminate the swollen material more completely. Del-Ti-MWW materials have a large surface area, which mitigates effectively the steric restrictions imposed by conventional microporous titanosilicates to bulky molecules. Del-Ti-MWW, maintaining the fundamental structure of MWW zeolite and tetrahedral Ti species in the framework position, proves to be superior to TS-1, Ti-Beta, three-dimensional Ti-MWW and even mesoporous Ti-MCM-41 in the epoxidation of a wide range of bulky alkenes with hydrogen peroxide.

The catalytic activity and selectivity of Ti-MWW in the epoxidation of diallyl ether (DAE) with hydrogen peroxide to allyl glycidyl ether (AGE) and diglycidyl ether (DGE) have been studied by a comparison with those of TS-1, and the issues concerning the consecutive reaction and the selective production of AGE have been considered. Ti-MWW catalyzed the DAE epoxidation in the presence of aprotic solvents such as acetonitrile or acetone, and produced only minor levels of solvolysis products. Ti-MWW proved to be a reusable catalyst standing up to the Ti leaching and maintaining the catalytic activity and the product selectivity in the reaction-regeneration cycles. Studies with different solvents, Ti contents, reaction times, temperature, and catalyst amounts confirmed that the DAE epoxidation was a typical consecutive reaction with AGE as an intermediate product and DGE as a secondary one. The reaction rate for AGE formation was much faster than that for DGE, making the selective production of AGE possible by controlling the reaction up to a DAE conversion level of ca. 30%.

Novel methods for enhancing the epoxide selectivity in the alkene epoxidation over [Ti,Al]-Beta have been developed. When as-synthesized [Ti,Al]-Beta was treated with aqueous ammonium nitrate solution and successively calcined at low temperature, a dramatic enhancement of epoxide selectivity was attained in the liquid-phase epoxidation of cyclohexene using H2O2 as an oxidant in protic solvent methanol. The optimum thermal treatment temperature to achieve the maximum epoxide yield was 473 K, where the postsynthetic [Ti,Al]-Beta exhibited a catalytic activity comparable to the sample directly calcined at 793 K; nevertheless, the epoxide selectivity was as high as 63% for the former in contrast to 0% for the latter. The ion-exchange treatments with quaternary ammonium salts over calcined [Ti,Al]-Beta showed similar effects, although the treatments with alkali and alkaline earth metal ions were detrimental to the catalytic activity. It is suggested that the quaternary ammonium cations selectively blocked the acid sites deriving from the framework Al, which resulted in preventing the ring-opening hydrolysis of the epoxide, whereas the inorganic cations poisoned not only the acid sites but also the Ti active sites contributing to the catalytic epoxidation. The ion-exchanged catalyst was regenerated readily by repeated calcination and following ion exchange and thus turned out to be an active, selective, and reusable epoxidation catalyst.

Al- and Ga-incorporated ETS-10, designated as ETAlS-10 and ETGaS-10, respectively, were synthesized by using P25 titania as a Ti source. The isomorphous substitution of Al and Ga for framework Si at the (4Si) environment was confirmed by 29Si MASNMR measurements. ETS-10 was more active in the Knoevenagel condensation than Y-type zeolites. The introduction of Al and Ga into ETS-10 enhanced the activity, due to the increase of the ion-exchange sites, which act as Br