Highly effective formation of cyclopentanol through the liquid-phase hydration of cyclopentene has been attempted on various zeolites catalysts. MCM-22 zeolite was the most selective catalyst, which actively converted cyclopentene to cyclopentanol with a selectivity up to 99%. The effects on the hydration of catalyst preparation method, reaction atmosphere and temperature have been investigated for the MCM-22 catalysts. On the basis of the effect of reaction atmosphere, the mechanism of liquid-phase cyclopentene hydration was proposed. The thermodynamic equilibrium between cyclopentene and cyclopentanol was suggested to control greatly the cyclopentene conversion. The cyclopentene conversion was increased to 10% by increasing the water/cyclopentene ratio. Poisoning using organic amines with different molecular sizes revealed that the hydration occurred mainly in the 10-membered ring channels of MWW structure, which had an elliptic aperture smaller than that of MFI structure, exhibiting a significant shape selectivity by suppressing the etherification cyclopentanol.

A series of mesoporous molecular sieves with various SiO2/Al2O3 ratios have been applied to the liquid-phase Beckmann rearrangement of cyclohexanone oxime. The influences of solvent, aluminum content, aluminum-incorporating method, and catalyst structure on the catalytic performance have been investigated. Benzonitrile has been found to be a suitable solvent. The surface silanol groups ineffectively catalyze the rearrangement, whereas the acid sites generated by incorporation of aluminum improve the activity and the selectivity to ε-caprolactam remarkably. Moreover, an Al-containing MCM-41 catalyst prepared by the postsynthetic method using AlCl3 as an aluminum precursor exhibits higher lactam selectivity than a directly synthesized one. For a given aluminum content, MCM-41 shows superior performance to beta zeolite and other mesoporous catalysts, SBA-1 and SBA-15. It has been suggested that a sufficient amount of acid sites with appropriate strength is of importance to the liquid-phase Beckmann rearrangement.

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

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.

Mesoporous Ti-SBA-15 has been postsynthesized by the titanation of pure silica SBA-15 in glycerol with the assistance of quaternary organic ammonium hydroxides, and has been extensively characterized by various techniques to investigate the mesostructural and catalytic properties, and the chemical nature of the incorporated Ti species, in comparison with those of Ti-MCM-41. To incorporate tetrahedral Ti species into the silica walls of SAB-15, the titanation needs to be carried out at elevated temperature and using an optimum amount of organic ammonium hydroxide. Ti-SBA-15 samples with a Si/Ti ratio ranging from 376 to 16 are successfully prepared with the retention of hexagonal mesostructure by elaborately conducting the titanation. The nature of the Ti species depends greatly on the Ti loading. At Si/Ti ratios higher than 50, the Ti species are mainly tetrahedrally coordinated in isolated states, while poorly dispersed Ti species of octahedral coordination are formed at higher Ti incorporation levels; however, no anatase phase is formed in all cases. The IR band at 948cm-1 due to Si-O-Ti bonds can be used to characterize the tetrahedral Ti species in mesoporous materials, but the techniques of dehydration or trimethylsilylation should be adopted to get rid of the influence of silanol groups. In an actual catalytic reaction, Ti-SBA-15 exhibits not only extremely high thermal stability but also outstanding endurance against Ti leaching not observed for Ti-MCM-41. Ti-SBA-15 is thus presumed to be a promising liquid-phase oxidation catalyst.

The shape selectivity in the liquid-phase hydroxylation of aromatic hydrocarbons with hydrogen peroxide has been studied on two kinds of titanosilicate, the large-pore Ti-M with MOR structure and medium-pore TS-1 with MFI structure, and the liquid-phase diffusion of aromatics into both catalysts was compared in the presence of H2O and H2O2 to clarify the origin of the shape selectivity. The hydroxylation rate on TS-1 decreased monotonically with increasing molecular size in the order benzene>toluene. ethylbenzene>cumene, while Ti-M showed the maximum rate for toluene hydroxylation. The apparent diffusivity of aromatics was lowered roughly by 1 order by adding H2O2 to H2O solvent for both titanosilicates but was not affected for their Ti-free derivatives, mordenite and silicalite-1. The reduction in diffusion rate in the presence of H2O2 was more pronounced for TS-1 and for Ti-rich samples. It is concluded that a bulky Ti peroxo species (Ti-OOH) formed by the interaction of Ti site with H2O2 mainly causes a transition-state shape selectivity in the hydroxylation of bulky aromatics in titanosilicate/H2O2 systems.

A new ferrisilicate molecular sieve with the MCM-22 structure is synthesized in Al-free form and exhibits low activity as a solid-acid catalyst and significant activity for the selective catalytic reduction of NO with NH3.

A novel titanosilicate with MWW topology, Ti-MWW, has been prepared by an acid treatment on a corresponding lamellar precursor which is hydrothermally synthesized with the coexistence of boron and titanium using piperidine (PI) or hexamethyleneimine (HM) as a structure-directing agent. TheMWWprecursor can be synthesized to have a Si/Ti ratio as low as 10 when the Si/B ratio of the gel is maintained at 0.75. Both the materials synthesized using PI and HM exhibit the crystal form of thin platelets, while the latter shows a larger crystal size. Besides the tetrahedral Ti species, the precursor always contains the octahedral Ti species showing a UV-vis band at 260nm, regardless of the Ti content. Calcination of the precursor results in a partial condensation of the octahedral Ti species to form the anatase phase, which is hardly removed by the acid treatment. MWW-type titanosilicate nearly free of both anatase and boron, however, is successively prepared by a cyclic treatment on the lamellar precursor, that is, an acid treatment, subsequent calcination, and a further acid treatment. After evacuation at 773K, the titanosilicate thus prepared shows a characteristic IR band at 960cm-1 not observed for the Ti-free sample. The intensity of the 960 cm-1 band increases linearly with the Ti content up to a level corresponding to Si/Ti) 40, indicating the limitation of incorporating Ti into the framework of MWW by the present method.

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%.

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.