The catalytic properties of Ti-MWW in the epoxidation of linear cis/trans-alkenes with hydrogen peroxide has been studied extensively, and a mechanistic investigation into its unique trans-selectivity has been carried out by comparing with TS-1 and Ti-Beta. Ti-MWW exhibits a singularity never observed on conventional titanosilicates, that it selectively epoxidizes the trans-isomer to give a selectivity of ca. 80% for corresponding trans-epoxide from an alkene mixture with a cis/trans ratio of 50:50. The trans-selective nature of Ti-MWW is affected neither by the reaction conditions nor by the kinds of alkenes. Ti-MWW retains the stereochemistry for both the substrates and the epoxides during the epoxidation reactions. Liquid-phase adsorption and the epoxidation reaction with bulky organic oxidant and position-selective poisoning reagents have revealed that the unique trans-selectivity of Ti-MWW originates mainly from its sinusoidal 10-MR channels.

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 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.

Disproportionation of toluene has been studied over dealuminated MCM-22 zeolites. The dealumination of MCM-22 was performed by acid reflux and the combination of calcination or steaming with the subsequent acid reflux, These treatments effectively eliminated A1 atoms from the framework site but left most of them in the crystallites as non-acidic extra-framework species. The activity of MCM-22 for the toluene disproportionation measured at relatively low temperatures (473-573K) was comparable to that of mordenite and much higher than that of ZSM-5. Toluene disproportionation was found to occur mainly within the supercages of MCM-22 but not in the 10-membered ring (10-MR) channels of MCM-22 at these temperatures. The fraction ofp-xylene in xylene isomers (para-selectivity) formed on MCM-22 was higher than its equilibrium value, and increased further by the dealumination. p-Xylene formed within the supercages as a primary product would be isomerized to o- and m-xylene by the acid sites not only on the external surface but also within the 10-MR channels. The improvement in para-selectivity by the dealumination resulted from the suppression of isomerization activity probably because the dealumination treatments eliminated framework A1 atoms predominantly on the external surface and inside the 10-MR channels compared with those inside the supercages.

B-free titanosilicate with the MWW topology, Ti-MWW, has　been successfully prepared from its highly siliceous analogue　through structural interconversion and simultaneous titanium incorporation in the presence of piperidine or hexamethyleneimine.