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.

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.

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.

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.

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.