Preparation of titanosilicate with mordenite structure by atom-planting method and its catalytic properties for hydroxylation of aromatics

Titanium mordenites (Ti-M) with different titanium and aluminum content have been prepared by the solid-gas reaction at elevated temperatures (atom-planting method) between highly dealuminated mordenites and TiCl ₄ vapor. Ti-M samples were characterized with MAS NMR, IR and UV spectroscopies, which indicates that Ti atoms have been incorporated tetrahedrally into the mordenite framework through the reaction of TiCl ₄ with hydroxyl nests composed of SiOH groups. The catalytic properties of Ti-M for the liquid phase hydroxylation of various aromatic substrates having different molecular sizes with H₂O₂ were studied by comparing with those of MFI-type titanosilicate (TS-1). Ti-M showed comparable specific activity to that of TS-1 for the hydroxylation of smaller substrates which can diffuse easily into the pores of both catalysts. However, Ti-M was more active than TS-1 in the hydroxylation of bulkier aromatics, because Ti-M has larger window size of pore than TS-1.