Ultrafast synthesis of nanosized Ti-Beta as an efficient oxidation catalyst via a structural reconstruction method

Abstract

As a representative selective oxidation titanosilicate catalyst, a Ti-Beta zeolite is less used in comparison with TS-1, Ti-MWW and Ti-MOR, mostly due to its high hydrophilicity originating from a BEA* intergrowth framework. A novel recrystallization method was proposed in the present study to prepare highly hydrophobic Ti-Beta with nanosized crystals (90 nm), high Ti content (Si/Ti = 20) and intercrystal mesoporosity. The fluoride-assisted recrystallization was realized quickly by dissolving extensively a dealuminated Beta zeolite in a mixture of a tetraethylammonium aqueous solution and Ti precursor, producing highly crystalline Ti-Beta in an extremely short time of 1 h. The obtained Ti-Beta zeolite exhibited superior catalytic activity in the liquid-phase epoxidation reactions of bulky alkenes like cyclohexene with hydrogen peroxide or tert-butyl hydroperoxide as an oxidant, compared to those Ti-Beta catalysts prepared by conventional hydrothermal or secondary synthesis routes.