Catalytic properties of highly ordered crystalline nanoporous tungsten oxide in butanol dehydration

Highly ordered mesoporous tungsten oxide (meso-WO₃) was successfully synthesized using mesoporous silica KIT-6 as a hard template via the nanoreplication method. The physicochemical properties of meso-WO₃ were characterized by X-ray diffraction, nitrogen adsorption-desorption, transmission electron microscopy, X-ray photoelectron spectroscopy, temperature-programmed desorption of ammonia, and infra-red spectroscopy of adsorbed pyridine. No oxidation state other than WO₃ was observed in the meso-WO₃ sample. Lewis acid sites were dominant in meso-WO₃, which could be confirmed by infra-red spectroscopy of pyridine and temperature-programmed desorption of ammonia. Its catalytic behavior in 2-butanol dehydration was investigated in a fixed bed reactor and compared with that of the WO₃/MCM-41 catalyst prepared by the atomic layer deposition method. The meso-WO₃ catalyst exhibited higher 2-butanol dehydration activity than that of the WO₃/MCM-41 catalyst, which is ascribed to the stronger acidity as well as higher amount of acid sites that are mainly composed of Lewis acid sites in the meso-WO₃ catalyst.