Characterization of NiO-TiO2 modified with WO3 and catalytic activity for acid catalysis

Abstract

A series of NiO-TiO2/WO3 catalysts was prepared by drying powdered Ni(OH)2-Ti(OH)4 with ammonium metatungstate aqueous solution, followed by calcining in air at high temperature. Characterization of prepared catalysts was performed by using FTIR, Raman, XPS, XRD, and DSC and by measuring surface area. Upon the addition of tungsten oxide to titania up to 25 wt%, the specific surface area and acidity of catalysts increased in proportion to the tungsten oxide content due to the interaction between tungsten oxide and titania. Since the TiO2 stabilizes the tungsten oxide species, for the samples equal to or less than 25 wt%, tungsten oxide was well dispersed on the surface of titania, but for the samples containing above 25 wt%, the triclinic phase of WO3 was observed at calcination temperature above 400 °C. The catalytic activities of 10-NiO-TiO2/WO3 for 2-propanol dehydration and cumene dealkylation were correlated with the acidity of catalysts measured by ammonia chemisorption method. NiO may attract reactants and enhance the local concentration of reactants near the acid sites, consequently showing the increased catalytic activities.