Investigation Of Catalytic Dehydration Of Glycerol Over WO_x/Clay Catalyst

Among several types of catalysts for glycerol conversion to glycerol,tungsten oxide catalysts have attracted much attention due to their strong uniform acidic sites.However,not many researches have been devoted toward understanding the relationships of different tungsten oxide species and their surface acidic characteristics for its effect on the catalytic performance during glycerol conversion to acrolein.In this work,the WOx /H+-mt catalyst calcined at 350,450,550 °C to study the variation of the WOx species with calcination temperature.The evolution of catalyst acidity and WOx species are carefully resolved and analyzed by using surface area and pore size distribution measurements,X-ray diffraction,NH3-TPD,X-ray photoelectron spectra,UV–vis spectroscopy,pyridine adsorbed FT-IR spectroscopy.The tungsten oxide species on H+-mt support are determined to be isolated WO6,a mixture of two surface WOx and crystalline WO3 nanoparticles with various calcination temperature.The WOx/H+-mt catalysts prepared by calcination at 350 and 450°C are shown amorphous WOx species.Therefore,calcination at 550°C are shown crystallized WOx species.The amorphous WOx species showed significantly higher acidity compared with the crystallized WOx species.The fraction of total acidity and medium acid sites are found to decrease with calcination temperature increasing.The mediun acid sites and Br?nsted acidic sites are essential for high glycerol conversion and acrolein selectivity.The WOx/ H+-mt-350 catalyst is found to be highly active during the dehydration reaction and exhibited 60.74% acrolein selectivity with 100% conversion of glycerol.