Effects of alkaline-earth oxide additives on silica-supported copper catalysts in ethanol dehydrogenation

The dehydrogenation of ethanol has been studied over a series of Cu/SiO₂ catalysts modified with alkaline-earth oxide (Cu-MO/SiO₂, M = Mg, Ca, Sr, and Ba). The additive effects of alkaline-earth oxides on copper catalysts were examined by X-ray diffraction, scanning electron microscopy, temperature-programmed reduction, H₂-N₂O titration, temperature-programmed desorption of CO₂, and dehydrogenation of ethanol. The results indicated that the initial turnover frequencies can be improved by adding alkaline-earth oxides into the catalysts. MgO is an excellent promoter for increasing both the activity and stability of Cu/SiO₂ catalyst; however, the other alkaline-earth oxide modified catalysts are poor in stability. The increase in turnover frequencies of the modified catalysts is mainly due to the promotional effects of weakly basic sites on Cu metal. The strong basic sites can harm the stabilities of the catalysts.