Effect of Calcination Temperatures and Mo Modification on Nanocrystalline (γ-χ)-Al2O3 Catalysts for Catalytic Ethanol Dehydration

Abstract

The mixed gamma and chi crystalline phase alumina (M-Al) catalysts prepared by the solvothermal method were investigated for catalytic ethanol dehydration. The effects of calcination temperatures and Mo modification were elucidated. The catalysts were characterized by X-ray diffraction (XRD), N2 physisorption, transmission electron microscopy (TEM), and NH3-temperature programmed desorption (NH3-TPD). The catalytic activity was tested for ethylene production by dehydration reaction of ethanol in gas phase at atmospheric pressure and temperature between 200°C and 400°C. It was found that the calcination temperatures and Mo modification have effects on acidity of the catalysts. The increase in calcination temperature resulted in decreased acidity, while the Mo modification on the mixed phase alumina catalyst yielded increased acidity, especially in medium to strong acids. In this study, the catalytic activity of ethanol dehydration to ethylene apparently depends on the medium to strong acid. The mixed phase alumina catalyst calcined at 600°C (M-Al-600) exhibits the complete ethanol conversion having ethylene yield of 98.8% (at 350°C) and the Mo-modified catalysts promoted dehydrogenation reaction to acetaldehyde. This can be attributed to the enhancement of medium to strong acid with metal sites of catalyst.