Synthesis and properties of template-free mesoporous alumina and its application in gas phase dehydration of glycerol

Abstract

Mesoporous alumina was prepared by varying the crystallization time and acid concentration and evaluated in the glycerol dehydration. The samples were characterized by X-ray diffractometry (XRD), specific surface area (SBET), NH3-Temperature-programmed desorption (NH3-TPD), and Temperature-programmed Oxidation (TPO). The gas phase dehydration of glycerol was performed in a fixed-bed quartz tubular reactor at 500 °C using a 10% glycerol aqueous solution. The specific surface area, the crystallinity and the acidic properties of the samples were dependent on both the crystallization time and the acid concentration. The catalytic properties are related to the specific surface area and acidic characteristics. Samples with higher crystallization time showed lower surface area and lower amount of acid sites. Samples with the highest acid concentration solution had the higher surface area. Conversions of glycerol above 92% were obtained for all samples. The selectivity for dehydration products was strongly related to the amount and strength of acid sites.