Binary oxides with defined hierarchy of pores in the esterification of glycerol

Abstract

Various porous binary oxides with elevated textural properties were obtained in this work. The as-synthesized solids were calcined or modified by reflux and extraction processes. Characterizations through SEM, nitrogen physisorption and TEM techniques demonstrated the formation of porous metal oxide networks over all solids. XRD, thermal analyses and FTIR measurements showed the existence of nanosized rutile TiO2, tetragonal ZrO2, SiO2 and -Al2O3 phases on the solids. The structure and texture of the as-synthesized SiAl sol-gel derived solid resulted in the formation of well-dispersed nanoparticles on the support. The removal of the organic compounds by ethanol extraction or reflux from SiAl resulted in the presence of structures with defined hierarchy of pores. Among the solids studied, the catalytic results in the esterification of glycerol with acetic acid indicated that best performances were obtained over SiAl sample when submitted to extraction and reflux treatments. This was due to the creation of accessible pores, which facilitated the reaction occurrence at glycerol to acetic acid molar ratio = 1:3 and T = 80 C for 20 h using 75 mg of catalyst. The solids can be reused three times without complete loss of their catalytic performance.