Relevant aspects of the biosynthesis of porous aluminas using glycosides and carbohydrates as biological templates

Abstract

This research paper comparison of the use of biological templates obtained from steviol glycosides and glucose (monosaccharide) directed toward the synthesis of metal oxides. The results obtained shown the synthesis of aluminum oxides in an aqueous medium, using different green porogenic agents. The influences of the aging period and its impact on the alumina's porosity and phase transition were evaluated. The FTIR studies provided evidence of the surface modification of the aluminum oxide by carboxylate groups generated in the hydrolysis of diterpenic glycosides. The application of prolonged aging periods favored the production of η-alumina vs γ-alumina in the synthesis in which Stevia rebaudiana was used. The materials were characterized, using XRD, TGA, N₂ physical adsorption, FE-SEM, NMR, FTIR and TPD-NH₃. The TGA profiles indicate appreciable differences as to the yields achieved between samples prepared with the two biological templates (alumina–stevia up to 62%, alumina–glucose yields of 30%). The acidity obtained for the different aluminas synthesized by the use of biological templates showed a trend toward: glucose > stevia > sol–gel method/stevia, in the range of 0.994–0.485 mmol/g.