The effects of processing parameters on structure of mesoporous γ-alumina granules synthesized by sol-gel/oil-drop method: Modelling via response surface methodology

Abstract

Sol-gel/oil-drop granulation technique was used to prepare mesoporous ?-Al2O3 granules of 1.5-2mm with high specific surface area and pore volume of 295m2/g and 0.47 cm3/g, respectively. The structure of granules was studied using powder XRD, DTA, TEM and N2 adsorption/desorption techniques. A response surface methodology (RSM) holding CCD approach was used for modelling the influence of process variables on the granule pore structure, having a quadratic function relating the independent variables (calcination temperature, acid amount and ammonia concentration) to the responses (specific surface area, mean pore diameter and pore volume). The interaction effect of variables on each response was studied and all were in acceptable accordance with experimental values. Accordingly, the granules synthesized using 20ml of nitric acid, aged in a 9.25wt.% ammonia solution and calcined at 450?C showed the best properties. The predicted values for the specific surface area and pore volume were 315.64m2/g, 7 nm and 0.53 cm3/g, respectively, which were compatible with experimental values.