Study of Gamma alumina synthesis – analysis of the specific surface area

Abstract

Different samples of pseudoboehmite (PB) were synthesized through the sol-gel process, using aluminum nitrate as precursor. The influence of variables on the synthesis and calcinations of the PB on the specific area of the obtained gamma-alumina were studied. The variables were the ageing temperature (25 and 130°C), addition or not of polyvinyl alcohol to the precursor solution and the ageing time of the PB. The pH adjustment of the precursor solution was made by using ammonium carbonate. The products, which were obtained on different conditions, were then characterized by x-ray diffraction, specific area measurements through the BET process, and afterwards by thermal analysis (DTA and TG). After characterization, the synthesis products were calcined at 500ºC; during this process the gamma-Alumina transformation was observed. The calcination products were characterized by the same methods (x-ray diffraction, DTA and TG) and the desorption-absorption curves were obtained as well, in order to measure the pore volume of the samples and the specific surface area through B.E.T. method. Finally, the results were analyzed through an experimental factorial planning, which showed that high specific surface area gamma-Al₂O₃ (around 330m²/g) can be obtained through this process.