| Abstract: | Gibbsite was treated in a series of primary alcohols at 250°C for 2 h. The surface area of the product increased with the increase in the carbon number of alcohol and reached a maximum when hexanol was used. Pore texture of aluminas, obtained by the calcination of these products, was investigated by means of the nitrogen adsorption technique. The aluminas prepared from the products of the treatment in alcohols other than propanol and butanol had a pore texture identical to the pore texture of the alumina from well-crystallized boehmite prepared by hydrothermal treatment of gibbsite. The pore texture of these aluminas was characterized by the presence of micropores. The aluminas prepared from the treatments in butanol and propanol had quite different pore texture. Micropores were not detected in these aluminas: instead, mesopores of c. 20 nm range were detected. These results are consistent with the reaction mechanisms for the formation of boehmite proposed in a previous paper on the basis of morphology of the products. In lower alcohols boehmite is formed by means of a resolution-crystallization mechanism, whereas in higher alcohols boehmite is formed by means of intraparticle hydrothermal reaction. In butanol and propanol, boehmite is crystallized from the alcoholic media and has a large population of crystal defects; therefore, pore texture of aluminas derived from these products resembles the aluminas from poorly crystallized aluminum hydroxides. |
