Dehydroxylation and structure of alumina gels prepared from trisecbutoxyaluminium

The dehydroxylation of alumina gels prepared from the hydrolysis of trisecbutoxyaluminium has been studied using a combination of differential thermal analysis and infrared emission spectroscopy. Trisecbutoxyaluminium was hydrolysed in water at both 25 degrees C and 90 degrees C. The alumina phase in the gel was found by both DTA and FTIR absorption and FTIR emission spectroscopy to be gibbsite. The 25 degrees C hydrolysed gel showed endotherms at 82 degrees C, 168 degrees C and 244 degrees C which were attributed to the dehydration of adsorbed and surface coordinated water, and to the dehydroxylation of the gibbsite in the alumina gel. The weight loss in the first two endotherms was 23% and 10% showing that the gel had a high water content. The gel formed at 90 degrees C shows endotherms at 62 degrees C, 251 degrees C, 277 degrees C, 404 degrees C and 538 degrees C. The first endotherm was attributed to the loss of adsorbed water, the 251 degrees C and 277 degrees C endotherms to the dehydroxylation of the gibbsite and the endotherms at 404 degrees C and 538 degrees C to the dehydroxylation of boehmite in the gel. The structure and dehydroxylation of the gel was determined by both infrared absorption and emission spectroscopy. (C) 1999 Elsevier Science B.V. All rights reserved.