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Title: The effect of digestion on the surface area and porosity of alumina
Authors: Chuah, G.K. 
Jaenicke, S. 
Xu, T.H.
Keywords: Alumina
Digestion of aluminium hydroxides
High surface area
Phase transformation
Thermal stability
Issue Date: Jun-2000
Citation: Chuah, G.K., Jaenicke, S., Xu, T.H. (2000-06). The effect of digestion on the surface area and porosity of alumina. Microporous and Mesoporous Materials 37 (3) : 345-353. ScholarBank@NUS Repository.
Abstract: The stability of gamma alumina with respect to phase transitions and loss of surface area can be greatly improved by digestion of the aluminium hydroxide precursor. Pseudoboehmite (aluminium hydroxide) was formed by precipitating aluminium nitrate with ammonium hydroxide at pH 6. The freshly precipitated gel has a very low surface area, but the surface area increases after digestion of the hydroxide in the mother liquour. Digestion leads to a 'drier' hydroxide as shown by thermogravimetry. After calcination to 500°C, the resulting alumina has a surface area of 230 to 310 m2 g-1, depending on the length of digestion of the hydroxide. Aluminas prepared from aged precursors have better thermal stability than those prepared without the digestion step. The digested alumina was able to withstand calcination to 1200°C for 12 h, and maintained a surface area of ~ 68 m2 g-1. The transformation to the alpha phase is delayed in the digested samples. The effect of digestion on the surface area and improved thermal stability are explained on the basis of a reduction in the number of defect sites responsible for surface diffusion. (C) 2000 Elsevier Science B.V. All rights reserved.
Source Title: Microporous and Mesoporous Materials
ISSN: 13871811
DOI: 10.1016/S1387-1811(99)00277-2
Appears in Collections:Staff Publications

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