Structure, surface area and morphology of aluminas from thermal decomposition of Al(OH)(CH3COO)2 crystals
Crystalline aluminium hydroxiacetate was prepared by reaction between aluminium powder (ALCOA 123) and aqueous solution of acetic acid at 96ºC ±1ºC. The white powder of Al(OH)(CH3COO)2 is constituted by agglomerates of crystalline plates, having size about 10mum. The crystals were fired from 200ºC t...
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Academia Brasileira de Ciências
2000-12-01
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doaj-befc5681f0b441ca9c308f74670119702020-11-25T00:11:07ZengAcademia Brasileira de CiênciasAnais da Academia Brasileira de Ciências0001-37651678-26902000-12-0172447149510.1590/S0001-37652000000400003Structure, surface area and morphology of aluminas from thermal decomposition of Al(OH)(CH3COO)2 crystalsPEDRO K. KIYOHARAHELENA SOUZA SANTOSANTONIO C. VIEIRA COELHOPÉRSIO DE SOUZA SANTOSCrystalline aluminium hydroxiacetate was prepared by reaction between aluminium powder (ALCOA 123) and aqueous solution of acetic acid at 96ºC ±1ºC. The white powder of Al(OH)(CH3COO)2 is constituted by agglomerates of crystalline plates, having size about 10mum. The crystals were fired from 200ºC to 1550ºC, in oxidizing atmosphere and the products characterized by X-ray diffraction, scanning electron microscopy and surface area measurements by BET-nitrogen method. Transition aluminas are formed from heating at the following temperatures: gamma (300ºC); delta (750ºC); alpha (1050ºC). The aluminas maintain the original morphology of the Al(OH)Ac2 crystal agglomerates, up to 1050ºC, when sintering and coalescence of the alpha-alumina crystals start and proceed up to 1550ºC. High surface area aluminas are formed in the temperature range of 700ºC to 1100ºC; the maximum value of 198m²/g is obtained at 900ºC, with delta-alumina structure. The formation sequence of transition aluminas is similar to the sequence from well ordered boehmite, but with differences in the transition temperatures and in the development of high surface areas. It is suggested that the causes for these diversities between the two sequences from Al(OH) Ac2 and boehmite are due to the different particle sizes, shapes and textures of the gamma-Al2O3 which acts as precursor for the sequence gamma- to alpha-Al2O3.http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652000000400003aluminium hydroxiacetateboehmitetransition aluminasactive aluminasaluminum hydroxides |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
PEDRO K. KIYOHARA HELENA SOUZA SANTOS ANTONIO C. VIEIRA COELHO PÉRSIO DE SOUZA SANTOS |
spellingShingle |
PEDRO K. KIYOHARA HELENA SOUZA SANTOS ANTONIO C. VIEIRA COELHO PÉRSIO DE SOUZA SANTOS Structure, surface area and morphology of aluminas from thermal decomposition of Al(OH)(CH3COO)2 crystals Anais da Academia Brasileira de Ciências aluminium hydroxiacetate boehmite transition aluminas active aluminas aluminum hydroxides |
author_facet |
PEDRO K. KIYOHARA HELENA SOUZA SANTOS ANTONIO C. VIEIRA COELHO PÉRSIO DE SOUZA SANTOS |
author_sort |
PEDRO K. KIYOHARA |
title |
Structure, surface area and morphology of aluminas from thermal decomposition of Al(OH)(CH3COO)2 crystals |
title_short |
Structure, surface area and morphology of aluminas from thermal decomposition of Al(OH)(CH3COO)2 crystals |
title_full |
Structure, surface area and morphology of aluminas from thermal decomposition of Al(OH)(CH3COO)2 crystals |
title_fullStr |
Structure, surface area and morphology of aluminas from thermal decomposition of Al(OH)(CH3COO)2 crystals |
title_full_unstemmed |
Structure, surface area and morphology of aluminas from thermal decomposition of Al(OH)(CH3COO)2 crystals |
title_sort |
structure, surface area and morphology of aluminas from thermal decomposition of al(oh)(ch3coo)2 crystals |
publisher |
Academia Brasileira de Ciências |
series |
Anais da Academia Brasileira de Ciências |
issn |
0001-3765 1678-2690 |
publishDate |
2000-12-01 |
description |
Crystalline aluminium hydroxiacetate was prepared by reaction between aluminium powder (ALCOA 123) and aqueous solution of acetic acid at 96ºC ±1ºC. The white powder of Al(OH)(CH3COO)2 is constituted by agglomerates of crystalline plates, having size about 10mum. The crystals were fired from 200ºC to 1550ºC, in oxidizing atmosphere and the products characterized by X-ray diffraction, scanning electron microscopy and surface area measurements by BET-nitrogen method. Transition aluminas are formed from heating at the following temperatures: gamma (300ºC); delta (750ºC); alpha (1050ºC). The aluminas maintain the original morphology of the Al(OH)Ac2 crystal agglomerates, up to 1050ºC, when sintering and coalescence of the alpha-alumina crystals start and proceed up to 1550ºC. High surface area aluminas are formed in the temperature range of 700ºC to 1100ºC; the maximum value of 198m²/g is obtained at 900ºC, with delta-alumina structure. The formation sequence of transition aluminas is similar to the sequence from well ordered boehmite, but with differences in the transition temperatures and in the development of high surface areas. It is suggested that the causes for these diversities between the two sequences from Al(OH) Ac2 and boehmite are due to the different particle sizes, shapes and textures of the gamma-Al2O3 which acts as precursor for the sequence gamma- to alpha-Al2O3. |
topic |
aluminium hydroxiacetate boehmite transition aluminas active aluminas aluminum hydroxides |
url |
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652000000400003 |
work_keys_str_mv |
AT pedrokkiyohara structuresurfaceareaandmorphologyofaluminasfromthermaldecompositionofalohch3coo2crystals AT helenasouzasantos structuresurfaceareaandmorphologyofaluminasfromthermaldecompositionofalohch3coo2crystals AT antoniocvieiracoelho structuresurfaceareaandmorphologyofaluminasfromthermaldecompositionofalohch3coo2crystals AT persiodesouzasantos structuresurfaceareaandmorphologyofaluminasfromthermaldecompositionofalohch3coo2crystals |
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1725405078466068480 |