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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Main Authors: PEDRO K. KIYOHARA, HELENA SOUZA SANTOS, ANTONIO C. VIEIRA COELHO, PÉRSIO DE SOUZA SANTOS
Format: Article
Language:English
Published: Academia Brasileira de Ciências 2000-12-01
Series:Anais da Academia Brasileira de Ciências
Subjects:
Online Access:http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652000000400003
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spelling 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
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