Synthesis of silica-sodalite from non-aqueous systems

Bibby, D.M.; Dale, M. P.

doi:10.1038/317157a0

Cited by 351 publications

(169 citation statements)

References 11 publications

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“…Although not concerned with alumina per se, organic media have recently been used for the synthesis of "silica-sodalite", Si,2024.2C2Ha(OH)z which cannot be formed under hydrothermal conditions (Bibby and Dale, 1985). …”

Section: Relation Of Earlier Studies To the Present Workmentioning

confidence: 99%

Alcohothermal Treatments of Gibbsite: Mechanisms for the Formation of Boehmite

Inoue

1989

Clays and clay miner.

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Abstract--Gibbsite samples of various particle sizes (0.2-80 #m) were heated at 250~ in a series of straight-chain primary alcohols under the autogenous vapor pressure of the alcohol (alcohothermal treatment of gibbsite). The treatment in ethanol yielded pure boehmite, the morphology of which was similar to that of the boehmite obtained by hydrothermal treatment of gibbsite. In middle-range alcohols, the boehmite yields were low (50% if 80 t~m gibbsite was used), and the products were contaminated by a poorly crystallized phase, having a x-alumina-like structure. The products preserved the morphology of the originating gibbsite, this feature being similar to the thermal dehydration of gibbsite. Complete conversion to boehmite was also attained in mineral oil (a hydrocarbon mixture, which was used as a limit of higher alcohol. The morphology of the boehmite formed in this medium was identical to that of the product prepared by thermal dehydration of gibbsite in a sealed bomb without a medium. If fine particle-size gibbsite was used, the yield of boehmite decreased and the yield of the poorly crystallized phase increased in all the media.The reaction mechanisms may be discussed in terms of the reported mechanisms for the thermal and hydrothermal formations of boehmite from gibbsite. Thus, in lower alcohols boehmite formed by a dissolution-recrystallization mechanism, whereas in middle-range or higher alcohols it formed by intraparticle hydrothermal reaction mechanism proposed by de Boer and coworkers for the thermal dehydration of gibbsite. The difference in behavior in middle-range and higher alcohols can be explained in terms of the solubility of water in the medium: In the middle-range alcohols, water molecules formed by partial dehydration of gibbsite were removed from the gibbsite particles into the medium so that dehydration proceeded in a manner similiar to that of thermal dehydration, whereas in the higher alcohols, the low solubility of water in the medium allowed the water molecules to remain on the surface of the particles, thereby promoting the complete hydrothermal formation of boehmite.

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Section: Relation Of Earlier Studies To the Present Workmentioning

confidence: 99%

Alcohothermal Treatments of Gibbsite: Mechanisms for the Formation of Boehmite

Inoue

1989

Clays and clay miner.

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“…32 The outside area of a sodalite crystal consists of six square facets and eight hexagonal facets having a similar topology to a sodalite cage, 33 so it is reasonable to approximate the shape of a SOD crystal by a single sphere.…”

Section: Computational Methodologymentioning

confidence: 99%

Molecular-dynamics analysis of the diffusion of molecular hydrogen in all-silica sodalite

Berg

Bromley

Flikkema

et al. 2004

The Journal of Chemical Physics

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In order to investigate the technical feasibility of crystalline porous silicates as hydrogen storage materials, the self-diffusion of molecular hydrogen in all-silica sodalite is modeled using large-scale classical molecular-dynamics simulations employing full lattice flexibility. In the temperature range of 700-1200 K, the diffusion coefficient is found to range from 1.6•10 Ϫ10 to 1.8•10 Ϫ9 m 2 /s. The energy barrier for hydrogen diffusion is determined from the simulations allowing the application of transition state theory, which, together with the finding that the pre-exponential factor in the Arrhenius-type equation for the hopping rate is temperature-independent, enables extrapolation of our results to lower temperatures. Estimates based on mass penetration theory calculations indicate a promising hydrogen uptake rate at 573 K.

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“…22 Com o desenvolvimento de diferentes métodos de síntese, tem-se chegado a sodalitas com uma vasta variedade na composição. [23][24][25][26][27] Com base nas interações entre átomos hospedeiros e átomos hóspedes, sodalitas com diferentes características químicas são descritas, as quais podem pertencer à categoria de feldspatoides, zeólitas ou clatratos. 23 Para os mineralogistas, a sodalita natural com composição típica descrita anteriormente é um feldspatoide, em vez de zeólita, porque não contém água nas cavidades, ocupadas somente por ânions de cloro.…”

Section: Introductionunclassified

“…[23][24][25][26][27] Com base nas interações entre átomos hospedeiros e átomos hóspedes, sodalitas com diferentes características químicas são descritas, as quais podem pertencer à categoria de feldspatoides, zeólitas ou clatratos.…”

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Síntese hidrotermal de sodalita básica a partir de um rejeito de caulim termicamente ativado

Paz¹,

Angélica²,

Neves³

2010

Quím. Nova

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Recebido em 8/3/09; aceito em 1/9/09; publicado na web em 23/2/10 HYDROTHERMAL SYNTHESIS OF BASIC SODALITE FROM A THERMICALLY ACTIVATED KAOLIN WASTE. Basic sodalite was successfully synthesized by hydrothermal method using kaolin waste as source of Aluminum and Silicon. This waste is mainly composed by kaolinite and is produced in large amount by kaolin processing industries for paper coating from the Amazon region. Initially, the waste has been calcined at 700 ºC for 2 h and then reacted with the following solutions: Na 2 CO 3 and mixture of Na 2 CO 3 + NaOH to 150 ºC with autogenous pressure for 24 h. The raw materials and transformed materials were characterized by XRD, FTIR and SEM. In both studied media, well-crystallized, basic sodalite was the only phase synthesized, while in the literature usually a mixture of zeolites is obtained.Keywords: synthesis; basic sodalite; kaolin waste. INTRODUÇÃOA região amazônica dispõe de grandes e valiosos depósitos de caulim que, por sua natureza geológica, são adequados ao seu uso mais nobre, a cobertura de papel. Só no Estado do Pará estão localizadas três grandes indústrias de beneficiamento de caulim do País, que geram de rejeito, somente nas etapas de separação granulométrica e branqueamento, mais de 1 milhão de toneladas por ano e, em função deste elevado volume, faz-se necessária a construção de onerosas lagoas de sedimentação para sua deposição.1-3 O rejeito depositado nas lagoas não apresenta consistência adequada que permita o recobrimento convencional para a recuperação da área, o que o torna um problema ambiental. No entanto, a utilização desse rejeito como matéria-prima na síntese de zeólitas tem-se mostrado bastante viável, 4,5 isso porque tal material é composto essencialmente por caulinita, argilomineral mais empregado como fonte de Si e Al em síntese de zeólita e de material com estrutura relacionada. [6][7][8][9] A caulinita é o principal constituinte do caulim, quimicamente é um silicato de alumínio hidratado, que normalmente se encontra associada a outros minerais sob a forma de impurezas, de modo geral, quartzo, mica, feldspato, óxidos de ferro e titânio. É formada pelo empilhamento regular de camadas 1:1, isto é, cada camada é constituída de uma folha de tetraedros SiO 4 e uma folha de octaedros de Al 2 (OH) 6 ligadas entre si por oxigênios comuns, dando uma estrutura fortemente polar. As ligações entre as camadas são feitas por ligações de hidrogênio, OH-O, uma vez que existe um plano de íons hidroxila numa das faces da camada e um plano de íons oxigênio na outra camada adjacente. A energia de ligação costuma variar para cada espécie, mas no geral é preciso temperaturas entre 500 e 700 ºC para que todas as OH -sejam eliminadas. A fórmula estrutural da cela unitária da caulinita é Al 2 Si 4 O 10 (OH) 8 e a composição percentual: SiO 2 -46,54%, Al 2 O 3 -39,50% e H 2 O -13,96%. 10-13As zeólitas são aluminossilicatos hidratados com uma estrutura cristalina de geometria precisa e nanoporos de tamanho uniforme, formando canais de dimensões moleculares, c...

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Synthesis of silica-sodalite from non-aqueous systems

Cited by 351 publications

References 11 publications

Alcohothermal Treatments of Gibbsite: Mechanisms for the Formation of Boehmite

Alcohothermal Treatments of Gibbsite: Mechanisms for the Formation of Boehmite

Molecular-dynamics analysis of the diffusion of molecular hydrogen in all-silica sodalite

Síntese hidrotermal de sodalita básica a partir de um rejeito de caulim termicamente ativado

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