Characterization of micro- and mesoporous solids by physisorption methods and pore-size analysis

Storck, Sebastian; Bretinger, Helmut; Maier, Wilhelm F.

doi:10.1016/s0926-860x(98)00164-1

Cited by 524 publications

(257 citation statements)

References 18 publications

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“…The pore size distribution was calculated using the Barrett−Joyner− Halenda (BJH) model, which is typically used for mesoporous materials. 24 2.2.3. Differential Scanning Calorimetry and Thermogravimetric Analysis.…”

Section: Methodsmentioning

confidence: 99%

Response to Extreme Temperatures of Mesoporous Silica MCM-41: Porous Structure Transformation Simulation and Modification of Gas Adsorption Properties

Zhang¹,

Pérez-Page²,

Guan³

et al. 2016

Langmuir

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Molecular dynamics (MD) and Monte Carlo (MC) simulations were applied together for the first time to reveal the porous structure transformation mechanisms of mesoporous silica MCM-41 subjected to temperatures up to 2885 K. Silica was experimentally characterized to inform the models and enable prediction of changes in gas adsorption/separation properties. MD simulations suggest that the pore closure process is activated by a collective diffusion of matrix atoms into the porous region, accompanied by bond reformation at the surface. Degradation is kinetically limited, such that complete pore closure is postponed at high heating rates. We experimentally observe decreased gas adsorption with increasing temperature in mesoporous silica heated at fixed rates, due to pore closure and structural degradation consistent with simulation predictions. Applying the Kissinger equation, we find a strong correlation between the simulated pore collapse temperatures and the experimental values which implies an activation energy of 416 ± 17 kJ/mol for pore closure. MC simulations give the adsorption and selectivity for thermally treated MCM-41, for N 2 , Ar, Kr, and Xe at room temperature within the 1−10 000 kPa pressure range. Relative to pristine MCM-41, we observe that increased surface roughness due to decreasing pore size amplifies the difference of the absolute adsorption amount differently for different adsorbate molecules. In particular, we find that adsorption of strongly interacting molecules can be enhanced in the low-pressure region while adsorption of weakly interacting molecules is inhibited. This then results in higher selectivity in binary mixture adsorption in mesoporous silica.

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Section: Methodsmentioning

confidence: 99%

Response to Extreme Temperatures of Mesoporous Silica MCM-41: Porous Structure Transformation Simulation and Modification of Gas Adsorption Properties

Zhang¹,

Pérez-Page²,

Guan³

et al. 2016

Langmuir

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“…Extrapolações para a região das isotermas entre o primeiro ponto e aquele ocorrido após a pressão relativa de 0,35 foram feitas para α-plot e permitiram inferências sobre o tipo de porosidade nos matériais segundo a forma assumida para α-plot (Storck et al, 1998). Os α-plot para a fração de argila do LVDf e do LVD tiveram formatos característicos de materiais mesoporosos, confirmando os resultados obtidos com o formato das isotermas de adsorção de N 2 e distribuição de volume e diâmetro de poros.…”

Section: Resultsunclassified

“…A contribuição dos poros para a área superficial específica pode ser avaliada por meio de isotermas de adsorção de gás (Storck et al, 1998). Com isotermas de adsorção de N 2 em regiões de baixa pressão, é possível calcular a área superficial específica de um sólido, conhecendo-se o volume do gás necessário para recobrir a superfície em monocamada e a área ocupada pela molécula do gás (Greeg & Sing, 1982).…”

Section: Introductionunclassified

Área superficial específica, porosidade da fração argila e adsorção de fósforo em dois latossolos vermelhos

Cessa

Celi

Vitorino³

et al. 2009

Rev. Bras. Ciênc. Solo

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RESUMOA porosidade da fração argila é muito importante para entendimento dos fenômenos físico-químicos que estão relacionados com a área superficial específica das partículas sólidas. Por meio de isotermas de adsorção e dessorção com N 2 , avaliaram-se a área superficial específica (S BET ) e a porosidade das frações argila de Latossolos Vermelhos do Estado de Mato Grosso do Sul, sendo um distroférrico (LVdf) e outro distrófico (LVd), além de caulinita natural (KGa 2 ), goethita (Gt) e hematita (Hm) sintéticas. Resultados referentes à S BET e à porosidade das partículas foram relacionados à adsorção máxima de P (P máx ) determinada pela isoterma de Langmuir. A classe de poros predominante nas frações argila avaliadas foi de mesoporos. As frações argila extraídas dos solos e KGa 2 adsorveram quantidades semelhantes de P por unidade de área, mas diferentes das quantidades de P adsorvido por Gt e Hm. Tal diferença, possivelmente, deu-se em função da quantidade e distribuição dos grupamentos OH em superfície, bem como imperfeições superficiais dos materiais. Os óxidos de Fe e de Al e outros materiais amorfos das frações argila extraídas dos solos foram mais importantes que a caulinita para a adsorção de P. A caulinita, embora sendo o filossilicato de maior representatividade nas frações argila de LVDf e LVD, teve menor importância sobre a adsorção de P.Termos de indexação: caulinita, hematita, goethita, mineralogia, argila, isoterma, fixação de fósforo.

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“…The adsorption isotherm and pore size distribution of the hollow spheres were calculated using Barrett-Joyner-Halenda (BJH) and Saito-Foley : Polystyrene particles : Aluminum isoporopoxide and tetraethoxysilane : Silica-alumina primary particles (SF) methods. The BJH method calculated the pore size distribution to be in the range of 2-50 nm based on the Kelvin equation, while the SF method calculated the pore size distribution to be in the range of 0.4-2.0 nm based on the Horvath-Kawazoe method [42,43]. The solid-state 27 Al magic angle spinning nuclear magnetic resonance (MAS NMR, JEOL ECA-800) spectra were recorded using an 18.8 tesla NMR spectrometer.…”

Section: Characterizationmentioning

confidence: 99%

Influence of morphology of hollow silica–alumina composite spheres on their activity for hydrolytic dehydrogenation of ammonia borane

et al. 2017

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Hollow silica-alumina composite spheres were prepared by a polystyrene (PS) template method using various amounts of PS suspension. Homogeneous hollow spheres prepared using 40 g were found to be with a diameter of about 300 nm in scanning electron microscopy, and transmission electron microscopy demonstrated their hollow sphere morphology. From the nitrogen adsorption isotherm results, the homogeneous hollow spheres prepared using 40 g of the PS suspension were found to be an ordered pore structure. The activities of the hollow spheres prepared using various amounts of the PS suspension for hydrolytic dehydrogenation of ammonia borane were compared. The results showed that 10, 7, and 6 mL of hydrogen were evolved from the aqueous ammonia borane solution in about 40 min in the presence of the hollow spheres prepared using 40, 80, and 120 g of PS suspension, respectively. The homogeneous hollow spheres with an ordered pore structure showed the highest activity among all the hollow spheres. The amount of acid sites and the coordination number of aluminum active species were characterized using neutralization titration and solid-state 27 Al magic angle spinning nuclear magnetic resonance spectroscopy. The homogeneous hollow spheres with an ordered pore structure had high amount of acid sites and 4-coordinated aluminum species. The relative proportion of 4-coordinated aluminum species was related to the dispersion of aluminum species. These results indicate that the homogeneous hollow spheres with an ordered pore structure showed the high activity because of high amount of acid sites induced by the highly dispersed aluminum species.

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Characterization of micro- and mesoporous solids by physisorption methods and pore-size analysis

Cited by 524 publications

References 18 publications

Response to Extreme Temperatures of Mesoporous Silica MCM-41: Porous Structure Transformation Simulation and Modification of Gas Adsorption Properties

Response to Extreme Temperatures of Mesoporous Silica MCM-41: Porous Structure Transformation Simulation and Modification of Gas Adsorption Properties

Área superficial específica, porosidade da fração argila e adsorção de fósforo em dois latossolos vermelhos

Influence of morphology of hollow silica–alumina composite spheres on their activity for hydrolytic dehydrogenation of ammonia borane

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