Brønsted acidity of Al/SBA-15

Koekkoek, Arjan J. J.; Veen, J.A.R. van; Gerrtisen, Paul B.; Giltay, Patricia; Magusin, Pieter C. M. M.; Hensen, Emiel J. M.

doi:10.1016/j.micromeso.2011.11.019

Cited by 75 publications

(52 citation statements)

References 48 publications

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“…4 encontram-se ilustradas as isotermas de adsorção/dessorção de N 2 como resultado da caracterização textural das amostras de ZrO 2 , antes e após sulfatação, cuja temperatura máxima de combustão alcançada foi 690 °C. Verificou-se que as isotermas de adsorção/dessorção das amostras foram compatíveis com o modelo tipo IV com loop de histerese do tipo H1, encontradas em materiais cujos poros são regulares, segundo a classificação de BrunauerEmmett-Teller (BET) [4,[35][36][37]. Mediante a literatura [38], as isotermas de adsorção/dessorção do tipo IV são típicas de materiais mesoporosos e a histerese do tipo H1 está associada a materiais porosos constituídos por aglomerados de partículas esféricas de tamanho uniforme, referenciado para isso a nomenclatura da IUPAC [39].…”

Section: Resultsunclassified

“…Com relação aos resultados de tamanho de partícula/tamanho de cristalito (D BET /T C ), observou-se pequeno aumento referente às amostras de ZrO 2 sulfatadas, indicando assim que as amostras sulfatadas foram mais policristalinas, ou seja, com a presença de mais cristais por partículas, e que se encontraram mais aglomeradas. Dessa forma, as amostras sem sulfatação apresentaram [4,36,37].…”

Section: Resultsunclassified

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Preparação e caracterização de catalisadores ácidos de zircônia sulfatada para aplicação na esterificação do óleo de algodão

et al. 2017

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INTRODUÇÃOA zircônia (ZrO 2 ) apresenta transformações polimórficas e sua estrutura cristalina pode sofrer alterações na medida em que variações ocorrem na temperatura, sem alteração da composição química. As mudanças cristalinas mais comuns são: monoclínica (m), tetragonal (t) e cúbica [1][2][3][4], apesar de outra fase de transição, não majoritária, possa ocorrer durante o processo de síntese, denominada de ortorrômbica [1,3,4]. O ZrO 2 é um material usado em diferentes setores tecnológicos, como na engenharia, na medicina, na odontologia e na catálise, devido às suas propriedades

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Section: Resultsunclassified

Preparação e caracterização de catalisadores ácidos de zircônia sulfatada para aplicação na esterificação do óleo de algodão

et al. 2017

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“…The I 4 /I all ratio of the homogeneous hollow spheres prepared using 40 g of the PS suspension was the highest among all the hollow spheres. It has been reported that 4-coordinated aluminum species are related to the dispersion of aluminum species [53]. These results indicated that the homogeneous hollow spheres prepared using 40 g of the PS suspension exhibited high dispersion of the aluminum species in the silica matrix.…”

Section: J Adv Cerammentioning

confidence: 62%

“…8. Three peaks were observed at around 62, 35, and 5 ppm in the spectra of all the hollow spheres, corresponding to 4-, 5-, and 6-coordinated aluminum species, respectively [52,53]. The 4-coordinated aluminum species were assigned to aluminum species in the silica matrix, while the 5-and 6-coordinated aluminum species were assigned to aluminum species outside the silica matrix [54,55].…”

Section: J Adv Cerammentioning

confidence: 98%

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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“…The 27 Al NMR spectrum shows just a signal at 53 ppm typically assigned to tetrahedral aluminium atoms suggesting the formation of Bronsted groups, because of the formation of Al-O-Si bonds in the structure. [35][36][37] The presence of this aluminium confers more acidic properties to the S-Al material compared with the S and S-NaF materials. 38 The nitrogen adsorption-desorption isotherms and BJH distributions for hosts are shown on Figure 3.…”

Section: Resultsmentioning

confidence: 99%

Polymerization of Aniline in Different Sba-16 Silica Hosts

Giraldo¹,

Vélez²,

Mesa³

2016

Química Nova

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publicado na web em 06/06/2016Polyaniline-silica composites made with mesoporous silica have been reported to improve the mechanical properties of the free polymer. However, there are not many studies about the effect of the chemical and physical properties of the inorganic material used as hosts over the final properties of polyaniline and the composites. Here, polyaniline-silica composites, exhibiting electrical conductivity, were synthesized using different types of SBA-16 mesoporous silica as hosts. The effects of the characteristics of the hosts in the polymerization kinetic, molecular weight and electrical conductivity of the final polymer were studied. The composites showed higher electrical conductivity in comparison with polyaniline synthesized under similar conditions of this work but in the absence of silica. The use of silica allowed to obtain composites with defined morphology, which did not occur in the absence of these hosts. From the results of this work, it can be concluded that SBA-16 mesoporous silica hosts have a bifunctional role in the formation of polyaniline-silica composites: the hosts behaved like nucleation sites, which favors polymerization of high molecular weight polyaniline and they catalyzed the polymerization reaction, especially when aluminum is present in the structure of the host.

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Brønsted acidity of Al/SBA-15

Cited by 75 publications

References 48 publications

Preparação e caracterização de catalisadores ácidos de zircônia sulfatada para aplicação na esterificação do óleo de algodão

Preparação e caracterização de catalisadores ácidos de zircônia sulfatada para aplicação na esterificação do óleo de algodão

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

Polymerization of Aniline in Different Sba-16 Silica Hosts

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