Isomerization of n-Hexane over Silica-Supported Heteropolyoxometallates Promoted by Pt-Ce Oxides

Gherib, Abdelaziz; Aouissi, Ahmed; Rives, Alain; Fournier, Michel; Hubaut, R.

doi:10.1016/s1872-2067(08)60006-6

Cited by 9 publications

(9 citation statements)

References 48 publications

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“…Lately, Gherib et al described a promotion effect of reduced Pt-Ce oxides in the isomerization of n-hexane for silica supported Keggin-based HPA, which was attributed to the enhanced hydrogenating/dehydrogenating properties of the final composites. 26 A similar promotion effect on n-pentane isomerization was observed by doping zirconia supported Pt-H 3 PW 12 O 40 catalysts with lanthanum or cerium. The benefit of La or Ce addition on activity and selectivity, although strongly dependent on the Pt loadings, was ascribed to a better dispersion of HPA over the solid surface.…”

Section: Introductionmentioning

confidence: 57%

The comparison of two classes of bifunctional SBA-15 supported platinum–heteropolyacid catalysts for the isomerization of n-hexane

et al. 2015

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Section: Introductionmentioning

confidence: 57%

The comparison of two classes of bifunctional SBA-15 supported platinum–heteropolyacid catalysts for the isomerization of n-hexane

et al. 2015

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“…As it can be seen on Figure 1, the activity decreases with time on stream. This deactivation is always observed on acid catalysts [23] and is related to the mechanisms of the isomerization reaction (see Schemes 2 and 3) and to the formation of coke. This decrease does not allow an easy comparison of different systems as various parameters should be taken into account such as the initial activity, the steady-state activity, and the deactivation rate.…”

Section: General Considerations On Silica-supportedmentioning

confidence: 80%

“…However, in this case they can be used only for gas-solid reactions or liquid-solid reactions with apolar reagents, due to their high solubility in polar compounds. As they are very acidic, they can be used in the isomerization and/or cracking reactions of alkanes such ashexane and -heptane [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] but to our knowledge only the cesium salts were studied in the isomerization of -butane to isobutene. This paper describes the use of silica-supported heteropolyacids for the isomerization of -butane with the aim to study some parameters such as the solvent used for the impregnation, the polyoxometalate loading, or the reaction temperature.…”

Section: Introductionmentioning

confidence: 99%

n-Butane Isomerization over Silica-Supported Heteropolyacids: Study of Some Parameters

Grinenval

Garron

Lefèbvre

2013

Journal of Catalysts

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Isomerization of n-butane was studied on silica-supported heteropolyacids. The activity depends strongly on the solvent used for the preparation and on the polyoxometalate loading. This behavior was explained by different proportions of isolated and bulk heteropolyacids. Silicotungstic acid is inherently more selective than phosphotungstic acid. In presence of platinum and hydrogen the catalysts are stable and highly selective (more than 97%) to isobutane. A study as a function of temperature shows that there is an optimal temperature for performing the reaction.

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“…n-Hexane isomerization was chosen as a model reaction as it requires highly acidic sites to proceed and several studies had shown the good catalytic performance of supported HPA in this reaction [36][37][38][39][40]. All experiments were performed with a dynamic system during 12 h in order to study the deactivation of the catalyst.…”

Section: Catalytic Experimentsmentioning

confidence: 99%

Comparison of the Acidity of Heteropolyacids Encapsulated in or Impregnated on SBA-15

Pinto

Szeto

Oueslati

et al. 2016

Oil Gas Sci. Technol. – Rev. IFP Energies nouvelles

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-Heteropolyacids (HPA) immobilized onto SBA-15 silica were prepared by two different ways using either impregnation or encapsulation methodologies. Two Keggin-type HPA, H 3 PW 12 O 40 and H 4 SiW 12 O 40 were considered in this study. The resulting hybrid materials were fully characterized by N 2 adsorption-desorption isotherms, XRD, FT-IR, Raman, diffuse reflectance UV-Vis spectroscopies and 31 P MAS NMR. All characterization methods showed that at room temperature the catalysts contained well-dispersed and intact Keggin units throughout the solid. The catalytic activity of these solids was investigated in the isomerization of n-hexane. The impregnated and encapsulated phosphotungstic catalysts performed similarly in catalysis showing that the amount of active sites was nearly the same in both catalysts. On the contrary, the tungstosilicic encapsulated material was completely inactive while its impregnated counterpart was even more active than the phosphotungstic derived catalysts. The acidity of the solids was measured by various methods: microcalorimetry of ammonia adsorption, ammonia desorption followed by Temperature Programmed Desorption (TPD) and DRIFT/GC-MS and pyridine adsorption followed by infrared spectroscopy. Only pyridine adsorption and ammonia desorption followed by DRIFT/GC-MS agreed with the catalytic data. Ammonia adsorption followed by microcalorimetry was not able to differentiate between the four catalysts while the TPD experiments led to unreliable results, as not only the evolved ammonia but also other molecules such as water were taken into account in the measurements. The behavior difference between the encapsulated silico-and phosphotungstic acids was explained by a more pronounced encapsulation in the case of silicon. de préparation. L'activité catalytique de ces matériaux a ensuite été étudiée dans l'isomérisation du n-hexane.

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Isomerization of n-Hexane over Silica-Supported Heteropolyoxometallates Promoted by Pt-Ce Oxides

Cited by 9 publications

References 48 publications

The comparison of two classes of bifunctional SBA-15 supported platinum–heteropolyacid catalysts for the isomerization of n-hexane

The comparison of two classes of bifunctional SBA-15 supported platinum–heteropolyacid catalysts for the isomerization of n-hexane

n-Butane Isomerization over Silica-Supported Heteropolyacids: Study of Some Parameters

Comparison of the Acidity of Heteropolyacids Encapsulated in or Impregnated on SBA-15

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