Influence of pH and Si content on Si incorporation in SAPO-5 and their catalytic activity for isomerisation of n-heptane over Pt loaded catalysts

Roldán, Rafael; Sánchez‐Sánchez, Manuel; Sankar, Gopinathan; Romero–Salguero, Francisco J.; Jiménez‐Sanchidrián, César

doi:10.1016/j.micromeso.2006.09.035

Cited by 66 publications

(33 citation statements)

References 60 publications

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“…The former small peak is for the reduction of PtO 2 and PtO located in zeolite channels [21], while the latter one indicates the strong interaction of Pt 2? with b zeolite with the formation of Pt À ðO À Si Þ 2Ày y species [22,23]. The bimetallic catalyst 5Cr0.4%Pt/Hb exhibits two reduction peaks: a large peak at around 168°C and a comparatively small peak at around 405°C.…”

Section: Resultsmentioning

confidence: 99%

A Highly Efficient Hβ Zeolite Supported Pt Catalyst Promoted by Chromium for the Hydroisomerization of n-Heptane

et al. 2008

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Hb zeolite supported Pt catalysts promoted by Cr, La, Ce, Al or Zn were prepared by the co-impregnation method, and characterized by XRD, BET, NH 3 -TPD and H 2 -TPR. Their catalytic activities were evaluated in the hydroisomerization of n-heptane with an atmospheric fixed-bed reactor. The Pt-bearing catalyst doped with Cr, La or Ce, especially Cr, is found to exhibit a much higher catalytic activity and isomerization selectivity than the catalyst without the dopant. At the low reaction temperature of 230°C, the catalyst with a Pt loading of 0.4% and a molar ratio of Cr to Pt of 5:1 shows a high conversion of nheptane of 77.1% coupled with a high selectivity to isomerization products of 94.4%. In contrast, over the counterpart catalyst without Cr, the conversion of n-heptane is 50.6% with a low selectivity to isomerization products of 82.4%. The substantial promotion effect of Cr is suggested to associate with the improved Pt dispersion, as well as the increased strong acid amount, due to the introducing of Cr into the catalyst.

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Section: Resultsmentioning

confidence: 99%

A Highly Efficient Hβ Zeolite Supported Pt Catalyst Promoted by Chromium for the Hydroisomerization of n-Heptane

et al. 2008

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“…Although alumina supported catalysts are more active at low temperatures, they are highly sensitive to poisoning by both water and sulfur and therefore require constant regeneration with chlorine which is hazardous and can potentially alter the structure of the precious metal. Consequently, enormous research effort has focused on using the more stable and environmental-friendly zeolite-based catalysts, since they possess the necessary acidity, internal structure and pore size distribution to be catalytically active and selective for these hydroisomerizations [6][7][8][9][10][11][12][13][14][15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Effect of the impregnation order on the nature of metal particles of bi-functional Pt/Pd-supported zeolite Beta materials and on their catalytic activity for the hydroisomerization of alkanes

Roldán

Beale²,

Sánchez‐Sánchez

et al. 2008

Journal of Catalysis

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A series of mono-and bi-metallic (Pt and/or Pd) impregnated zeolite Beta samples have been prepared, characterized using a number of experimental techniques and catalytically tested for the hydroisomerization of a mixture of light paraffins. In particular, the effect of the order of Pt and Pd impregnation on the type/structure of the metallic species of the zeolite support and on the catalytic activity has been studied. Studied samples included a zeolite Beta in which both Pt and Pd (0.5 wt% of each) were simultaneously impregnated (and subsequently calcined and reduced) and two equally metal-loaded samples where the metals were sequentially impregnated (samples Pt*-Pd/Beta and Pd*-Pt/Beta, in which Pt and Pd were impregnated first, respectively). Mono-metallic samples were also prepared for comparison. TPR, DR-UV-visible, TEM, and XAS studies confirm that the order of impregnation plays a key role in the formation of metallic particles, influencing aspects as decisive in their catalytic behavior as their size, their dispersion and their composition (e.g., mono-or bi-metallic). The initial impregnation of Pd and subsequently of Pt produces a higher number of hetero-metallic (Pt-Pd) bonds than the simultaneous co-impregnation and especially for the impregnation in reverse order, which does not produce Pt-Pd bonds in a detectable amount. Based on the results from the different characterization techniques, a model of the metal distribution and composition of the particles was proposed for each bi-metallic sample. In good agreement, the order of the catalytic activity was found to be Pd*-Pt/Beta > Pd-Pt/Beta > Pt/Beta > Pt*-Pd/Beta > Pd/Beta, making clear that not only the presence of both metals, but also an adequate preparation method generating a high number of hetero-metallic bonds must be taken into account to improve the catalytic properties in relation to the mono-metallic samples.

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“…By contrast, when the water content was increased to the H 2 O/Al ratio of 50, the Si content in the sample was increased; simultaneously, the Al and P contents were relatively decreased. Roldán et al have reported that in the synthesis of SAPO-5, Si species are incorporated into the AlPO framework through the substitution of one Si 4+ for one P 5+ in the starting gel with high pH, while silica islands can be formed as a result of the substitution of two Si 4+ for one P 5+ and one Al 3+ in the starting gel with low pH [30]. Thus, it is suggested that Si species were incorporated into the AlPO framework in replace of P species, independent of the water content in the range of the H 2 O/Al ratio of 5-25 due to the dissolution of Si species in the concentrated gel.…”

Section: Synthesis Of Sapo-5 With Different Morphologiesmentioning

confidence: 99%

Control of Morphology and Acidity of SAPO-5 for the Methanol-To- Olefins (MTO) Reaction

2015

J Adv Chem Eng

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Influence of pH and Si content on Si incorporation in SAPO-5 and their catalytic activity for isomerisation of n-heptane over Pt loaded catalysts

Cited by 66 publications

References 60 publications

A Highly Efficient Hβ Zeolite Supported Pt Catalyst Promoted by Chromium for the Hydroisomerization of n-Heptane

A Highly Efficient Hβ Zeolite Supported Pt Catalyst Promoted by Chromium for the Hydroisomerization of n-Heptane

Effect of the impregnation order on the nature of metal particles of bi-functional Pt/Pd-supported zeolite Beta materials and on their catalytic activity for the hydroisomerization of alkanes

Control of Morphology and Acidity of SAPO-5 for the Methanol-To- Olefins (MTO) Reaction

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