Hydroisomerization of a hydrocarbon feed containing n-hexane, n-heptane and cyclohexane on zeolite-supported platinum catalysts

Jiménez, César; Romero, Francisco J.; Roldán, Rafael; Marinas, J. M.; Gómez, Juan Pedro Montávez

doi:10.1016/s0926-860x(03)00177-7

Cited by 70 publications

(45 citation statements)

References 32 publications

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“…The purpose of introducing cyclohexane in this feed is to mimic the real refinery light naphtha used in the industrial process, which can include variable concentrations of naphthenes. It is known that presence of naphthenes inhibits the activity of some acid sites by adsorption, which has been confirmed in a previous work [10]. The reaction conditions were: 1 g of catalyst, 250 • C, 1 bar, WHSV = 3.7 h −1 , carrier gas: H 2 (60 ml min −1 ), feed rate: 5.4 ml h −1 , H 2 /hydrocarbon molar ratio = 4.…”

Section: Catalytic Testsmentioning

confidence: 52%

“…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%

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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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Section: Catalytic Testsmentioning

confidence: 52%

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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“…The profiles of the temperature programmed reduction of Pt-zeolites show peaks below 500°C, characteristics of reduction of different Pt species to Pt 0 [11]. The prepared catalysts presented similar profiles with the highest temperature reduction peak around 440°C.…”

Section: Resultsmentioning

confidence: 77%

Acid Strength of Pt-Zeolite Catalysts: Evidence of Metal-Support Interaction from Linear Free-Energy Relationship

et al. 2011

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The acid strength of Pt-HBeta and Pt-HMordenite zeolite catalysts were estimated by H/D exchange of substituted benzenes with the use of linear free-energy relationship, through the use of the Hammet-Brown equation. The results indicated that compared with the parent acidic zeolite, the incorporation of Pt metal leads to a significant decrease in the acid strength, estimated by the slope (q) of the logarithm of the relative rate (k X /k H ) with the r ? constant of the substituent, indicating a lower degree of proton transfer to the ring in the transition state.The results support the model of metal-support interaction in Pt-zeolite catalyst, with formation of a metal-proton adduct.

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“…Activity and selectivity of the bifunctional catalyst depends on the character of its metal and acid functions, as well as on their balance, only if there are no diffusive limitations [29]. When the catalysts contain zeolites (or materials of zeolite type), their catalytic properties are influenced by the shape-selectivity phenomenon, whereas their activity and selectivity depend strongly on the geometry and dimensionality of the zeolite channel [30,31].…”

Section: Introductionmentioning

confidence: 99%

Effect of Metal-Support Interactions in Ni/ZSM-5 + Al2O3 Catalysts on the Transformation of n-Paraffins

2013

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NiO(8 %)/Ni,H-ZSM-5 ? Al 2 O 3 (1:1) catalysts differing in metal-support interactions, which influenced the metal-to-acid ratios, were examined. The interactions were changed by modifying the method of zeolite and aluminium hydroxide combining and the method of Ni incorporation. The catalysts were characterised by ICP, XRD, N 2 sorption, SEM, TEM, NH 3 -TPD, Py-IR, TPR, H 2 chemisorption and XPS. The effect of metal-support interactions was determined during n-C 6 conversion in a continuous system at H 2 :CH = 7:1 Nm 3 /m 3 , 0.1 MPa and LHSV = 1 h -1 . It was found that over the catalysts with weaker Ni-alumina interactions (n Ni_a /n, 3.2 9 10 -2 and 4.8 9 10 -2 ), selectivity to isomerisation products was by 10-35 % higher, and selectivity to high boiling hydrocarbons by 10-30 % lower than over the catalysts with stronger Ni-support interactions (n Ni_a /n, 1.2 9 10 -2 and 1.8 9 10 -2 ).

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Hydroisomerization of a hydrocarbon feed containing n-hexane, n-heptane and cyclohexane on zeolite-supported platinum catalysts

Cited by 70 publications

References 32 publications

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

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

Acid Strength of Pt-Zeolite Catalysts: Evidence of Metal-Support Interaction from Linear Free-Energy Relationship

Effect of Metal-Support Interactions in Ni/ZSM-5 + Al2O3 Catalysts on the Transformation of n-Paraffins

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