The number of active sites for the disproportionation of ethylene on supported rhenium oxide catalysts

Aldag, A.W.; Lin, Chenxi; Clark, Alfred

doi:10.1016/0021-9517(78)90301-9

Cited by 32 publications

(15 citation statements)

References 17 publications

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“…However, the reduction peaks of the ReO x /CeO 2 catalysts were symmetrically shifted to 690-753 K. With increasing Re loading, the reduction temperature for the ReO x /CeO 2 catalysts gradually shifted to low region and reached the lowest value of 690 K at Re loading of 6.4 wt.%. It was previously proposed that the monolayer dispersion of ReO x corresponded to a surface coverage of about one Re atom per 0.35 nm 2 [9][10][11][12]. By considering the BET surface area of 64 m 2 g -1 , the loading of 6.4 wt.% Re equaled to a Re surface density of one Re atom per 0.31 nm 2 , indicating the monolayer dispersion of ReO x on ceria.…”

Section: Catalytic Evaluationmentioning

confidence: 99%

Methanol Selective Oxidation to Methyl Formate over ReOx/CeO2 Catalysts

et al. 2007

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Methanol selective oxidation to methyl formate was investigated over ReO x /CeO 2 catalysts in terms of Re loading and reaction mechanism. It was found that Re loading with monolayer dispersion on ceria exhibited promising reaction rate of methanol of 16 mmol g cat.-1 h -1 and methyl formate selectivity of about 90% at 513 K. The surface reaction of methanol, formaldehyde, and methyl formate over the ReO x /CeO 2 catalyst was investigated by in situ Fourier transform infrared spectroscopy and it was revealed that the formate species, formed by the oxidation of adsorbed -OCH 3 species, could act as the key reaction intermediate, which further reacted with gaseous methanol to form methyl formate and/or decompose into CO and CO 2 , depending on the reaction temperature.

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Section: Catalytic Evaluationmentioning

confidence: 99%

Methanol Selective Oxidation to Methyl Formate over ReOx/CeO2 Catalysts

et al. 2007

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“…8 By combining steady-state kinetic studies with simultaneous thermal gravimetric analysis (TGA) to determine the quantity of adsorbed ethylene during the reaction, the metathesis reaction rate was found to vary with the square of the adsorbed ethylene. 8 It was proposed that the ethylene metathesis reaction involves two mobile adsorbates, resulting in second-order kinetics with respect to the adsorbate concentration. 8,9 This suggests that ethylene self-metathesis proceeds via a four-membered reaction intermediate.…”

Section: Introductionmentioning

confidence: 99%

“…This suggests that the surface intermediates present on the catalyst at high temperature are adsorbed C 3 = π complexes and that the hightemperature reaction pathway proceeds via a four-centered intermediate proposed in some of the early metathesis studies. 8,9,11,12 According to this bimolecular reaction mechanism, the olefins can exchange their individual half-components to yield the metathesis products. The kinetics for the secondorder self-metathesis of propylene are derived by assuming reaction between two surface C 3 = π complexes:…”

Section: Introductionmentioning

confidence: 99%

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Reaction Mechanism and Kinetics of Olefin Metathesis by Supported ReO_x/Al₂O₃ Catalysts

Lwin

Wachs

2015

ACS Catal.

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The self-metathesis of propylene by heterogeneous supported ReO x /Al2O3 catalysts was investigated with in situ Raman spectroscopy, isotopic switch (D–C3 = → H–C3 =), temperature-programmed surface reaction (TPSR) spectroscopy, and steady-state kinetic studies. The in situ Raman studies showed that two distinct surface ReO4 sites are present on alumina and that the olefins preferentially interact with surface ReO4 sites anchored at acidic surface sites of alumina (olefin adsorption: C4 = > C3 = > C2 =). The isotopic switch experiments demonstrate that surface Re*CH3 and Re*CHCH3 are present during propylene metathesis, with Re* representing activated surface rhenia sites. At low temperatures (<100 °C), the rate-determining step is adsorption of propylene on two adjacent surface sites (rate ≈ [C3 =][Re*]2. At high temperatures (>100 °C), the rate-determining step is the recombination of two surface propylene molecules (rate ≈ [C3 =]2[Re*]). To a lesser extent, the recombination of surface Re*CH3 and Re*CHCH3 intermediates also contributes to self-metathesis of propylene at elevated reaction temperatures.

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“…[1][2][3][4][5][6][7][8] Some studies reported the number of activated rhenia sites to only be ~1-2% of the total supported Re atoms after activation with olefins at room temperature and evacuation for 1-6…”

Section: Introductionmentioning

confidence: 99%

Determination of Number of Activated Sites Present during Olefin Metathesis by Supported ReO_x/Al₂O₃ Catalysts

Lwin

Wachs

2015

ACS Catal.

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The number of surface rhenia sites on alumina participating in olefin metathesis, usually counted by chemical titration of surface reaction intermediates with olefins, has been debated for several decades. The current olefin titration measurements, however, demonstrate that the number of reactive surface intermediates on supported rhenia/alumina catalysts is strongly dependent on the experimental variables. The new findings reveal that the accepted titration procedures significantly undercount the number of activated surface rhenia sites upon exposure to olefins by ~10 1 -10 2 because of invalid assumptions.

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The number of active sites for the disproportionation of ethylene on supported rhenium oxide catalysts

Cited by 32 publications

References 17 publications

Methanol Selective Oxidation to Methyl Formate over ReOx/CeO2 Catalysts

Methanol Selective Oxidation to Methyl Formate over ReOx/CeO2 Catalysts

Reaction Mechanism and Kinetics of Olefin Metathesis by Supported ReO_x/Al₂O₃ Catalysts

Determination of Number of Activated Sites Present during Olefin Metathesis by Supported ReO_x/Al₂O₃ Catalysts

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The number of active sites for the disproportionation of ethylene on supported rhenium oxide catalysts

Cited by 32 publications

References 17 publications

Methanol Selective Oxidation to Methyl Formate over ReOx/CeO2 Catalysts

Methanol Selective Oxidation to Methyl Formate over ReOx/CeO2 Catalysts

Reaction Mechanism and Kinetics of Olefin Metathesis by Supported ReOx/Al2O3 Catalysts

Determination of Number of Activated Sites Present during Olefin Metathesis by Supported ReOx/Al2O3 Catalysts

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Reaction Mechanism and Kinetics of Olefin Metathesis by Supported ReO_x/Al₂O₃ Catalysts

Determination of Number of Activated Sites Present during Olefin Metathesis by Supported ReO_x/Al₂O₃ Catalysts