High-throughput experimentation in multicomponent bulk mixed metal oxides: Mo-V-Sb-Nb-O system for selective oxidation of propane to acrylic acid

Al-Saeedi, Jamal N.; Guliants, Vadim V.

doi:10.1016/s0926-860x(02)00324-1

Cited by 35 publications

(9 citation statements)

References 28 publications

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“…Ethoxide species can undergo either -hydride elimination to form ethene and *OH (step 3), or further oxidation via R-hydride abstraction by O* with acetic acid as the final product (steps 4,6,7,8). Recombination of *OH groups forms H 2 O and an oxygen vacancy (step 9) and oxygens are ultimately restored via irreversible dissociation of O 2 to complete a catalytic turnover (step 10).…”

Section: Elementary Steps In Catalytic Ethanementioning

confidence: 99%

Kinetics and Mechanism of Ethane Oxidation to Acetic Acid on Catalysts Based on Mo−V−Nb Oxides

Iglesia

2008

J. Phys. Chem. C

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Kinetic and isotopic studies showed that C-H bond activation in ethane by surfaces essentially saturated with lattice oxygens is the sole kinetically relevant step in ethane oxidation on Mo-V-NbO x mixed oxides. These conclusions are consistent with the dependence of oxidation rates on O 2 and C 2 H 6 pressures, with H/D exchange and kinetic isotope effects, and with the preferential initial incorporation of 16 O atoms from the oxide lattice into products formed from 18 O 2 -C 2 H 6 mixtures. The precipitation of active components (Mo 0.61 V 0.31 Nb 0.08 O x ) in the presence of colloidal TiO 2 led to 10-fold increases in all rate constants (per active component), consistent with higher dispersion of active components resembling in structure and surface reactivity those prevalent in bulk powders. The concurrent presence of PdO x cocatalyst, even as a separate solid, markedly increased all rate constants for oxidation of ethene intermediates and specifically that for ethene oxidation to acetaldehyde molecules, which are rapidly converted to acetic acid on active Mo-V-NbO x sites. Water, whether formed as a byproduct or added with C 2 H 6 -O 2 reactants, increases acetic acid selectivities by promoting the desorption of adsorbed acetate species as acetic acid. Ethene molecules, formed as reactive intermediates, inhibit ethane oxidation rates by depleting surface lattice oxygen atoms in fast oxidation reactions, thus decreasing the number of sites available at steady state for the kinetically relevant C-H bond activation step required for ethane conversion.

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Section: Elementary Steps In Catalytic Ethanementioning

confidence: 99%

Kinetics and Mechanism of Ethane Oxidation to Acetic Acid on Catalysts Based on Mo−V−Nb Oxides

Iglesia

2008

J. Phys. Chem. C

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“…The bulk mixed metal Mo-V-M-O (M=Te and Nb) catalysts received considerable attention in recent years because of their unique ability to transform propane and ethane into selective oxidation products, namely acrylonitrile, acrylic acid and ethylene [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. The mixed Mo-V-Te-Nb oxides, originally developed by Mitsubishi, contained several crystalline phases [2,3] among which socalled M1 and M2 phases are important catalytically [14,20].…”

Section: Introductionmentioning

confidence: 99%

M1 to M2 Phase Transformation and Phase Cooperation in Bulk Mixed Metal Mo–V–M–O (M=Te, Nb) Catalysts for Selective Ammoxidation of Propane

et al. 2008

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In the present study we systematically explored hydrothermal synthesis of bulk mixed metal Mo-V-(TeNb)-O catalysts and investigated the bulk characteristics of the resulting M1 and M2 phases as well as their roles in the selective ammoxidation of propane. It was found that unlike Mo-V-Te-Nb-O M1 phases, the Mo-V-Te-O M1 phases may be quantitatively transformed into M2 phases of the same chemical composition indicating that Nb stabilizes the M1 structure. The stabilizing role of Nb and Te was further observed in high resolution TEM studies of Mo-V-(Te-Nb)-O catalysts which indicated that structural order and the M1 phase domain size progressively decreased in this order: Mo-V-Te-Nb-O [ Mo-V-Te-O [ Mo-V-O. The cooperation between the M1 and M2 phases in propane ammoxidation to acrylonitrile was observed only at low propane conversions suggesting that the M1 phase is the only crystalline phase required for the activity and selectivity of the Mo-V-Te-Nb-O catalysts in propane ammoxidation to acrylonitrile at practical propane conversions.

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“…However, and although Sb-containing catalysts are active and selective in the (amm)oxidation of propane [6][7][8][9][10][11][12][13] and in the ODH of ethane [14], they generally present a selectivity to partial oxidation products lower than those obtained over the corresponding Te-containing catalyst [1-4, 13, [15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Selective Oxidation of Propane Over AMoVSbO Catalysts (A = Li, Na, K, Rb or Cs)

et al. 2008

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Alkali metal-containing Mo-V-Sb-O catalysts (AMoVSbO, with A = Li, Na, K, Rb or Cs), prepared hydrothermally and activated at 600°C in N 2 , have been characterized and tested for the selective oxidation of propane. Alkali-doped catalysts resulted to be more selective to acrylic acid and less selective to acetic acid than the corresponding alkali-free Mo-V-Sb-O catalyst. However, the nature of crystalline phases and the catalytic behaviour strongly depend on the alkali metal added. In this way, the catalytic activity decreases as follows: unpromoted [ Li-* Na-* K-[ Rb-[ Cs-containing catalyst. However the selectivity to acrylic acid decreases in the order: K-[ Rb-* Na-[ unpromoted [ Li-[ Cscontaining catalyst. The role of the presence/absence of acid sites and cations on both the nature of crystalline phases and the catalytic performance will be discussed.

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High-throughput experimentation in multicomponent bulk mixed metal oxides: Mo-V-Sb-Nb-O system for selective oxidation of propane to acrylic acid

Cited by 35 publications

References 28 publications

Kinetics and Mechanism of Ethane Oxidation to Acetic Acid on Catalysts Based on Mo−V−Nb Oxides

Kinetics and Mechanism of Ethane Oxidation to Acetic Acid on Catalysts Based on Mo−V−Nb Oxides

M1 to M2 Phase Transformation and Phase Cooperation in Bulk Mixed Metal Mo–V–M–O (M=Te, Nb) Catalysts for Selective Ammoxidation of Propane

Selective Oxidation of Propane Over AMoVSbO Catalysts (A = Li, Na, K, Rb or Cs)

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