Methanol oxidation as a catalytic surface probe

Tatibouët, Jean‐Michel

doi:10.1016/s0926-860x(96)00236-0

Cited by 443 publications

(391 citation statements)

References 133 publications

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“…H 2 O desorption via recombination of OH groups forms an oxygen vacancy (0) (Step 3), and O 2 dissociative chemisorption (Step 4) ultimately restores the missing lattice oxygen in a series of steps that complete a Mars-van Krevelen redox cycle. 1,19 These steps are consistent with the kinetic dependence of reaction rates on CH 3 OH and O 2 partial pressures, as we discuss next. Figure 3 shows CH 3 OH oxidative dehydrogenation rates and product selectivities as a function of CH 3 OH partial pressure (0-40 kPa) at 393 K and 9 kPa O 2 on RuO 2 /TiO 2 (3.1 Ru/ nm 2 ).…”

Section: Resultssupporting

confidence: 79%

“…These reduction rates and the corresponding CH 3 OH oxidation rates ( A plausible sequence of elementary steps for methanol oxidation on RuO x domains is shown as steps 1-4 below; it is consistent with the results presented above and with HCHO synthesis pathways previously proposed. 1,5,7,8 In this sequence, the {-O*-Ru-O*-Ru-O*-} is meant to depict in general RuO x structures with reactive lattice oxygen atoms (O*). These postulated elementary steps include dissociative CH 3 OH chemisorption to form methoxide (CH 3 O -) intermediates (Step 1), followed by hydrogen abstraction from CH 3 Ousing lattice oxygen atoms (O*) in RuO x to form HCHO (Step 2).…”

Section: Resultsmentioning

confidence: 99%

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Selective Oxidation of Methanol and Ethanol on Supported Ruthenium Oxide Clusters at Low Temperatures

2004

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catalyze the oxidative conversion of methanol to formaldehyde, methylformate, and dimethoxymethane with unprecedented rates and high combined selectivity (>99%) and yield at low temperatures (300-400 K). Supports influence turnover rates and the ability of RuO 2 domains to undergo redox cycles required for oxidation turnovers. Oxidative dehydrogenation turnover rates and rates of stoichiometric reduction of RuO 2 in H 2 increased in parallel when RuO 2 domains were dispersed on more reducible supports. These support effects, the kinetic effects of CH 3 OH and O 2 on reaction rates, and the observed kinetic isotope effects with CH 3 OD and CD 3 OD reactants are consistent with a sequence of elementary steps involving kinetically relevant H-abstraction from adsorbed methoxide species using lattice oxygen atoms and with methoxide formation in quasi-equilibrated CH 3 OH dissociation on nearly stoichiometric RuO 2 surfaces. Anaerobic transient experiments confirmed that CH 3 OH oxidation to HCHO requires lattice oxygen atoms and that selectivities are not influenced by the presence of O 2 . Residence time effects on selectivity indicate that secondary HCHO-CH 3 OH acetalization reactions lead to hemiacetal or methoxymethanol intermediates that convert to dimethoxymethane in reactions with CH 3 OH on support acid sites or dehydrogenate to form methylformate on RuO 2 and support redox sites. These conclusions are consistent with the tendency of Al 2 O 3 and SiO 2 supports to favor dimethoxymethane formation, while SnO 2 , ZrO 2 , and TiO 2 preferentially form methylformate. These support effects on secondary reactions were confirmed by measured CH 3 OH oxidation rates and selectivities on physical mixtures of supported RuO 2 catalysts and pure supports. Ethanol also reacts on supported RuO 2 domains to form predominately acetaldehyde and diethoxyethane at 300-400 K. The bifunctional nature of these reaction pathways and the remarkable ability of RuO 2 -based catalysts to oxidize CH 3 OH to HCHO at unprecedented low temperatures introduce significant opportunities for new routes to complex oxygenates, including some containing C-C bonds, using methanol or ethanol as intermediates derived from natural gas or biomass.

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Section: Resultssupporting

confidence: 79%

Section: Resultsmentioning

confidence: 99%

Selective Oxidation of Methanol and Ethanol on Supported Ruthenium Oxide Clusters at Low Temperatures

2004

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“…Figure 7 shows temperature dependent IR spectra after exposure of the partially reduced surface (second trace from bottom) to methanol at 88 K and subsequent stepwise heating to 660 K. In comparison, the spectrum of the fully vanadyl terminated surface is shown. The vanadyl groups had been partially labeled with 18 O isotopes giving rise to the doublet at 998 and 1032 cm -1 respectively. It is interesting to note that this doublet shifts by more than 10 cm -1 to lower energies (982 and 1021 cm -1 , see the right panel) upon reduction indicating the influence of the modified electronic structure discussed above in connection with the low temperature STM data.…”

Section: Resultsmentioning

confidence: 99%

“…The role of vanadyl species will be investigated in this paper with respect to alcohol oxidation even though in this case the process used commercially involves silver and ironmolybdate catalysts [17,18]. In this publication we present detailed catalytic studies on alcohol oxidation for supported vanadia and for ordered V 2 O 3 (0001) thin films grown on Au(111).…”

Section: Introductionmentioning

confidence: 99%

Selectivity in Methanol Oxidation as Studied on Model Systems Involving Vanadium Oxides

et al. 2008

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Oxidation catalysts are modeled by oxide single crystals, thin oxide films, as well as supported oxide nanoparticles. We characterize the surface of those materials using a variety of surface sensitive techniques including scanning tunneling microscopy and spectroscopy, photoelectron spectroscopy, infrared spectroscopy, and thermal desorption spectroscopy. We find temperature dependent structural transformations from V 2 O 5 (001) to V 2 O 3 (0001) via V 6 O 13 (001). V 2 O 3 (0001) is found to be vanadyl terminated in an oxygen ambient and it loses the vanadyl termination after electron bombardment. It is shown that the concentration of vanadyl groups controls the selectivity of the methanol oxydehydrogenation towards formaldehyde. A proposal for the mechanism is made. The results on single crystalline thin films are compared with similar measurements on deposited vanadia nanoparticles. The experimental results are correlated with theoretical calculations and models.

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“…6. Indeed, the interaction of methanol on both an oxidation catalysts surface and bulk has been well studied [42,68,69].…”

Section: Catalyst Activitymentioning

confidence: 99%

A Combined Multi-Technique In Situ Approach Used to Probe the Stability of Iron Molybdate Catalysts During Redox Cycling

et al. 2009

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A setup combining a number of techniques (WAXS, XANES and UV-Vis) has been used to probe the stability of an iron molybdate catalyst during redox cycling. The catalyst was first reduced under anaerobic methanol/ helium conditions, producing formaldehyde and then regenerated using air. Although in this test-case the catalyst and conditions differ from that of a commercial catalyst bed we demonstrate how such a setup can reveal new information on catalyst materials.

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Methanol oxidation as a catalytic surface probe

Cited by 443 publications

References 133 publications

Selective Oxidation of Methanol and Ethanol on Supported Ruthenium Oxide Clusters at Low Temperatures

Selective Oxidation of Methanol and Ethanol on Supported Ruthenium Oxide Clusters at Low Temperatures

Selectivity in Methanol Oxidation as Studied on Model Systems Involving Vanadium Oxides

A Combined Multi-Technique In Situ Approach Used to Probe the Stability of Iron Molybdate Catalysts During Redox Cycling

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