Methyl formate from methanol oxidation over coprecipitated V-Ti-O catalysts

Tronconi, Enrico; Elmi, Ahmed S.; Ferlazzo, N.; Forzatti, Pio; Busca, Guido; Tittarelli, Paolo

doi:10.1021/ie00067a001

Cited by 58 publications

(81 citation statements)

References 9 publications

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“…20 A band was observed at ∼993 cm -1 in all RuO x /ZrO 2 samples. Taken together with the XPS spectra and stoichiometric H 2 reduction data, this new band can be tentatively assigned to terminal RudO stretching vibrations for RuO 4 2-species (Ru 6+ ) probably present in Zr(RuO 4 ) 2 structures formed via reactions of ZrO 2 with RuO x during treatment in air at 673 K.…”

Section: Resultsmentioning

confidence: 56%

“…The reducibility of RuO x species was probed by temperature-programmed reduction (TPR) in H 2 . RuO 4 2-structures, containing Ru 6+ and likely present as Zr-(RuO 4 ) 2 , were detected and found to be active and selective for MF synthesis.…”

Section: Introductionmentioning

confidence: 96%

“…[2][3][4][5] These processes involve waste byproducts, energy inefficiencies, or thermodynamic constraints. Oxidation processes are catalyzed by dispersed VO x and MoO x domains [4][5][6][7] with favorable thermodynamics and modest MF selectivities, but improvements in reaction rates and selectivities are required for industrial practice.…”

Section: Introductionmentioning

confidence: 99%

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Structures and Properties of Zirconia-Supported Ruthenium Oxide Catalysts for the Selective Oxidation of Methanol to Methyl Formate

Liu

Iglesia

2006

J. Phys. Chem. B

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The effects of RuO x structure on the selective oxidation of methanol to methyl formate (MF) at low temperatures were examined on ZrO 2 -supported RuO x catalysts with a range of Ru surface densities (0.2-3.8 Ru/nm 2 ). Their structure was characterized using complementary methods (X-ray diffraction, Raman and X-ray photoelectron spectra, and reduction dynamics). The structure and reactivity of RuO x species change markedly with Ru surface density. RuO x existed preferentially as RuO 4 2-species below 0.4 Ru/nm 2 , probably as isolated Zr(RuO 4 ) 2 interacting with ZrO 2 surfaces. At higher surface densities, highly dispersed RuO 2 domains coexisted with RuO 4 2-and ultimately formed small clusters and became the prevalent form of RuO x above 1.9 Ru/nm 2 . CH 3 OH oxidation rates per Ru atom and per exposed Ru atom (turnover rates) decreased with increasing Ru surface density. This behavior reflects a decrease in intrinsic reactivity as RuO x evolved from RuO 4 2-to RuO 2 , a conclusion confirmed by transient anaerobic reactions of CH 3 OH and by an excellent correlation between reaction rates and the number of RuO 4 2-species in RuO x /ZrO 2 catalysts. The high intrinsic reactivity of RuO 4 2-structures reflects their higher reducibility, which favors the reduction process required for the kinetically relevant C-H bond activation step in redox cycles using lattice oxygen atoms involved in CH 3 -OH oxidation catalysis. These more reactive RuO 4 2-species and the more exposed ZrO 2 surfaces on samples with low Ru surface density led to high MF selectivities (e.g. ∼96% at 0.2 Ru/nm 2 ). These findings provide guidance for the design of more effective catalysts for the oxidation of alkanes, alkenes, and alcohols by the synthesis of denser Zr(RuO 4 ) 2 monolayers on ZrO 2 and other high surface area supports.

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Section: Resultsmentioning

confidence: 56%

Section: Introductionmentioning

confidence: 96%

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Structures and Properties of Zirconia-Supported Ruthenium Oxide Catalysts for the Selective Oxidation of Methanol to Methyl Formate

Liu

Iglesia

2006

J. Phys. Chem. B

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“…2,3 The direct oxidative conversion of methanol to methylformate occurs only at modest reaction rates. [2][3][4][5] DMM is produced in a two-step process involving methanol oxidation to HCHO followed by acetalization of HCHO-CH 3 OH mixtures with liquid or solid acids. Direct CH 3 OH oxidation with significant DMM yields has been recently reported on ReO x -based catalysts 6 and on polyoxometalate Keggin clusters.…”

Section: Introductionmentioning

confidence: 99%

“…15,16 Methanol reactions were carried out in a packed-bed quartz microreactor. Catalyst powders (0.1-0.3 g) were diluted with quartz powder (∼0.5 g) to prevent temperature gradients and treated in 20% O 2 Reactants and products were analyzed by on-line gas chromatography (Hewlett-Packard 6890GC) using a methyl-silicone capillary column (HP-1; 50 m × 0.25 mm, 0.25 µm film thickness) and a Porapak Q packed column (80-100 mesh, 1.82 m × 3.18 mm) connected to flame ionization and thermal conductivity detectors, respectively. Selectivities are reported on a carbon basis as the percentage of the converted CH 3 OH appearing as a given product.…”

Section: Introductionmentioning

confidence: 99%

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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Low Temperature‐High Selectivity Process over Supported Pd Nanoparticles in Partial Oxidation of Methanol

2011

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The most important challenge in gas phase heterogeneous catalysis is to reach high selectivity in a desired process. Many efforts are made at present to improve selectivity in high temperature reactions (> 350 8C); however, under high temperature, it seems very difficult to reach a very high (about 100 %) selectivity. The main reason for this is probably the difficulty (and maybe the impossibility) to separate the reactivity of the selective and non-selective active sites of the catalyst. In general, both sites form a part of the same structure of the active phase and they are located in a near proximity. Then, under the reaction conditions, the dynamic phenomena (oxidation and reduction rates, acid and base properties, restructuration of active sites and phases, formation of new phases, migration and reactivity of chemical species, formation of intermediates etc.) on which selectivity depends, are simultaneously involved and concern selective and non-selective sites. For these reasons, it could be stated that probably the only way to get high selectivity in gas phase heterogeneous catalysis is to work under "low temperature conditions".It is well known that the nanosize of the catalytic particles could play an important role in the design of new catalytic processes. The decrease in size increases the catalytic activity. The small size can provide a large amount of surface atoms, which results in the high catalytic activity per unit amount of metal. Because surface atoms tend to be coordinatively unsaturated, there is a large energy associated with this surface. The smaller the nanoparticles, the larger the contribution made by the surface energy to the overall energy of the system will be. On the other hand, when the particles are too small, quantum effects prevail over the classical size effect giving the particles new and unexpected properties. Therefore, it is absolutely necessary to use synthesis techniques capable of producing nanoparticles of the catalytic active phases with a tailored-size distribution. In contrast, the partial oxidation of methanol (POMeOH) is usually performed at a relatively high temperature (above 250 8C), but the selectivity of the reaction is very low. Several reaction products, such as formaldehyde and dimethoxymethane (on the redox sites) and dimethyl ether and carbon oxides (on the basic and acidic sites), can be obtained. [1][2][3] We report that methyl formate (MF) could be produced directly from methanol under the oxidation reaction conditions, with a very high selectivity, in a one step reaction performed on catalysts formed by Pd nanoparticles supported on TiO 2 at low temperature and under atmospheric pressure.The Pd/TiO 2 catalysts were prepared by using the water-inoil microemulsion method (Scheme 1). This method is interesting because the chemical reduction and then the precipitation from solutions is a highly versatile and simple method to perform the synthesis of small supported particles. It is well recognized that the size control of nanoparticles can be achieved by ...

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Methyl formate from methanol oxidation over coprecipitated V-Ti-O catalysts

Cited by 58 publications

References 9 publications

Structures and Properties of Zirconia-Supported Ruthenium Oxide Catalysts for the Selective Oxidation of Methanol to Methyl Formate

Structures and Properties of Zirconia-Supported Ruthenium Oxide Catalysts for the Selective Oxidation of Methanol to Methyl Formate

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

Low Temperature‐High Selectivity Process over Supported Pd Nanoparticles in Partial Oxidation of Methanol

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