Catalytic oxidation of methanol on Pd metal and oxide clusters at near-ambient temperatures

Lichtenberger, Janine; Lee, Doohwan; Iglesia, Enrique

doi:10.1039/b707465d

Cited by 62 publications

(65 citation statements)

References 41 publications

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“…Formyl species have also been found at this temperature, but they promptly disappear if the catalyst is heated and the formation of CO and H 2 prevails 28. 30 Methyl formate can be formed through the condensation of adsorbed methoxides with HCHO to form methoxymethanol intermediates, which then dehydrogenate to methyl formate 31. The esterification of formic acid intermediates formed by HCHO oxidation is also possible, but the high selectivities to methyl formate reported here indicate that fast reactions occur through condensation of HCHO to methyl formate.…”

Section: Discussionmentioning

confidence: 99%

Direct Methyl Formate Formation from Methanol over Supported Palladium Nanoparticles at Low Temperature

2012

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Palladium nanoparticles of different sizes and supported on TiO2 (2 wt. %) were synthesized by using the water‐in‐oil microemulsion method. The control of palladium nanoparticles was investigated in terms of the nature of organic surfactant and solvent. Attention was paid to the reduction of palladium ions in solution during synthesis. Materials were characterized by N2‐BET at low temperature, XRD, XPS, H2 chemisorption, and TEM and were tested in the gas phase oxidation of methanol. The results confirmed the effect of microemulsion composition on the size of palladium nanoparticles. The direct formation of methyl formate from methanol was observed. Supported palladium catalysts produced methyl formate at low temperature (<150 °C) with a very high selectivity, and, in some cases, a selectivity of approximately 100 %. At higher temperature, methyl formate is not formed at all and the total oxidation to CO2 occurs. A linear correlation between palladium particle size and methanol conversion was observed. Conversion and selectivity were correlated with the acidity of the catalysts. Very small particles were more active but less selective. A mechanism was proposed to explain the formation of methyl formate from methanol.

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Section: Discussionmentioning

confidence: 99%

Direct Methyl Formate Formation from Methanol over Supported Palladium Nanoparticles at Low Temperature

2012

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“…[13,15] Methyl formate can form through the condensation of adsorbed methoxides with HCHO to form methoxymethanol intermediates (CH 3 OCH 2 OH) that then dehydrogenate to methyl formate. [16] The esterification of formic acid (HCOOH) intermediates formed by HCHO oxidation is also possible but the high selectivities to methyl formate reported here indicate that fast reactions through condensation of HCHO to methyl formate occur. However, works using DRIFT in operando mode are presently in progress to understand the mechanism of methyl formate formation.…”

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confidence: 89%

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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“…Except for noble‐metal‐based catalysts, the aforementioned oxides perform modestly in the reaction . The performance of noble metals has been related to their reducibility . Lichtenberger et al .…”

Section: Introductionmentioning

confidence: 99%

“…The performance of noble metals has been related to their reducibility . Lichtenberger et al . showed that reduced palladium species perform better in the reaction than oxidized PdO.…”

Section: Introductionmentioning

confidence: 99%

“…This bimetallic system was selected to benefit from the probable synergetic effects coming from the individual properties of each metal in oxidation. On the one hand, platinum is known to be a very efficient catalyst in oxidation reactions, and, on the other hand, palladium has shown a high selectivity to MF . Several papers report on the synergy between Pd and Pt for diverse reactions such as the hydrogenation of aromatics and oxygenates, and the combustion of hydrocarbons .…”

Section: Introductionmentioning

confidence: 99%

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Synergetic Behavior of TiO₂‐Supported Pd(z)Pt(1−z) Catalysts in the Green Synthesis of Methyl Formate

et al. 2016

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Methyl formate (MF) is a valuable platform molecule, the industrial production of which is far from being green. In this contribution, TiO2‐supported Pd(z)Pt(1−z) catalysts were found to be effective in the green synthesis of methyl formate (MF)—at T=323 K and ambient pressure—through methanol (MeOH) oxidation. Two series of catalysts with similar bulk Pd/(Pd+Pt) molar ratios, z, were prepared; one by a water‐in‐oil microemulsion (MicE) method and the other by an incipient wetness impregnation (IWI). The MicE method led to more efficient catalysts owing to a weak influence of z on particle size distributions and nanoparticles composition. Pd(z)Pt(1−z)‐MicE catalysts exhibited strong synergistic effects for MF production but weak synergistic effects for MeOH conversion. The catalytic performance of Pd(z)Pt(1−z)‐MicE was superior to that of Pd(z)Pt(1−z)‐IWI catalysts despite the latter displaying synergetic effects during the reaction. The catalytic behavior of TiO2‐supported Pd(z)Pt(1−z) catalysts was explained from correlations between XRD, TEM, and X‐ray photoelectron spectroscopy characterizations.

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Catalytic oxidation of methanol on Pd metal and oxide clusters at near-ambient temperatures

Cited by 62 publications

References 41 publications

Direct Methyl Formate Formation from Methanol over Supported Palladium Nanoparticles at Low Temperature

Direct Methyl Formate Formation from Methanol over Supported Palladium Nanoparticles at Low Temperature

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

Synergetic Behavior of TiO₂‐Supported Pd(z)Pt(1−z) Catalysts in the Green Synthesis of Methyl Formate

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Catalytic oxidation of methanol on Pd metal and oxide clusters at near-ambient temperatures

Cited by 62 publications

References 41 publications

Direct Methyl Formate Formation from Methanol over Supported Palladium Nanoparticles at Low Temperature

Direct Methyl Formate Formation from Methanol over Supported Palladium Nanoparticles at Low Temperature

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

Synergetic Behavior of TiO2‐Supported Pd(z)Pt(1−z) Catalysts in the Green Synthesis of Methyl Formate

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Synergetic Behavior of TiO₂‐Supported Pd(z)Pt(1−z) Catalysts in the Green Synthesis of Methyl Formate