Oxidative Coupling Of Methanol Research Articles

Oxidative Coupling of Methanol with Molecularly Adsorbed Oxygen on Au Surface to Methyl Formate.

Supported Au catalysts efficiently catalyze the oxidative coupling of methanol with O2 to methyl formate, in which the atomic O species (O(a)) formed via O2 dissociation on the Au surface has been considered as the active oxygen species. Herein we report for the first time that the oxidative coupling of methanol can occur facilely with molecularly adsorbed O2 species (O2(a)) on a Au(997) surface at temperatures as low as around 125 K, while that with O(a) occurs at around 175 K. Both experimental and theoretical calculation results demonstrate a novel reaction mechanism of oxidative coupling of CH3OH with O2(a) via a dioxymethylene (H2COO) intermediate, resulting in the production of both HCOOCH3 and HCOOCH3. These results reveal the unique reactivity of molecularly adsorbed O2 species on Au surfaces for low-temperature oxidation reactions.

Synthesis of acrolein by oxidative coupling of alcohols over spinel catalysts: microcalorimetric and spectroscopic approaches

Oxidative coupling of methanol and ethanol is becoming a promising alternative to produce sustainable acrolein.

Oxidative coupling of a mixture of bio-alcohols to produce a more sustainable acrolein: An in depth look in the mechanism implying aldehydes co-adsorption and acid/base sites

The industrial synthesis of acrolein is mainly performed by propylene oxidation over bismuth-iron-molybdate catalysts. Among cleaner alternatives to produce acrolein, oxidative coupling of methanol and ethanol represents a promising way. In this work, the reaction has been performed in two separate reactors (for oxidation and aldolization) to study the role of the acid/base properties but also the competition of aldehydes adsorption over environmentally friendly spinel catalysts with various Al/Mg ratios. The acid/base properties of catalysts were investigated by NH3 and SO2 adsorption microcalorimetry. Further adsorption microcalorimetry studies were performed with methanol, formaldehyde, acetaldehyde and propionaldehyde to investigate the bounding properties of the reactants. The acid/base properties were correlated with acrolein yield and selectivity under oxidizing conditions. Co-adsorption of aldehydes was also investigated allowing justification of the absence of crotonaldehyde formation.

Evolution of steady-state material properties during catalysis: Oxidative coupling of methanol over nanoporous Ag0.03Au0.97

Activating pretreatments are used to tune surface composition and structure of bimetallic-alloy catalysts. Herein, the activation-induced changes in material properties of a nanoporous Ag0.03Au0.97 alloy and their subsequent evolution under steady-state CH3OH oxidation conditions are investigated. Activation using O3 results in AgO and Au2O3, strongly enriching the near-surface region in Ag. These oxides reduce in the O2/CH3OH mixture, yielding CO2 and producing a highly Ag-enriched surface alloy. At the reaction temperature (423 K), Ag realloys gradually with Au but remains enriched (stabilized by surface O) in the top few nanometers, producing methyl formate selectively without significant deactivation. At higher temperatures, bulk diffusion induces sintering and Ag redistribution, leading to a loss of activity. These findings demonstrate that material properties determining catalytic activity are dynamic and that metastable (kinetically trapped) forms of the material may be responsible for catalysis, providing guiding principles concerning the activation of heterogeneous catalysts for selective oxidation.

Design of catalytically active porous gold structures from a bottom-up method: The role of metal traces in CO oxidation and oxidative coupling of methanol

By using a bottom-up approach, we prepared 3D self-supported porous structures made of gold nanoparticles and applied them as oxidation catalysts. To do so we used the established cryogelation technique, in which nanoparticle units were frozen in liquid nitrogen and the ice-template was subsequently sublimated by a freeze-drying process, resulting in a 3D self-standing monolith of nanoparticles. The sample was characterized with different techniques to understand the evolution of the microscopic structure before and after exposure to catalytic environments. In addition, the synthesized materials were tested in the CO oxidation and in the oxidative methanol coupling, in the attempt to compare the prepared materials against established nanoporous gold systems synthesized by a top-down approach. The as-prepared gold sample was inactive in the CO oxidation and surprisingly, highly active in the oxidative methanol coupling. A set of analyses revealed the presence of sodium species on the catalyst surface, which correlated to the extremely high activity of the catalyst. When such traces were removed, the pure gold samples was found to be inactive also in the methanol coupling reaction. Finally, our results proved that pure porous gold systems were not able to catalyze the investigated oxidation reactions, but instead traces of alkali metal ions in these systems could enhance the catalytic activity.

A Comparative Study of Basic, Amphoteric, and Acidic Catalysts in the Oxidative Coupling of Methanol and Ethanol for Acrolein Production.

The impact of acid/base properties (determined by adsorption microcalorimetry) of various catalysts on the cross-aldolization of acetaldehyde and formaldehyde leading to acrolein was methodically studied in oxidizing conditions starting from a mixture of methanol and ethanol. The aldol condensation and further dehydration to acrolein were carried out on catalysts presenting various acid/base properties (MgO, Mg-Al oxides, Mg/SiO2 , NbP, and heteropolyanions on silica, HPA/SiO2 ). Thermodynamic calculations revealed that cross-aldolization is always favored compared with self-aldolization of acetaldehyde, which leads to crotonaldehyde formation. The presence of strong basic sites is shown to be necessary, but a too high amount drastically increases COx production. On strong acid sites, production of acrolein and carbon oxides (COx ) does not increase with temperature. The optimal catalyst for this process should be amphoteric with a balanced acid/base cooperation of medium strength sites and a small amount (<100 μmol g-1 ) of very strong basic sites (Qdiff >150 kJ mol-1 ).

Influence of Catalyst Acid/Base Properties in Acrolein Production by Oxidative Coupling of Ethanol and Methanol.

Oxidative coupling of methanol and ethanol represents a new route to produce acrolein. In this work, the overall reaction was decoupled in two steps, the oxidation and the aldolization, by using two consecutive reactors to investigate the role of the acid/base properties of silica-supported oxide catalysts. The oxidation of a mixture of methanol and ethanol to formaldehyde and acetaldehyde was performed over a FeMoOx catalyst, and then the product mixture was transferred without intermediate separation to a second reactor, in which the aldol condensation and dehydration to acrolein were performed over the supported oxides. The impact of the acid/base properties on the selectivity towards acrolein was investigated under oxidizing conditions for the first time. The acid/base properties of the catalysts were investigated by NH3 -, SO2 -, and methanol-adsorption microcalorimetry. A MgO/SiO2 catalyst was the most active in acrolein production owing to an appropriate ratio of basic to acidic sites.

ChemInform Abstract: Applications of Metal Nanopore Catalysts in Organic Synthesis

AbstractReview: [129 refs.

Applications of Metal Nanopore Catalysts in Organic Synthesis

Reducing the size of bulk metals to nanometer scale can result in the display of extraordinary physical and chemical properties. Typically, metal nanoparticles (MNPs) are prepared from metal atoms or metal salts and show remarkable catalytic properties. Metal nanopores (MNPores) are prepared through a totally reverse approach (from bulk metal to nanosized metal): alloy M¹M² is fabricated from metal M¹ and metal M², and then dealloying of M² results in a nanoporous framework of metal M¹. This account summarizes MNPore-catalyzed reactions developed in our group, and their comparison with other representative catalytic reactions. 1 Introduction 1.1 Fabrication and Structural Characteristics of Nanoporous Gold 2 Oxidation Reactions 2.1 Oxidation of Alcohols 2.2 Synthesis of Formamides Through Oxidative Coupling of Methanol with Amines 2.3 Oxidation of Silanes 3 Reduction Reactions 3.1 Semihydrogenation of Alkynes 3.2 Reduction of Quinoline 3.3 Reduction of Imines and Reductive Amination of Carbonyls 3.4 Reduction of α,β-Unsaturated Aldehydes 3.5 1,4-Hydrosilylation of Cyclic Enones 4 Formation of C–Si, C–B, and C–C Bonds Using Alkynes 4.1 Hydrosilylation of Alkynes 4.2 Diboration of Alkynes 4.3 Benzannulation Reaction 5 CuNPore-Catalyzed Click Reaction 6 Suzuki, Negishi and Heck Coupling Reactions 7 Concluding Remarks

Methyl ester synthesis catalyzed by nanoporous gold: from 10−9 Torr to 1 atm

Highly selective synthesis of methyl esters can be achieved by oxidative coupling of methanol and aldehydes (acetaldehyde, butyraldehyde) under mild conditions using unsupported nanoporous gold catalysts over a wide pressure range (from 10−9 Torr to 1 atm).

Dealloying Shows the Way to New Catalysts

The preparation of highly effective catalysts by dealloying Au–Ag alloys was recently reported, and is discussed in this Highlight. The nanoporous gold catalysts are highly effective for the gas-phase oxidative coupling of methanol to form methyl formate under mild reaction conditions; the reaction is shown to proceed through a formate intermediate.