Partial Oxidation Of Alcohols Research Articles

Two-Dimensional Bimetallic Hydroxide Nanostructures for Catalyzing Low-Temperature Aerobic C–H Bond Activation in Alkylarene and Alcohol Partial Oxidation

Two-dimensional (2D) bimetallic NixMn1–x(OH)y layered double hydroxide (LDH) nanostructures were synthesized and optimized as a remarkably active catalytic platform for low-temperature aerobic C–H bond activation in alkylarenes and partial oxidation of alcohols using a wide substrate (i.e., reactant) and diverse solvent scope. The NixMn1–x(OH)y structure consists of nonprecious and earth-abundant metals that can effectively operate at low catalyst loadings, requiring only molecular oxygen as the stoichiometric oxidant. Structurally diverse alkylarenes as well as primary and secondary alcohols were shown to be competent substrates where oxidation products were obtained in excellent yields (93–99%). Comprehensive catalyst structural characterization via XRD, ATR-IR, TEM, EDX, XPS, BET, and TGA indicated that the ultimately optimized Ni0.6Mn0.4(OH)y-9S catalyst possessed not only particular rotational faults in its β-Ni0.6Mn0.4(OH)y domains but also distinct α/β-Ni0.6Mn0.4(OH)y interstratification disorders, in addition to a relatively high specific surface area of 125 m2/g, a 2D platelet morphology, and an average Mn oxidation state of +3.5, suggesting the presence of both Mn3+ and Mn4+ species in its structure working in a synergistic fashion with the Ni2+/x+ cations (the latter is justified by the lack of catalytic activity in the monometallic LDH catalysts Ni(OH)2 and Mn(OH)2). Kinetic isotope effect studies carried out in the fluorene oxidation reaction (kH/kD = 5.7) revealed that the rate-determining step of the catalytic oxidation reaction directly involved the scission of a C–H bond. Moreover, the optimized catalyst was demonstrated to be reusable through the application of a regeneration protocol, which can redeem the full initial activity of the carbon-poisoned spent catalyst in the fluorene oxidation reaction.

Coupled CO2 reduction and Alcohol Oxidation for Fuel Synthesis and CO2 Utilization

Electro-conversion CO2 to fuels like formic acid, methanol, and ethanol is an attractive method to recycle CO2 and close the carbon cycle associated with these fuels, which could benefit the environment, national energy security Many CO2 electrolyzers oxidize water or hydroxyl ions as a counter reaction which releases oxygen. However, this can lead to a large cell potential due to oxygen’s large, positive reduction potential. Further, oxygen is a relatively low-value product. These systems also use an ion exchange membrane to prevent crossover of CO2 reduction products to the anode while conducting ions between the electrodes.Instead of oxygen evolution, the partial oxidation of alcohols could serve as the anodic counter reaction to synthesize oxygenated fuel additives. Partial alcohol oxidation could be coupled with CO2 reduction which could regenerate the alcohol. Coupling the anodic and cathodic reactions in this way could preclude the need for an ion exchange membrane, and lower required energy input by decreasing the thermodynamic cell voltage. Our system is also capable of high-pressure operation, which could allow higher concentrations of CO2 in the electrolyte. This study examines the use of alcohol/water mixtures as a working fluid for a CO2 electrolyzer, and the effect of pressure and catalyst composition on the current density and product selectivity. Linear sweep voltammetry and chronoamperometry will be used to evaluate the current densities and cell voltages for different catalysts at pressures up to 90 bar. Gas and liquid products will be analyzed following chronoamperometry studies to determine the faradaic efficiencies. Noble and transition metal catalysts will be used at the cathode and anode based on their purported ability to drive CO2 reduction to alcohol and partial oxidation of alcohols.

Silver catalysts for the partial oxidation of alcohols

The review analyzes state of the art in the partial oxidation of alcohols to carbonyl compounds over Ag catalysts, including the partial oxidation of methanol to formaldehyde, oxidation of ethylene glycol to glyoxal, and oxidation of ethanol to acetaldehyde. For the methanol oxidation process, conditions for implementing the BASF and ICI technologies are considered and the entire chain of transformations from natural gas to formaldehyde is estimated in terms of exergy. When considering modern kinetic studies for the partial oxidation of alcohols on silver, some recent publication are analyzed, particularly those devoted to the application of a ring-shaped reactor to suppress the homogeneous steps of formaldehyde decomposition, the development of a new approach to simulation of the process taking into account different reactivity of the catalyst, and the creation of a simulator to calculate the methanol oxidation process using a neural network with a genetic algorithm. Main steps in the development of a technology for the partial oxidation of ethylene glycol to glyoxal on Ag catalysts are briefly described. The author analyzes modern experimental and theoretical works devoted to the formation mechanisms of oxygencontaining active sites on the silver surface and their involvement in the conversion of alcohols to carbonyl compounds, as well as the new Ag-containing catalytic compositions.

Photoconversion of 2-Propanol on Rutile Titania: A Combined Liquid-Phase and Surface Science Study

A fundamental reaction in industries for producing aldehydes and ketones is the partial oxidation of alcohols. As a model reaction, we investigated the photo-oxidation of 2-propanol on rutile titan...

Partial Oxidation of Alcohols on Visible-Light-Responsive WO3 Photocatalysts Loaded with Palladium Oxide Cocatalyst

Particles of tungsten oxide loaded with a palladium oxide cocatalyst (PdOx/WO3) exhibit higher selectivity in comparison to other photocatalysts, such as Pt/WO3, Pd/TiO2, and Pt/TiO2, in the partial oxidation of alcohols such as 2-propanol to the corresponding aldehydes or ketones (e.g., 80% selectivity for acetone production with ca. 96% conversion of 2-propanol) in water containing molecular O2. A detailed investigation of 2-propanol oxidation as a model reaction revealed significant differences between the reactivities of the WO3 and TiO2 systems. On TiO2 photocatalysts, complete decomposition to CO2 proceeded readily, due to the occurrence of direct oxidation of 2-propanol and acetone adsorbed by holes, resulting in significantly low selectivity for partial oxidation. On the other hand, the rates of acetone peroxidation on WO3 photocatalysts were much lower than those on TiO2 due to the low affinity of the WO3 surface to the substrates, particularly acetone. The low affinity of the WO3 surface also en...

Designing for selectivity: weak interactions and the competition for reactive sites on gold catalysts.

A major challenge in heterogeneous catalysis is controlling reaction selectivity, especially in complex environments. When more than one species is present in the gas mixture, the competition for binding sites on the surface of a catalyst is an important factor in determining reaction selectivity and activity. We establish an experimental hierarchy for the binding of a series of reaction intermediates on Au(111) and demonstrate that this hierarchy accounts for reaction selectivity on both the single crystal surface and under operating catalytic conditions at atmospheric pressure using a nanoporous Au catalyst. A partial set of measurements of relative binding has been measured by others on other catalyst materials, including Ag, Pd and metal oxide surfaces; a comparison demonstrates the generality of this concept and identifies differences in the trends. Theoretical calculations for a subset of reactants on Au(111) show that weak van der Waals interactions are key to predicting the hierarchy of binding strengths for alkoxides bound to Au(111). This hierarchy is key to the control of the selectivity for partial oxidation of alcohols to esters on both Au surfaces and under working catalytic conditions using nanoporous gold. The selectivity depends on the competition for active sites among key intermediates. New results probing the effect of fluorine substitution are also presented to extend the relation of reaction selectivity to the hierarchy of binding. Motivated by an interest in synthetic manipulation of fluorinated organics, we specifically investigated the influence of the -CF3 group on alcohol reactivity and selectivity. 2,2,2-Trifluoroethanol couples on O-covered Au(111) to yield CF3CH2O-C([double bond, length as m-dash]O)(CF3), but in the presence of methanol or ethanol it preferentially forms the respective 2,2,2-trifluoroethoxy-esters. The ester is not the dominant product in any of these cases, though, indicating that the rate of β-H elimination from adsorbed trifluoroethoxy is slower than that for either adsorbed methoxy or ethoxy, consistent with their relative estimated β-C-H bond strengths. The measured equilibrium constants for the competition for binding to the surface are 2.9 and 0.38 for ethanol and methanol, respectively, vs. 2,2,2-trifluoroethanol, indicating that the binding strength of 2,2,2-trifluoroethoxy is weaker than ethoxy, but stronger than methoxy. These results are consistent with weakening of the interactions between the surface and the alkyl group due to Pauli repulsion of the electron-rich CF3 group from the surface, which offsets the van der Waals attraction. These experiments provide guiding principles for understanding the effect of fluorination on heterogeneous synthesis and further demonstrate the key role of molecular structure in determining reaction selectivity.

Partial Oxidation of Alcohols with O2 Catalyzed by Ru0/Al2O3

Abstract Partial oxidation of alcohols was performed over Ru/Al2O3 using O2 as the oxidizing agent. The catalytic activity increased with an increase in the thermal treatment temperature under both N2 and H2. The highest activity was attained by the sample treated at 1073 K in H2. Further enhancement in the activity was achieved by washing the catalyst with aqueous NH3. The catalyst could be reused after additional pretreatment with H2. Based on X-ray absorption fine structure (XAFS), CO adsorption, and transmission electron microscopy (TEM) analysis, the active species was determined to be highly dispersed 1.6 nm Ru0 particles.

Carbon-coated magnetic palladium: applications in partial oxidation of alcohols and coupling reactions

A carbon-coated magnetic Pd catalyst has been synthesized via in situ generation of nanoferrites and incorporation of carbon from renewable cellulose via calcination; the catalyst can be used for oxidation of alcohols, amination reaction and arylation of aryl halides (cross-coupling reaction).

Development of Nanoalloy Catalysts for Realization of Carbon-Neutral Energy Cycles

Increase of CO2 concentration in the atmosphere is one of reasons for the global warming. Development of energy circulation systems, which do not emit CO2 in the atmosphere, is an emergent issue for present-generation scientists [1]. As an answer, we have proposed a new type of energy circulation system, namely, carbon-neutral energy (CN) cycle. With a practical application in mind, three limitations are imposed on the CN cycle; (1) no CO2 emissions, (2) utilization of liquid fuels and (3) minimizing the use of precious metal catalysts. In anticipation of a practical use in the near future, an alkaline fuel cell will be adapted for the CN cycle where non-platinum catalysts can work. For our purpose, electric power will be generated by partial oxidation of alcohols to carboxylic acids.[2] In view of ease in handling, fuels having a high boiling point (b.p.) are favorable for the CN cycles. To this end, glycol (EG) of which b.p. is 470 K an ideal candidate as a fuel. In this case, an oxidized product of EG can be oxalic acid. Compared to the energy obtained by the complete oxidation of EG into CO2, we can derive ca. 80 % of energy even in the partial oxidation of EG to oxalic acid, implying that the EG/oxalic cycle possibly works as an energy cycle. We herein show an example of selective EG oxidation catalysts working in alkaline conditions.

Oxygen and Hydroxyl Species Induce Multiple Reaction Pathways for the Partial Oxidation of Allyl Alcohol on Gold

Partial oxidation of alcohols is a topic of great interest in the field of gold catalysis. In this work, we provide evidence that the partial oxidation of allyl alcohol to its corresponding aldehyde, acrolein, over oxygen-precovered gold surfaces occurs via multiple reaction pathways. Utilizing temperature-programmed desorption (TPD) with isotopically labeled water and oxygen species, reactive molecular beam scattering, and density functional theory (DFT) calculations, we demonstrate that the reaction mechanism for allyl alcohol oxidation is influenced by the relative proportions of atomic oxygen and hydroxyl species on the gold surface. Both atomic oxygen and hydroxyl species are shown to be active for allyl alcohol oxidation, but each displays a different pathway of oxidation, as indicated by TPD measurements and DFT calculations. The hydroxyl hydrogen of allyl alcohol is readily abstracted by either oxygen adatoms or adsorbed hydroxyl species on the gold surface to generate a surface-bound allyloxide intermediate, which then undergoes α-dehydrogenation via interaction with an oxygen adatom or surface hydroxyl species to generate acrolein. Mediation of a second allyloxide with the hydroxyl species lowers the activation barrier for the α-dehydrogenation process. A third pathway exists in which two hydroxyl species recombine to generate water and an oxygen adatom, which subsequently dehydrogenates allyloxide. This work may aid in the understanding of oxidative catalysis over gold and the effect of water therein.

Role of Surface-Bound Intermediates in the Oxygen-Assisted Synthesis of Amides by Metallic Silver and Gold

A general mechanism for the oxygen-assisted synthesis of amides over metallic gold and silver surfaces has been derived from the study of acetaldehyde and dimethylamine in combination with previous work, allowing detailed comparison of the two surfaces' reactivities. Facile acetylation of dimethylamine by acetaldehyde occurs with high selectivity on oxygen-covered silver and gold (111) crystals via a common overall mechanism with different rate-limiting steps on the two metals. Adsorbed atomic oxygen activates the N-H bond of the amine leading to the formation of an adsorbed amide, which attacks the carbonyl carbon of the aldehyde, forming an adsorbed hemiaminal. Because aldehydes are known to form readily from partial oxidation of alcohols, our mechanism also provides insight into the related catalytic coupling of alcohols and amines. The hemiaminal β-H eliminates to form the coupled amide product. On silver, β-H elimination from the hemiaminal is rate-limiting, whereas on gold desorption of the amide is the slow step. Silver exhibits high selectivity for the coupling reaction for adsorbed oxygen concentrations between 0.01 and 0.1 monolayer, whereas gold exhibits selectivity more strongly dependent on oxygen coverage, approaching 100% at 0.03 monolayer. The selectivity trends and difference in rate-limiting steps are likely due to the influence of the relative stability of the adsorbed hydroxyl groups on the two surfaces. Low surface coverages of oxygen lead to the highest selectivity. This study provides a general framework for the oxygen-assisted coupling of alcohols and aldehydes with amines over gold- and silver-based catalysts in either the vapor or the liquid phase.

Graphical Abstracts

Synth. Commun. 2004, 34, 1753 Partial Oxidation of Alcohols to Aldehydes and Ketones Under Mild Conditions Guang Qian, Rui Zhao, Gaomeng Lu, Yanxing Qi,* and Jishuan Suo Lanzhou Institute of Chemical Physics, The Chinese Academy of Sciences, Lanzhou, P.R. China A number of aldehydes and ketones were prepared by partial oxidation of alcohols in air catalyzed by RuO2/ZSM‐5 which can be easily prepared with the industrial grade ZSM‐5 and RuCl3 · xH2O.

Partial Oxidation of Alcohols to Aldehydes and Ketones Under Mild Conditions

A number of aldehydes and ketones were prepared by partial oxidation of alcohols in air catalyzed by RuO2/ZSM‐5 which can be easily prepared with the industrial grade ZSM‐5 and RuCl3 · xH2O.

Partial oxidation of alcohols in supercritical carbon dioxide

Oxidation of water-insoluble alcohols in supercritical CO2 over a Pd–Pt–Bi/C catalyst in a continuous fixed bed reactor affords high reaction rates and yields up to 98% of the corresponding ketones, aromatic and α,β-unsaturated aliphatic aldehydes, without the risk of using a flammable organic solvent.

Catalytic Partial Oxidation of Alcohols in the Vapor Phase—III1,2

Catalytic Partial Oxidation of Alcohols in the Vapor Phase—III^1,2