CH3OH Oxidation Research Articles

Oxidation of methanol and total reduced sulfur compounds with ozone over V 2O 5/TiO 2 catalyst: Effect of humidity

The purpose of this study was to investigate the feasibility of using ozone-enhanced catalytic oxidation for the treatment of high volume, low concentration (HVLC) waste gas streams at a Kraft pulp and paper mill that contain hazardous air pollutants such as methanol (CH 3OH), reduced sulfur compounds (TRS), including dimethyl sulfide (DMS), dimethyl disulfide (DMDS), methanethiol (MT), hydrogen sulfide (H 2S), and saturated with moisture. This paper reports that ozone-enhance V 2O 5-TiO 2 catalyzed oxidation is a stable and effective process to remove methanol and TRS compounds in the presence of moisture that has composition similar to the effluent stream coming out of a pulp mill blow tank. The effect of moisture on the oxidation of CH 3OH, MT and DMS was studied using V 2O 5/TiO 2 as a catalyst at different feed compositions (C methanol: 1000 and 7500 ppm; C DMS: 250 and 1000 ppm; and C MT: 250 and 1000 ppm) and gas hourly space velocities (37,000–150,000 h −1) at 250 °C and O 3-to-substrate mole ratio of 2.1. Conversions of methanol and TRS compounds were high and the main products were CO 2, CO and SO 2 with small amounts of partial oxidation products. Increasing the relative humidity of the gas stream from zero to 18,000 ppm reduced the conversion of methanol, whereas the conversion of TRS compounds was not affected, although the selectivity for partial oxidation products of TRS compounds decreased. High moisture levels have inhibition effect on the reactions because of competitive adsorption of methanol and water on to the same sites. The increase in the complete oxidation of TRS products could be due to forming hydroxyl ion radicals in presence of ozone and water molecules. Possible reaction mechanisms have been proposed for the complete oxidation of methanol and TRS compounds with ozone based on the product distribution.

Effects of iron and cerium in La1−yCeyCo1−xFexO3 perovskites as catalysts for VOC oxidation

Perovskite-type mixed oxides La1−yCeyCo1−xFexO3 with high specific surface area were prepared by reactive grinding. These catalysts were characterized by N2 adsorption, X-ray diffraction, oxygen storage capacity (OSC), H2-temperature-programmed reduction (TPR-H2), O2-, and CH3OH-temperature-programmed desorption (TPD). The catalytic performance of the samples for volatile organic compounds (VOC), CH3OH, CO and CH4 oxidation was evaluated. Cerium allows an enhancement of the reducibility of the B-site cations in perovskite structure during OSC and TPR-H2 and an increase in the amount of β-O2 desorbed during TPD-O2. As opposed to cerium, the addition of iron in the perovskite structure causes a drop in B-site cations reducibility and a decrease of the oxygen mobility in the bulk. As a consequence, the catalytic activity in VOC oxidation is enhanced by introduction of cerium and weakened by iron in the lattice.

Mechanism of Visible Light Photocatalytic Oxidation of Methanol in Aerated Aqueous Suspensions of Carbon-Doped TiO2

Visible photolysis of aerated carbon-doped TiO2 (C-TiO2) aqueous suspensions induces methanol oxidation to formaldehyde. The rate of HCHO formation increases with the concentration of CH3OH or C-TiO2 and is nearly doubled in the presence of catalase or excess of H2O2. The mechanism involves oxidation of CH3OH by surface trapped holes, although these holes have lower energy than those formed upon UV photolysis of undoped TiO2. The C-TiO2 electrons reduce O2 to H2O2. CH3OH oxidation via reduction of H2O2 by the C-TiO2 electrons was observed in the presence of added H2O2, where it competes efficiently with O2 for the C-TiO2 electrons. At [H2O2] > 0.1 mM, the yield of HCHO is about twice that in the absence of added H2O2. Light absorption measurements in an integrating sphere show that the limiting absorption fraction at high [C-TiO2] is 0.5 at 450 nm, the rest of the light being mostly scattered backward. The HCHO quantum yield depends on the square root of the absorbed light density and is only a few percent at the intensities used in this work. A parallel photocatalytic decomposition of H2O2 has been observed, which is not associated with HCHO formation.

Methanol oxidation in a flow reactor: Implications for the branching ratio of the CH3OH+OH reaction

AbstractThe oxidation of methanol in a flow reactor has been studied experimentally under diluted, fuel‐lean conditions at 650–1350 K, over a wide range of O2 concentrations (1%–16%), and with and without the presence of nitric oxide. The reaction is initiated above 900 K, with the oxidation rate decreasing slightly with the increasing O2 concentration. Addition of NO results in a mutually promoted oxidation of CH3OH and NO in the 750–1100 K range. The experimental results are interpreted in terms of a revised chemical kinetic model. Owing to the high sensitivity of the mutual sensitization of CH3OH and NO oxidation to the partitioning of CH3O and CH2OH, the CH3OH + OH branching fraction could be estimated as α = 0.10 ± 0.05 at 990 K. Combined with low‐temperature measurements, this value implies a branching fraction that is largely independent of temperature. It is in good agreement with recent theoretical estimates, but considerably lower than values employed in previous modeling studies. Modeling predictions with the present chemical kinetic model is in quantitative agreement with experimental results below 1100 K, but at higher temperatures and high O2 concentration the model underpredicts the oxidation rate. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 423–441, 2008

CH 3OH oxidation over well-defined supported V 2O 5/Al 2O 3 catalysts: Influence of vanadium oxide loading and surface vanadium–oxygen functionalities

A series of supported V 2O 5/Al 2O 3 catalysts were synthesized by incipient wetness impregnation with vanadium isopropoxide in isopropanol solutions and subsequent calcination. The vanadium surface density was varied from 0.3 to 11.4 V atoms/nm 2 spanning the sub-monolayer and above-monolayer regions. The resulting supported vanadium oxide catalysts were physically characterized with in situ Raman spectroscopy and chemically probed by CH 3OH TPSR and steady-state methanol oxidation. The Raman characterization under dehydrated conditions revealed that the supported vanadium oxide catalysts contained only surface vanadia species below monolayer coverage (100% dispersed) and both surface vanadia species and crystalline V 2O 5 nanoparticles (NPs) above monolayer coverage. The CH 3OH oxidative dehydrogenation kinetic parameters were found to be independent of the surface bridging V O V bond concentration (polymerization extent), surface V O bond length/strength, vanadium surface density on the alumina support, surface acidity, and surface vanadia reduction characteristics during H 2-TPR. The crystalline V 2O 5 NPs above monolayer coverage were relatively inactive and served only to decrease the number of exposed catalytic active surface vanadia sites by covering them.

Phase transfer catalysis: Synthesis of monodispersed FePt nanoparticles and its electrocatalytic activity

Using dibenzo-24-crown-8-ether (DB24C8) as phase transfer catalyst, the monodispersed iron–platinum (FePt) alloy nanoparticles with size of ∼17 nm were synthesized by reduction of H 2PtCl 6·6H 2O and FeCl 2·4H 2O in the solvothermal system. The structure, magnetic property and electrocatalytic activity of FePt nanoparticles were characterized by transmission electron microscopy (TEM), X-ray diffraction system (XRD), vibration sample magnetometer (VSM) and CHI 820 electrochemical analyser (three electrodes system, the reference electrode is saturated calomel electrode (SCE), the counter electrode is platinum electrode and the glassy carbon electrode is used as working electrode (GCE)), respectively. The results show that the as-synthesized FePt nanoparticles have a chemically disordered fcc structure and can be transformed into chemically ordered fct structure after annealing treatment above 400 °C, simultaneously accompanying with the coercivity changed from 5 to 2400 Oe. CVs of 0.5 M H 2SO 4/0.5 M CH 3OH on GCE modified with FePt nanoparticles monolayer illustrate that the as-synthesized FePt nanoparticles have strong electrocatalytic activity toward the oxidation of CH 3OH in aqueous solution.

Design of High‐Quality Pt–CeO2 Composite Anodes Supported by Carbon Black for Direct Methanol Fuel Cell Application

A Pt on nano‐sized CeO2 particles that in turn are supported on carbon black (CB) was synthesized using the co‐impregnation method. This potential anode material for fuel cell applications was synthesized in a stepwise process. The pure CeO2 was synthesized using an ammonium carbonate precipitation method, and the Pt particles dispersed on the CeO2 in such a way that a uniform dispersion with the CB was obtained (Pt–CeO2/CB). The electrochemical activity of the methanol (CH3OH) oxidation reaction on the Pt–CeO2/CB was investigated using cyclic voltammetry and chronoamperometry experimentation. The onset potential of CH3OH oxidation reaction on the Pt–CeO2/CB anode was shifted to a lower potential as compared with that on commercially available Pt–Ru/carbon (C) alloy anode. In addition, the activation energy of the Pt–CeO2/CB anode was much lower than that of the Pt–Ru/C alloy anode. Moreover, the current density of the Pt–CeO2/CB anode was much higher than that of the Pt–Ru/C alloy anode at temperatures between 28° and 60°C. These results suggest that the anode performance of the Pt–CeO2/CB anode at the operating temperature of typical fuel cells (80°C) is superior to that of the more usual Pt–Ru/C alloy anode. Importantly, the rare metal, Ru, is not required in the present anode material and the amount of Pt required is also significantly reduced. As a consequence, we report a promising candidate Pt–CeO2/CB composite anode for application in the development of direct methanol fuel cells.

Mechanism of methanol oxidation by quinoprotein methanol dehydrogenase

At neutral pH, oxidation of CH(3)OH --> CH(2)O by an o-quinone requires general-base catalysis and the reaction is endothermic. The active-site -CO(2)(-) groups of Glu-171 and Asp-297 (Glu-171-CO(2)(-) and Asp-297-CO(2)(-)) have been considered as the required general base catalysts in the bacterial o-quinoprotein methanol dehydrogenase (MDH) reaction. Based on quantum mechanics/molecular mechanics (QM/MM) calculations, the free energy for MeOH reduction of o-PQQ when MeOH is hydrogen bonded to Glu-171-CO(2)(-) and the crystal water (Wat1) is hydrogen bonded to Asp-297-CO(2)(-) is DeltaG++ = 11.7 kcal/mol, which is comparable with the experimental value of 8.5 kcal/mol. The calculated DeltaG++ when MeOH is hydrogen bonded to Asp-297-CO(2)(-) is >50 kcal/mol. The Asp-297-CO(2)(-)...Wat1 complex is very stable. Molecular dynamics (MD) simulations on MDH.PQQ.Wat1 complex in TIP3P water for 5 ns does not result in interchange of Asp-297-CO(2)(-) bound Wat1 for a solvent water. Starting with Wat1 removed and MeOH hydrogen bonded to Asp-297-CO(2)(-), we find that MeOH returns to be hydrogen bonded to Glu-171-CO(2)(-) and Asp-297-CO(2)(-) coordinates to Ca(2+) during 3 ns simulation. The Asp-297-CO(2)(-)...Wat1 of reactant complex does play a crucial role in catalysis. By QM/MM calculation DeltaG++ = 1.1 kcal/mol for Asp-297-CO(2)(-) general-base catalysis of Wat1 hydration of the immediate CH(2)==O product --> CH(2)(OH)(2). By this means, the endothermic oxidation-reduction reaction is pulled such that the overall conversion of MeOH to CH(2)(OH)(2) is exothermic.

A comprehensive kinetic mechanism for CO, CH2O, and CH3OH combustion

AbstractNew experimental profiles of stable species concentrations are reported for formaldehyde oxidation in a variable pressure flow reactor at initial temperatures of 850–950 K and at constant pressures ranging from 1.5 to 6.0 atm. These data, along with other data published in the literature and a previous comprehensive chemical kinetic model for methanol oxidation, are used to hierarchically develop an updated mechanism for CO/H2O/H2/O2, CH2O, and CH3OH oxidation. Important modifications include recent revisions for the hydrogen–oxygen submechanism (Li et al., Int J Chem Kinet 2004, 36, 565), an updated submechanism for methanol reactions, and kinetic and thermochemical parameter modifications based upon recently published information. New rate constant correlations are recommended for CO + OH = CO2 + H (R23) and HCO + M = H + CO + M (R24), motivated by a new identification of the temperatures over which these rate constants most affect laminar flame speed predictions (Zhao et al., Int J Chem Kinet 2005, 37, 282). The new weighted least‐squares fit of literature experimental data for (R23) yields k23 = 2.23 × 105T1.89exp(583/T) cm3/mol/s and reflects significantly lower rate constant values at low and intermediate temperatures in comparison to another recently recommended correlation and theoretical predictions. The weighted least‐squares fit of literature results for (R24) yields k24 = 4.75 × 1011T0.66exp(−7485/T) cm3/mol/s, which predicts values within uncertainties of both prior and new (Friedrichs et al., Phys Chem Chem Phys 2002, 4, 5778; DeSain et al., Chem Phys Lett 2001, 347, 79) measurements. Use of either of the data correlations reported in Friedrichs et al. (2002) and DeSain et al. (2001) for this reaction significantly degrades laminar flame speed predictions for oxygenated fuels as well as for other hydrocarbons. The present C1/O2 mechanism compares favorably against a wide range of experimental conditions for laminar premixed flame speed, shock tube ignition delay, and flow reactor species time history data at each level of hierarchical development. Very good agreement of the model predictions with all of the experimental measurements is demonstrated. © 2007 Wiley Periodicals, Inc. 39: 109–136, 2007

A study of formaldehyde formation during methanol oxidation over PtRu bulk alloys and nanometer scale catalyst

The oxidation of 1.0 M CH3OH in 0.1 M H2SO4 was carried out over PtRu bulk alloy and nanometer scale catalyst materials. The H2CO produced as a stable by-product during brief (180 s) electrolysis periods was determined quantitatively for potentials (measured vs a reversible hydrogen electrode reference) in the range of 0.5–0.8 V. Electrolysis was performed in a cell that accommodated a small (∼50 μL) sample volume. The experimental conditions kept the reactant depletion in the cell below 1%. Three arc melted bulk alloys were employed with respective Ru mole fractions (XRu) of 0.1, 0.3 and 0.9. The alloy surfaces were cleaned by bench top methods prior to measurements. For reaction potentials ⩾0.7 V, H2CO yields tended to become lower as the Ru content of the alloy electrode increased. However, at low (0.5 V) potentials the H2CO yields were at a minimum in reactions over the XRu = 0.3 bulk alloy. The oxidation of CH3OH over bulk polycrystalline Pt produced H2CO yields that were greater than those of the PtRu alloys, with the largest differences occurring for the XRu = 0.3 sample. For CH3OH oxidation over nanometer scale PtRu catalyst, the metal loadings (50–100 μg/cm2) were in a range known to be favorable for conversion of CH3OH to CO2 owing to a porous, multilayer structure formed by the particles on the support (Au) electrode which enables partial oxidation products to undergo multiple encounters with catalytic sites within the film. The nanometer scale catalyst materials studied (Pt and PtRu with XRu ≈ 0.1, 0.25 and 0.5) produced H2CO yields below 10% for all reaction potentials. Although the H2CO yields were low, trends similar to those of the bulk materials are apparent.

Structure and redox properties of Ce xPr 1− xO 2− δ mixed oxides and their catalytic activities for CO, CH 3OH and CH 4 combustion

A series of Ce x Pr 1− x O 2− δ mixed oxides were synthesized by a sol–gel method and characterized by Raman, XRD and TPR techniques. The oxidation activity for CO, CH 3OH and CH 4 on these mixed oxides was investigated. When the value x was changed from 1.0 to 0.8, only a cubic phase CeO 2 was observed. The samples were greatly crystallized in the range of the value x from 0.99 to 0.80, which is due to the formation of solid solutions caused by the complete insertion of Pr into the CeO 2 crystal lattices. Raman bands at 465 and 1150 cm −1 in Ce x Pr 1− x O 2− δ samples are attributed to the Raman active F 2g mode of CeO 2. The broad band at around 570 cm −1 in the region of 0.3 ≤ x ≤ 0.99 can be linked to oxygen vacancies. The new band at 195 cm −1 may be ascribed to the asymmetric vibration caused by the formation of oxygen vacancies. The TPR profile of Pr 6O 11 shows two reduction peaks and the reduction process is followed: Pr O 1.83 ⟶ 530 ° C Pr O 1.61 ⟶ 650 ° C Pr O 1.5 . The reduction temperature of Ce x Pr 1− x O 2− δ mixed oxides is lower than those of Pr 6O 11 or CeO 2. TPR results indicate that Ce x Pr 1− x O 2− δ mixed oxides have higher redox properties because of the formation of Ce x Pr 1− x O 2− δ solid solutions. The presence of the oxygen vacancies favors CO and CH 3OH oxidation, while the activity of CH 4 oxidation is mostly related to reduction temperatures and redox properties.

Design of Electrocatalysts for Fuel Cells and the Catalyses

It is essential to develop high performance Pt electrocatalysts and to reduce the amounts used in polymer electrolyte fuel cells. Design of high performance cathode alloy catalysts for O2 reduction and anode alloy catalysts for highly CO-tolerant H2 oxidation as well as direct CH3OH oxidation will be introduced, based on the results investigated by our group. Problems accompanied with practical catalysts highly dispersed on carbon black supports and some solutions to the problems will also be discussed.

Carbon nanotubes with Pt–Ru catalyst for methanol fuel cell

Multiwalled carbon nanotubes (NTs) have been used as an attractive support of catalytic metallic particles for methanol electrooxidation in acidic medium. Pt–Ru (50:50) nanoparticles were deposited on the different type of nanotubular materials to select the best support and to estimate the efficiency of CH 3OH oxidation. Pt–Ru supported on NTs graphitized at 2500 °C supply the optimal voltage/current characteristics with a maximum current load of 2.7 A/g. Mesoporous network of nanotubes combined with their excellent conducting properties allows a quick transport and easy accessibility of the reagent molecules to the catalytic sites of electrode interface giving a good performance of methanol anode.

Comparative studies of a single cell and a stack of direct methanol fuel cells

Comparative studies have been conducted to observe the characteristics of a single cell and a stack of direct methanol fuel cells (DMFC) at ambient conditions. The maximum power density of a single cell was about 70 mW/ cm2 at 2M methanol (CH3OH) of 3.75 cc/min and dry air of 250 cc/min at room temperature and atmospheric pressure. In a stack, on the other hand, the maximum power density of the stack was 85mW/cm2 which was about a 20% higher value. This could be attributed to higher internal temperature than that of the single cell: the temperature of single cell increased up to 35 °C, while the highest temperature of the stack was 69 °C. This is because the cell temperature in DMFC was autonomously increased by exothermal reaction such as chemical oxidation of CH3OH and oxygen reduction. The temperature was strongly dependent on the number of unit cells in a stack and the amount of electric load applied. In DMFC stacks, the performance of an individual cell showed uneven distribution when the electric load was increased and it was mostly influenced by different local concentration of reactants and non-uniform temperature

Influence of plasma reactor structure on methanol oxidation

AbstractPlasma oxidation of methanol (CH3OH) in oxygen and nitrogen was investigated using two dielectric barrier discharge (DBD) reactors with or without Al2O3 as a catalyst and using a DC circle‐to‐plate (CTP) reactor. An AC power supply was used for the DBD reactors to generate corona discharges. A DC power supply, a 20‐MΩ resistor, and a 100‐pF capacitor were used to yield pulselike discharges. CH3OH was oxidized to formaldehyde (HCHO), carbon monoxide (CO), and carbon dioxide (CO2). HCHO was the main product when using DBD reactors and without Al2O3. CO was the main product when using the DBD reactor with Al2O3 and CTP reactor. Al2O3 could inhibit CH3OH further oxidation. The energy efficiency of the DBD reactors decreased with increasing power input and power density. The energy efficiency of the CTP reactor peaked with 7 g CH3OH/kWh that was three times as high as that with the DBD reactors at the same power input. Furthermore, the power density of the CTP reactor was higher than that of the DBD reactors, implying that the CTP reactor could be used for CH3OH oxidation with a small discharge space volume. © 2005 American Institute of Chemical Engineers AIChE J, 2005

Homogeneous, catalytic, oxidative coupling of methane to acetic acid in one step

Acetic acid is an important petrochemical that is currently produced from methane (or coal) in a three-step process based on carbonylation of methanol. We report a direct, selective, oxidative condensation of two methane molecules to acetic acid at 180°C in concentrated sulfuric acid. 13C isotopic labeling studies show that both carbons of acetic acid originate from two methane molecules in a formal eight-electron redox reaction. The reaction is catalyzed by palladium and the results are consistent with the reaction occurring by tandem catalysis involving methane C–H activation to generate Pd-CH3 species, followed by efficient oxidative carbonylation with methanol, generated in situ from methane, to produce acetic acid. Control Experiments suggest that the carbonylation occurs via the in situ oxidation of CH3OH to low levels of CO.

Note on the oxidation of methanol at Pt(1 1 1) and Pt(3 3 2) electrodes in alkaline solutions

The cyclic voltammetric behavior of different concentrations of CH 3OH has been studied in alkaline solutions on Pt(1 1 1) and Pt(3 3 2). The oxidation of CH 3OH gives well-defined current density–potential curves at around the potential where the adsorption of OH occurs on Pt. The current–potential behavior of the hydrogen adsorption–desorption shows that CH 3OH or related species adsorbs on the step sites of (3 3 2) surface, but less on the (1 1 1) surface. The analysis of the voltammograms with less concentrated methanol solutions is suggested in order to understand the mechanism of CH 3OH oxidation reaction in alkaline media.

Kinetics of CH 3OH oxidation on PtRu/C studied by impedance and CO stripping voltammetry

The kinetics of the CH 3OH oxidation reaction at 60 °C on well-alloyed platinum–ruthenium supported on carbon (Pt 50Ru 50/C) was studied by electrochemical impedance spectroscopy and compared with carbon-supported platinum (Pt/C). The reaction rate of the overall CH 3OH oxidation increased with increasing electrode potential for both Pt/C and PtRu/C. In the case of Pt/C, when the electrode potential was E ⩽ 450 mV vs. RHE only a capacitive behavior was observed. Resistive and pseudo-inductive types of behavior were evident above 500 and 600 mV vs. RHE. In the case of PtRu/C, a similar change in behavior was observed, except that the two types of behavior were observed at 200 mV lower electrode potentials than for Pt/C. Correlation of the impedance data with pre-adsorbed carbon monoxide (CO ad) stripping voltammetry allowed the understanding of the methanol oxidation reaction. The change in the reaction rate of the oxidation of CH 3OH to CO ad as a function of the electrode potential as well as the promotional effect of Ru was evident from a change in the frequency where the frequency deviated from the ∼90° phase angle. The change in the reaction rate of the oxidation of CO ad to CO 2 as a function of the electrode potential as well as the alloying with Ru was evident from a change in the frequency where the phase angle approached zero.

Characteristics of adsorbed CO and CH 3OH oxidation reactions for complex Pt/Ru catalyst systems

Pt/Ru powder catalysts of the same nominal Pt to Ru composition were prepared using a range of methods resulting in different catalyst properties. Two PtRu alloy catalysts were prepared, one of which has essentially the same surface and bulk Pt to Ru composition, while the second catalyst is surface enriched with Ru. Two powders consisting of non-alloyed Pt phases and surfaces enriched with Ru were also prepared. The oxidation state of the surface Ru of the latter two catalysts is mainly metallic Ru or Ru-oxides. The catalyst consisting of Ru-oxides was formed at 500 °C. Part of this catalyst was then reduced in a H 2 atmosphere under “mild” conditions, thus catalyst properties such as particle size are not changed, as they are locked in during previous high temperature treatment. The oxidation kinetics of adsorbed CO (CO ads) and solution CH 3OH were studied and compared to the Ru ad-metal state and Pt to Ru site distribution of the as-prepared catalysts. The kinetics of the CO ads oxidation reaction were observed to be slower for the catalyst containing Ru-oxides as opposed to mainly Ru metal. The CH 3OH oxidation activities measured per Pt surface area, i.e., the catalytic activities are better (by ca. seven times) for the alloy catalysts than the non-alloyed Pt/Ru catalysts. The latter two catalysts showed essentially the same catalytic CH 3OH oxidation activities, i.e., independent of the Ru ad-metal oxidation state of the as-prepared catalysts. Furthermore, it is shown that CO ads oxidation experiments can be used to extract characteristics that allow the comparison of catalytic activities for the CO ads oxidation reaction and Pt to Ru site distribution for complex catalyst systems.

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

RuO2 domains supported on SnO2, ZrO2, TiO2, Al2O3, and SiO2 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 RuO2 domains to undergo redox cycles required for oxidation turnovers. Oxidative dehydrogenation turnover rates and rates of stoichiometric reduction of RuO2 in H2 increased in parallel when RuO2 domains were dispersed on more reducible supports. These support effects, the kinetic effects of CH3OH and O2 on reaction rates, and the observed kinetic isotope effects with CH3OD and CD3OD 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 CH3OH dissociation on nearly stoichiometric RuO2 surfaces. Anaerobic transient experiments confirmed that CH3OH oxidation to HCHO requires lattice oxygen atoms and that selectivities are not influenced by the presence of O2. Residence time effects on selectivity indicate that secondary HCHO-CH3OH acetalization reactions lead to hemiacetal or methoxymethanol intermediates that convert to dimethoxymethane in reactions with CH3OH on support acid sites or dehydrogenate to form methylformate on RuO2 and support redox sites. These conclusions are consistent with the tendency of Al2O3 and SiO2 supports to favor dimethoxymethane formation, while SnO2, ZrO2, and TiO2 preferentially form methylformate. These support effects on secondary reactions were confirmed by measured CH3OH oxidation rates and selectivities on physical mixtures of supported RuO2 catalysts and pure supports. Ethanol also reacts on supported RuO2 domains to form predominately acetaldehyde and diethoxyethane at 300-400 K. The bifunctional nature of these reaction pathways and the remarkable ability of RuO2-based catalysts to oxidize CH3OH 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.