Kinetics of the production of chain-end groups and methanol from the depolymerization of cellulose during the ageing of paper/oil systems. Part 1: Standard wood kraft insulation

Recently, the existence of a relation between the rupture of 1,4-β-glycosidic bonds in the cellulose during thermal-ageing of paper/oil systems and the detection of methanol in the oil has been reported for the first time in this journal (Jalbert et al. 2007). The present study addresses the rate constants of the reaction for standard wood kraft papers, two immersed in inhibited naphthenic oil under air (paper/oil weight–volume ratio of 1:18) and one in non-inhibited paraffinic oil under nitrogen (paper/oil weight–volume ratio of 1:30). The isotherms in the range of 60–130 °C show that the initial rate of methanol production markedly increases with temperature and to a lesser extent with the moisture of the specimens (initially between 0.5 and 2.25% (w/w)), similarly to what is noted for the depolymerization through the Ekenstam’s pseudo-zero order model. The Arrhenius expression of the rate constants reveals linear relationships that confirm the dominance of a given mechanism in both cases. A very good agreement is also noted for the activation energy over the entirely paper/oil systems studied (106.9 ± 4.3 and 103.5 ± 3.7 kJ mol^?1 for methanol and scissions, respectively). Furthermore, a comparison of the rate constants $ \left( {k_{{{\text{CH}}_{ 3} {\text{OH}}}} /k_{\text{scissions}} } \right) Recently, the existence of a relation between the rupture of 1,4-β-glycosidic bonds in the cellulose during thermal-ageing of paper/oil systems and the detection of methanol in the oil has been reported for the first time in this journal (Jalbert et al. 2007). The present study addresses the rate constants of the reaction for standard wood kraft papers, two immersed in inhibited naphthenic oil under air (paper/oil weight–volume ratio of 1:18) and one in non-inhibited paraffinic oil under nitrogen (paper/oil weight–volume ratio of 1:30). The isotherms in the range of 60–130 °C show that the initial rate of methanol production markedly increases with temperature and to a lesser extent with the moisture of the specimens (initially between 0.5 and 2.25% (w/w)), similarly to what is noted for the depolymerization through the Ekenstam’s pseudo-zero order model. The Arrhenius expression of the rate constants reveals linear relationships that confirm the dominance of a given mechanism in both cases. A very good agreement is also noted for the activation energy over the entirely paper/oil systems studied (106.9 ± 4.3 and 103.5 ± 3.7 kJ mol⁻¹ for methanol and scissions, respectively). Furthermore, a comparison of the rate constants shows approximately constant values indicating an apparent yield for the methanol of about one-third molecule per every scission for the tests under air (0.27 ± 0.04 for Clupak HD75 and 0.37 ± 0.14 for Munksj? TH70) and even lower for the ones under N₂ (0.12 ± 0.03 for Munksj? E.G.). As expected from a pseudo-zero order model, these values were shown to be consistent with a similar comparison of the amount of CH₃OH and chain-end groups produced under specific time–temperature ageing conditions (168 h at 120 °C). Finally, an additional test carried out with unaged cellulose in contact with a fresh solution of methanol in oil (cellulose/oil weight–volume ratio of 1:18) shows that at equilibrium, over 58% of the species is lost from the solution due to penetration into the fibres. Such results reveal the importance of the species partitioning in establishing the true correspondence between the molecules of CH₃OH produced and the scissions.     

Direct ab initio MD study on the hydrogen abstraction reaction of triplet state acetone from methanol molecule

Solvent re-orientation process of triplet acetone/methanol complex and intermolecular hydrogen atom abstraction reaction on the triplet state energy surface, (CH₃)₂C=O (T₁) + CH₃OH → (CH₃)₂C–OH + CH₂OH in gas phase, have been investigated by means of density functional theory (DFT) and direct ab initio molecular dynamics (MD) methods. The static DFT calculation of hydrogen abstraction reaction at the T₁ state showed that the transition state is 16.4 and 30.9 kcal/mol lower than the energy levels of S₁ and S₂ states, respectively, and 9.2 kcal/mol higher than the bottom of T₁ state. The product state, (CH₃)₂C–OH⋯CH₂OH, is 8.4 kcal/mol lower in energy than the level of T₁ state. The direct ab initio MD calculation showed that the product is rapidly formed within 150 fs and the separated products (CH₃)₂C–OH + CH₂OH were formed. The mechanism of reaction dynamics of the triplet acetone/methanol complex was discussed on the basis of theoretical results.     

Role of CH, CH3, and OH Radicals in Organic Compound Decomposition by Water Plasmas

Decomposition of acetone, methanol, ethanol, and glycerine by water plasmas at atmospheric pressure has been investigated using a direct current discharge. At torch powers of 910–1,050 W and organic compound concentrations of 1–10 mol%, the decomposition rate of methanol and glycerine was over 99%, while those of acetone and ethanol was 95.4–99%. The concentrations of H₂ obtained were 60–80% in the effluent gas for any compounds by pyrolysis. Based on the experimental results, the decomposition mechanism of organic compounds in water plasmas was proposed and the roles of intermediate species such as CH, CH₃, and OH have been investigated; CH radical generated from organic compounds decomposition was easily oxidized to form CO; incomplete oxidation of CH₃ leads to C₂H₂ generation as well as soot formation; and negligible amount of soot observed from glycerine decomposition even at high concentration indicated that oxidation of CH_×(×:1–3) was enhanced by OH radical.     

Composition of Vapor and Liquid Phases in the Potassium Hydroxide + Methanol Reaction System at 25 °C

The composition of the vapor and liquid phases of the KOH + CH₃OH system has been studied by the gas chromatography (GC) method at 25 °C. It has been found that the methanol vapor concentration, and the quantity of potassium methoxide formed as a result of the acid–base reaction of potassium hydroxide with methanol, both depend on the KOH/CH₃OH mole ratio. The maximum mass fraction of potassium methoxide that forms is 2.6% at the mole ratio 0.018.     

Kinetics and quantification of the electrophilic reactivities of substituted thiophenes and structure‐reactivity relationships

Second‐order rate constants (k₁) have been measured spectrophotometrically for reactions of 2‐methoxy‐3‐X‐5‐nitrothiophene 1a‐c (X = NO₂, CN, and COCH₃) with secondary cyclic amines (pyrrolidine 2a , piperidine 2b , and morpholine 2 c ) in CH₃CN and 91:9 (v/v) CH₃OH/CH₃CN at 20°C. The experimental data show that the rate constants (k₁) values exhibit good correlation with the parameters of nucphilicity (N) of the amines 2a‐c and are consistent with the Mayr's relationship log k (20°C) = s(E + N). We have shown that the electrophilicity parameters E derived for 1a–c and those reported previously for the thiophenes 1d‐g (X = SO₂CH₃, CO₂CH₃, CONH₂, and H) are linearly related to the pK_a values for their gem‐dimethoxy complexes in methanol. Using this correlation, we successfully evaluated the electrophilicity E values of 12 structurally diverse electrophiles in methanol for the first time. In addition, a satisfactory linear correlation (r² = 0.9726) between the experimental (log k_exp) and the calculated (log k_calcd) values for the σ‐complexation reactions of these 12 electrophiles with methoxide ion in methanol has been observed and discussed.     

Thermal unimolecular decomposition mechanism of 2,4,6-trinitrotoluene: a first-principles DFT study

Simple C–NO₂ homolysis, 4,6-dinitroanthranil (DNAt) production by dehydration, and the nitro-nitrite rearrangement–homolysis for gas-phase TNT decomposition were recently studied by Cohen et al. (J Phys Chem A 111:11074, 2007), based on DFT calculations. Apart from those three pathways, other possible initiation processes were suggested in this study, i.e., CH₃ removal, O elimination, H escape, OH removal, HONO elimination, and nitro oxidizing adjacent backbone carbon atom. The intermediate, 3,5-dinitro-2(or 4)-methyl phenoxy, is more favor to decompose into CO and 3,5-dinitro-2(or 4)-methyl-cyclopentadienyl than to loss NO following nitro-nitrite rearrangement. Below ~1,335 K, TNT condensing to DNAt by dehydration is kinetically the most favor process, and the formations of substituted phenoxy and following cyclopentadienyl include minor contribution. Above ~1,335 K, simple C–NO₂ homolysis kinetically dominates TNT decomposition; while the secondary process changes from DNAt production to CH₃ removal above ~2,112 K; DNAt condensed from TNT by dehydration yields to that by sequential losses of OH and H above ~1,481 K and to nitro-nitrite rearrangement–fragmentation above ~1,778 K; O elimination replaces DNAt production above ~2,491 K, playing the third role in TNT decomposition; H escaping directly from TNT thrives in higher temperature (above ~2,812 K), as the fourth largest process. The kinetic analysis indicates that CH₃ removal, O elimination, and H escape paths are accessible at the suggested TNT detonation time (~100–200 fs), besides C–NO₂ homolysis. HONO elimination and nitro oxidizing adjacent backbone carbon atom paths are negligible at all temperatures. The calculations also demonstrated that some important species observed by Rogers and Dacons et al. are thermodynamically the most favor products at all temperatures, possibly stemmed from the intermediates including 4,6-dinitro-2-nitroso-benzyl alcohol, 3,5-dinitroanline, 2,6-dinitroso-4-nitro-phenylaldehyde, 3,5-dinitro-1-nitrosobenzene, 3,5-dinitroso-1-nitrobenzene, and nitrobenzene. All transition states, intermediates, and products have been indentified, the structures, vibrational frequencies, and energies of them were verified at the uB3LYP/6-311++G(d,p) level. Our calculated energies have mean unsigned errors in barrier heights of 3.4–4.2 kcal/mol (Lynch and Truhlar in J Phys Chem A 105:2936, 2001), and frequencies have the recommended scaling factors for the B3-LYP/6-311+G(d,p) method (Andersson and Uvdal in J Phys Chem A 109:2937, 2005; Merrick et al. in J Phys Chem A 111:11683, 2007). All calculations corroborate highly with the previous experimental and theoretical results, clarifying some pertinent questions.     

On the kinetic mechanism of reactions of hydroxyl radical with CHF2CH3 − n F n (n = 1–3)

The potential energy surfaces of the reactions CHF₂CH_3 − n F _n (n = 1–3) + OH were investigated by MPWB1K and BMC-CCSD (single-point) methods. Furthermore, with the aid of canonical variational transition state theory including the small-curvature tunneling correction, the rate constants of the title reactions were calculated over a wide temperature range of 220–1,500 K. Agreement between the CVT/SCT rate constants and the experimental values is good. Our results show that the order of rate constants is CHF₂CH₂F + OH > CHF₂CHF₂ + OH > CHF₂CF₃ + OH. For reaction CHF₂CH₂F + OH, the 1-H-abstraction channel dominates the reaction at the whole temperature, while 2-H-abstraction channel appears to be competitive with the increase of temperature.     

A theoretical kinetic study of the reactions of NH2 radicals with methanol and ethanol and their implications in kinetic modeling

Amino (NH₂) radicals play a central role in the pyrolysis and oxidation of ammonia. Several reports in the literature highlight the importance of the reactions of NH₂ radicals with fuel in NH₃-dual-fuel combustion. Therefore, we investigated the reactions of NH₂ radicals with methanol (CH₃OH) and ethanol (C₂H₅OH) theoretically. We explored the various reaction pathways by exploiting CCSD(T)/cc-pV(T, Q)Z//M06-2X/aug-cc-pVTZ level of theory. The reaction proceeds via complex formation at the entrance and exit channels in an overall exothermic process. We used canonical transition state theory to obtain the high-pressure limiting rate coefficients for various channels over the temperature range of 300–2000 K. We discerned the role of various channels in the potential energy surface (PES) of NH₂ + CH₃OH/C₂H₅OH reactions. For both reactions, the hydrogen abstraction pathway at the OH-site of alcohols plays a minor role in the entire T-range investigated. By including the title reactions into an extensive kinetic model, we demonstrated that the reaction of NH₂ radicals with alcohols plays a paramount role in accurately predicting the low-temperature oxidation kinetics of NH₃-alcohols dual fuel systems (e.g., shortening the ignition delay time). On the contrary, these reactions have negligible importance for high-temperature oxidation kinetics of NH₃-alcohol blends (e.g., not affecting the laminar flame speed). In addition, we calculated the rate coefficients for NH₂ + CH₄ = CH₃ + NH₃ reaction that are in excellent agreement with the experimental data.     

Catalytic Consequences of the Thermodynamic Activities at Metal Cluster Surfaces and Their Periodic Reactivity Trend for Methanol Oxidation

The periodic reactivity trend and the connection of kinetics to the thermodynamic activity of oxygen are established for the oxidation of methanol on metal clusters. First‐order rate coefficients are a single‐valued function of the O₂‐to‐CH₃OH ratio, because this ratio, together with the rate constants for O₂ and CH₃OH activation, determine the oxygen chemical potential, thus the relative abundance of active sites and bulk chemical state of the clusters. CH₃OH activation rate constants on oxygen‐covered Ag, Pt, and Pd and on RuO₂ clusters vary with the metal–oxygen binding strength in a classical volcano‐type relation, because the oxygen‐binding strength directly influences the reactivities of oxygen as H abstractors during the kinetically relevant CH₃OH activation step. The differences in oxygen thermodynamic activity lead to five orders of magnitude variation in rates (Pt>Pd>RuO₂>Ag, 373 K), because of its strong effects on the activation enthalpy and more prominently activation entropy in CH₃OH activation.     

Rate coefficients for reactions of OH radicals with CH3D,CH2D2, CHD3, and CD4

Fourier transform infrared (FTIR) smog chamber techniques were used to investigate the atmospheric chemistry of the isotopologues of methane. Relative rate measurements were performed to determine the kinetics of the reaction of the isotopologues of methane with OH radicals in cm³ molecule⁻¹ s⁻¹ units: k(CH₃D + OH) = (5.19 ± 0.90) × 10⁻¹⁵, k(CH₂D₂ + OH) = (4.11 ± 0.74) × 10⁻¹⁵, k(CHD₃ + OH) = (2.14 ± 0.43) × 10⁻¹⁵, and k(CD₄ + OH) = (1.17 ± 0.19) × 10⁻¹⁵ in 700 Torr of air diluent at 296 ± 2 K. Using the determined OH rate coefficients, the atmospheric lifetimes for CH_4–xD_x (x = 1–4) were estimated to be 6.1, 7.7, 14.8, and 27.0 years, respectively. The results are discussed in relation to previous measurements of these rate coefficients.     

<Emphasis Type="Italic">Ab initio</Emphasis> spectroscopic studies of non-rigid molecules: an application to acetic acid

The torsional levels of various isotopologues of acetic acid are determined from an ab initio potential energy surface using a flexible model depending on the OH-torsion and the methyl-torsion coordinates. Previous calculations for CH₃–COOH and CH₃–COOD are review and first theoretical energies of the one-deuterated species CH₂D–COOH are provided. The zero point vibrational energy correction and an exact definition for the methyl-torsional coordinate have been considered. The levels are compared with previous calculations (Senent in Mol Phys 99:1311, 2001) and experimental data (Havey et al. in J Mol Spectrosc 229:151, 2005). Isotopic effects on the torsional barriers and energies are discussed. For CH₂D–COOD, the deuteration splits by 25 cm⁻¹ the zero vibrational energy level.     

CH3OH electrooxidation by nanosized Pd loaded on porous LaMnO3

Generating the multifunctional influence by adding a promoter or employing a support for electrocatalytic particles is a remarkable approach to advance the efficiency and stability of anode electrode in the non-reforming methanol fuel cell. So, the coprecipitation assisted with ultrasonic is selected to fabricate porous LaMnO₃; and the nanosized Pd is loaded on LaMnO₃ via wetness incorporation. The samples are characterized through scanning electron microscopy, Fourier-transform infrared spectroscopy (FT-IR), vibrating sample magnetometry, Energy-dispersive X-ray spectroscopy (EDX), Transmission electron microscopy (TEM), Brunauer-Emmett-Teller and X-ray diffraction analysis. The electrochemical studies are carried out to identify the behavior and efficiency of electrocatalysts toward CH₃OH electrooxidation. Based on adsorption/desorption of hydrogen, the electrochemical surface area presented an ascending performance as nanosized Pd (76.63 m² g^?1) < Pd/LaMnO₃ (93.35 m² g^?1). The Pd/LaMnO₃ has higher electrocatalytic activity, stability, and CO-tolerance ability for the CH₃OH electrooxidation of as compared with nanosized Pd as non-supported Pd. The functions of current vs. time were determined by fitting and simulating of the experimental data. The transferred charge throughout CH₃OH electrooxidation vs. time was computed using the lower Riemann sum of plots, corresponding to experimental results and the integration of obtained functions. The introduced nanocomposite was used as anodic material in a single CH₃OH fuel cell.     

Theoretical study on the gas-phase reaction mechanism between rhodium monoxide cation and methane

The gas-phase reaction mechanism between rhodium monoxide cation and methane has been investigated on the singlet and triplet state potential energy surfaces at the CCSD(T)/6-311+G(2d,2p), SDD//B3LYP/6-311+G(2d,2p), SDD level. Over the 300–1100 K temperature range, the branching ratios of Rh⁺ + CH₃OH and RhCH₂ ⁺ + H₂O are 83.8–52.6% and 16.2–47.4%, respectively, whereas the branching ratio of CH₂ORh⁺ + H₂ is so small to be negligible. For the main products (Rh⁺ + CH₃OH and RhCH₂ ⁺ + H₂O) formation, the minimum energy reaction pathway involves singlet–triplet spin inversion, and both b-RhCH₃OH⁺ and H₂ORhCH₂ ⁺ are the energetically preferred intermediates. Alternatively, in the CH₂ORh⁺ + H₂ reaction, both b-RhCH₃OH⁺ and H₂RhOCH₂ ⁺ are the energetically favorable intermediates, and the main products are Rh⁺ + CH₃OH. In the RhCH₂ ⁺ + H₂O reaction, the main products are Rh⁺ + CH₃OH with the energetically predominant intermediate b-RhCH₃OH⁺. In the reaction of Rh⁺ + CH₃OH, both b-RhCH₃OH⁺ and H₂RhOCH₂ ⁺ are the energetically preferable intermediates, and the main products are CH₂ORh⁺ + H₂. Besides, toward methane activation, the cation RhO⁺ exhibits higher reaction efficiency than the cation Rh⁺, the neutral RhO, and its first-row congener CoO⁺, and it exhibits lower methanol branching ratio and higher water branching ratio than RhO and CoO⁺.     

On the nature of radicals formed in methanol catalytic oxidation

The quantum-chemical calculations of the hydroxymethyl radical •CH₂OH were performed for the first time and a theoretical EPR spectrum of this radical was constructed. The formation of the hydroxymethyl radical in the reaction of methanol oxidation is thermodynamically favorable. The shape and parameters of the constructed spectrum differed from those for radicals experimentally detected in the catalytic oxidation of methanol using the matrix isolation method. However, they are consistent with the spectrum ascribed to the EPR spectrum of •CH₂OH observed in the direct photolysis of methanol. This result allows one to refine the identification of the nature of radicals formed in the catalytic reaction of methanol oxidation.     

Rheology of cellulose/KSCN/ethylenediamine solutions and coagulation into filaments and films

Dissolution of cellulose in ethylenediamine/potassium thiocyanate (KSCN) was studied as a function of cellulose and KSCN concentration. Concentrations of up to 9% (w/w) cellulose were obtained. Large variations in solution rheology with salt and cellulose concentration were observed, and phases including flowing solutions and gels were identified visually. Rheological data indicated that viscosity decreased with increasing salt or cellulose concentration in certain composition ranges. Viscosity decrease with concentration increase is associated with either onset of liquid crystalline ordering or phase separation in the system. Both of these are quite likely in the cellulose/ethylenediamine/KSCN system, depending on composition. Additionally, comparison of loss (G′′) and storage (G′) moduli confirmed that compositions that exhibited gel behavior at zero shear became liquid at shear rates as low as 1 Hz. Solutions were coagulated into filaments and films using ethanol (CH₃CH₂OH) and methanol (CH₃OH). Infrared spectroscopy (FTIR) indicated that significant quantities of KSCN salt remained in the fibers and films after coagulation. Subsequent washing removed residual KSCN and improved physical properties. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2013–2022, 2005     

Platinum nanocube catalysts for methanol and ethanol electrooxidation

We prepared Pt nanocube catalyst with about 3.6 nm in size by a polyol process in the presence of PVP as a stabilizer and Fe ion as a kinetic controller. The crystal structure of Pt nanocube with {1 0 0} faces was confirmed by field-emission transmission electron microscopy. In a cyclic voltammogram, we found that the Pt nanocube catalyst showed relatively high ratio of the forward anodic peak current to the reverse anodic peak current resulting in less accumulation of residues on the catalyst. The Pt nanocube catalyst with the edge of stepped {1 0 0} faces was preferable to breakage of CH₃OH and CH₃CH₂OH compared to polycrystalline Pt nanocatalyst. In an electrochemical measurement for methanol and ethanol electrooxidation, the Pt nanocube catalyst showed an excellent catalytic activity, i.e., lower onset potential and higher current density, compared to the polycrystalline Pt nanocatalyst.     

Methanol adsorption on γ-irradiated SiO2 surface

The adsorption of methanol on γ-irradiated and un-irradiated SiO₂ surfaces pretreated at 473 K was investigated by Fourier transform infrared spectroscopy, temperature programmed desorption (TPD) and pulse methods. Methanol adsorbed only in molecular form on the un-irradiated sample. Treating the pre-irradiated silica surface with methanol at room temperature formaldehyde and hydrogen were formed. The methanol adsorbed on the irradiated silica transformed to formyl groups during a longer time at room temperature and desorbed as formaldehyde simultaneously with CH₃OH (T_max=395 K) on the TPD.     

Influence of structural defects on the electrocatalytic activity of platinum

Structural defects play major role in catalysis and electrocatalysis. Nanocrystalline (or nanostructured) materials composed of nanometer-sized crystallites joined via grain boundaries have been recognized for their specific structure and properties, differentiating them from single crystals, coarsely grained materials or nanometer-sized supported single-grained particles (Gleiter, Nanostruct Mater 1:1–19, 1992). In this paper, we use Pt electrodes, prepared by electrodeposition on glassy carbon and gold supports, as model nanocrystalline materials to explore the influence of grain boundaries and other structural defects on electrocatalysis of CO and methanol oxidation. We build on the recently established correlations between the nanostructure (lattice parameter, grain size, and microstrains) of electrodeposited Pt and the deposition potential (Plyasova et al., Electrochim. Acta 51:4447–4488, 2006) and use the latter to obtain materials with variable density of grain boundary regions. The activity of electrodeposited Pt in the oxidation of methanol and adsorbed CO exceeds greatly that for Pt(111), polycrystalline Pt, or single-grained Pt particles. It is proposed that active sites in nanostructured Pt are located at the emergence of grain boundaries at the surface. For methanol electrooxidation, the electrodes with optimal nanostructure exhibit relatively high rates of the “direct” oxidation pathway and of the oxidation of strongly adsorbed poisoning intermediate (CO_ads), but not-too-high methanol dehydrogenation rate constant. These electrodes exhibit an initial current increase during potentiostatic methanol oxidation explained by the CO_ads oxidation rate constant exceeding the methanol decomposition rate constant.

Atmospheric chemistry of n‐CH3(CH2)xCN (x = 0–3): Kinetics and mechanisms

Smog chamber/Fourier transform infrared (FTIR) techniques were used to measure the kinetics of the reaction of n‐CH₃(CH₂)_xCN (x = 0–3) with Cl atoms and OH radicals: k(CH₃CN + Cl) = (1.04 ± 0.25) × 10⁻¹⁴, k(CH₃CH₂CN + Cl) = (9.20 ± 3.95) × 10⁻¹³, k(CH₃(CH₂)₂CN + Cl) = (2.03 ± 0.23) × 10⁻¹¹, k(CH₃(CH₂)₃CN + Cl) = (6.70 ± 0.67) × 10⁻¹¹, k(CH₃CN + OH) = (4.07 ± 1.21) × 10⁻¹⁴, k(CH₃CH₂CN + OH) = (1.24 ± 0.27) × 10⁻¹³, k(CH₃(CH₂)₂CN + OH) = (4.63 ± 0.99) × 10⁻¹³, and k(CH₃(CH₂)₃CN + OH) = (1.58 ± 0.38) × 10⁻¹² cm³ molecule⁻¹ s⁻¹ at a total pressure of 700 Torr of air or N₂ diluents at 296 ± 2 K. The atmospheric oxidation of alkyl nitriles proceeds through hydrogen abstraction leading to several carbonyl containing primary oxidation products. HC(O)CN, NCC(O)OONO₂, ClC(O)OONO₂, and HCN were identified as the main oxidation products from CH₃CN, whereas CH₃CH₂CN gives the products HC(O)CN, CH₃C(O)CN, NCC(O)OONO₂, and HCN. The oxidation of n‐CH₃(CH₂)_xCN (x = 2–3) leads to a range of oxygenated primary products. Based on the measured OH radical rate constants, the atmospheric lifetimes of n‐CH₃(CH₂)_xCN (x = 0–3) were estimated to be 284, 93, 25, and 7 days for x = 0,1, 2, and 3, respectively.     

Methanol oxidation on the PtPd(111) alloy surface: A density functional theory study

The mechanisms of methanol (CH₃OH) oxidation on the PtPd(111) alloy surface were systematically investigated by using density functional theory calculations. The energies of all the involved species were analyzed. The results indicated that with the removal of H atoms from adsorbates on PtPd(111) surface, the adsorption energies of (i) CH₃OH, CH₂OH, CHOH, and COH increased linearly, while those of (ii) CH₃OH, CH₃O, CH₂O, CHO, and CO exhibited odd‐even oscillation. On PtPd(111) surface, CH₃OH underwent the preferred initial C H bond scission followed by successive dehydrogenation and then CHO oxidation, that is, CH₃OH → CH₂OH → CHOH → CHO → CHOOH → COOH → CO₂. Importantly, the rate‐determining step of CH₃OH oxidation was found to switch from CO → CO₂ on Pt(111) to COOH → CO₂ + H on PtPd(111) with a lower energy barrier of 0.96 eV. Moreover, water also decomposed into OH more easily on PtPd(111) than on Pt(111). The calculated results indicate that alloying Pt with Pd could efficiently improve its catalytic performance for CH₃OH oxidation through altering the primary pathways from the CO path on pure Pt to the non‐CO path on PtPd(111).