Atmospheric Pressure Of O2 Research Articles

Titania nanoparticles embedded in functionalized carbon for the aqueous phase oxidation of 5-hydroxymethylfurfural

Titania nanoparticles have huge potential due to their low cost, easy preparation, separation and high catalytic application. As-synthesized titania nanoparticles embedded at the functionalized acidic carbon act as effective heterogeneous catalyst for the selective oxidation of 5-hydroxylmethylfurfural (HMF) to 2,5-diformylfuran (DFF) and 2,5-furandicarboxylic acid (FDCA) in water. It was found that the doping of Ti (IV) with sulfonated carbon improve the catalytic effectiveness of resulting materials. The oxidation reaction and selectivity of the oxidation products, DFF, FDCA and FFCA were monitored by use of oxygen through manometric apparatus and a GC chromatogram. Titania nanoparticles embedded at the functionalized carbon gave higher selectivity for DFF (88% yield) under 1 atmospheric pressure of O2 at 70°C. The catalyst was characterized by the XPS, XRD, FESEM, HRTEM, FTIR and Raman spectroscopic techniques. The characterization data reveal the presence of the acid sites and titania in +4 oxidation state.

EcoMnOx, a Biosourced Catalyst for Selective Aerobic Oxidative Cleavage of Activated 1,2-Diols

A novel catalyst, EcoMnOx, was prepared from waste biomass of Mn-hyperaccumulating plants. The valorization of this Mn-rich biomass is an alternative to its costly usual disposing and provides a new source of Mn. Extracted metal ions, including Mn2+, were oxidized in mild conditions by H2O2/NaOH to afford EcoMnOx, as a polymetallic oxide material containing from 8.9 to 14.1 wt % Mn. Spectroscopic studies of this material revealed the presence of Mn layered mixed oxides, rich in MnIV along with MnIII and MnII species. EcoMnOx catalytic properties were assessed in the aerobic oxidative cleavage of 1,2-diols, under atmospheric pressure of O2 or air. With only 10 mol % Mn, up to complete conversions were obtained on activated benzylic and allylic diols, with excellent selectivity toward aldehydes or ketones (98–99%). Moreover, because of its heterogeneous nature, the catalyst can be removed easily by filtration, and reapplied for a minimum of six successive runs without any loss of activity. Finally, E-factor...

Electrochemical Property of LiCoMnO4 Cathode Thin Film Prepared By PLD and Oxygen Post Annealing

Introduction Lithium ion batteries used in electric vehicles and high power/energy storage systems are required to improve their high voltage and capacity. Spinel structured lithium manganese cobalt oxide (LiMnCoO4) is a potential cathode material to solve these problems. Since, its operating potential (about 5V) is very high compared to other cathode materials. [1]. Moreover, its theoretical discharge capacity is 740 Wh/kg, which is 1.3 times higher than LiCoO2: the most popular cathode material at present. However, previous reports on cyclic voltammetry studies on LiCoMnO4 revealed an unexpected peak around 4V, in addition to the main peak at 5V corresponding to the Co3+/4+ redox couple. This electrochemical reaction at 4V reduces the capacity of LiCoMnO4 above 5V. [2]. This peak at 4V is associated with the Mn3+/4+ redox couple in the spinel structure. Pasero et al. reported that Mn3+/4+ redox peak is due to the loss of oxygen content in the LiCoMn1-2δ +4Mn2δ +3O4-δ structure where the oxygen loss increases the Mn3+ content [3]. They reported that the control of oxygen content is effective to increase the capacity above 5V. In this study, we tried to control the loss of oxygen content in LiCoMnO4thin films by post annealing process and to improve its capacity around 5V. Experiment LiCoMnO4 was prepared by solid-state reaction method using mixtures of Li2CO3, Co3O4 and MnCO3. All starting materials were ground thoroughly in an gate mortar, treated in a muffle furnace at 850℃ for 24 hour at a rate of 100℃/h. Following this, the samples were ball milled in a planetary mill for 2 hours and calcined at 600℃ for 12 h. The process was repeated thrice. A PLD target of LiCoMnO4was prepared by hydrostatic pressing at 75 MPa for 15 min and 90 MPa for 15 min followed by sintering at 600℃ for 24 h. LiCoMnO4 thin-films were grown by pulsed laser deposition (PLD) at room temperature with an oxygen partial pressure of 0.1Pa. After preparing the films were treated by post annealing condition to study the difference in structural change and electrochemical property by post annealing condition. After preparing the thin films, the samples were heated in atmospheric pressure of O2 at 500, 600, and 700℃ for 1 ~ 72 h at a rate of 800℃/h in a tube furnace and then cooled rapidly to room temperature. An electrochemical cell was assembled with the LiCoMnO4 thin film as positive electrode on a Pt/Cr/SiO2 glass substrate, Li metal as the negative electrode and reference electrode, and 1 mol/L LiPF6 in ethylene carbonate (EC:DMC, 1:1 volume,) as the electrolyte. Cyclic voltammetry (CV) was performed on the cell in the potential range of 3.0 - 5.3 V vs. Li/Li+at a scan rate of 0.5 mV/s. Results & Discussion The results of post annealing of LiCoMnO4 suggests that the optimum temperature is 600℃. Fig.1 shows the XRD peak profile for LiCoMnO4/Pt/Cr/SiO2 heated at 600℃ for 0h~72h. The as-prepared sample shows no peak corresponding to LiCoMnO4, confirming its amorphous structure. Upon annealing a peak appeared at 2θ value of 18° which is attributed to the (111) Bragg reflection of LiCoMnO4. Similarly, the XRD peaks of (311), (400), (333) and (400) are observed after post-annealing, which shows the formation of spinel structure of LiCoMnO4. Fig.2 shows the enlarged XRD spectra in the (311) reflection region as shown in Fig.1. The peaks were fitted with voigt profiles. All peaks are found to shift toward lower 2θ against the LiCoMnO4 target peak, which is shown the black line in Fig.2. These shifts are caused by oxygen deficiency in LiCoMnO4 thin-films. Oxygen deficiency is related to the crystal spacing and hence XRD peak shift. This result confirms that the post-anneal time strongly affects the oxygen deficiency amount in the LiCoMnO4 thin films. The CV of LiCoMnO4 ­thin films are shown in Fig.3. This result confirm that the post-annealing increases the capacity of LiCoMnO4 at 5V region due to the decrease in oxygen loss. However, the 4V region increases if the annealing time is longer than 6h. Thus, this study shows that the optimum condition for post-annealing is found to be at 600℃ for 6 h in 1 atm O2.

Effects of Atmospheric-Pressure N2, He, Air, and O2 Microplasmas on Mung Bean Seed Germination and Seedling Growth

Atmospheric-pressure N2, He, air, and O2 microplasma arrays have been used to investigate the effects of plasma treatment on seed germination and seedling growth of mung bean in aqueous solution. Seed germination and growth of mung bean were found to strongly depend on the feed gases used to generate plasma and plasma treatment time. Compared to the treatment with atmospheric-pressure O2, N2 and He microplasma arrays, treatment with air microplasma arrays was shown to be more efficient in improving both the seed germination rate and seedling growth, the effect attributed to solution acidification and interactions with plasma-generated reactive oxygen and nitrogen species. Acidic environment caused by air discharge in water may promote leathering of seed chaps, thus enhancing the germination rate of mung bean, and stimulating the growth of hypocotyl and radicle. The interactions between plasma-generated reactive species, such as hydrogen peroxide (H2O2) and nitrogen compounds, and seeds led to a significant acceleration of seed germination and an increase in seedling length of mung bean. Electrolyte leakage rate of mung bean seeds soaked in solution activated using air microplasma was the lowest, while the catalase activity of thus-treated mung bean seeds was the highest compared to other types of microplasma.

Highly efficient self-esterification of aliphatic alcohols using supported gold nanoparticles under mild conditions

Long aliphatic esters were prepared by the one-step catalytic self-esterification of primary alcohols using molecular oxygen as a green oxidant and supported gold nanoparticles (Au NPs) as catalyst. This heterogeneous catalyst achieved high activity and selectivity in a wide range of less reactive straight-chain alcohols (C4-C12) at atmospheric pressure O2 and near ambient temperature (45°C). Under optimised conditions, the catalyst with Au loading of 3wt% achieved the highest catalytic activity and selectivity. The AuNP catalysts are efficient and readily recyclable. The finding of this study may inspire further studies on new efficient catalytic systems for a wide range of organic syntheses using supported AuNP catalysts.

High-Up: A Remote Reservoir of Microbial Extremophiles in Central Andean Wetlands.

The Central Andes region displays unexplored ecosystems of shallow lakes and salt flats at mean altitudes of 3700 m. Being isolated and hostile, these so-called “High-Altitude Andean Lakes” (HAAL) are pristine and have been exposed to little human influence. HAAL proved to be a rich source of microbes showing interesting adaptations to life in extreme settings (poly-extremophiles) such as alkalinity, high concentrations of arsenic and dissolved salts, intense dryness, large daily ambient thermal amplitude, and extreme solar radiation levels. This work reviews HAAL microbiodiversity, taking into account different microbial niches, such as plankton, benthos, microbial mats and microbialites. The modern stromatolites and other microbialites discovered recently at HAAL are highlighted, as they provide unique modern—though quite imperfect—analogs of environments proxy for an earlier time in Earth's history (volcanic setting and profuse hydrothermal activity, low atmospheric O2 pressure, thin ozone layer and high UV exposure). Likewise, we stress the importance of HAAL microbes as model poly-extremophiles in the study of the molecular mechanisms underlying their resistance ability against UV and toxic or deleterious chemicals using genome mining and functional genomics. In future research directions, it will be necessary to exploit the full potential of HAAL poly-extremophiles in terms of their biotechnological applications. Current projects heading this way have yielded detailed molecular information and functional proof on novel extremoenzymes: i.e., DNA repair enzymes and arsenic efflux pumps for which medical and bioremediation applications, respectively, are envisaged. But still, much effort is required to unravel novel functions for this and other molecules that dwell in a unique biological treasure despite its being hidden high up, in the remote Andes.

ChemInform Abstract: Efficient Synthesis of Amides and Esters from Alcohols under Aerobic Ambient Conditions Catalyzed by a Au/Mesoporous Al2O3 Nanocatalyst.

An efficient heterogeneous Au/mesoporous alumina nanocatalyst has been successfully developed for the synthesis of amides and esters from simple building blocks of readily available alcohols and amines. The processes were simple and were performed at room temperature and atmospheric pressure of O2 to form the desired products with up to 97 % isolated yield. The ability of Au/mesoporous alumina to catalyze these reactions under ambient conditions further enhances the sustainability of these chemical processes. Furthermore, the nanocatalyst was stable to air and water and could be recovered and reused easily. The enhanced catalytic activity of Au/mesoporous alumina might be attributed to the presence of negatively charged Au nanoparticles that could promote oxidation processes as well as the stability of the mesoporous alumina support calcined at a high temperature of 800 °C.

Atmospheric-pressure O2 plasma treatment of Au/TiO2 catalysts for CO oxidation

Atmospheric-pressure O2 plasma generated by dielectric barrier discharge (DBD) is applied to treat Au/TiO2 catalysts synthesized via the deposition–precipitation method for CO oxidation. The plasma-treated sample (S-P) presents a higher activity than the calcined one (S-C). To elucidate the plasma treatment effect, XPS, TEM/HRTEM, sub-ambient pulse CO chemisorption and in situ DRIFTS techniques were used for catalyst characterization. In comparison with S-C, TEM/HRTEM reveals that the S-P catalyst has small particle size and narrow size distribution; XPS and DRIFTS analyses indicate plentiful surface hydroxyl groups on S-P sample. Pulse CO chemisorption and in situ DRIFTS of CO adsorption show that significant increase of low-coordinated Au species has been achieved by the plasma treatment. The improved activity of S-P is ascribed to large amount of low-coordinated Au species and interface active sites as well as abundant surface hydroxyl groups.

Efficient Synthesis of Amides and Esters from Alcohols under Aerobic Ambient Conditions Catalyzed by a Au/Mesoporous Al2 O3 Nanocatalyst.

An efficient heterogeneous Au/mesoporous alumina nanocatalyst has been successfully developed for the synthesis of amides and esters from simple building blocks of readily available alcohols and amines. The processes were simple and were performed at room temperature and atmospheric pressure of O2 to form the desired products with up to 97 % isolated yield. The ability of Au/mesoporous alumina to catalyze these reactions under ambient conditions further enhances the sustainability of these chemical processes. Furthermore, the nanocatalyst was stable to air and water and could be recovered and reused easily. The enhanced catalytic activity of Au/mesoporous alumina might be attributed to the presence of negatively charged Au nanoparticles that could promote oxidation processes as well as the stability of the mesoporous alumina support calcined at a high temperature of 800 °C.

ChemInform Abstract: Imidazolidinone Nitroxides as Catalysts in the Aerobic Oxidation of Alcohols, en Route to Atroposelective Oxidative Desymmetrization.

New chiral nitroxides based on the imidazolidin-4-one skeleton, and the corresponding hydroxylamines, have been prepared from cyclic nitrones by a straightforward reaction sequence. They were evaluated as catalysts in the aerobic oxidation of benzyl alcohol using different co-catalysts. Both the imidazolidinone nitroxides and hydroxylamines were proven to catalyze the reaction, with the ring substituent having an effect depending on the co-catalytic system. In some cases, rapid oxidation to benzaldehyde was accomplished at room temperature under an atmospheric O2 pressure. Moreover, atroposelective desymmetrization was achieved during the aerobic oxidation of a diol catalyzed by an enantiopure imidazolidinone nitroxide. Finally, the electrochemical behavior of the new hydroxylamines and nitroxides was investigated by cyclic voltammetry, which gave insights into the observed catalytic properties.

Visible-Light-Driven Aerobic Oxidation of Amines to Nitriles over Hydrous Ruthenium Oxide Supported on TiO2

Aerobic oxidation of amines to nitriles under visible light irradiation was catalyzed by supported hydrous ruthenium oxide catalyst. Both LED (blue, green, or red) and the Sun were effective light sources for the transformation of benzylic and aliphatic amines to the corresponding nitriles under atmospheric pressure of O2. Water can be used as a solvent instead of toluene without the loss of activity and selectivity.

Imidazolidinone Nitroxides as Catalysts in the Aerobic Oxidation of Alcohols, en Route to Atroposelective Oxidative Desymmetrization

AbstractNew chiral nitroxides based on the imidazolidin‐4‐one skeleton, and the corresponding hydroxylamines, have been prepared from cyclic nitrones by a straightforward reaction sequence. They were evaluated as catalysts in the aerobic oxidation of benzyl alcohol using different co‐catalysts. Both the imidazolidinone nitroxides and hydroxylamines were proven to catalyze the reaction, with the ring substituent having an effect depending on the co‐catalytic system. In some cases, rapid oxidation to benzaldehyde was accomplished at room temperature under an atmospheric O2 pressure. Moreover, atroposelective desymmetrization was achieved during the aerobic oxidation of a diol catalyzed by an enantiopure imidazolidinone nitroxide. Finally, the electrochemical behavior of the new hydroxylamines and nitroxides was investigated by cyclic voltammetry, which gave insights into the observed catalytic properties.

Atmospheric Pressure Plasma Pretreatment of Sugarcane Bagasse: the Influence of Biomass Particle Size in the Ozonation Process

Atmospheric pressure O₂ plasma was used to produce ozone in order to treat sugarcane bagasse as a function of particle sizes. The fixed bagasse moisture content was 50%. The delignification efficiency had small improvement due to ozonation process as a function of particle size, varying from 75 up to 80%. Few amounts of hemicellulose were removed, but the ozonation has not been affected significantly with particle size variance as well (from 30 up to 35%). The cellulose presented some losses below 1.0 mm size (8-15%) which was an unexpected result. The conversion of cellulose content into free sugar has shown a significant increase as the particle size has diminished as well. The best condition of the bagasse particle size was for 0.08 mm. For this case, a great quantity of cellulose (78.8%) was converted into glucose. Optical absorption spectroscopy was applied to determine ozone concentrations in real time where the samples with typical bagasse particle sizes equal or below to 0.5 mm had shown a better absorption of ozone in comparison with greater particle size samples.

Atmospheric Pressure Plasma Pretreatment of Sugarcane Bagasse: The Influence of Moisture in the Ozonation Process

Sugarcane bagasse samples were pretreated with ozone via atmospheric O2 pressure plasma. A delignification efficiency of approximately 80 % was observed within 6 h of treatment. Some hemicelluloses were removed, and the cellulose was not affected by ozonolysis. The quantity of moisture in the bagasse had a large influence on delignification and saccharification after ozonation pretreatment of the bagasse, where 50 % moisture content was found to be best for delignification (65 % of the cellulose was converted into glucose). Optical absorption spectroscopy was applied to determine ozone concentrations in real time. The ozone consumption as a function of the delignification process revealed two main reaction phases, as the ozone molecules cleave the strong carbon-carbon bonds of aromatic rings more slowly than the weak carbon-carbon bonds of aliphatic chains.

Aerobic oxidative deprotection of benzyl-type ethers under atmospheric pressure catalyzed by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ)/tert-butyl nitrite

A facile and efficient protocol for the oxidative deprotection of benzyl-type ethers has been developed. The reaction was performed with catalytic amounts of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and tert-butyl nitrite (TBN) under atmospheric pressure of O2. Under the optimal reaction conditions, a variety of p-methoxybenzyl (PMB), p-phenylbenzyl (PPB), and benzyl (Bn) ethers can be deprotected to their corresponding alcohols in excellent conversions and selectivities.

Selective Amine Oxidation Using Nb2O5 Photocatalyst and O2

Niobium oxide (Nb2O5) can function as a photocatalyst for selective oxidation of benzylamine rather than other semiconductor metal oxides such as TiO2, ZnO, and WO3. Various amines including primary, secondary, and cyclic amines are also photocatalytically converted to corresponding imines in excellent yields by using Nb2O5 in an atmospheric pressure of O2. Nb2O5 exhibits a catalytic activity with high selectivity even under visible light (λ > 390 nm) irradiation, although Nb2O5 does not absorb visible light.

Membrane-inlet mass spectrometry reveals a high driving force for oxygen production by photosystem II

Oxygenic photosynthesis is the basis for aerobic life on earth. The catalytic Mn(4)O(x)CaY(Z) center of photosystem II (PSII), after fourfold oxidation, extracts four electrons from two water molecules to yield dioxygen. This reaction cascade has appeared as a single four-electron transfer that occurs in typically 1ms. Inevitable redox intermediates have so far escaped detection, probably because of very short lifetime. Previous attempts to stabilize intermediates by high O(2)-back pressure have revealed controversial results. Here we monitored by membrane-inlet mass spectrometry (MIMS) the production of from (18)O-labeled water against a high background of in a suspension of PSII-core complexes. We found neither an inhibition nor an altered pattern of O(2) production by up to 50-fold increased concentration of dissolved O(2). Lack of inhibition is in line with results from previous X-ray absorption and visible-fluorescence experiments, but contradictory to the interpretation of previous UV-absorption data. Because we used essentially identical experimental conditions in MIMS as had been used in the UV work, the contradiction was serious, and we found it was not to be resolved by assuming a significant slowdown of the O(2) release kinetics or a subsequent slow conformational relaxation. This calls for reevaluation of the less direct UV experiments. The direct detection of O(2) release by MIMS shows unequivocally that O(2) release in PSII is highly exothermic. Under the likely assumption that one H(+) is released in the S(4)→S(0) transition, the driving force at pH 6.5 and atmospheric O(2) pressure is at least 220meV, otherwise 160meV.

Efficient Synthesis of Lactic Acid by Aerobic Oxidation of Glycerol on Au–Pt/TiO2 Catalysts

Go for the burn! A one-pot approach to the efficient synthesis of lactic acid through the aerobic oxidation of glycerol in the presence of bases at an atmospheric pressure of O2 is reported, which combines two consecutive reactions, including oxidative dehydrogenation of glycerol to its dehydrogenated intermediates and their subsequent isomerization (see scheme).

Silicon‐Assisted Direct Covalent Grafting on Metal Oxide Surfaces: Synthesis and Characterization of Carboxylate N,N′‐Ligands on TiO2

AbstractThe easy covalent bonding of an OH‐bearing molecule onto a metal oxide surface can be done by transesterifying a trimethylsilylated hydroxy function with the surface OH groups. This results in the grafting of the organic molecule directly on the matrix, accompanied by the formation of trimethylsilanol, which can easily be eliminated as volatile hexamethyldisiloxane and water. This was accomplished on a TiO2 matrix with three carboxylic acids: acetic, isonicotinic, and 2,2′‐bipyridyl‐4,4′‐dicarboxylic acids. The N,N′‐immobilized ligand was then used for a dioxidomolybdenum entity and tested as such at room temperature and under atmospheric pressure O2 oxidation of ethylbenzene. All intermediates and grafted species were fully characterized by 13CMAS NMR spectroscopy, and thermogravimetric and elemental analysis.

Aerobic Oxidation of Benzylic Alcohols in Water by 2,2,6,6‐Tetramethylpiperidine‐1‐oxyl (TEMPO)/Copper(II) 2‐N‐Arylpyrrolecarbaldimino Complexes

AbstractNovel copper(II) 2‐N‐arylpyrrolecarbaldimine‐based catalysts for the aerobic oxidation of benzylic alcohols mediated by the 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) radical are reported. The catalytic activity for both synthesized and in situ made complexes in alkaline water solutions was studied revealing high efficiency and selectivity (according to GC selectivity always >99%) for both of these catalytic systems. For example, quantitative conversion of benzyl alcohol to benzaldehyde can be achieved with the in situ prepared bis[2‐N‐(4‐fluorophenyl)‐pyrrolylcarbaldimide]copper(II) catalysts in 2 h with atmospheric pressure of O2 at 80 °C. Interestingly, these catalysts can utilize dioxygen as well as air or hydrogen peroxide as the end oxidants, producing water as the only by‐product.