Direct Oxidation Method Research Articles

Palladium-charcoal Catalyzed Direct Esterification of Aldehydes to Esters by NaIO4

Abstract:: An efficient direct oxidation method was developed to oxidize some aromatic and aliphatic aldehydes to esters by the dual utilization of NaIO4 and Pd-C. At ambient conditions, various aldehydes were employed in a clean esterification reaction to afford numerous esters in good to excellent yields. By this adopted method, some multifunctional aldehydes, high-energy-containing aromatic and unsaturated aldehydes, were advantageously oxidized to esters without noticeable difficulties. Moreover, no over-oxidation occurred to alcohols, and mostly by products were not formed during this oxidation process. Conventional and some modern methods lag behind owing to their easier operability and easy work-up process. This investigation has proven that the required oxidant (NaIO4) or catalyst (Pd-C) is useless to employ in excess, although some current methods utilize hugely expensive reagents for such conversions. Mundane reaction set-up, easy product recovery technique, nontoxic catalyst, and cheap and available starting materials are the noteworthy advantages of this method.

Enhanced hydrogen barrier performance of ZrH1.8 via yttria-zirconia composite film developed through the ECD-MAO technique

To address the inherent shortcomings of the direct micro-arc oxidation method, this study employed a combination of electroplating and micro-arc oxidation techniques. This approach successfully fabricated a hydrogen permeation barrier film on the surface of ZrH1.8, featuring a yttria-stabilized zirconia (YSZ) composite oxide. The prepared composite film layer underwent thorough evaluations, encompassing assessments of its microstructure, phase structure, adhesion strength, thickness, barrier properties, and hydrogen permeation performance. The findings indicated that the electroplated yttrium layer contributes to the stabilization of the tetragonal phase of zirconia (T-ZrO2) during the micro-arc oxidation process, thereby enhancing the discharge behavior of the film layer. By employing this treatment method, the content of T-ZrO2 in the film layer increased to 26.70%, and the film became denser with a thickness of 60.93 μm. Additionally, the adhesion strength between the film layer and the substrate significantly improved, reaching 75.95 N, with a hardness of 393.24 HV. Furthermore, the film layer exhibited an increased hydrogen release temperature of 680 °C, demonstrating excellent performance as a hydrogen permeation barrier.

Mild oxidizing synthesis of non-agglomerated Fe2O3 nanoparticles for H2S gas sensing

Agglomeration is the most common phenomenon in synthesizing nanopowders, which strictly reduces the quality of the products. In the present study, a non-agglomerated iron oxide nanopowder was synthesized via direct oxidation method from metallic iron by hydrogen peroxide. The H2S gas sensing of the nanoparticles was also investigated. The products were evaluated via XRD, TEM, XPS and BET techniques. The results showed that a precisely size-controlled iron oxide with an average particle size of 12 nm was obtained. XRD results confirmed the amorphous nature of the particles. The produced nanoparticles had a high surface area of about 92 m2/g. The powders were dispersed in water for more than three months without sedimentation. XPS results showed the existence of Fe3+ in the samples which confirms the formation of the Fe2O3 phase. The finding showed that the produced samples exhibited a high H2S detection ability. The detection limit was about 100 ppb, and the greatest sensitivity was attained at 100 ppm concentration of H2S. Additionally, the sensor's behavior in the presence of other gases shows that it has high H2S selectivity. This synthesis method introduces a new approach for producing non-agglomerated oxide ceramics with nanoscale via a mild oxidizing media from metal powders.

A preparative small-molecule mimic of liver CYP450 enzymes in the aliphatic C–H oxidation of carbocyclic N-heterocycles

An emerging trend in small-molecule pharmaceuticals, generally composed of nitrogen heterocycles (N-heterocycles), is the incorporation of aliphatic fragments. Derivatization of the aliphatic fragments to improve drug properties or identify metabolites often requires lengthy de novo syntheses. Cytochrome P450 (CYP450) enzymes are capable of direct site- and chemo-selective oxidation of a broad range of substrates but are not preparative. A chemoinformatic analysis underscored limited structural diversity of N-heterocyclic substrates oxidized using chemical methods relative to pharmaceutical chemical space. Here, we describe a preparative chemical method for direct aliphatic oxidation that tolerates a wide range of nitrogen functionality (chemoselective) and matches the site of oxidation (site-selective) of liver CYP450 enzymes. Commercial small-molecule catalyst Mn(CF3-PDP) selectively effects direct methylene oxidation in compounds bearing 25 distinct heterocycles including 14 out of 27 of the most frequent N-heterocycles found in U.S. Food and Drug Administration (FDA)-approved drugs. Mn(CF3-PDP) oxidations of carbocyclic bioisostere drug candidates (for example, HCV NS5B and COX-2 inhibitors including valdecoxib and celecoxib derivatives) and precursors of antipsychotic drugs blonanserin, buspirone, and tiospirone and the fungicide penconazole are demonstrated to match the major site of aliphatic metabolism obtained with liver microsomes. Oxidations are demonstrated at low Mn(CF3-PDP) loadings (2.5 to 5 mol%) on gram scales of substrate to furnish preparative amounts of oxidized products. A chemoinformatic analysis supports that Mn(CF3-PDP) significantly expands the pharmaceutical chemical space accessible to small-molecule C-H oxidation catalysis.

Peroxymonosulfate activation by Cu2O@CuO nanowires array-based electroactive filter for efficient ofloxacin removal

A homemade flow-through electroactive filter was constructed to activate peroxymonosulfate (PMS) for ofloxacin (OFL) fast removal. The Cu2O@CuO nanowires (NWs) electrode was prepared using copper foam as both substrate and Cu source by direct oxidation method. The obtained electrode with abundant surface-active sites and good electrochemical reactivity markedly improved the activation and utilization efficiency of PMS, thus significantly promoting the catalytic removal reactions. The pH, PMS concentration, and applied voltage were optimized for the filter performance. Consequently, the removal efficiency of OFL reached about 80% in a single-pass mode (τ < 5 min). Electron paramagnetic resonance (EPR) and radical scavenging tests confirmed the contribution of diversified active species in OFL removal. The Cu2O@CuO NWs electrode exhibited reliable regenerative properties, which maintained high OFL removal activity after 5 rebuild cycles. Furthermore, the developed electroactive filter exhibited relatively less consumption of energy and PMS dosage compared with the published research. Finally, the underlying mechanism for the outstanding performance of OFL removal was also revealed as well. This work illustrated new light on high-efficient and low-cost remediation strategies for antibiotic wastewater.

Emerging trends in the sustainable synthesis of N-N bond bearing organic scaffolds.

N-N bond bearing organic frameworks such as azos, hydrazines, indazoles, triazoles and their structural moieties have piqued the interest of organic chemists due to the intrinsic nitrogen electronegativity. Recent methodologies with atom efficacy and a greener approach have overcome the synthetic obstacles of N-N bond construction from N-H. As a result, a wide range of amine oxidation methods have been reported early on. This review's vision emphasizes the emerging methods of N-N bond formation, particularly photo, electro, organo and transition metal free chemical methods.

Modeling optimization for a typical VOCs thermal conversion process

Aiming at the current environmental problems, the thermal oxidation treatment for industrial VOCs emission is a common and effective measure. This paper studies on the optimization effect of one optimization method for direct VOCs thermal oxidation of a color aluminum spraying production line based on Aspen-Plus. According to the direct VOCs thermal oxidation process with a 30000 m³/h circulating air volume, propose the flue gas reflux and coating room drainage technology. Use the second law of thermodynamics, and the exergy flow analysis shows the methane consumption could be reduced 12%. Carbon emissions also decreased significantly, with 3.42% reduction. These findings are practical for industrial production cost saving and environmental protection problems solving.

Electrosynthesis of C−3 Phosphorylated 2H-Indazoles from Trialkyl Phosphites and 2H-Indazoles

A facile and efficient direct electrochemical oxidation method for C−3 phosphorylation of 2H-indazoles with trialkyl phosphites as the phosphorylation reagents has been developed. Introducing electricity to the green and sustainable synthetic procedures allowed the reactions to be carried out under simple and mild conditions without any metal salts and additional oxidants. Electrochemical data asserted that the cation radical species which were generated from the oxidation of 2H-indazoles were stabilized by 1,1,1,3,3,3-hexafluoro-2-propanol and could be captured by trialkyl phosphites effectively to form C−3 phosphorylated 2H-indazoles. In an undivided cell, a board range of functional groups on various substrates were well tolerated and the yield of the desired phosphorylated products was up to 84%. Moreover, a plausible mechanistic proposal involving radical pathway was established based on the results of cyclic voltammetry, in situ FTIR and control experiments.

Steady-state deformation of asphalt concrete

• An expression has been obtained for the steady-state deformation rate of the asphalt concrete. • The steady-state deformation rate depends on the viscosity, a stress, a temperature and an activation energy. • The graphs for “the steady-state deformation rate – a temperature” are similar. • “The stress substitution principle” has been proposed. • The test for creep is an alternative method for determination of the materials viscosity. The steady-state deformation rate of an asphalt concrete is investigated in details within a wide range of a stress variation (from 0.0081 MPa to 3.0 MPa) and a temperature variation (from + 60 °C to −24 °C). A hot dense fine-grained asphalt concrete of type B accepted for the investigation has been prepared with the use of a road viscous bitumen (4.8 % by weight of a dry mineral material) of the grade 100–130 under penetration. The bitumen was produced by the Pavlodar petrochemical plant (Kazakhstan) by the direct oxidation method from an oil of the Western Siberia (Russian Federation). The investigation of the steady-state deformation of the asphalt concrete has been performed by testing of samples (50x50x150 mm) for creep at direct tension. A load and a temperature have been kept as the constant ones from the beginning to the end of testing of all the samples (241 units). The tests of the asphalt concrete samples for creep have been performed in a device, which has been specially invented and assembled. It has been found out that the tested asphalt concrete is deformed under the impact of a constant stress and at a constant temperature during some period in a steady-state regime, i.e. it is deformed with a constant rate; the dependence of a steady-state deformation rate on a stress is described by power function with a high accuracy at all the considered temperatures; a fundamental expression has been obtained which connects the steady-state deformation rate with its viscosity, stress, temperature and activation energy of the viscous deformation; a simplified expression has been obtained for the steady-state deformation rate of the asphalt concrete for the practical use; a similarity has been shown for the dependence of the steady-state deformation rate on a temperature at various stresses in semi-logarithmic coordinates; “the stress substitution principle” has been formulated. The results obtained in this work have shown that the viscous flow and the steady state deformation (steady-state creep) of the elastoviscoplastic materials as the physical phenomena can be explained on the basis of the kinetic theory of liquids (Ya.I. Frenkel) and the theory of rate processes (H. Eyring). The test for the creep can be considered as an alternative method of the experimental determination for the viscosity of the materials.

Preparation and characterization of self-assembled ZnO nanowire devices: nanowire strain sensor and homogeneous p–n junction

In this work, intrinsic and p-type ZnO nanowires (NWs) have been synthesized. Pure intrinsic ZnO nanowires have been fabricated by direct oxidation method and their aspect ratio reached up to 271.3. Sb-doped ZnO nanowires were uniformly grown on Si substrates by chemical vapor deposition with diameters ranging from 0.5 to 5 μm and lengths ranging from 100 μm to 3 mm. Directional arrangement of nanowires has been realized by two self-assembly methods, pulling method and water flow method, and two kinds of ZnO nanodevices (strain sensor and homogenous p–n junction) were prepared and characterized based on the directional arranged nanowires. According to the current response of ZnO nanowire strain sensor, the deformation quantities of elastic plate under the action of external forces in orthogonal X and Y direction were calculated respectively. The ZnO nanowire homogenous p–n junction was made of two vertical Sb-doped and intrinsic ZnO nanowires. The I–V characteristic curve showed good rectification characteristics, and the forward turn-on voltage was about 10 V. However, since the current was too small due to the small carrier concentration in the ZnO single crystal, it is difficult to achieve electroluminescence at present.

Investigation on Catalytic N2O Conversion to NO for Potential Nitric Acid Production from Industrial Waste Gas

It is well known that N2O has a very significant impact on the greenhouse effect. Although N2O is not the major contributor to the global warming, while it could stay in atmosphere for about 150 years, and its global warming potential (GWP) is about 2.5 and 310 times as that of CH4 and CO2, respectively. The main source of N2O emission from chemical industries is originated from the process of adipic/nitric acid production. The emission of N2O due to adipic acid production in China is about 0.48∼0.72 million tons per year based on the mass ratio between N2O emission and adipic acid production, which is equivalent to 150∼250 million tons CO2 emission. However, there are few reports on economically reusing N2O from flue gas by direct oxidation method. Therefore, a series of catalysts applied on catalytic N2O conversion to NO for potential production of nitric acid from flue gas have been prepared by co-precipitation method. The basic property of catalysts was characterized by BET, laser particle size analyzer, FT-IR, TG/DTA, and CO2-TPD, etc. The catalyst’s performance was evaluated in a fixed-bed reactor with mixture of 40%(v)N2O+40%(v)N2+20%(v)O2 under 3000 h −1 space velocity and 0.1MPa system pressure. Results showed that catalysts of Pt/Cu-Zn-O and Pt/Zr-Zn-O have good selectivity on NO production, which was about 10% and 15%, respectively, in the temperature range from 550°C to 650°C. The basic experimental results show that it is a promising method to be applied for N2O reuse in adipic acid production and nitric acid industries and also provide the basis for further relative theoretical and experimental studies.

Effect of post-oxidation processes and thickness of SnO2 films prepared by vacuum evaporation on CO gas sensing characteristics

This report discusses the effect of post-oxidation processes and thickness of SnO2 thin films on their physical properties and CO gas sensing characteristics. SnO2 films have been grown by simple vacuum evaporation of Sn metal and post-oxidation process. The post-oxidation of Sn films was performed by two different methods, i.e., step-oxidation and direct-oxidation, at a maximum temperature of 850 °C. The thickness of Sn films was varied as 100, 200 and 500 nm. As characterized by x-ray diffraction technique, the SnO2 thin films have a tetragonal rutile structure with crystallite size of 21 and 27 nm for direct-oxidation and step-oxidation methods, respectively. The SnO2 films produced by both oxidation methods possess a porous, granular surface morphology as revealed by scanning electron microscopy. The band gap of SnO2 films calculated using ultraviolet–visible spectroscopy in absorption mode is found to be in the range of 3.36–3.59 eV. The CO sensing performance has been examined at various measurement temperatures up to 400 °C using calibrated CO gas. It is found that the CO sensitivity is significantly higher for the direct-oxidized SnO2 films as compared to the step-oxidized films. Also, thinner SnO2 film, i.e. 100 nm of thickness, obtained by direct-oxidation method is found to have the highest sensitivity of 70.7% against CO gas of 915 ppm concentration with a fast response time of 21 s. The effective CO sensing of thinner SnO2 film is understood based on the formation of smaller grains with the uniform surface distribution. The film is more selective towards CO gas as compared to NH3 and NO2 gases and shows a CO limit-of-detection of 10 ppm.

Formation Mechanism of Nanoparticles in Fe–Cr–Al ODS Alloy Fabricated by Direct Oxidation Method

This study presents the fabrication of 14Cr Fe–Cr–Al oxide dispersion strengthened (ODS) alloy by a direct oxidation process. In order to explain how oxide nanoparticles are formed in the consolidation process, the powders after oxidation are subjected to vacuum thermal treatment at high temperatures. Differential scanning calorimeter, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy techniques are used to detect the generation, evolution of oxides on both the surface and interior of the powder, as well as the type of oxide nanoparticles in the fabricated ODS alloy. It is found that an iron oxide layer is formed on the surface of the powder during low temperature oxidation. And the iron oxide layer would be decomposed after thermal treatment at high temperature. In the consolidation process, the oxygen required by the reaction of alumina and yttrium oxide to produce nanoscale Y–Al–O particles mainly derives from the decomposition of iron oxide layer at elevated temperature and the inward diffusion of oxygen. Using the direct oxidation process, YAlO3 nanoparticles are dispersed in the grains and at the grain boundaries of Fe–Cr–Al ODS alloy.

Coconut shell derived activated biochar–manganese dioxide nanocomposites for high performance capacitive deionization

In this study, a Faradaic/electric double-layer hybrid capacitor using coconut shell derived activated biochar (AB) and MnO2 nanocomposite was fabricated for capacitive deionization (CDI) applications. Three different co-precipitation methods including indirect, direct, and acid-assisted grafting oxidation methods were explored to produce the AB-MnO2 nanocomposites. The α-MnO2 with an excellent ion intercalation ability was successfully deposited onto the AB, making the AB-MnO2 an excellent electrode material for CDI application in the presence of neutral Na2SO4 electrolytes. Notably, the AB-MnO2 nanocomposites prepared by indirect co-precipitation method (AB-MnO2-indirect) has shown a high specific surface area of 304 m2 g−1 with high mesopore volume ratio, high capacitance retention, good hydrophilicity and suitable pore texture to shorten the diffusion distance of ions. Cyclic voltammetric (CV) and electrochemical impedance spectroscopic (EIS) spectra showed that the AB-MnO2 yields a quasi-rectangular and symmetric CV plot, and specific capacitances of 410–523 F g−1 at 5 mV s−1 were observed. Moreover, the AB-MnO2-indirect exhibits excellent CDI performance at 1.2 V, and the specific electrosorption capacity of 33.9–68.4 mg g−1 was obtained. Results of this study demonstrate that AB-MnO2 nanocomposites are superior electrochemical materials for CDI application, which can serve as alternative materials for designing an innovative electrochemical technology for water purification, desalination, and energy storage.

LaCl3 flux mediated Ta3N5 planar photoanode for solar water oxidation

Ta3N5 is a promising candidate for photoelectrochemical (PEC) water splitting. Recently gratifying photocurrents have been reported through various advanced techniques. However, obtaining high performance Ta3N5 photoanode prepared by direct oxidation and nitridation remains challenging. In this work, efficient Ta3N5 photoanode was fabricated on Ta foil by direct oxidation and nitridation method with LaCl3 flux mediated treatment. The highest photoresponse (8.2 mA cm−2 @ 1.23 VRHE) for direct oxidized and nitrided Ta3N5 is achieved with the help of LaCl3 flux, which is nearly doubled compared to the untreated counterparts. Theoretical analysis suggests an interfacial charge transfer in LaTaON2/Ta3N5 heterostructure and significant increase in carrier concentration on La doped Ta3N5 surface. The introduction of LaCl3 flux brings a new look to this traditional method and it may potentially be applied to large area and low cost photoanodes.

Electrical, structural, and photocatalytic properties of copper oxide nanowire

Using a direct oxidation method in a horizontal quartz tube, copper oxide nanowires are grown on a Cu substrate. In order to investigate the growth temperature effects on the structural, morphological, electrical, and photocatalytic properties of the copper oxide nanowires, X-ray diffraction, scanning electron microscopy, a KEITHLEY 2361 system, and a homemade photoreactor are used. The X-ray diffraction results show that both CuO and Cu2O phases are formed, and while increasing the growth temperature, the crystallinity is improved and the intensity of most of the diffraction peaks increases. The scanning electron microscopy images at different growth temperatures show that the number, density, and length of the copper oxide nanowires on pre-formed micro-scaled grains increase, when the growth temperature increases to 700°C and sharper nanowires with average diameters of 1–3 µm grow on the surface. Also I–V curves show that by raising the growth temperature, the conductivity of the samples increases. In addition, the photocatalytic activities are studied by photocatalytic degradation of Congo red dye, and based on these results, the sample grown at 700°C with the highest number and density of the nanowires showed the best photocatalytic performance and electrical conductivity. The results can be used to guide better understanding of the growth behavior of copper oxide nanowires and can be useful for the development of novel photocatalytic nanodevices.

Plasma–Chemical Hybrid NOx Removal in Flue Gas from Semiconductor Manufacturing Industries Using a Blade-Dielectric Barrier-Type Plasma Reactor

NOx is emitted in the flue gas from semiconductor manufacturing plants as a byproduct of combustion for abatement of perfluorinated compounds. In order to treat NOx emission, a combined process consisting of a dry plasma process using nonthermal plasma and a wet chemical process using a wet scrubber is performed. For the dry plasma process, a dielectric barrier discharge plasma is applied using a blade-barrier electrode. Two oxidation methods, direct and indirect, are compared in terms of NO oxidation efficiency. For the wet chemical process, sodium sulfide (Na2S) is used as a reducing agent for the NO2. Experiments are conducted by varying the gas flow rate and input power to the plasma reactor, using NO diluted in air to a level of 300 ppm to simulate exhaust gas from semiconductor manufacturing. At flow rates of ≤5 L/min, the indirect oxidation method verified greater removal efficiency than the direct oxidation method, achieving a maximum NO conversion rate of 98% and a NOx removal rate of 83% at 29.4 kV and a flow rate of 3 L/min. These results demonstrate that the proposed combined process consisting of a dry plasma process and wet chemical process is promising for treating NOx emissions from the semiconductor manufacturing industry.

Surface functionalization of polypropylene and polyethylene films with allylamine by γ radiation

Abstract

Removal of Methylene Blue by Direct Electrochemical Oxidation Method Using a Graphite Anode

The present work is to degrade methylene blue dye from aqueous solution by direct electrochemical oxidation technique. For this purpose an electrochemical cell was used comprising of two electrodes made from graphite as anode and stainless steel 316 grade as cathode. Different operating parameters that affected the treatment process such as current density, electrolyte temperature and initial dye concentration had also been studied. The reaction mechanism of direct anodic oxidation of M.B. is undertaken and the kinetic follows a pseudo first order reaction. Results revealed that at 20ºC electrolyte temperature, 10 mA/cm2 current density, 0.5 g/l Na2SO4 as supporting electrolyte and 60 min electrolysis time, the decolorization percents for initial concentrations of M.B. 50 and 400 mg/L were 72.51% and 77.94% respectively while at 60ºC the decolorization percent 99.75% and 99.60% respectively for the same others operating conditions. The power consumption increased from 2.055 to 11.714 Kw.h/m3 at applied voltage 14.6 V and 28.5 V respectively.

Oxyfunctionalization of Active Methylene Compounds Using Sodium Chlorite in Water

AbstractA methylene group inserted between proximal carbonyl groups underwent exclusive oxyfunctionalization with sodium chlorite in the presence of redox‐inert HfIV in water. Direct oxidation methods have conventionally suffered from manifold side reactions such as oxidative fragmentation, dimerization, and overreactions, together with the use of toxic and intractable oxidants. Although alternative routes involving prior α‐functionalization can be executed under mild conditions, preparatively valuable oxidation methods that deliver high levels of both conversion and selectivity remain a prized goal from the standpoint of streamlining organic synthesis. Chlorine dioxide, which was generated as a yellowish gas during the reaction, is considered to be a bona fide oxidant against active methylene compounds. The pivotal role of water was clear, given that the reaction was significantly retarded in both aqueous acetonitrile and ethanol, which can solubilize sodium chlorite.