Air Oxidation Reaction Research Articles

Constructing boiling water resistant and flame-retardant wood composites based on enzyme catalyzed synergistic high branching crosslinking strategy

In the realm of sustainable and regenerative environments, the development of a biomass-based laminated composites endowed with boiling water resistance and flame retardant capabilities holds paramount importance. First of all, a novel maleic anhydride-based polyamine (MAN) was designed and synthesized, characterized by its branched structure replete with numerous reactive sites. Subsequently, utilizing sucrose, MAN, and sucrase (I), a novel sucrose-based adhesive (S-I-MAN) was synthesized, capable of fostering a multifaceted chemical network through enzyme-catalyzed air oxidation cross-linking. And the enzyme-catalysed air oxidation reaction can provide a milder and more specific reaction pathway when catalysed by sucrase. Next, the laminated composites prepared from wood and biomass adhesive (S-I-MAN) exhibited excellent flame retardant properties by organic–inorganic surface modification using tannic acid (TA) and sodium perborate (NaBO3). Further research showed that potassium persulfate can effectively initiate the free radical polymerisation of the carbon–carbon double bond in S-I-MAN, increase the strength and stability of S-I-MAN, and make the laminated composites have more excellent mechanical properties. On the one hand this study developed a new organic–inorganic biomass-based composite adhesive. On the other hand, the surface modification of laminated composites with excellent flame retardant properties provided a new “organic-inorganic composite system with flame retardant” idea.

Quantitative analysis of air-oxidation reactions of thiolate-protected gold nanoclusters.

The interaction of dioxygen (O2) with inorganic nanomaterials is one of the most essential steps to understanding the reaction mechanism of O2-related reactions. However, quantitative analyses for O2-binding processes and subsequent oxidation reactions on the surface are still elusive, whereas the reaction of O2 with molecules such as transition metal complexes has been widely explored. Herein, we have quantitatively evaluated reaction processes of air-oxidation reactions of atomically precise thiolate-protected Au25 nanoclusters ([Au25(SR)18]-) as a model of O2 activation by inorganic nanomaterials. Kinetic analyses on the air-oxidation reaction of [Au25(SR)18]- revealed a controlling factor for O2-activation processes, which could be finely tunable by the protecting thiolate ligands.

Preparation a novel high performance glucose-based wood adhesive with hyperbranched cross-linked network by air oxidation

Utilizing biomass resources to develop environmentally friendly and sustainable adhesives, replacing traditional petroleum-based adhesives, has become an effective way to solve resource shortages and environmental pollution. Glucose, as the most widely distributed reducing monosaccharide in nature, has great potential to replace aldehyde-based adhesives in the production of artificial boards. In this study, G-PEI adhesive was prepared from glucose and PEI by one pot one-step method on the basis of air oxidation and Maillard reaction. The crosslinking mechanism between glucose and PEI was confirmed through detailed Fourier transform-infrared (FT-IR), 13C nuclear magnetic resonance (13C NMR), X-ray photoelectron spectroscopy (XPS), and liquid chromatography-mass spectrometry (LC-MS) analysis. The results showed that the improvement of G-PEI adhesive bonding properties was attributed to the formation of cross-linking network and the synergistic effect of covalent bond and hydrogen bond. As a biomass adhesive prepared without additional oxidant, the maximum wet strength in boiling water of wood-based panels prepared with G-PEI adhesive reaches 1.55 Mpa under the hot pressure condition of 200 °C. Even if the hot-pressing temperature drops to 160 °C, the wet shear strength in boiling water can still reach 0.67 MPa, which is better than relevant reports. This study revealed a method for the simple preparation of high performance wood adhesives by oxidizing glucose through air.

Microinterface intensification in hydrogenation and air oxidation processes

Hydrogenations and air oxidations usually have low apparent reaction rate, generally controlled by mass transfer rate, and widely exist in the modern chemical manufacturing process. The key to increase the mass transfer rate is the reduction of the liquid film resistance 1/ k L a . In this work, the original concept of microinterface intensification for mass transfer and then for these reactions has been proposed. We derived the regulation model and set up the mathematical calculation method of micron-scale gas-liquid interface structure on mass transfer and reaction, designed the mechanical energy exchange device that can produce gas-liquid microinterface system on a large scale, and established the OMIS system which is able on line to measure the diameter and distribution of millions of microbubbles, interface area a and mass transfer film thickness δ M , as well as developed a series of microinterface intensified reactor systems (MIRs) for the applications of hydrogenation and air oxidation processes. It is believed that this research will provide an up-to-date development for the intensification of hydrogenation and air oxidation reactions.

Nucleation–Oxidation coupled technology for High-Nickel ternary cathode recycling of spent Lithium-ion batteries

Demand of ternary Li-ion batteries (LIBs) has risen dramatically in recent times, making it necessary to efficiently recycle spent cathode materials to reduce environmental pollution and alleviate the tight supply of various elements including Li, Co, and Ni. Co-precipitative regeneration of spent LIBs is typically employed to recycle Li, Co, Ni, and Mn. However, it is difficult to evenly distribute metals in the regenerated materials. Moreover, the emission of heavy-metal ions makes it difficult to meet the environmental guidelines. Here, we develop a nucleation–oxidation coupled technology to efficiently recover Ni, Co, and Mn from spent ternary cathodes by forming layered double hydroxides (LDHs) in a micro-liquid-film reactor. After recycling, 98% Li remains in the liquid phase, while the Ni, Co, and Mn in the filtrate decrease to the ppb level. Atomic distribution of Ni, Co, and Mn can be achieved in LDH, which helps realize the full-life-cycle of ternary cathode materials. It is difficult for the high-nickel ternary e.g., LiNi0.8Co0.1Mn0.1O2 to regenerate into LDH through spontaneous air oxidation. The micro-liquid-film reactor has a strong shear rate (maximum 1.04 × 106 s−1 is three orders of magnitude larger than that of the stirred reactor) and large vorticity (∼1.18 × 105 s−1, three orders of magnitude greater than that of the stirred reactor). It can enhance the transfer and diffusion of oxygen in the liquid phase. Hence, the micro-liquid-film reactor can greatly strengthen air-oxidation reaction of Ni2+, Co2+, and Mn2+ to sufficiently form trivalent cations, while the nucleation–oxidation-coupled regeneration is realized during the nucleation stage.

1,3‐Dimethylbarbituric Acid Promoted Metal‐Free Cascade Annulation for Straightforward Access to Benzimidazole‐Fused Heterocycles

A convenient and novel 1,3-dimethylbarbituric acid-mediated methodology for constructing diverse benzimidazole-fused heteroaromatics has been developed. This metal-free cascade annulation of readily available 3-formylchromones, 1,2-diaminoarenes, and cyclic 1,3-dicarbonyl compounds provides an alternative synthetic route in the green conditions. 1,3-Dimethylbarbituric acid acts as a protecting group and accelerates intramolecular cyclization. This one-pot protocol proceeds through cascade nucleophilic addition, ring-opening, Michael-type addition, intramolecular cyclization, elimination, and air oxidation reactions.

Manganese-doped molybdenum oxide boosts catalytic performance of electrocatalytic wet air oxidation at ambient temperature

Mn-doping strategy was adopted to modify the structure of MoO2 for enhancing its catalytic activity towards room-temperature electrocatalytic wet air oxidation (ECWAO) reaction. A series of Mn-doped MoO2 were prepared on carbon support, and their structures were investigated to elucidate the productive effect of Mn doping on the catalytic activity of MoO2. The incorporation of MnIII/MnII into the MoO2 lattice induced the transformation from MoIV to MoV and created more oxygen vacancies. Such structural modifications promoted the electron transfer of MoO2 through the redox couples between MoVI/MoV/MoIV and MnIII/MnII, and facilitated the transformation from O2 to adsorbed oxygen species on MoO2 surface. As a result, the ECWAO catalytic activities of Mn-doped MoO2/graphite felt (MoO2/GF) outperformed the activity of MoO2/GF. Among the synthesized series, Mn0.066:MoO2/GF exhibited the highest activity with the maximum turnover frequency (TOF) promoted by 59% than the undoped MoO2/GF. Under the catalysis of Mn0.066:MoO2/GF, the ECWAO process obtains mineralization efficiencies generally above 85% in degrading typical pharmaceutics and person care products (PPCPs). These findings are anticipated to open up a new venue in the design and fabrication of highly active catalysts for air oxidation reactions by using the strategy of selective dopant-induced structure modification.

A mechanism study of acid-assisted oxidative stabilization of asphaltene-derived carbon fibers

The development of inexpensive carbon fiber precursors is necessary to meet the future demands of carbon fibers. This work shows how asphaltenes, which are obtained as a by-product in bitumen production, can play an important role as such inexpensive carbon fiber precursors. To synthesize carbon fibers from asphaltene, stabilization by means of oxidizing acids (HNO3 and H2SO4) was developed. Stabilization could not be achieved by a non-oxidizing acid (HCl). The reactions leading to fiber stabilization was investigated for nitric acid treatment, which led to oxidation and the incorporation of nitro-groups. Further thermal treatment caused an increase in C/H ratio that was related to decomposition of nitro-groups, which facilitated air oxidation and other reactions leading to the loss of volatile hydrogen-rich products, such as light hydrocarbons. Additionally, the influence of the acid concentration during treatment on fiber properties, such as fiber diameter, composition, tensile strength and elastic modulus, has been examined. The application of the acid treatment leads to carbon fibers with good tensile properties, with a tensile strength and elastic modulus of 811 MPa and 32.7 GPa, respectively. The overall yield of carbon fibers is 37 – 38 wt.%.

Magnet-assisted laser hole-cutting in magnesium alloys with and without water immersion

The magnet-assisted laser hole-cutting in magnesium alloys was explored systematically with and without using water immersion, including femtosecond laser multilayer center-oriented hole-cutting and millisecond laser helical hole-cutting of both blind holes and through holes. The effect of the magnetic field and water immersion on laser hole-cutting quality, efficiency and performance is first reported for magnesium alloys with mechanism analysis and comparable discussion. It was shown that the magnetic assistance and/or the water medium improved the hole wall formation especially for underwater laser cutting of blind holes. Compared to laser hole-cutting in air, the underwater laser hole-cutting generated higher-quality holes in magnesium alloys. For laser hole-cutting in magnesium alloys in water, it is first reported that the magnetic field increases the entrance diameters for blind and through holes while decreases the blind-hole depth. The water cooling-insulating effect prevented the molten and vaporized material from re-solidifying and re-depositing onto the workpiece, and the laser-induced ignition and explosion were also prevented by water. The local laser-induced ignition and explosion were weakened when increasing the magnetic flux density. The local oxidation and carbonization reactions in air as a result of the laser-induced ignition and explosion were suppressed while the laser hole-cutting efficiency was enhanced by using the transverse magnetic assistance. The blind-hole recast layer was significantly reduced nearly without accumulated residues and carbonized or oxidized debris by using underwater laser hole-cutting, indicating that the water suppressed the laser-induced melting, vaporization, ignition and explosion and blocked the re-solidification and re-deposition surrounding the hole entrance and onto the hole wall for the recast layer formation. The average grain size number in the heat affected zone (HAZ) near the hole was improved for grain refinement by increasing the magnetic flux density, demonstrating the magnetic field-induced reduction for the local excessive thermal effect of the femtosecond laser-generated plasma on laser hole-cutting and recrystallization. The micro hardness was improved after laser hole-cutting with and without magnetic assistance mainly due to the HAZ recrystallization-induced grain refinement, and the hardness value roughly increased with the magnetic flux density.

Effective removal of naproxen from aqueous solutions by CWAO process using noble metals supported on carbon nanospheres catalysts

In this research the technical feasibility of catalytic wet air oxidation reactions (CWAO) with a novel ruthenium supported onto carbon nanospheres (CNS-Ru) catalyst for the degradation of a non-steroidal anti-inflammatory drug (NSAID), naproxen (NPR), has been tested. The operating conditions of the reaction, the different loads of ruthenium in the catalyst, the reuse of the material, the reaction kinetics and the degradation mechanism of the pollutant were studied. The complete degradation of the compound was reached in one cycle at the following conditions: 130 °C, 20 bar, [NPR]0 = 20 mg∙L−1, [CNS-Ru] = 0.75 g∙L−1, 2%wt. of ruthenium and an initial pH of 7.0. At these conditions, the efficiency for the pollutant degradation of a platinum-based catalyst (CNS-Pt) as well as its reusability were also tested. In this sense, better results regarding to the NPR degradation were obtained with the CNS-Ru material. Nevertheless, both catalysts could be considered stable after 4 consecutive runs. Furthermore, two potential kinetic models were investigated in order to simulate the degradation of NPR in both WAO and CWAO processes. Thus, the detection of 13 reaction compounds allowed to propose a degradation mechanism for NPR by CWAO. The efficiency of both catalysts was tested in a real hospital wastewater matrix; it was also proved that the NPR degradation decreased in comparison to that one found for the ultrapure water solutions, and that CNS-Ru catalyst achieved a higher pollutant degradation rather than that obtained for CNS-Pt catalyst.

Regeneration process using CO2in situ of Ni-Y2O3-Al2O3 aerogel spent catalysts from dry reforming with continuous syngas production

Deactivation by coke deposition is one of the most important challenges during reforming processes. High active and coke resistant catalysts, Ni-Y2O3-Al2O3 aerogel, were used in dry reforming reaction and an innovative regeneration process using in situ CO2 was proposed. Results showed that the catalytic activity is recovered using in situ CO2 coke gasification at 650–700 °C. However, temperature higher than 700 °C causes deactivation by sintering. An extended test of 10 successive reforming/regeneration cycles at 700 °C was performed using a catalyst containing 2.5 wt% of Y2O3 and the catalytic activity was completely preserved. CO2 regeneration at same temperature of dry reforming proved to be an excellent alternative to conventional air oxidation reactions to remove the coke. This advantageous catalyst regeneration not only produces useful CO by reaction between coke and CO2, but also allows the maintenance of operating conditions in reactor and enables the use of greenhouse gas.

Catalytic behaviors of manganese oxides in electro-assisted catalytic air oxidation reaction: Influence of structural properties

The electro-assisted catalytic wet air oxidation (ECWAO) process is effective for pollutants removal, by taking advantage of an anodic electric field to activate O2 on a catalyst surface. Herein, three different manganese oxides, including MnO2, Mn3O4 and MnO, are fabricated on graphite felt (GF) support to serve as the catalysts of ECWAO reaction. Structural properties of these manganese oxides are analyzed, and their catalytic behaviors in ECWAO reaction are investigated with bisphenol A as a probe pollutant. The manganese centers on the surface of manganese oxides are found to be present in multi-valence states, favoring the formation of chemisorbed oxygen species which are responsible for pollutants oxidation in the ECWAO process. Therefore, the manganese oxides demonstrate good and stable activity for catalytic oxidation of bisphenol A under room condition. The sequence of their catalytic activities is as follows: Mn3O4 > MnO > MnO2, depending on their low-temperature reducibility and oxygen mobility in them. These results illustrate a guideline to the design of highly active manganese oxide catalysts for the ECWAO reaction.

Syngas production from municipal solid waste with a reduced tar yield by three-stages of air inlet to a downdraft gasifier

Municipal solid waste is potentially converted into gaseous fuel through gasification. Tar, the by product, must be reduced to a minimum. In this study, tar was suppressed by applying multi-stage downdraft gasifier with three air inlets in the zone of pyrolysis, oxidation, and reduction in which the whole air for the entire zone was regulated at 21.12 kg/h according to the equivalent ratio (ER) of 0.4. Fixed equivalent ratio was used as a benchmark for single stage numerous air ratios for the three zones were investigated used to obtain optimum performance. The optimum ratio was found to be 10:80:10. LHV and CGE were increased as the increase in CO, H2 and CH4 concentrations which were triggered by the increase in temperature and the increased rate of the reaction that produces the gas. Char and air oxidation reactions not only occurred in the partial oxidation zone but also occurred in the pyrolysis and reduction zones or the oxidative pyrolysis and heterogeneous oxidation reactions so that the layers of hot zones increased. Tar passed the larger hot zones was favorable for the thermal cracking of tar. Pyrolysis temperature rose of from 449 °C to 521 °C and energy neutral point has been reached so that changes like endothermic be exothermic. The air in the reduction zone activated the char layer to be more reactive. Improved performance multi-stage air inlet as compared with single stage gasifier can be used as a reference in the optimization of operating parameters for the wider applications of further MSW gasification.

Syntheses, crystal structures and photocatalytic properties of transition metal complexes based on 9,10-anthraquinone-1,3-dicarboxylate

Five transition metal complexes based on the ligand 9,10-anthraquinone-1,3-dicarboxylate acid (1,3-H2AQDC) have been synthesized and characterized by physico-chemical and spectroscopic methods. Single-crystal analyses show that the complexes {Mn(1,3-AQDC)(H2O)4·(H2O)}n, {Zn(1,3-AQDC)(H2O)4·(H2O)}n, {Ni(1,3-AQDC)(4,4′-bpy)(H2O)2(CH3OH)}n and {Co(1,3-AQDC)(4,4′-bpy)(H2O)2(CH3OH)}n (4,4′-bpy = 4,4′-bipyridine) comprise one-dimensional (1D) chains in their crystal structures, while [Ni(1,3-AQDC)(H2O)4·(H2O)3]2 bears dimeric units, and these secondary building units are further linked by hydrogen bonding to form three-dimensional structures. These compounds proved to be able to catalyze visible-light-driven air-oxidation reactions of diarylethyne into diketones under mild conditions.

Oxidation Behavior of the Skutterudite Material Ce0.75Fe3CoSb12

A thermoelectric generator is a powerful system used to produce electricity by the action of heat. The development of nanostructured thermoelectric materials is widespread with the objective to improve their efficiency. However, if these materials are used at high temperatures under oxidative atmosphere (e.g., in air), they may suffer degradation in service, drastically decreasing their lifespan. This work investigates the oxidation behavior of an innovative skutterudite material made of cerium, iron, cobalt and antimony (Ce0.75Fe3CoSb12) either microstructured or nanostructured. For that purpose, several oxidation experiments are carried out under a flow of synthetic air at 650 K (15 h, 50 h and 100 h). The oxide layers formed on surface are observed, and their characteristics (chemical composition, thickness, structure) are compared to those obtained with microstructured Ce0.75Fe3CoSb12 samples. As a result, it is observed that the nanostructuring of the skutterudite materials slightly slow down the oxidation reactions in air. Consequently, the nanostructured Ce0.75Fe3CoSb12 is established to be a promising thermoelectric material for use in oxidative environments.

Air-stable metal hydride-polymer composites of Mg(NH2)2–LiH and TPX™

Light metal hydrides are prone to react with oxygen and/or water to produce oxides and/or hydroxides leading to reduction of hydrogen capacities, and deterioration of the hydrogen storage properties. It is therefore critical to address these issues when the materials are to be exposed to air or moisture. In this work, the combination of light metal hydrides, Mg(NH2)2–nLiH with polymethylpentene (TPX™), an air/moisture protective barrier is presented. It was found that the fabricated composites exhibit significant improvement of the metal hydrides stability in air. No oxidation reactions in air can be proven even after air exposure for 90 min. Extending the air-exposure time to 12 h, the reversible hydrogen capacities of these composites are much higher and more stable than they are in the case of the pure metal hydrides. In comparison to the pure metal hydrides, the composites retain the same hydrogen loading capacities and kinetic properties, with respect to the metal hydrides contents. Further, in situ synchrotron radiation powder X-ray radiation diffraction (SR-PXRD) experiments reveal that the thermal decomposition reaction pathways of the 90 min air-exposed composites are the same under air or H2 atmosphere. Moreover, morphology analysis confirms that the metal hydrides remain stable in the polymeric matrix and the three-dimensional integrity is retained, even after performing tens of de/re-hydrogenation cycles. The present study shows a promising way to fabricate air-stable metal hydride-polymer composite hydrogen storage materials that can be handled in ambient conditions.

Prediction of by-Products from Wet Air Oxidation Module for Sludge Treatment of Produced Water

This study presents and verifies the deep-well wet air oxidation (WAO) reaction model for treating organic sludge (among the various by-products discharged from produced water treatment facilities) for recycling, and predicts the reaction characteristics. The deep-well WAO reaction model is established theoretically and a simulation model is developed. The validity of the simulation model is examined by comparing the modeled pressure change inside the reactor with that given by a model developed in a previous study. In terms of the pressure profile inside the reactor, the developed simulation model shows a 2.3% difference from the previously proposed model. It is confirmed that the increase in reaction pressure and residence time inside the deep-well WAO reactor improves organic decomposition by increasing the oxygen mass transfer rate in water containing such organics.

Recent progress and challenges in membrane-based O2/N2separation

AbstractCompared with current conventional technologies, oxygen/nitrogen (O2/N2) separation using membrane offers numerous advantages, especially in terms of energy consumption, footprint, and capital cost. However, low product purity still becomes the major challenge for commercialization of membrane-based technologies. Therefore, numerous studies on membrane development have been conducted to improve both membrane properties and separation performance. Various materials have been developed to obtain membranes with high O2permeability and high O2/N2selectivity, including polymer, inorganic, and polymer-inorganic composite materials. The results showed that most of the polymer membranes are suitable for production of low to moderate purity O2and for production of high-purity N2. Meanwhile, perovskite membrane can be used to produce a high-purity oxygen. Furthermore, the developments of O2/N2separation using membrane broaden the applications of oxygen enrichment for oxy-combustion, gasification, desulfurization, and intensification of air oxidation reactions, while nitrogen enrichment is also important for manufacturing pressure-sensitive adhesive and storing and handling free-radical polymerization monomers.

Catalytic wet air oxidation of phenol over carbon nanotubes: Synergistic effect of carboxyl groups and edge carbons

It has been widely documented that the oxygen-containing functionalities, especially carboxyl groups, on carbon surfaces play crucial roles in the catalytic wet air oxidation (CWAO) reactions. Herein, the CWAO of phenol with molecular O2 as terminal oxidant using cylindrical and herringbone carbon nanotubes (CNTs) underwent different treatments as catalysts were conducted in batch mode. It was uncovered that the catalytic function of carboxyl groups strongly depended on the structure of CNTs. Parallel CNTs (p-CNTs) with cylindrical graphitic walls displayed the highest catalytic activity after nitric acid oxidation, due to the carboxylated carbon debris (CDs) coating on surfaces. For herringbone CNTs (h-CNTs), carboxyl groups are mostly linked to its sidewalls, where abundant edge carbons were exposed, providing an enhanced CWAO activity. The positively synergistic effect of carboxyl groups and adjacent edge carbons was responsible for the activation of O2, leading to the improved CWAO activity. This study provides a new insight into the structural effect of carbon materials on the CWAO of phenol.

Noncatalytic Liquid Phase Air Oxidation of Ethylbenzene to 1-Phenyl Ethyl Hydroperoxide in Low Oxygen Volume Fraction

The catalyst- and solvent-free liquid phase air oxidation reaction of ethylbenzene (EB) to 1-phenyl ethyl hydroperoxide (PEHP) was investigated at scheduled temperature and pressure with a separate deacidifying zone. The oxidation reaction was done in the titanium fabricated reactor at an oxygen volume fraction in the outlet gas less than 0.3%. The effects of several reaction parameters were studied in detail. In the optimal reaction conditions and instructions given in this work, the high selectivity to PEHP (above 95%) was achieved with EB conversion around 13%, and a clean feed (water and acid-free) was provided for the propene epoxidation reaction.