Oxidation Of Ethylene Research Articles

Kinetic modeling of the effect of the conditions of conjugate oxidation of propane and ethylene on the yield of propylene

The study of the oxidation of propane-ethylene mixtures by numerical kinetic modeling allowed us to establish that in the range of 400–600 oC with an increase in the conversion of propane with an increase in temperature, the selectivity of propylene formation passes through a maximum, the position of which depends on the concentration of ethylene in the initial mixture. The addition of ethylene to the initial mixture leads to a reduction in propane consumption and an increase in the selectivity of propylene formation. The conditions under which ethylene introduced into the initial mixture is not consumed during the process are determined, so formally it can be considered as a catalyst, and the process of propane oxidation as proceeding in a pseudo-catalytic regime.

Operando spectroelectrochemical insights into the selectivity difference of photoelectrocatalytic alcohol oxidation to aldehyde on hematite and titania

Operando spectroelectrochemical spectroscopy is employed to investigate the selectivity of ethanol oxidation on hematite and titania photoanodes. High selectivity of acetaldehyde formation from ethanol oxidation has been identified using the hematite photoanode, whilst modest selectivity and over-oxidation of acetaldehyde are observed using titania photoanodes. This difference in the acetaldehyde selectivity is correlated with the valence band potential. The valence band potential is also associated with the activation energy required for the over-oxidation of acetaldehyde. The activation energy of acetaldehyde oxidation by the photogenerated holes in hematite is 427 meV whilst only 45 meV is required for titania. Kinetic isotope effect shows that the rate-limiting step of ethanol oxidation on hematite and titania involves α-C–H bond breaking, and solvent molecules are important to assist the rehybridization of this α-C. The spectral analyses emphasize the importance of considering the band potential upon the selectivity of alcohol oxidation on a broad scope.

Accelerating the production of formate radicals for nitrate purification via a redox-regulated photocatalysis route

The treatment of nitrate (NO3−) pollutants is crucial for human health in the context of environmental pollution. Synergistic photocatalytic redox technology is feasible for reducing low-concentrated NO3− to achieve environmental purification. As combined redox reactions proceed in one photocatalysis system, incorporating suitable oxidative reactions is one potential strategy to enhance photocatalytic NO3− reduction efficiency. Herein, almost 100 % removal efficiency of NO3− and superior N2 selectivity of 93.99±0.45 % is achieved through the precise matching of synergistic oxidative half-reactions. The crucial role of active radicals is revealed. Specifically, the conversion efficiency of NO3− is determined by the cooperation of formate radicals (•CO2−), which are generated from the selective oxidation of formaldehyde, acetaldehyde or glyoxal. Among them, the optimum yield of •CO2− radicals are reached from the formaldehyde oxidative reaction. It is clarified that this research will contribute to a deep understanding of the removal and purification of NO3− in wastewater.

Nano zero valent iron stimulated acetaldehyde oxidation, electron transfer, and RBO pathway for enhanced medium-chain carboxylic acids production

Nano zero-valent iron (NZVI) has been shown to effectively enhance the chain elongation (CE) process, addressing the issue of limited yield of medium-chain carboxylic acids (MCCA) from organic wastewater. However, the specific impact of NZVI on the metabolism of CE bacteria (CEB) is not well understood. In this study, it was aimed to investigate the mechanism by which an optimal concentration of NZVI influences CE metabolism, particularly in relation to ethanol oxidation, electron transfer, and MCCA synthesis. This was achieved through single-factor influence experiments and metagenomic analysis. The results showed that the addition of 1 g/gVSS NZVI achieved the highest MCCA yield (n-caproic acid + n-octanoic acid) at 2.02 g COD/L, which was 4.9 times higher than the control. This improvement in MCCA production induced by NZVI was attributed to several factors. Firstly, NZVI facilitated the oxidation of acetaldehyde, leading to its reduced accumulation in the system (from 18.4 % to 5.8 %), due to the optimized chemical environment created by NZVI corrosion, including near-neutral pH and a more reductive oxidation–reduction potential (ORP). Additionally, the inherent conductivity property of NZVI and the additional Fe ions released during corrosion improved the electron transfer efficiency between CEB. Lastly, both the composition of microbial communities and the abundance of unique enzyme genes confirmed the selective stimulation of NZVI on the reverse β-oxidation (RBO) pathway. These findings provide valuable insights into the role of NZVI in CEB metabolism and its potential application for enhancing MCCA production in CE bioreactors.

Diastereoselective Synthesis of Pyridone ribo‐C‐Nucleosides via Heck Reaction and Oxidation

AbstractNucleosides find applications in medicinal chemistry, chemical biology and diagnostics. Among the nucleosides, C‐nucleosides have attracted particular attention because their carbon‐carbon bond between nucleobase and ribose provides stability against degradation. While several well‐established methods exist for the synthesis of 2′‐deoxy‐C‐nucleosides, the preparation of their ribofuranosyl counterparts is more challenging. Established methods for their synthesis give mixtures of anomers and require harsh reagents or conditions. Here we report a diastereoselective glycosylation method involving a Heck reaction between a glycal and an aryl iodide, followed by oxidation of the silyl enol ether with methyl(trifluoromethyl)dioxirane (TFDO). The resulting ketone is then diastereoselectively reduced to the ribonucleoside. The new route has been applied to pyridones and is expected to also yield other ribo‐C‐nucleosides in diastereoselective fashion.

Rutile TiO2-Supported Pt Nanoparticle Catalysts for the Low-Temperature Oxidation of Ethane to Ethanol.

Structure-function relationships of supported metal nanoparticle catalysts in the CO-assisted oxidation of ethane to ethanol were investigated. A rutile TiO2-supported Pt nanoparticle catalyst exhibited the highest ethanol production rate and selectivity. During the reaction, sequential changes in the geometric/electronic states and the particle size of the Pt nanoparticles were observed. The comparison of the catalytic performances of model catalysts with controlled metal-support interactions revealed that Pt0 nanoparticles of 2-3 nm with a high fraction of the surface Ptδ+ species are highly active for the oxidation of ethane to ethanol. The coadded CO plays a pivotal role not only in tuning the oxidation state of the surface Pt but also in producing H2O2, which is the true oxidant for the reaction. The supported Pt nanoparticle uses in situ-generated H2O2 to activate ethane, where the C2H5OOH intermediate is formed through a nonradical mechanism and subsequently converted to C2H5OH. This reaction occurs even at 50 °C with an apparent activation energy of 32 kJ mol-1. The present study sheds light on the usefulness of surface-engineered Pt nanoparticles for the low-temperature oxidation of ethane to ethanol.

Evaluation of hydrogen production via steam reforming and partial oxidation of dimethyl ether using response surface methodology and artificial neural network

This study aims to develop two models for thermodynamic data on hydrogen generation from the combined processes of dimethyl ether steam reforming and partial oxidation, applying artificial neural networks (ANN) and response surface methodology (RSM). Three factors are recognized as important determinants for the hydrogen and carbon monoxide mole fractions. The RSM used the quadratic model to formulate two correlations for the outcomes. The ANN modeling used two algorithms, namely multilayer perceptron (MLP) and radial basis function (RBF). The optimum configuration for the MLP, employing the Levenberg–Marquardt (trainlm) algorithm, consisted of three hidden layers with 15, 10, and 5 neurons, respectively. The ideal RBF configuration contained a total of 80 neurons. The optimum configuration of ANN achieved the best mean squared error (MSE) performance of 3.95e−05 for the hydrogen mole fraction and 4.88e−05 for the carbon monoxide mole fraction after nine epochs. Each of the ANN and RSM models produced accurate predictions of the actual data. The prediction performance of the ANN model was 0.9994, which is higher than the RSM model's 0.9771. The optimal condition was obtained at O/C of 0.4, S/C of 2.5, and temperature of 250 °C to achieve the highest H2 production with the lowest CO emission.

Highly Selective Photocatalytic Synthesis of Acetic Acid at 0-25 °C.

Acetic acid (AA), a vital compound in chemical production and materials manufacturing, is conventionally synthesized by starting with coal or methane through multiple steps including high-temperature transformations. Here we present a new synthesis of AA from ethane through photocatalytic selective oxidation of ethane by H2O2 at 0-25 °C. The catalyst designed for this process comprises g-C3N4 with anchored Pd1 single-atom sites. In situ studies and computational simulation suggest the immobilized Pd1 atom becomes positively charged under photocatalytic condition. Under photoirradiation, the holes on the Pd1 single-atom of OH-Pd1 /g-C3N4 serves as a catalytic site for activating a C-H instead of C-C of C2H6 with a low activation barrier of 0.14 eV, through a concerted mechanism. Remarkably, the selectivity for synthesizing AA reaches 98.7 %, achieved under atmospheric pressure of ethane at 0 °C. By integrating photocatalysis with thermal catalysis, we introduce a highly selective, environmentally friendly, energy-efficient synthetic route for AA, starting from ethane, presenting a promising alternative for AA synthesis. This integration of photocatalysis in low-temperature oxidation demonstrates a new route of selective oxidation of light alkanes.

Highly Selective Photocatalytic Synthesis of Acetic Acid at 0‐25oC

Abstract Acetic acid (AA), a vital compound in chemical production and materials manufacturing, is conventionally synthesized by starting with coal or methane through multiple steps including high‐temperature transformations. Here we present a new synthesis of AA from ethane through photocatalytic selective oxidation of ethane by H2O2 at 0‐25°C. The catalyst designed for this process comprises g‐C3N4 with anchored Pd1 single‐atom sites. In‐situ studies and computational simulation suggest the immobilized Pd1 atom becomes positively charged under photocatalytic condition. Under photoirradiation, the holes on the Pd1 single‐atom of OH‐Pd1Å/g‐C3N4 serves as a catalytic site for activating a C‐H instead of C‐C of C2H6 with a low activation barrier of 0.14 eV, through a concerted mechanism. Remarkably, the selectivity for synthesizing AA reaches 98.7%, achieved under atmospheric pressure of ethane at 0°C. By integrating photocatalysis with thermal catalysis, we introduce a highly selective, environmentally friendly, energy‐efficient synthetic route for AA, starting from ethane, presenting a promising alternative for AA synthesis. This integration of photocatalysis in low‐temperature oxidation demonstrates a new route of selective oxidation of light alkanes.

New insights and reaction mechanisms in the design of catalysts for the synergistic removal of NOx and VOCs from coke oven flue gas: Dual regulation of oxidative properties and acidic sites

The acid and redox sites of the MnCo catalysts are simultaneously fine-tuned by the addition of V. A dual-function catalyst, designated as V0.5Mn5Co5, has been constructed for the synergistic removal of NOx and volatile organic compounds under coke-oven flue gas conditions, which exhibits > 95 % NOx conversion and > 80 % N2 selectivity at 180–300 °C. Meanwhile, it removes 70 % of ethylene at 240 °C. Besides it has excellent sulfur and water resistance. The characterization results indicate that this acid-redox dual sites modulation strategy appropriately weakens the oxidation capacity of the catalysts while increasing the surface acidity of the catalysts. The catalyst mainly performs SCR reaction through the E-R mechanism, and N2O is generated through the transition dehydrogenation of NH3 and NSCR reaction. Ethylene is first adsorbed on the catalyst surface then oxidized to form carbonate species, and finally decomposed to CO2. Ethylene oxidation follows the MvK mechanism. There is a competitive adsorption between NH3 and C2H4, and a mutual inhibition between the SCR reaction and the ethylene oxidation reaction. V0.5Mn5Co5 exhibits excellent synergistic removal of NOx and VOCs in coke oven flue gas compared with commercial VWTi catalysts, which indicates great promise for industrial application.

Construction of an aptasensor based on the composite nanomaterial IL-rGO-TEPA/SiO2-AuPt and its high-sensitive detection of cardiac troponin I

To accurately diagnose and evaluate the degree of myocardial injury and predict myocardial infarction disease, the rapid and sensitive detection of cardiac troponin I (cTnI) is required. Therefore, a label-less electrochemical aptasensor was prepared for cTnI determination. Ionic liquid 1-hydroxyethy l-3- methyl imidazole four fluorine boric acid salt (IL)-reduced graphene oxide − four ethylene oxidation reduction five amine (rGO-TEPA)/silica (SiO2)- gold platinum (AuPt) (IL-rGO-TEPA/SiO2-AuPt) nanocomposites were synthetized as the substrate nanocomposite and were characterized using a series of characterization methods. The performance of the prepared aptasensor was characterized through electrochemical methods. Result displayed that better substrate materials were synthesized, and the prepared electrochemical aptasensor showed excellent electrochemical performance. Under optimal conditions, the electrochemical aptasensor had a salient analytical performance. The electrochemical signals linearly decreased with the logarithm of the cTnI concentration between the 0.5 pg·mL−1 and 1 × 106 pg·mL−1 concentration range (R2 value = 0.9955) and the aptasensor had a wide detection range (0.5 ∼ 1 × 106 pg·mL−1) and a low detection limit of 0.4 pg·mL−1. At the same time, the aptasensor had good selectivity, repeatability and stability. Relative standard deviation (RSD) values ranged from 3.45 % ∼ 4.97 % and the recovery rate was 97.5 % ∼ 103 % in human serum samples, the RSD values of the spiked recovery and ELISA method were less than 5 %. This study provides a new theoretical basis and method for the clinical detection of cTnI.

Aerobic Oxidation of PMB Ethers to Carboxylic Acids.

The first aerobic protocol of direct transformation of p-methoxybenzyl (PMB) ethers to carboxylic acids efficiently with Fe(NO3)3 ⋅ 9H2O and TEMPO as catalysts at room temperature has been developed. The reaction accommodates C-Br bond, terminal/non-terminal C-C triple bond, amide, cyano, nitro, ester, and trifluoromethyl groups. Even highly selective oxidative deprotection of different benzylic PMB ethers has been realized. The reaction has been successfully applied to the total synthesis of natural product, (R)-6-hydroxy-7,9-octadecadiynoic acid, demonstrating the practicality of the method. Based on experimental studies, a possible mechanism involving oxygen-stabilized benzylic cation has been proposed.

Impact of B-site cations of MgX2O4 (X=Cr, Fe, Mn) spinels on the chemical looping oxidative dehydrogenation of ethane to ethylene

Chemical looping oxidative dehydrogenation (CL-ODH) provides a multifunctional conversion platform that can take advantage of the selective oxidation of lattice oxygen in oxygen carrier to achieve high-valued ethane to ethylene conversion. In this study, we explored the effect of B-site element in MgX2O4 (X=Cr, Fe, or Mn) spinel-type oxygen carriers on the performance of ethane CL-ODH. The properties test and characterization of MgX2O4 spinel were tested by fixed bed and H2-TPR, O2-TPD, TG, in-situ Raman, SEM, and TEM. The results showed that because MgCr2O4 only released a small amount of adsorbed surface oxygen, it tended to catalyze the conversion of ethane to coke and hydrogen. MgFe2O4 facilitated the deep oxidation of ethane into CO2 by providing more surface lattice oxygen. Meanwhile, since a significant amount of bulk lattice oxygen was released by the MgMn2O4 oxygen carrier, it could burn hydrogen in a targeted manner to advance the reaction and increased ethylene’s selectivity. Thereby, MgMn2O4 achieved an ethane conversion of 73.72% with an ethylene selectivity of 81.46%. Furthermore, the MgMn2O4 catalyst demonstrated stable reactivity and an ethylene yield of about 62.00% in ethane CL-ODH over the 30 redox cycles. The screening tests indicated that the B-site elements in MgX2O4 spinel oxides could significantly influence their ability to supply lattice oxygen, thereby affecting their performance in ethane CL-ODH reaction.

Coupling Nitrate-Dependent Anaerobic Ethane Degradation with Anaerobic Ammonium Oxidation.

The microbial oxidation of short-chain gaseous alkanes (SCGAs, consisting of ethane, propane, and butane) serves as an efficient sink to mitigate these gases' emission to the atmosphere, thus reducing their negative impacts on air quality and climate. "Candidatus Alkanivorans nitratireducens" are recently found to mediate nitrate-dependent anaerobic ethane oxidation (n-DAEO). In natural ecosystems, anaerobic ammonium-oxidizing (anammox) bacteria may consume nitrite generated from nitrate reduction by "Ca. A. nitratireducens", thereby alleviating the inhibition caused by nitrite accumulation on the metabolism of "Ca. A. nitratireducens". Here, we demonstrate the coupling of n-DAEO with anammox in a laboratory-scale model system to prevent nitrite accumulation. Our results suggest that a high concentration of ethane (6.9-7.9%) has acute inhibition on anammox activities, thus making the coupling process a significant challenge. By maintaining ethane concentrations within the range of 1.7-5.5%, stable ethane and ammonium oxidation, nitrate reduction, and dinitrogen gas generation without nitrite accumulation were finally achieved. After the accomplished coupling of n-DAEO with anammox, nitrate reduction rates increased by 8.1 times compared to the rate observed with n-DAEO alone. Microbial community profiling via 16S rRNA gene amplicon sequencing showed "Ca. A. nitratireducens" (6.6-12.9%) and anammox bacteria "Candidatus Kuenenia" (3.4-5.6%) were both dominant in the system, indicating they potentially form a syntrophic partnership to jointly contribute to nitrogen removal. Our findings offer insights into the cross-feeding interaction between "Ca. A. nitratireducens" and anammox bacteria in anoxic environments.

Isomolar high-entropy engineering and Ac-coordination regulated nanocubic hydroxystannate for synergistic adsorption-photocatalytic acetaldehyde abatement under anoxic conditions

High-entropy materials have attracted increasing attention in many applications due to their unusual properties, yet little is known about the effects of cationic ratios and anionic ligands on their catalytic activity. Herein, a novel isomolar high-entropy and Ac-coordinated hydroxystannate nanocube (iHEOH-Ac) is fabricated using NaOH as precipitant and acetate anion as ligand in one step. The unique strategy simultaneously employing isomolar high-entropy engineering and Ac coordination in iHEOH-Ac synergistically facilitates the formation of oxygen vacancies and acid sites and significantly enhances optical absorption, charge separation and acetaldehyde activation, leading to the highest amount of ROS (•OH and •O2– and h+). The synergistic adsorption-photocatalytic performance of iHEOH-Ac in acetaldehyde abatement outperforms its net photocatalytic mode and other counterparts, with maximum removal ratio up to ∼ 100% under anoxic conditions and reversible deactivation of ∼ 10% over 360 min. This work not only sheds light on the enhancement mechanism on the acetaldehyde oxidation performance through isomolar high-entropy and Ac-coordinated strategy, but also successfully regulates the acetaldehyde oxidation pathways by the reaction mode and anionic coordination environment, providing a new route for the design of high-performance acetaldehyde oxidation photocatalysts under anoxic environments.

Nitrite-driven anaerobic ethane oxidation

Ethane, the second most abundant gaseous hydrocarbon in vast anoxic environments, is an overlooked greenhouse gas. Microbial anaerobic oxidation of ethane can be driven by available electron acceptors such as sulfate and nitrate. However, despite nitrite being a more thermodynamically feasible electron acceptor than sulfate or nitrate, little is known about nitrite-driven anaerobic ethane oxidation. In this study, a microbial culture capable of nitrite-driven anaerobic ethane oxidation was enriched through the long-term operation of a nitrite-and-ethane-fed bioreactor. During continuous operation, the nitrite removal rate and the theoretical ethane oxidation rate remained stable at approximately 25.0 mg NO2–N L−1 d−1 and 11.48 mg C2H6 L−1 d−1, respectively. Batch tests demonstrated that ethane is essential for nitrite removal in this microbial culture. Metabolic function analysis revealed that a species affiliated with a novel genus within the family Rhodocyclaceae, designated as 'Candidatus Alkanivoras nitrosoreducens', may perform the nitrite-driven anaerobic ethane oxidation. In the proposed metabolic model, despite the absence of known genes for ethane conversion to ethyl-succinate and succinate-CoA ligase, 'Ca. A. nitrosoreducens' encodes a prospective fumarate addition pathway for anaerobic ethane oxidation and a complete denitrification pathway for nitrite reduction to nitrogen. These findings advance our understanding of nitrite-driven anaerobic ethane oxidation, highlighting the previously overlooked impact of anaerobic ethane oxidation in natural ecosystems.

Infrared spectroscopy of the syn-methyl-substituted Criegee intermediate: A combined experimental and theoretical study.

An IR-vacuum ultraviolet (VUV) ion-dip spectroscopy method is utilized to examine the IR spectrum of acetaldehyde oxide (CH3CHOO) in the overtone CH stretch (2νCH) spectral region. IR activation creates a depletion of the ground state population that reduces the VUV photoionization signal on the parent mass channel. IR activation of the more stable and populated syn-CH3CHOO conformer results in rapid unimolecular decay to OH + vinoxy products and makes the most significant contribution to the observed spectrum. The resultant IR-VUV ion-dip spectrum of CH3CHOO is similar to that obtained previously for syn-CH3CHOO using IR action spectroscopy with UV laser-induced fluorescence detection of OH products. The prominent IR features at 5984 and 6081cm-1 are also observed using UV + VUV photoionization of OH products. Complementary theoretical calculations utilizing a general implementation of second-order vibrational perturbation theory provide new insights on the vibrational transitions that give rise to the experimental spectrum in the overtone CH stretch region. The introduction of physically motivated small shifts of the harmonic frequencies yields remarkably improved agreement between experiment and theory in the overtone CH stretch region. The prominent features are assigned as highly mixed states with contributions from two quanta of CH stretch and/or a combination of CH stretch with an overtone in mode 4. The generality of this approach is demonstrated by applying it to three different levels of electronic structure theory/basis sets, all of which provide spectra that are virtually indistinguishable despite showing large deviations prior to introducing the shifts to the harmonic frequencies.

Redox-induced controllable engineering of MnO2-MnxCo3-xO4 interface to boost catalytic oxidation of ethane

Multicomponent oxides are intriguing materials in heterogeneous catalysis, and the interface between various components often plays an essential role in oxidations. However, the underlying principles of how the hetero-interface affects the catalytic process remain largely unexplored. Here we report a unique structure design of MnCoOx catalysts by chemical reduction, specifically for ethane oxidation. Part of the Mn ions incorporates with Co oxides to form spinel MnxCo3-xO4, while the rests stay as MnO2 domains to create the MnO2-MnxCo3-xO4 interface. MnCoOx with Mn/Co ratio of 0.5 exhibits an excellent activity and stability up to 1000 h under humid conditions. The synergistic effects between MnO2 and MnxCo3-xO4 are elucidated, in which the C2H6 tends to be adsorbed on the interfacial Co sites and subsequently break the C-H bonds on the reactive lattice O of MnO2 layer. Findings from this study provide valuable insights for the rational design of efficient catalysts for alkane combustion.

Derivatives of Br-doped metal-organic framework for improved acetaldehyde adsorption-photocatalytic oxidation

Different Br-doped metal-organic frameworks (MOFs) derived (Brx@UiO-66) have been prepared by heat treatment using UiO-66 as the precursor. The experimental results showed that Br0.2@UiO-66 exhibited the best photocatalytic oxidation and adsorption performances toward acetaldehyde. In the dynamic system, the acetaldehyde removal rate and adsorption capacity of Br0.2@UiO-66 were 93.2 % and 230.59 mg/g, respectively. The improvement of the photocatalytic performance can be attributed to the presence of Br ions and CBr bonds, which facilitated the rapid separation of electrons and holes and the production of •O2−. In addition, Br0.2@UiO-66 had a better adsorption performance than 300UiO-66, mainly because of the increased Lewis acidity of the metal active sites due to Br doping. Radical capture experiments indicated that •O2− and e- were the primary active substances in acetaldehyde oxidation, and allowed establishing the possible mechanism of acetaldehyde oxidation. This work shows that MOFs can have high catalytic oxidation performances toward volatile organic compounds (VOCs) while retaining their adsorption capacity, and can be used for practical applications in the adsorption-catalytic integrated degradation of VOCs.

Oxidative C–N Bond Formation of Isochromans Using an Electronically Tuned Nitroxyl Radical as Catalyst

AbstractThe cross-dehydrogenative coupling between isochromans and nucleophiles using an electronically tuned nitroxyl radical catalyst, which effectively promotes the oxidation of benzylic ethers, has been investigated. Using sulfonamides as a nucleophile, modification of isochromans via oxidative C–N bond formation has been achieved at ambient temperature.