Oxidation Of Ethylene Research Articles

Numerical simulation of stable and unstable ram-mode operation of an axisymmetric ethylene-fueled inlet-isolator-combustor configuration

Large-eddy simulations of stable and unstable ramjet operational modes are presented for an axisymmetric inlet-isolator-combustor configuration experimentally tested in the University of Illinois's ACT-II arc-heated combustion tunnel. A 32 species ethylene oxidation mechanism including nitrous oxide formation reactions is used in the calculations (HyChem FFCM 2.0). Conjugate heat-transfer models based on an assumed penetration depth of the applied heating load are used to account for localized wall heating during the short durations (∼0.2 to 0.3 s) of the parts of the experiments simulated in this work. The results show a marked sensitivity to trace levels of atomic oxygen (∼1% by mass) in the free stream, a consequence of the arc-heating process. Atomic oxygen significantly reduces ignition delay at the relatively low pressures present within the configuration. With 1% atomic oxygen in the free stream, a jet-wake stabilized, partially-premixed flame structure emerges during thermal-throat ramjet operation at an equivalence ratio of 1.24, in accord with available experimental pressure and imaging measurements. Considering the free stream as pure air results in a cavity-wake stabilized, rich premixed flame. Simulations of unstable ram-mode operation leading to inlet unstart at an equivalence ratio of 1.97 also indicate a sensitivity to the free-stream composition. A reduction in atomic oxygen concentration to 0.8% by mass yields good agreement with the experimentally-observed isolator shock-train propagation speed. Both the computational and experimental results indicate that the shock train accelerates before being disgorged from the inlet. This acceleration stems from a rapid increase in the sizes of regions of low speed, sometimes separated flow behind Mach disks that form as the shock train proceeds upstream.

Observations and modelling of glyoxal in the tropical Atlantic marine boundary layer

Abstract. In situ field measurements of glyoxal at the surface in the tropical marine boundary layer have been made with a temporal resolution of a few minutes during two 4-week campaigns in June–July and August–September 2014 at the Cape Verde Atmospheric Observatory (CVAO; 16∘52′ N, 24∘52′ W). Using laser-induced phosphorescence spectroscopy with an instrumental detection limit of ∼1 pptv (1 h averaging), volume mixing ratios up to ∼10 pptv were observed, with 24 h averaged mixing ratios of 4.9 and 6.3 pptv observed during the first and second campaigns, respectively. Some diel behaviour was observed, but this was not marked. A box model using the detailed Master Chemical Mechanism (version 3.2) and constrained with detailed observations of a suite of species co-measured at the observatory was used to calculate glyoxal mixing ratios. There is a general model underestimation of the glyoxal observations during both campaigns, with mean midday (11:00–13:00) observed-to-modelled ratios for glyoxal of 3.2 and 4.2 for the two campaigns, respectively, and higher ratios at night. A rate of production analysis shows the dominant sources of glyoxal in this environment to be the reactions of OH with glycolaldehyde and acetylene, with a significant contribution from the reaction of OH with the peroxide HC(O)CH2OOH, which itself derives from OH oxidation of acetaldehyde. Increased mixing ratios of acetaldehyde, which is unconstrained and potentially underestimated in the base model, can significantly improve the agreement between the observed and modelled glyoxal during the day. Mean midday observed-to-modelled glyoxal ratios decreased to 1.3 and 1.8 for campaigns 1 and 2, respectively, on constraint to a fixed acetaldehyde mixing ratio of 200 pptv, which is consistent with recent airborne measurements near CVAO. However, a significant model under-prediction remains at night. The model showed limited sensitivity to changes in deposition rates of model intermediates and the uptake of glyoxal onto aerosol compared with sensitivity to uncertainties in chemical precursors. The midday (11:00–13:00) mean modelled glyoxal mixing ratio decreased by factors of 0.87 and 0.90 on doubling the deposition rates of model intermediates and aerosol uptake of glyoxal, respectively, and increased by factors of 1.10 and 1.06 on halving the deposition rates of model intermediates and aerosol uptake of glyoxal, respectively. Although measured levels of monoterpenes at the site (total of ∼1 pptv) do not significantly influence the model calculated levels of glyoxal, transport of air from a source region with high monoterpene emissions to the site has the potential to give elevated mixing ratios of glyoxal from monoterpene oxidation products, but the values are highly sensitive to the deposition rates of these oxidised intermediates. A source of glyoxal derived from production in the ocean surface organic microlayer cannot be ruled out on the basis of this work and may be significant at night.

Enhanced photocatalytic activity of TiO2 by K incorporation towards acetaldehyde and NO oxidation: The role of K single-ion dopants and additional K-compound structures

Various amounts of K were deposited on TiO2 (P25), and the resulting structures were used as photocatalysts for acetaldehyde and NO oxidation. For acetaldehyde under dry and moderately humid conditions, 0.008 wt% of K boosted photocatalytic activity, whereas higher K contents resulted in declined activity. A small amount of K modified the lattice and optical properties of TiO2, resulting in the enhanced photocatalytic activity, whereas excessive K formed separate and less active K-compound structures on the TiO2 surface. In contrast, the photocatalytic activity was gradually decreased with increasing K content for acetaldehyde oxidation under higher humidity conditions, whereas the NO3– selectivity for NO oxidation gradually increased as K content increased. We highlight different roles of K species in TiO2 samples with dissimilar structural properties, and the necessity of fine adjustment of the K content in K-TiO2, depending on the reactions and conditions, to which photocatalysts are applied.

Manganese Catalyzed Partial Oxidation of Light Alkanes

The catalytic partial oxidation of methane is achieved at low temperatures (<200 °C) using manganese oxides and manganese salts in mixtures of trifluoroacetic acid and trifluoroacetic anhydride. Dioxygen is used as the in situ terminal oxidant. For Mn oxides (e.g., MnO2, Mn2O3, and Mn3O4), we studied stoichiometric methane partial oxidation in HTFA (TFA = trifluoroacetate). Using a Mn trifluoroacetate salt, at 180 °C and under 25 psig of methane, product selectivity for the mono-oxidized product methyl trifluoroacetate (MeTFA) is observed to be >90% at ∼35% methane conversion at approximately 6 turnovers. Under our catalytic methane oxidation reaction conditions, MeTFA is stable against overoxidation, which explains the likely high selectivity at conversions >15%. Using combined experimental studies and DFT calculations, a mechanism involving soluble and molecular Mn species in the catalytic cycle is proposed. The proposed reaction pathway involves initial activation of MnII by dioxygen, cleavage of a methane C–H bond by a MnIII hydroxo intermediate, rebound of the methyl radical to generate MeTFA, and finally regeneration of the starting MnII complex. Also, this process is shown to be applicable to the oxidation of ethane, favoring the mono-oxidized product ethyl trifluoroacetate (EtTFA) and reaching ∼46% conversion.

Formation of PAHs, phenol, benzofuran, and dibenzofuran in a flow reactor from the oxidation of ethylene, toluene, and n-decane

The necessity to reveal the formation mechanism of not only polycyclic aromatic hydrocarbons (PAHs) but also oxygenated PAHs (OPAHs) during combustion is increasing. Although many studies on PAHs have been conducted, fundamental studies investigating OPAH formation are still limited. Phenol, benzofuran, and dibenzofuran were selected as OPAHs in this study. We experimentally investigated fuel-rich oxidation in a flow reactor at atmospheric pressure, mean gas temperatures from 1050 to 1350 K, residence times from 0.2 to 1.5 s, and equivalence ratios from 3.0 to 12.0. Ethylene, toluene, and n-decane were used as fuels. Three kinds of OPAHs as well as 23 kinds of PAHs including monocyclic structures were quantitatively measured through a direct sampling using gas chromatography mass spectrometry. The results showed that concentrations of PAHs and OPAHs were strongly affected by the fuel type, with increasing concentrations in the following order: ethylene < n-decane < toluene. A chemical kinetic model for OPAH formation was developed based on a recent PAH growth model. The model showed that the predicted concentrations of OPAHs and PAHs were in reasonable agreement with the measured data in this study. Some modifications were made to the previous model based on recent literature studies and on the comparison of the simulated and measured results. The effect of the fuel type on the formation of PAHs and OPAHs was investigated through kinetic analysis using the model to discuss their reaction pathways.

Copper‐Mediated Relay Strategy Using Chlorination/Oxidation: An Effective Synthesis of Functionalized Coumarin Derivatives

AbstractChromene‐fused heterocyclic compounds have shown fascinating biological and physiochemical properties and thus, the design and development of chromene‐fused heterocyclic molecules is of significant interest in the field of synthetic organic chemistry. We report an innovative ligand‐ and additive‐free synthetic approach of 4‐(phenylethynyl)‐2H‐chromene‐3‐carbaldehyde with phenylacetylenes has been described through sequential chlorination, benzannulation, benzylic sp3 C−H bond functionalization, and ether oxidation for the formation of chloro‐substituted‐9‐phenyl‐6H‐benzo[c]chromen‐6‐ones with readily available chemicals under one‐pot, base‐free conditions using CuCl2 as sustainable catalyst. In this regioselective approach, we defined a reasonably longer cascade, which reveals the multiple role of chlorine as chlorine supplier, Lewis acid catalyst and oxidation rate promoter that tolerates a broad substrate scope and allows good product yields. The authenticated mechanism proceeds in a cascading fashion through the formation of multiple bonds.

Enantioselective Organocopper-Catalyzed Hetero Diels-Alder Reaction through in Situ Oxidation of Ethers into Enol Ethers.

We disclose a catalytic method for the enantio- and diastereoselective union of alkyl ethers and heterodienes. We demonstrate that a chiral Cu-BOX complex catalyzes the efficient oxidation of ethers into enol ethers in the presence of trityl acetate. Then, the organocopper promotes stereoselective hetero Diels-Alder reaction between the in situ generated enol ethers and β,γ-unsaturated ketoesters, allowing for rapid access to an array of dihydropyran derivatives possessing three vicinal stereogenic centers.

Seasonal characteristics of atmospheric peroxyacetyl nitrate (PAN) in a coastal city of Southeast China: Explanatory factors and photochemical effects

Abstract. Peroxyacetyl nitrate (PAN) acting as a typical indicator of photochemical pollution can redistribute NOx and modulate O3 production. Coupled with the observation-based model (OBM) and a generalized additive model (GAM), the intensive observation campaigns were conducted to reveal the pollution characteristics of PAN and its impact on O3, the contributions of influencing factors to PAN formation were also quantified in this paper. The F values of GAM results reflecting the importance of the influencing factors showed that ultraviolet radiation (UV; F value = 60.64), Ox (Ox = NO2 + O3, 57.65), and air temperature (T, 17.55) were the main contributors in the PAN pollution in spring, while the significant effects of Ox (58.45), total VOCs (TVOCs, 21.63), and T (20.46) were found in autumn. The PAN formation rate in autumn was 1.58 times higher than that in spring, relating to the intense photochemical reaction and meteorological conditions. Model simulations revealed that acetaldehyde oxidation (46 %±4 %) contributed to the dominant formation pathway of PA (hence PAN), followed by methylglyoxal oxidation (28 %±3 %) and radical cycling (19 %±3 %). The PAN formation was highly VOC sensitive, as surplus NOx (compared with VOCs abundance) prevented NOx from being the limiting factor photochemical formation of secondary pollution. At our site, PAN promoted and inhibited O3 formation under high and low ROx levels, respectively. The PAN promoting O3 formation mainly occurred during the periods of 11:00–16:00 (local time) when the favourable meteorological conditions (high UV and T) stimulated the photochemical reactions to offer ROx radicals, which accounted for 17 % of the whole monitoring periods in spring and 31 % in autumn. The analysis of PAN formation mechanism and its positive or negative effect on ozone provided scientific insights into photochemical pollution mechanisms under various pollution scenarios in coastal areas.

Graphene modified “black {0 0 1}TiO2” nanosheets for photocatalytic oxidation of ethylene: The implications of chemical surface characteristics in the reaction mechanism

In this work, crystal facets, bandgap, size and shape of reduced graphene oxide (rGO) modified anatase {001} black TiO2 nanosheets (rGO-B-TiO2 NSTs) were tailored for the photocatalytic oxidation of ethylene under high humidity content. XRD, Raman and HR-TEM analyses confirm that rGO-B-TiO2 NSTs have a 94 % of exposed {001} facets with high number of oxygen vacancies. In addition, rGO-B-TiO2 NSTs exhibit increased values of surface area and porosity compared to its pristine form. A 48 and 34 μmol g−1 of ethylene are adsorbed at the surface of rGO-B-TiO2 NSTs in the absence and in the presence of humidity, respectively. In addition, operando DRIFTS analyses provide the insight of surface interactions between ethylene molecules and adsorption sites of rGO-B-TiO2 NSTs. The photocatalytic removal efficiencies of the synthesized materials under both UV and visible light irradiation proceed as follows: rGO-B-TiO2 NSTs > B-TiO2 NSTs > TiO2 NSTs > commercial TiO2 NPs. Further, ethylene is very quickly photocatalytic oxidized when rGO-B-TiO2 NSTs is applied under UV light irradiation, having a 72 and 92 % ethylene removal in the absence and in the presence of humidity, respectively. Moreover, a 48 and 58 % of ethylene removal takes place in the absence and presence of humidity under visible light irradiation, respectively. Results indicate that rGO-B-TiO2 NSTs boost the photocatalytic activity through their virtue of visible-light absorption properties (Bandgap = 2.61 eV) and the rapid electron-hole separation at the rGO {001} black TiO2 NSTs interfaces. Such findings are confirmed through UV-visible diffused reflectance, photoelectrochemical and photoluminescence analyses. Nanosheets made of rGO modified {001} black TiO2 could be used as an effective photocatalyst for the removal of ethylene from large volume fruit storage areas by exploiting a simple light source in the presence of high content of humidity.

Electrochemically activated copper nitroprusside as a catalyst for sensing of carcinogenic acetaldehyde in red wine

Acetaldehyde (AcH) is a carcinogenic, neurotoxic and genotoxic volatile organic compound present in beverages and pose hazardous effects on human health. Herein, we report electrochemically activated copper nitroprusside (CuNPr)-based sensor for the ultra-trace detection of AcH. CuNPr was synthesized by simple co-precipitation method and its physicochemical properties were characterized using spectroscopy and microscopy techniques. CuNPr-modified glassy carbon electrode (CuNPr/GCE) has been electrochemically activated prior to deploying for AcH sensing. The influence of electrochemical activation and supporting electrolytes (LiCl, NaCl, KCl, CsCl, KNO3, Na2HPO4/NaH2PO4, K2HPO4/KH2PO4) have been investigated. A better sensitivity of the sensor was obtained with potassium phosphate (K2HPO4/KH2PO4, pH 7.4) buffer. The electrochemical oxidation of AcH to acetate ions by CuNPr has been studied using in-situ spectroelectrochemical (UV absorption and Raman spectroscopy) analyses. Under optimized differential pulse voltammetric conditions, electrochemically activated CuNPr/GCE exhibited a wide linear range (2.5 × 10−8 – 2.5 × 10−1 M) with a limit of detection towards AcH as low as 41 × 10−8 M. The developed CuNPr/GCE sensor was employed for the sensing of AcH in undiluted commercial red wine sample and found to have good stability and anti-interference ability towards various co-existing ions in undiluted red wine.

Role of the Hydroxyl Groups Coordinated toTiO2 Surface on the Photocatalytic Decomposition of Ethylene at Different Ambient Conditions

The titania pulp—a semi product received from the industrial production of titania white—was submitted for the thermal heating at 400–600 °C under Ar and H2 to obtain TiO2 with different structure and oxygen surface defects. Heating of titania in H2 atmosphere accelerated dehydration and crystallisation of TiO2 compared to heating in Ar. TiO2 prepared at 500 and 600 °C under H2 had some oxygen vacancies and Ti3+ centres (electron traps), whereas TiO2 obtained at 450 °C under H2 exhibited some hole traps centres. The presence of oxygen vacancies induced adsorption of atmospheric CO2. It was evidenced, that ethylene reacted with TiO2 after UV irradiation. Formic acid was identified on TiO2 surface as the reaction product of ethylene oxidation. Hydroxyl radicals were involved in complete mineralisation of ethylene. TiO2 prepared at 500 °C under H2 was poorly active because some active sites for coordination of ethylene molecules were occupied by CO2. The most active samples were TiO2 with high quantity of OH terminal groups. At 50 °C, the physically adsorbed water molecules on titania surface were desorbed, and then photocatalytic decomposition of ethylene was more efficient. TiO2 with high quantity of chemisorbed OH groups was very active for ethylene decomposition. The acidic surface of TiO2 enhances its hydroxylation. Therefore, it is stated that TiO2 having acidic active sites can be an excellent photocatalyst for ethylene decomposition under UV light.

Nature and Reactivity of Oxygen Species on/in Silver Catalysts during Ethylene Oxidation

Nature and Reactivity of Oxygen Species on/in Silver Catalysts during Ethylene Oxidation

Cerium-Copper Oxides Synthesized in a Multi-Inlet Vortex Reactor as Effective Nanocatalysts for CO and Ethene Oxidation Reactions

In this study, a set of CuCeOx catalysts was prepared via the coprecipitation method using a Multi-Inlet Vortex Reactor: the Cu wt.% content is 5, 10, 20, 30 and 60. Moreover, pure CeO2 and CuO were synthesized for comparison purposes. The physico-chemical properties of this set of samples were investigated by complementary techniques, e.g., XRD, N2 physisorption at −196 °C, Scanning Electron Microscopy, XPS, FT-IR, Raman spectroscopy and H2-TPR. Then, the CuCeOx catalysts were tested for the CO and ethene oxidation reactions. As a whole, all the prepared samples presented good catalytic performances towards the CO oxidation reaction (1000 ppm CO, 10 vol.% O2/N2): the most promising catalyst was the 20%CuCeOx (complete CO conversion at 125 °C), which exhibited a long-term thermal stability. Similarly, the oxidative activity of the catalysts were evaluated using a gaseous mixture containing 500 ppm C2H4, 10 vol.% O2/N2. Accordingly, for the ethene oxidation reaction, the 20%CuCeOx catalyst evidenced the best catalytic properties. The elevated catalytic activity towards CO and ethene oxidation was mainly ascribed to synergistic interactions between CeO2 and CuO phases, as well as to the high amount of surface-chemisorbed oxygen species and structural defects.

A DFT study on the reaction mechanisms of the oxidation of ethylene mediated by technetium and manganese oxo complexes.

The oxidation of ethylene catalyzed by manganese and technetium oxo complexes of the type MO3L (M = Tc, Mn, and L = O-, Cl-, F-, OH-, Br-, I-) on both singlet and triplet potential energy surfaces (PESs) have been studied. All molecular structures were stable on the singlet PES except for the formation of the dioxylate intermediate for the MnO3L (L = O-, Cl-, F-, OH-, Br-, I-) catalyzed pathway. Frontier molecular orbital calculations showed that electrons flow from the HOMO of ethylene into the LUMO of the metal-oxo complex for all complexes studied except for MO3L (M = Tc, Mn, and L = O-) where the vice versa occurs. In the reaction of both TcO3L and MnO3L (L = O-, Cl-, F-, OH-, Br-, I-) with ethylene, it was observed that the formation of the dioxylate intermediate along the [3 + 2] addition pathway on the singlet reaction surface is both kinetically and thermodynamically favorable over its formation via the [2 + 2] pathway. Furthermore, it was observed that TcO4- and MnO4- catalyzed pathways exclusively form diols on the singlet PES. The formation of epoxides on the singlet surface is kinetically favorable through the [2 + 1] and [2 + 2] channel for the MnO3L (L = F-, Cl-, Br-, I-, OH-) and TcO3L (L = F-, Cl-, Br-, I-, OH-) catalyzed surfaces respectively. In all cases, the TcO3L complexes were found to be polar compared to the MnO3L complexes. The MnO4- (singlet) and MnO3F (singlet) are the best catalysts for the exclusive formation of the diols and epoxides respectively.

Controlled reaction depth by metal (M=Fe, Ni, Mn and Ti) doped ceria in selective oxidation of ethane with carbon dioxide

Fe, Ni, Mn, and Ti were directly doped into CeO2 lattice by hydrothermal method to form solid solution catalysts. Various techniques including N2 adsorption/desorption, XRD, HRTEM, XPS, H2-TPR, CO2-TPD, O2-TPD, Raman, and thermogravimetric techniques were applied to study the structural evolution under the preparation/reaction conditions. The incorporation of metal elements distorted the lattice, the difference of interaction resulted in the differences of redox, oxygen activity, basicity and surface etc. properties. The catalytic conversion of ethane with CO2 exhibited dry reforming feature on Ni doped ceria because of the in situ formed metallic Ni0, and selective oxidation feature on Fe, Mn and Ti doped samples. The number and activity of lattice oxygen played the dominant role in affecting activity and selectivity. The solid solution catalysts revealed good coke resistance.

Auger- and photoelectron coincidences of molecular O2 adsorbed on Ag(111)

The oxygen on Ag(111) system has been investigated with Auger electron–photoelectron coincidence spectroscopy (APECS). The coincidence spectra between O 1s core level photoelectrons and O KLL Auger electrons have been studied together with Ag3d/AgM4,5NN coincidences. We also describe the electron–electron coincidence spectrometer setup, CoESCA, consisting of two angle resolved time-of-flight spectrometers at a synchrotron light source. Contributions from molecular oxygen and chemisorbed oxygen are assigned using the coincidence data, conclusions are drawn primarily from the O 1s/O KLL data. The data acquisition and treatment procedure are also outlined. The chemisorbed oxygen species observed are relevant for the catalytic ethylene oxidation.

Metal organic framework assisted Co-Ce mixed oxide catalyst for carbon monoxide and ethylene oxidation

A series of CeO2/Co3O4 mixed nanocomposites with various Ce loading were fabricated by the pyrolysis of MOFs (metal organic frameworks), and their catalytic performance were evaluated by CO and C2H4 oxidation reaction. The prepared catalysts inherited polyhedral morphology of ZIF-67 (Zeolitic Imidazolate Framework-67) nanoparticles. By means of the synergistic effect of two different transition metal oxides, the catalysts exhibited superior performance for CO and C2H4 oxidation. The results show that for 2% - 8% doping ratio of CeO2, the T50 (50% conversion temperature) of CO and C2H4 decreased by 32 and 33 °C, respectively, as compared with the MOF-assisted pure Co3O4 catalyst. Stability of the catalyst was greatly enhanced with optimal Ce doping to Co3O4. A number of characterization techniques were used to study the morphology and physicochemical properties of the prepared catalysts. With the incorporation of Ce, polyhedral Co-Ce catalysts promoted specific surface area and lower reduction temperature. Likewise, Co3+/Co2+ and Oads/Olatt improved with the addition of Ce, which played a significant role in CO and C2H4 oxidation at low temperatures.

The effect of the addition of nitrogen oxides on the oxidation of ethane: An experimental and modelling study

This study reports new ignition delay time (IDT) measurements of ethane (C2H6)/‘air’ mixtures with NOx (nitric oxide (NO), nitrogen dioxide (NO2), and nitrous oxide (N2O)) addition in the range 0 – 1000 ppm at stoichiometric fuel to air (φ) ratios, at compressed temperatures (TC) of 851 – 1390 K and at compressed pressures (pC) of 20 – 30 bar. In addition, new IDT measurements of three highly diluted C2H6/NO2 mixtures at φ = 0.5, TC = 805 – 1038 K, and pC = 20 – 30 bar are also studied. These new experimental data, together with data already available in the literature, are used to validate NUIGMech1.2 with an updated NOx sub-mechanism. Although the addition of 200 ppm of NO or NO2 to ethane shows a minimal promoting effect, the addition of 1000 ppm significantly promotes its reactivity. The similarity of the effect of the addition of both NO and NO2 addition is due to the fast conversion of NO into NO2 in the presence of molecular oxygen. However, the 1000 ppm NO doped ethane mixtures exhibit ∼20% shorter IDTs compared to the NO2 blended ones. The addition of 1000 ppm of N2O exhibits no effect on ethane oxidation at the conditions studied. The NUIGMech1.2 predictions can reproduce the sensitisation effect of NOx on ethane with good agreement over a wide range of pressure, temperature, equivalence ratio, and percentage dilution. Sensitivity and flux analyses of C2H6/NOx are performed to highlight the key reactions controlling ignition over the different temperature regimes studied. The analyses show that there is a competition between the reactions Ṙ + NO2 ↔ RȮ + NO and Ṙ + NO2 (+M) ↔ RNO2 (+M). This governs NOx sensitization on C2H6 ignition.

Low- and intermediate-temperature oxidation of dimethyl ether up to 100 atm in a supercritical pressure jet-stirred reactor

Understanding the low- and intermediate-temperature oxidation chemistry of oxygenated fuels like dimethyl ether (DME) at high pressure is paramount to the development of advanced engines with low carbon emissions. The supercritical pressure jet-stirred reactor (SP-JSR) recently developed at Princeton provides a new platform for conducting kinetic studies at low and intermediate temperatures at extremely high pressures with a uniform temperature distribution and a short flow residence time. This paper uses the SP-JSR to investigate DME oxidation at equivalence ratios of 0.175, 1.0, and 1.72, for pressures of 10 and 100 atm, and temperatures ranging from 400 to 900 K. The results demonstrate weakened NTC behavior at 100 atm relative to 10 atm due to increased flux through QOOH + O2 = O2QOOH relative to QOOH = 2 CH2O + OH at 100 atm. Furthermore, the intermediate-temperature oxidation window is shifted to lower temperatures at 100 atm. The experimental data are compared with several chemical kinetic models from the literature. The existing models are seen to agree quite well with the experimental data at 10 atm. However, the models fail to properly capture the NTC behavior at 100 atm. Reaction pathway analyses indicate that both the low- and intermediate-temperature chemistries are controlled by RO2 consumption pathways. The reaction rates for several of the important reactions, such as DME + OH = CH3OCH2 + H2O, H2O2 (+M) = 2 OH (+M), and 2 HO2 = 2 OH + O2 are updated in this work. The updated model improves the predictability for all key species compared to the original model.

Quantitative analysis of the interaction of ethanol metabolism with gluconeogenesis and fatty acid oxidation in the perfused liver of fasted rats

Ethanol is known to significantly affect gluconeogenesis and lipid metabolism in the liver, primarily by altering the redox ratio in both cytosol and mitochondria. The effect of ethanol was analyzed using a comprehensive, dynamic model of liver metabolism that takes into account sub-cellular compartmentation, detailed kinetics for the citric acid cycle, ethanol and acetaldehyde oxidation, and gluconeogenesis, and inter-compartmental transport of metabolites, including the malate-aspartate shuttle. The kinetic expression for alcohol dehydrogenase takes into account inhibition by ethanol and NADH. Simulations of perfusions of the rat liver were performed with various combinations of substrates (lactate, pyruvate, and fatty acids), with subsequent addition of ethanol to the perfusate. The model successfully predicts NADH/NAD+, in both cytosol and mitochondria, the expected directional flux of reducing equivalents between the two compartments during perfusion with different gluconeogenic precursors, and the effect of ethanol on glucose and ketone body production. This model can serve as a platform for in silico experiments investigating the effects of ethanol on the many dehydrogenases, and thus the major carbohydrate and lipid metabolic pathways in the liver, as well as potential effects of various drugs that may interact with ethanol.