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Journal articles on the topic "CH4 oxidation"
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Liu, Shanfu, Sagar Udyavara, Chi Zhang, Matthias Peter, Tracy L. Lohr, Vinayak P. Dravid, Matthew Neurock, and Tobin J. Marks. "“Soft” oxidative coupling of methane to ethylene: Mechanistic insights from combined experiment and theory." Proceedings of the National Academy of Sciences 118, no. 23 (June 1, 2021): e2012666118. http://dx.doi.org/10.1073/pnas.2012666118.
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The oxidative coupling of methane to ethylene using gaseous disulfur (2CH4 + S2 → C2H4 + 2H2S) as an oxidant (SOCM) proceeds with promising selectivity. Here, we report detailed experimental and theoretical studies that examine the mechanism for the conversion of CH4 to C2H4 over an Fe3O4-derived FeS2 catalyst achieving a promising ethylene selectivity of 33%. We compare and contrast these results with those for the highly exothermic oxidative coupling of methane (OCM) using O2 (2CH4 + O2 → C2H4 + 2H2O). SOCM kinetic/mechanistic analysis, along with density functional theory results, indicate that ethylene is produced as a primary product of methane activation, proceeding predominantly via CH2 coupling over dimeric S–S moieties that bridge Fe surface sites, and to a lesser degree, on heavily sulfided mononuclear sites. In contrast to and unlike OCM, the overoxidized CS2 by-product forms predominantly via CH4 oxidation, rather than from C2 products, through a series of C–H activation and S-addition steps at adsorbed sulfur sites on the FeS2 surface. The experimental rates for methane conversion are first order in both CH4 and S2, consistent with the involvement of two S sites in the rate-determining methane C–H activation step, with a CD4/CH4 kinetic isotope effect of 1.78. The experimental apparent activation energy for methane conversion is 66 ± 8 kJ/mol, significantly lower than for CH4 oxidative coupling with O2. The computed methane activation barrier, rate orders, and kinetic isotope values are consistent with experiment. All evidence indicates that SOCM proceeds via a very different pathway than that of OCM.
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Preuss, I., C. Knoblauch, J. Gebert, and E. M. Pfeiffer. "Improved quantification of microbial CH<sub>4</sub> oxidation efficiency in arctic wetland soils using carbon isotope fractionation." Biogeosciences 10, no. 4 (April 16, 2013): 2539–52. http://dx.doi.org/10.5194/bg-10-2539-2013.
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Abstract. Permafrost-affected tundra soils are significant sources of the climate-relevant trace gas methane (CH4). The observed accelerated warming of the arctic will cause deeper permafrost thawing, followed by increased carbon mineralization and CH4 formation in water-saturated tundra soils, thus creating a positive feedback to climate change. Aerobic CH4 oxidation is regarded as the key process reducing CH4 emissions from wetlands, but quantification of turnover rates has remained difficult so far. The application of carbon stable isotope fractionation enables the in situ quantification of CH4 oxidation efficiency in arctic wetland soils. The aim of the current study is to quantify CH4 oxidation efficiency in permafrost-affected tundra soils in Russia's Lena River delta based on stable isotope signatures of CH4. Therefore, depth profiles of CH4 concentrations and δ13CH4 signatures were measured and the fractionation factors for the processes of oxidation (αox) and diffusion (αdiff) were determined. Most previous studies employing stable isotope fractionation for the quantification of CH4 oxidation in soils of other habitats (such as landfill cover soils) have assumed a gas transport dominated by advection (αtrans = 1). In tundra soils, however, diffusion is the main gas transport mechanism and diffusive stable isotope fractionation should be considered alongside oxidative fractionation. For the first time, the stable isotope fractionation of CH4 diffusion through water-saturated soils was determined with an αdiff = 1.001 &pm; 0.000 (n = 3). CH4 stable isotope fractionation during diffusion through air-filled pores of the investigated polygonal tundra soils was αdiff = 1.013 &pm; 0.003 (n = 18). Furthermore, it was found that αox differs widely between sites and horizons (mean αox = 1.017 ± 0.009) and needs to be determined on a case by case basis. The impact of both fractionation factors on the quantification of CH4 oxidation was analyzed by considering both the potential diffusion rate under saturated and unsaturated conditions and potential oxidation rates. For a submerged, organic-rich soil, the data indicate a CH4 oxidation efficiency of 50% at the anaerobic–aerobic interface in the upper horizon. The improved in situ quantification of CH4 oxidation in wetlands enables a better assessment of current and potential CH4 sources and sinks in permafrost-affected ecosystems and their potential strengths in response to global warming.
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van Grinsven, Sigrid, Kirsten Oswald, Bernhard Wehrli, Corinne Jegge, Jakob Zopfi, Moritz F. Lehmann, and Carsten J. Schubert. "Methane oxidation in the waters of a humic-rich boreal lake stimulated by photosynthesis, nitrite, Fe(III) and humics." Biogeosciences 18, no. 10 (May 20, 2021): 3087–101. http://dx.doi.org/10.5194/bg-18-3087-2021.
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Abstract. Small boreal lakes are known to contribute significantly to global CH4 emissions. Lake Lovojärvi is a eutrophic lake in southern Finland with bottom water CH4 concentrations up to 2 mM. However, the surface water concentration, and thus the diffusive emission potential, was low (< 0.5 µM). We studied the biogeochemical processes involved in CH4 removal by chemical profiling and through incubation experiments. δ13C-CH4 profiling of the water column revealed a methane-oxidation hotspot just below the oxycline and zones of CH4 oxidation within the anoxic water column. In incubation experiments involving the addition of light and/or oxygen, CH4 oxidation rates in the anoxic hypolimnion were enhanced 3-fold, suggesting a major role for photosynthetically fueled aerobic CH4 oxidation. We observed a distinct peak in CH4 concentration at the chlorophyll-a maximum, caused by either in situ CH4 production or other CH4 inputs such as lateral transport from the littoral zone. In the dark anoxic water column at 7 m depth, nitrite seemed to be the key electron acceptor involved in CH4 oxidation, yet additions of Fe(III), anthraquinone-2,6-disulfonate and humic substances also stimulated anoxic CH4 oxidation. Surprisingly, nitrite seemed to inhibit CH4 oxidation at all other depths. Overall, this study shows that photosynthetically fueled CH4 oxidation can be a key process in CH4 removal in the water column of humic, turbid lakes, thereby limiting diffusive CH4 emissions from boreal lakes. Yet, it also highlights the potential importance of a whole suite of alternative electron acceptors, including humics, in these freshwater environments in the absence of light and oxygen.
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Nielsen, Cecilie Skov, Niles J. Hasselquist, Mats B. Nilsson, Mats Öquist, Järvi Järveoja, and Matthias Peichl. "A Novel Approach for High-Frequency in-situ Quantification of Methane Oxidation in Peatlands." Soil Systems 3, no. 1 (December 31, 2018): 4. http://dx.doi.org/10.3390/soilsystems3010004.
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Methane (CH4) oxidation is an important process for regulating CH4 emissions from peatlands as it oxidizes CH4 to carbon dioxide (CO2). Our current knowledge about its temporal dynamics and contribution to ecosystem CO2 fluxes is, however, limited due to methodological constraints. Here, we present the first results from a novel method for quantifying in-situ CH4 oxidation at high temporal resolution. Using an automated chamber system, we measured the isotopic signature of heterotrophic respiration (CO2 emissions from vegetation-free plots) at a boreal mire in northern Sweden. Based on these data we calculated CH4 oxidation rates using a two-source isotope mixing model. During the measurement campaign, 74 % of potential CH4 fluxes from vegetation-free plots were oxidized to CO2, and CH4 oxidation contributed 20 ± 2.5 % to heterotrophic respiration corresponding to 10 ± 0.5 % of ecosystem respiration. Furthermore, the contribution of CH4 oxidation to heterotrophic respiration showed a distinct diurnal cycle being negligible during nighttime while contributing up to 35 ± 3.0 % during the daytime. Our results show that CH4 oxidation may represent an important component of the peatland ecosystem respiration and highlight the value of our method for measuring in-situ CH4 oxidation to better understand carbon dynamics in peatlands.
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Yoshimura, Masahiro, Jun-ichiro Kase, and Shigeyuki Sōmiya. "Oxidation of SiC powder by high-temperature, high-pressure H2O." Journal of Materials Research 1, no. 1 (February 1986): 100–103. http://dx.doi.org/10.1557/jmr.1986.0100.
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The reaction between SiC powder and H2O has been studied at 400°–800 °C under 10 and 100 MPa. Silicon carbide reacted with H2O to yield amorphous SiO2 and CH4 by the reaction SiC + 2H2O→SiO2 + CH4 above 500 °C. Cristobalite and tridymite crystallized from amorphous silica after the almost complete oxidation of SiC above 700 °C. The oxidation rate, as calculated from the weight gain, increased with temperature and pressure. The Arrhenius plotting of the reaction rate based on a Jander-type model gave apparent activation energies of 167–194 kJ/mol. Contrasted with oxidation in oxidative atmosphere, oxidation in H2O is characterized by the diffusion of H2O and CH4 in an amorphous silica layer where the diffusion seemed to be rate determining. Present results suggest that the oxidation of SiC includes the diffusion process of H2O in silica layers when atmospheres contain water vapor.
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Nykänen, H., S. Peura, P. Kankaala, and R. I. Jones. "Recycling and fluxes of carbon gases in a stratified boreal lake following experimental carbon addition." Biogeosciences Discussions 11, no. 11 (November 28, 2014): 16447–95. http://dx.doi.org/10.5194/bgd-11-16447-2014.
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Abstract. Partly anoxic stratified humic lakes are important sources of methane (CH4) and carbon dioxide (CO2) to the atmosphere. We followed the fate of CH4 and CO2 in a small boreal stratified lake, Alinen Mustajärvi, during 2007–2009. In 2008 and 2009 the lake received additions of dissolved organic carbon (DOC) with stable carbon isotope ratio (δ13C) around 16‰ higher than that of local allochthonous DOC. Carbon transformations in the water column were studied by measurements of δ13C of CH4 and of the dissolved inorganic carbon (DIC). Furthermore, CH4 and CO2 production, consumption and emissions were estimated. Methane oxidation was estimated by a diffusion gradient method. The amount, location and δ13C of CH4-derived biomass and CO2 in the water column were estimated from the CH4 oxidation pattern and from measured δ13C of CH4. Release of CH4 and CO2 to the atmosphere increased during the study. Methane production and almost total consumption of CH4 mostly in the anoxic water layers, was equivalent to the input from primary production (PP). δ13C of CH4 and DIC showed that hydrogenotrophic methanogenesis was the main source of CH4 to the water column, and methanogenic processes in general were the reasons for the 13C-enriched DIC at the lake bottom. CH4 and DIC became further 13C-enriched in the anoxic layer of the water column during the years of DOC addition. Even gradient diffusion measurements showed active CH4 oxidation in the anoxic portion of the water column; there was no clear 13C-enrichment of CH4 as generally used to estimate CH4 oxidation strength. Increase in δ13C-CH4 was clear between the metalimnion and epilimnion where the concentration of dissolved CH4 and the oxidation of CH4 were small. Thus, 13C-enrichment of CH4 does not reveal the main location of methanotrophy in a lake having simultaneous anaerobic and aerobic oxidation of CH4. Overall the results show that organic carbon is processed efficiently to CH4 and CO2 and recycled in the anoxic layer of stratified boreal lakes by CH4 oxidation. In spite of this, increased DOC input led to increased greenhouse gas release, mainly as CO2 but also as CH4. Due to the predominantly anaerobic CH4 oxidation, a relatively small amount of CH4-derived biomass was produced, while a large amount of CH4-derived CO2 was produced in the anoxic bottom zone of the lake.
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Zheng, Jianqiu, Taniya RoyChowdhury, Ziming Yang, Baohua Gu, Stan D. Wullschleger, and David E. Graham. "Impacts of temperature and soil characteristics on methane production and oxidation in Arctic tundra." Biogeosciences 15, no. 21 (November 8, 2018): 6621–35. http://dx.doi.org/10.5194/bg-15-6621-2018.
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Abstract. Rapid warming of Arctic ecosystems accelerates microbial decomposition of soil organic matter and leads to increased production of carbon dioxide (CO2) and methane (CH4). CH4 oxidation potentially mitigates CH4 emissions from permafrost regions, but it is still highly uncertain whether soils in high-latitude ecosystems will function as a net source or sink for CH4 in response to rising temperature and associated hydrological changes. We investigated CH4 production and oxidation potential in permafrost-affected soils from degraded ice-wedge polygons on the Barrow Environmental Observatory, Utqiaġvik (Barrow), Alaska, USA. Frozen soil cores from flat and high-centered polygons were sectioned into organic, transitional, and permafrost layers, and incubated at −2, +4 and +8 ∘C to determine potential CH4 production and oxidation rates. Significant CH4 production was only observed from the suboxic transition layer and permafrost of flat-centered polygon soil. These two soil sections also exhibited highest CH4 oxidation potentials. Organic soils from relatively dry surface layers had the lowest CH4 oxidation potential compared to saturated transition layer and permafrost, contradicting our original assumptions. Low methanogenesis rates are due to low overall microbial activities measured as total anaerobic respiration and the competing iron-reduction process. Our results suggest that CH4 oxidation could offset CH4 production and limit surface CH4 emissions, in response to elevated temperature, and thus must be considered in model predictions of net CH4 fluxes in Arctic polygonal tundra. Future changes in temperature and soil saturation conditions are likely to divert electron flow to alternative electron acceptors and significantly alter CH4 production, which should also be considered in CH4 models.
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Ren, Tie, John A. Amaral, and Roger Knowles. "The response of methane consumption by pure cultures of methanotrophic bacteria to oxygen." Canadian Journal of Microbiology 43, no. 10 (October 1, 1997): 925–28. http://dx.doi.org/10.1139/m97-133.
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The rates of CH4 oxidation by strains of groups I and II methanotrophs in pure culture were studied at various O2 concentrations from 0 to 63 % v/v. In the presence of nonlimiting dissolved CH4 and inorganic nitrogen, O2 concentrations from 0.45 to 20% v/v supported maximum rates of CH4 oxidation. The critical dissolved O2 concentration under our conditions was about 5.7 μM, below which O2 was limiting for CH4 oxidation. Concentrations of O2 up to 63% v/v depressed the activity of CH4 oxidation by ≥ 23%. We conclude that methanotrophs are not microaerophilic under the conditions of our experiments and that they have a high affinity for O2.Key words: CH4 oxidation, O2 response, Methylosinus trichosporium, Methylobacter luteus.
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Preuss, I., C. Knoblauch, J. Gebert, and E. M. Pfeiffer. "Improved quantification of microbial CH<sub>4</sub> oxidation efficiency in Arctic wetland soils using carbon isotope fractionation." Biogeosciences Discussions 9, no. 12 (December 4, 2012): 16999–7035. http://dx.doi.org/10.5194/bgd-9-16999-2012.
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Abstract. Permafrost-affected tundra soils are significant sources of the climate-relevant trace gas methane (CH4). The observed accelerated warming of the Arctic will cause a deeper permafrost thawing followed by increased carbon mineralization and CH4 formation in water saturated tundra soils which might cause a positive feedback to climate change. Aerobic CH4 oxidation is regarded as the key process reducing CH4 emissions from wetlands, but quantification of turnover rates has remained difficult so far. The application of carbon stable isotope fractionation enables the in situ quantification of CH4 oxidation efficiency in arctic wetland soils. The aim of the current study is to quantify CH4 oxidation efficiency in permafrost-affected tundra soils in Russia's Lena River Delta based on stable isotope signatures of CH4. Therefore, depth profiles of CH4 concentrations and δ13CH4-signatures were measured and the fractionation factors for the processes of oxidation (αox) and diffusion (αdiff) were determined. Most previous studies employing stable isotope fractionation for the quantification of CH4 oxidation in soils of other habitats (e.g. landfill cover soils) have assumed a gas transport dominated by advection (αtrans = 1). In tundra soils, however, diffusion is the main gas transport mechanism, aside from ebullition. Hence, diffusive stable isotope fractionation has to be considered. For the first time, the stable isotope fractionation of CH4 diffusion through water-saturated soils was determined with an αdiff = 1.001 ± 0.000 (n = 3). CH4 stable isotope fractionation during diffusion through air-filled pores of the investigated polygonal tundra soils was αdiff = 1.013 ± 0.003 (n = 18). Furthermore, it was found that αox differs widely between sites and horizons (mean αox, = 1.017 ± 0.009) and needs to be determined individually. The impact of both fractionation factors on the quantification of CH4 oxidation was analyzed by considering both the potential diffusion rate under saturated and unsaturated conditions and potential oxidation rates. For a submerged organic rich soil, the data indicate a CH4 oxidation efficiency of 50% at the anaerobic-aerobic interface in the upper horizon. The improved in situ quantification of CH4 oxidation in wetlands enables a better assessment of current and potential CH4 sources and sinks in permafrost affected ecosystems and their potential strengths in response to global warming.
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Martinez-Cruz, K., A. Sepulveda-Jauregui, K. Walter Anthony, and F. Thalasso. "Geographic and seasonal variation of dissolved methane and aerobic methane oxidation in Alaskan lakes." Biogeosciences Discussions 12, no. 5 (March 9, 2015): 4213–43. http://dx.doi.org/10.5194/bgd-12-4213-2015.
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Abstract. Methanotrophic bacteria play an important role oxidizing a significant fraction of methane (CH4) produced in lakes. Aerobic CH4 oxidation depends on lake CH4 and oxygen (O2) concentrations, temperature, and organic carbon input to lakes, including from thawing permafrost in thermokarst (thaw)-affected lakes. Given the large variability in these environmental factors, CH4 oxidation is expected to be subject to large seasonal and geographic variations, which have been scarcely reported in the literature. In the present study, we measured CH4 oxidation rates in 30 Alaskan lakes along a north–south latitudinal transect during winter and summer with a new field laser spectroscopy method. Additionally, we measured dissolved CH4 and O2 concentrations. We found that in the winter, aerobic CH4 oxidation was mainly controlled by the dissolved O2 concentration, while in the summer it was controlled primarily by the CH4 concentration, which was in deficit compared to dissolved O2. The permafrost environment of the lakes was identified as another key factor. Thermokarst (thaw) lakes formed in yedoma-type permafrost had significantly higher CH4 oxidation rates compared to other thermokarst and non-thermokarst lakes formed in non-yedoma permafrost environments. These results confirm that landscape processes play an important role in lake CH4 cycling.
Dissertations / Theses on the topic "CH4 oxidation"
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Singh, Rahul. "Electrochemical and Partial Oxidation of CH4." University of Akron / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1208025200.
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Cehic, Eldina. "An annual evaluation of CH4 oxidation in a freshwater lake." Thesis, Linköpings universitet, Tema Miljöförändring, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-165902.
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Freshwater lakes constrain its methane (CH4) emissions through CH4 oxidation. CH4 includes three carbon (C) isotopes; the stable isotopes 12C,13C and the unstable and more uncommon isotope 14C. Methanotrophs (i.e. methane oxidizing bacteria) oxidize the lighter isotope more rapidly. Changes in relative isotopic composition can therefore be used to calculate how much CH4 is oxidized in a system. This study investigates an annual CH4 oxidation in a freshwater lake. Water samples and bubbles of CH4 gas were collected once a month, from March to November, in lake Gundlebosjön. The CH4 gas was separated from the water samples with a headspace extraction technique. The concentration and isotopic composition of CH4 was analyzed in a cavity ring down spectrometer. The isotopic data was used in two mathematical models, based on open-steady state and closed systems. It was found that the stable isotope method to estimate CH4 oxidation was only useful during periods when clear concentration and isotope differences could be observed in the water column. CH4 oxidation could only be estimated in the water column in August, and in the surface layer in June and July.Utsläppen av metan (CH4) från sötvattensjöar begränsas genom CH4 oxidation. Det är två stabila kolisotoper som dominerar i CH4; 12C och 13C. Den ostabila kolisotopen 14C finns även i CH4, men den är mer ovanlig i naturen. Metantrofer (metanoxiderande bakterier) oxiderar den lättare kolisotopen snabbare. Förändringar i isotopsammansättningen kan användas för att beräkna hur mycket CH4 som oxideras i ett system. Denna studie undersöker en årlig CH4 oxidation i en sötvattensjö. Vattenprover och bubblor av CH4-gas samlades en gång i månaden, från mars till november, i Gundlebosjön. CH4 gasen separerades från vattenproverna med en ”headspace extraction” teknik. Koncentration och isotopsammansättningen av CH4 analyserades i en ”cavity ring down spectrometer”. Isotopdata användes i två matematiska modeller, baserade på öppet-stabilt tillstånd och stängt system. Den stabila isotopmetoden för att uppskatta CH4 oxidation var endast användbar under perioder då tydliga skillnader i koncentrationen och isotopsammansättningen kunde observeras i vattenpelaren. CH4 oxidation kunde endast uppskattas i vattenpelaren i augusti, och i vattenpelarens ytskikt i juni och juli.
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Han, Jinyi. "Kinetic and Morphological Studies of Pd Oxidation in O2-CH4 mixtures." Digital WPI, 2004. https://digitalcommons.wpi.edu/etd-dissertations/219.
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The oxidation of Pd single crystals: Pd(111), Pd(100) and Pd(110) was studied using Temperature Programmed Desorption (TPD), X-ray Photoelectron Spectroscopy (XPS), Auger Electron Spectroscopy (AES), Low Electron Energy Diffraction (LEED) and Scanning Tunneling Microscopy (STM) as they were subjected to O2 in the pressure range between 1 and 150 Torr at temperatures 600-900 K. The oxygen species formed during oxidation, the oxygen uptake dependence on the sample history, the Pd single crystal surface morphology transformations, and the catalytic methane combustion over Pd single crystals were investigated in detail. The Pd single crystal oxidation proceeded through a three-step mechanism. Namely, (1) oxygen dissociatively adsorbed on Pd surface, forming chemisorbed oxygen and then surface oxide; (2) atomic oxygen diffused through a thin surface oxide layer into Pd metal, forming near surface and bulk oxygen; (3) bulk PdO formed when a critical oxygen concentration was reached in the near surface region. The diffusion of oxygen through thin surface oxide layer into Pd metal decreased in the order: Pd(110)>Pd(100)>Pd(111). The oxygen diffusion coefficient was estimated to be around 10-16 cm2 s-1 at 600 K, with an activation energy of 80 kJ mol-1. Once bulk PdO was formed, the diffusion of oxygen through the bulk oxide layer was the rate-determining step for the palladium oxidation. The diffusion coefficient was equal to 10-18 cm2 s-1 at 600 K and the activation energy was approximately 120 kJ mol-1. The oxygen diffusion through thin surface oxide layer and bulk PdO followed the Mott-Cabrera parabolic diffusion law. The oxygen uptake on Pd single crystals depended on the sample history. The uptake amount increased with the population of the bulk oxygen species, which was achieved by high oxygen exposure at elevated temperatures, for example in 1 Torr O2 at above 820 K. Ar+ sputtering or annealing in vacuum at 1300 K depleted the bulk oxygen. The Pd single crystal surface morphology was determined by the oxidation conditions: O2 pressure, treatment temperature and exposure time. When bulk PdO was formed, the single crystal surface was covered with semi-spherical agglomerates 2-4 nm in size, which tended to aggregate to form a“cauliflower-like" superstructure. The single crystal surface area during oxidation, determined by integrating the STM image, experienced three major expansions in consistent with a three-step oxidation mechanism. The surface area on the oxidized single crystals increased in the order: Pd(110)
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Rismanchian, Azadeh. "Electrochemical and Photocatalytic Oxidation of Hydrocarbons." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1415799133.
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Zinner, Christopher. "METHANE AND DIMETHYL ETHER OXIDATION AT ELEVATED TEMPERATURES AND PRESSURE." Master's thesis, University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3457.
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Autoignition and oxidation of two Methane (CH4) and Dimethyl Ether (CH3OCH3 or DME) mixtures in air were studied in shock tubes over a wide range of equivalence ratios at elevated temperatures and pressures. These experiments were conducted in the reflected shock region with pressures ranging from 0.8 to 35.7 atmospheres, temperatures ranging from 913 to 1650 K, and equivalence ratios of 2.0, 1.0, 0.5, and 0.3. Ignition delay times were obtained from shock-tube endwall pressure traces for fuel mixtures of CH4/CH3OCH3 in ratios of 80/20 percent volume and 60/40 percent volume, respectively. Close examination of the data revealed that energy release from the mixture is occurring in the time between the arrival of the incident shock wave and the ignition event. An adjustment scheme for temperature and pressure was devised to account for this energy release and its effect on the ignition of the mixture. Two separate ignition delay correlations were developed for these pressure- and temperature-adjusted data. These correlations estimate ignition delay from known temperature, pressure, and species mole fractions of methane, dimethyl ether, and air (0.21 O2 + 0.79 N2). The first correlation was developed for ignition delay occurring at temperatures greater than or equal to 1175 K and pressures ranging from 0.8 to 35.3 atm. The second correlation was developed for ignition delay occurring at temperatures less than or equal to 1175 K and pressures ranging from 18.5 to 40.0 atm. Overall good agreement was found to exist between the two correlations and the data of these experiments. Findings of these experiments also include that with pressures at or below ten atm, increased concentrations of dimethyl ether will consistently produce faster ignition times. At pressures greater than ten atmospheres it is possible for fuel rich mixtures with lower concentrations of dimethyl ether to give the fastest ignition times. This work represents the most thorough shock tube investigation for oxidation of methane with high concentration levels of dimethyl ether at gas turbine engine relevant temperatures and pressures. The findings of this study should serve as a validation for detailed chemical kinetics mechanisms.M.S.M.E.
Department of Mechanical, Materials and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering MSME
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Brauneder, Kerstin M. "Geochemistry of Forest Rings in Northern Ontario: Identification of Ring Edge Processes in Peat and Soil." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23205.
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Forest rings are large features common in Ontario’s boreal forests that comprise circular topographic depressions in carbonate mineral soil that are filled with peat. This thesis documents differences in peat and soil chemistry along transects across the “Bean” and “Thorn North” rings, which are centered on accumulations of CH4 and H2S, respectively. Within the mineral soil, ring edges are characterized by strong negative anomalies in pH, ORP and carbonate, as well as positive anomalies of Al, Fe and Mn in the results of aqua regia and hydroxylamine-hydrochloride digestions. Within the peat, positive carbonate and pH anomalies are recorded. This antithetic relationship suggests vertical migration of carbonate species from clay to peat. An inverse relationship exists between ORP, versus redox inferred from aqua regia. Strong ORP lows occur where oxidized products show highest concentrations. This is interpreted to reflect the proliferation of autotrophic organisms occupying the strong redox gradient at the ring edge.
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Herrera, Delgado Karla [Verfasser], and O. [Akademischer Betreuer] Deutschmann. "Surface Reaction Kinetics for Oxidation and Reforming of H2, CO, and CH4 over Nickel-based Catalysts / Karla Herrera Delgado. Betreuer: O. Deutschmann." Karlsruhe : KIT-Bibliothek, 2014. http://d-nb.info/1056955864/34.
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Preuss, Inken-Marie [Verfasser], and Eva-Maria [Akademischer Betreuer] Pfeiffer. "In-situ Studies of Microbial CH4 Oxidation Efficiency in Arctic Wetland Soils– Application of Stable Carbon Isotopes / Inken-Marie Preuss. Betreuer: Eva-Maria Pfeiffer." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2013. http://d-nb.info/1038789451/34.
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Guérin, Frédéric. "Emission de gaz à effet de serre (CO2,CH4) par une retenue de barrage hydroélectrique en zone tropicale (Petit-saut, Guyane française) : expérimentation et modélisation." Toulouse 3, 2006. https://tel.archives-ouvertes.fr/tel-00079947.
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Les émissions de dioxyde de carbone (CO2) et de méthane (CH4) et le cycle du carbone dans la retenue de barrage de Petit-Saut et la rivière Sinnamary (Guyane Française) ont été étudiés dans le but de développer un modèle couplé hydrodynamique-biogéochimie. Le développement de ce modèle a nécessité l'étude de trois processus contrôlant ces émissions : (i) la production de CO2 et de CH4 lors de la dégradation de la matière organique (MO) des sols et de végétaux, (ii) l'oxydation aérobie du CH4 dans la colonne d'eau du barrage et (iii) les processus d'échange gazeux à l'interface air-eau. Sur 10 ans, les émissions atmosphériques se sont avérées très significatives, notamment les trois premières années ayant suivies la mise en eau, puis décroissent au cours du temps. Tandis que 50% des émissions de CO2 ont lieu à la surface du lac, les émissions de CH4 sont principalement localisées en aval des turbines. Les émissions atmosphériques résultent de la dégradation de la MO (sol et biomasse issus de la forêt tropicale) immergée lors de la mise en eau et leur diminution au cours du temps découle de l'épuisement du stock de MO. Au terme de 10 ans, 20% du stock de carbone a été minéralisé et émis vers l'atmosphère sous forme de CO2 et de CH4. L'oxydation aérobie du CH4 transforme plus de 95% du CH4 diffusant depuis l'hypolimnion en CO2 dans la colonne d'eau du lac et 40% du CH4 entrant dans la rivière à l'aval. A l'échelle du barrage ce processus est responsable de l'oxydation de 90% du CH4 produit et de 30% des émissions totales de CO2. Le CH4 et le CO2 qui atteignent les eaux de surface du barrage sont émis vers l'atmosphère par flux diffusifs. L'étude de ce processus de transfert gazeux à l'interface air-eau montre que, en milieu tropical, les flux diffusifs sont accélérés par les fortes températures et les phénomènes pluvieux. Le modèle est basé sur le modèle hydrodynamique SYMPHONIE 2D et les modules biogéochimiques développés dans le cadre de cette étude à partir des données cinétiques des processus étudiés. Les profils verticaux simulés de température, d'oxygène, de CO2 et de CH4 sont bien reproduits. Ce modèle pose les bases d'un outil opérationnel de modélisation pour la retenue de Petit Saut ainsi que pour d'autres réservoirs en milieu tropicalThe emissions of carbon dioxide (CO2) and methane (CH4) and the carbon cycle in the Petit-Saut reservoir and in the Sinnamary River (French Guiana) were studied with an aim of developing a coupled physical/biogeochemical model. The development of this model required the study of three processes controlling these emissions: (i) CO2 and CH4 production during the mineralization in anoxic condition of organic matter (OM) from soils and plants, (ii) aerobic CH4 oxidation in the water column of the lake and (iii) the processes involved in gas exchange at the air-water interface. Over 10 years, atmospheric emissions were shown to be very significant, in particular the first three years having followed the reservoir impoundment and then decreased with time. While 50% of the CO2 emissions take place at the surface of the lake, the emissions of CH4 are mainly localized downstream from the turbines. The atmospheric emissions result from the degradation of OM (soil and biomass originating from the tropical forest) flooded during impoundment and their reduction with time rises from the exhaustion of the OM stock. 10 years after impoundement, 20% of the carbon stock were mineralized and emitted to the atmosphere in the form of CO2 and of CH4. Aerobic CH4 oxidation transforms more than 95% of the CH4 diffusing upward from the hypolimnion into CO2 in the water column of the lake and 40% of the CH4 entering the river downstream of the dam. In the whole Petit Saut system, this process is responsible for the oxidation of 90% of the produced CH4 and 30% of the total CO2 emissions. The CH4 and CO2 which reach the water surface of the reservoir and of the river downstream of the dam are emitted to the atmosphere by diffusive flux. The study of this process of gas transfer to the interface air-water shows that, in tropical environment, diffusive fluxes are enhanced by the elevated temperatures and the rainy phenomena. The model is based on the hydrodynamic model SYMPHONY 2D and the biogeochemical model developed during this study starting from the kinetic data of the studied processes. The simulated vertical profiles of temperature, oxygen, CO2 and CH4 are well reproduced. This model poses the bases of an operational tool of modeling for the Petit-Saut reservoir like for other reservoirs in tropical environments
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Fairbrass, Danielle L. "Engineering oxidative stress resistance in CHO cell factories." Thesis, University of Sheffield, 2016. http://etheses.whiterose.ac.uk/16227/.
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Oxidative stress is a phenomenon created by an imbalance in the amount of Reactive Oxygen Species (ROS) created within a cell, and the ability of its defence mechanisms to effectively deal with ROS. Oxidative stress is extremely deleterious to the cell, and is known to cause damage to DNA, proteins and lipids (Turrens, 2003). Mitochondria are the cell’s predominant producer of ROS (Murphy, 2009), but it has also been shown that increased protein folding in the Endoplasmic Reticulum (ER) results in an increase in ROS levels (Malhotra, 2008), an issue particularly pertinent as developers move towards hard-to-express proteins. As well as many enzymes dedicated to the eradication of ROS, such as caspases, peroxidases and superoxide dismutases (SODs) the cell maintains a glutathione pool to buffer the increase of ROS (Lu, 2009). Design of Experiment models were designed and implemented using the growth, productivity and ROS content data from batch experiments in order to design anti-oxidant supplementation strategies. Two rounds of fed-batch screening were performed and a feeding strategy identified that improved the growth and ROS burden of three cell lines producing the same recombinant MAb product. A directed evolution strategy was employed to engineer oxidative stress resistant host cell lines through chronic exposure to Hydrogen Peroxide. Following transfection with a recombinant MAb product, the novel engineered cell line consistently outperformed the original cell line in terms of growth and ROS content, in both transient and stable transfection processes. Doubling time of stably transfected evolved cell line was reduced to 23 hours, a substantial time frame reduction. A link between ROS level reduction and improvement in cell line performance was demonstrated, with further investigation needed to unpick the mechanistic underpinnings of the oxidative stress resistance as well as to attempt to address the imbalance of improvements in growth compared to productivity.
Book chapters on the topic "CH4 oxidation"
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Nemera, Dessalegn B., Amy R. Jones, and Edward J. Merino. "DNA Oxidation." In Molecular Basis of Oxidative Stress, 93–112. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2013. http://dx.doi.org/10.1002/9781118355886.ch4.
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Croguennec, Thomas. "Lipid Oxidation." In Handbook of Food Science and Technology 1, 99–131. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2016. http://dx.doi.org/10.1002/9781119268659.ch4.
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Arends, I. W. C. E., and R. A. Sheldon. "Modern Oxidation of Alcohols Using Environmentally Benign Oxidants." In Modern Oxidation Methods, 83–118. Weinheim, FRG: Wiley-VCH Verlag GmbH & Co. KGaA, 2005. http://dx.doi.org/10.1002/3527603689.ch4.
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Berkessel, Albrecht. "Catalytic Oxidations with Hydrogen Peroxide in Fluorinated Alcohol Solvents." In Modern Oxidation Methods, 117–45. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2010. http://dx.doi.org/10.1002/9783527632039.ch4.
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Spector, Abraham. "Oxidation and Cataract." In Ciba Foundation Symposium 106 - Human Cataract Formation, 48–64. Chichester, UK: John Wiley & Sons, Ltd., 2008. http://dx.doi.org/10.1002/9780470720875.ch4.
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Duan, Lele, Lianpeng Tong, and Licheng Sun. "Towards the Visible Light-Driven Water Splitting Device: Ruthenium Water Oxidation Catalysts with Carboxylate-Containing Ligands." In Molecular Water Oxidation Catalysis, 51–76. Chichester, UK: John Wiley & Sons, Ltd, 2014. http://dx.doi.org/10.1002/9781118698648.ch4.
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Kholdeeva, Oxana A. "Selective Oxidations Catalyzed by Mesoporous Metal Silicates." In Liquid Phase Oxidation via Heterogeneous Catalysis, 127–219. Hoboken, New Jersey: John Wiley & Sons, Inc., 2013. http://dx.doi.org/10.1002/9781118356760.ch4.
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Mingxing, Wang, Li Jing, and Xiong Xiaozhen. "CH4 Emission and Oxidation in Rice Paddies." In Trace Gas Emissions and Plants, 181–95. Dordrecht: Springer Netherlands, 2000. http://dx.doi.org/10.1007/978-94-017-3571-1_8.
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Sizer, Irwin W. "Oxidation of Proteins by Tyrosinase and Peroxidase." In Advances in Enzymology - and Related Areas of Molecular Biology, 129–61. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2006. http://dx.doi.org/10.1002/9780470122594.ch4.
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Meydani, Mohsen, Eunhee Kong, and Ashley Knight. "LDL Oxidation as a Biomarker of Antioxidant Status." In Biomarkers for Antioxidant Defense and Oxidative Damage: Principles and Practical Applications, 51–64. Oxford, UK: Wiley-Blackwell, 2010. http://dx.doi.org/10.1002/9780813814438.ch4.
Full textConference papers on the topic "CH4 oxidation"
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CHEN, QI, JINTAO SUN, JIANYU LIU, and BAOMING ZHAO. "ROLES OF IONIC REACTIONSIN NANOSECOND DISCHARGE PLASMA-ASSISTED TEMPERATURE-DEPENDENT PYROLYSISAND OXIDATION OF METHANE FUEL." In 9th International Symposium on Nonequilibrium Processes, Plasma, Combustion, and Atmospheric Phenomena. TORUS PRESS, 2020. http://dx.doi.org/10.30826/nepcap9b-02.
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Kinetic roles of ionic reactions in nanosecond discharge (NSD) plasma-assisted temperature-dependent pyrolysis and oxidation of methane fuel were investigated by integrated studies of experimental measurements and mathematical simulation. A~detailed plasma chemistry mechanism governing the pyrolysis and oxidation processes in a He/CH4/O2 combustible mixture was proposed and studied by including a set of electron impact reactions, ionic reactions, dissociative recombination reactions, reactions involving excited species, and some important three-body recombination reactions. The calculation results of fractional power dissipated by electrons show that at the studied E/N of 78—281~Td, most of the nonequilibrium cold discharge power can be focused on the ion and radical production. The rate coefficients for CH4 and O2 ionization by electron impact increase with the increasing of E/N values, demonstrating that increasing the system temperature and, thus, the E/N values will have increasing kinetic effects on plasma-enhanced decomposition and oxidation. By modeling the reaction pathways of key ions, it is seen that O2+ presents the largest concentration in the discharge mixture, followed by CH4+, CH3+, and CH2+, which agrees well with the molecular beam mass spectrometric investigation. The calculation results further indicate that with the mixture temperature increasing, production of major ions including CH4+, CH3+, CH2, and O2+ play more and more important roles in CH4 pyrolysis and oxidation.
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Koroglu, Batikan, Owen Pryor, Joseph Lopez, Leigh Nash, and Subith Vasu. "Shock Tube Ignition and CH4 Time-Histories during Propanal Oxidation." In 54th AIAA Aerospace Sciences Meeting. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2016. http://dx.doi.org/10.2514/6.2016-0179.
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Nitta, Yoshifuru, and Yudai Yamasaki. "Effect of Support Materials on Pd Methane Oxidation Catalyst Using Dynamic Estimation Method." In ASME 2020 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/icef2020-2930.
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Abstract In the maritime industry, lean burn gas engines have been expected to reduce emissions such as NOx, SOx and CO2. On the other hand, the slipped methane, which is the unburned methane (CH4) emitted from lean burn gas engines have a concern for impact on global warming. It is therefore important to make a progress on the exhaust aftertreatment technologies for lean burn gas engines. As a countermeasure for the slipped methane, Palladium (Pd) catalyst for CH4 oxidation can be expected to provide one of the most feasible methods because Palladium (Pd) catalyst for CH4 oxidation can activate in the lower temperature. However, recent studies have shown that the reversible adsorption by water vapor (H2O) inhibits CH4 oxidation on the catalyst and deactivates its CH4 oxidation capacity. It can be known that the CH4 oxidation performance is influenced by active sites on the Pd catalyst. However, measuring methods for active sites on Pd catalyst under exhaust gas conditions could not be found. Authors thus proposed a dynamic estimation method for the quantity of effective active sites on Pd catalyst in exhaust gas temperature using water-gas shift reaction between the saturated chemisorbed CO and the pulse induced H2O. The previous study clarified the relationship between adsorbed CO volume and Pd loading in gas engine exhaust gas temperature and revealed the effects of flow conditions on the estimation of adsorbed CO volume. However, in order to improve CH4 oxidation performance on Pd catalyst under exhaust gas conditions, it is important that effects of support materials on active sites should clarify. This paper introduced experimental results of estimation of absorbed CO volume on different support materials of Pd catalysts by using the dynamic evaluation method. Experimental results show that chemisorbed CO volume on Pd/Al2O3 catalyst exhibits higher chemisorbed CO volume than that of Pd/SiO2 and Pd/Al2O3-SiO2 catalyst in 250–450 °C. These results can provide a part of the criteria for the application of Pd catalyst for reducing the slipped methane in exhaust gas of lean burn gas engines.
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Nitta, Yoshifuru, and Yudai Yamasaki. "Evaluation of Effective Active Site on Pd Methane Oxidation Catalyst in Exhaust Gas of Lean Burn Gas Engine." In ASME 2019 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/icef2019-7152.
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Abstract Lean-burn gas engines have recently attracted attentions in the maritime industry, because they can reduce NOx, SOx and CO2 emissions. However, since methane (CH4) is the main component of natural gas, the slipped methane which is the unburned methane emitted from the lean-burn gas engines likely contributes to global warming. It is thus important to make progress on exhaust aftertreatment technologies for lean-burn gas engines. A Palladium (Pd) catalyst for CH4 oxidation is expected to provide a countermeasure for slipped methane, because it can activate at lower exhaust gas temperature. However, a deactivation in higher water (H2O) concentration should be overcome, because H2O inhibits CH4 oxidation. This study was performed investigates the effects of exhaust gas temperature or gas composition on active Pd catalyst sites to clarify CH4 oxidation performance in the exhaust gas of lean-burn gas engines. The authors developed the method of estimating effective active sites for the Pd catalyst at various exhaust gas temperature. The estimation method is based on the assumption that active sites used for CH4 oxidation process can be shared with the active sites used for Carbon mono-oxide (CO) oxidation. The molecular of chemisorbed CO on the active sites of the Pd catalyst can provide effective active sites for CH4 oxidation process. To clarify the effects of exhaust gas temperature and compositions on active Pd catalyst sites, the authors developed an experimental system for the new estimation method. This paper introduces experimental results and verifications of the new method, showing that chemisorbed CO volume on a Pd/Al2O3 catalyst is increased with increasing Pd loading in 250–450 °C, simulated as a typical exhaust gas temperature range of lean-burn gas engines. The results provide a part of the criteria for the application of Pd catalysts to the reduction of slipped methane in exhaust gas of lean-burn gas engines.
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Petersen, Eric L., Joel M. Hall, Schuyler D. Smith, Jaap de Vries, Anthony Amadio, and Mark W. Crofton. "Ignition of Lean Methane-Based Fuel Blends at Gas Turbine Pressures." In ASME Turbo Expo 2005: Power for Land, Sea, and Air. ASMEDC, 2005. http://dx.doi.org/10.1115/gt2005-68517.
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Shock-tube experiments and chemical kinetics modeling were performed to further understand the ignition and oxidation kinetics of lean methane-based fuel blends at gas turbine pressures. Ignition delay times were obtained behind reflected shock waves for fuel mixtures consisting of CH4, CH4/H2, CH4/C2H6, and CH4/C3H8 in ratios ranging from 90/10 to 60/40%. Lean fuel/air equivalence ratios (φ = 0.5) were utilized, and the test pressures ranged from 0.54 to 25.3 atm. A methane-oxidation kinetics mechanism based on GRI-Mech 3.0 was assembled to reproduce the methane/air mixtures. Additional reactions involving CH3O and CH3O2 chemistry and modifications to a few of the pressure-dependent reaction rate coefficients were needed to achieve good agreement between data and model.
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SAVELIEVA, V. A., N. S. TITOVA, and O. N. FAVORSKII. "NUMERICAL STUDY OF H2 PRODUCTION DURING THE PARTIAL OXIDATION OF CH4-H2S MIXTURE." In NONEQUILIBRIUM PROCESSES. TORUS PRESS, 2018. http://dx.doi.org/10.30826/nepcap2018-1-08.
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Gokulakrishnan, P., S. Kwon, A. J. Hamer, M. S. Klassen, and R. J. Roby. "Reduced Kinetic Mechanism for Reactive Flow Simulation of Syngas/Methane Combustion at Gas Turbine Conditions." In ASME Turbo Expo 2006: Power for Land, Sea, and Air. ASMEDC, 2006. http://dx.doi.org/10.1115/gt2006-90573.
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The reduced kinetic mechanism for syngas/methane developed in the present work consists of a global reaction step for fuel decomposition in which the fuel molecule breaks down into CH2O and H2. A detailed CH2O/H2/O2 elementary reaction sub-set is included as the formation of intermediate combustion radicals such as OH, H, O, HO2, and H2O2 is essential for accurate predictions of non-equilibrium phenomena such as ignition and extinction. Since the chemical kinetics of H2 and CH2O are the fundamental building blocks of any hydrocarbon oxidation, the inclusion of detailed kinetic mechanisms for CH2O and H2 oxidation enables the reduced mechanism to predict over a wide range of operating conditions provided the reaction rate parameters of fuel-decomposition reaction is optimized over those conditions. Therefore, the rate coefficients for the fuel-decomposition step are estimated and optimized for the ignition delay time measurements of CH4, H2, CH4/H2, CH4/CO and CO/H2 mixtures available in the literature over a wide range of pressures, temperatures and equivalence ratios that are relevant to gas turbine operating conditions. The optimized reduced mechanism, consisting of 15 species and around 40 reactions, is able to predict the ignition delay time and laminar flame speed measurements of CH4, H2, CH4/H2, CH4/CO and CO/H2 mixtures fairly well over a wide range conditions. The model predictions are also compared with that of GRI3.0 mechanism. The reduced kinetic mechanism predicts the ignition delay time of CH4 and CH4/H2 mixtures far better than GRI mechanism at higher pressures. To demonstrate the predictive capability of the model in reactive flow systems, the reduced mechanism was implemented in Star-CD/KINetics commercial code using a RANS turbulence model to simulate CH4/air premixed combustion in a backward facing step. The CFD model predictions of the stable species in the exhaust gas agree well with the GRI mechanism predictions in a chemical reactor network modeling by approximating the backward facing step with a series of perfectly-stirred reactor and plug-flow reactor.
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Smit, N., E. C. Hopmans, L. Villanueva, D. Boukhchtaber Castillo, F. Grassa, C. Hogendoorn, R. A. Schmitz, et al. "Diversity of Nitrogen-Containing Bacteriohopanepolyols: Biomarkers for Aerobic Methane Oxidation in Terrestrial CH4 Seeps." In 30th International Meeting on Organic Geochemistry (IMOG 2021). European Association of Geoscientists & Engineers, 2021. http://dx.doi.org/10.3997/2214-4609.202134088.
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Arabian, Ehsan, and Thomas Sattelmayer. "Investigation of NO2 Formation Kinetics in Dual-Fuel Engines With Lean Premixed Methane-Air Charge." In ASME 2018 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/icef2018-9581.
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A dual fuel engine concept with lean premixed methane-air charge ignited by a diesel pilot flame is highly promising for reducing NOx and soot emissions. One drawback of this combustion method, however, is the high nitric dioxide (NO2) emissions observed at certain operating points. NO2 is a toxic gas, which is identifiable by its yellow color. In this paper the conditions leading to increased NO2 formation have been investigated using a batch reactor model in Cantera. In a first step, it has been found that the high emission levels of NO2 can be traced back to the mixing of small amounts of quenched CH4 with NO from the hot combustion zones followed by post-oxidation in the presence of O2, requiring that the temperatures are within a certain range. In the second step, NO2 formation in the exhaust duct of a test engine has been modeled and compared to the experimental results. For that purpose a well-stirred reactor model has been used that calculates the steady-state of a uniform composition for a certain residence time. An appropriate reaction mechanism that considers the effect of NO/NO2 on methane oxidation at low temperature levels has been used. The numerical results of NO to NO2 conversion in the duct at low temperature and pressure levels show good agreement with the experimental results for various temperatures and concentrations of unburned methane. The partial oxidation of CH4 can be predicted well. It can be shown that methane oxidation in the presence of NO/NO2 at low temperature levels is enhanced via the reaction steps CH3 + NO2 ⇌ CH3O + NO and CH3O2 + NO ⇌ CH3O + NO2. In addition the elementary reaction HO2 + NO ⇌ NO2 + OH is the important NO oxidizing step.
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Kim, Jong Won, Kyu Sung Sim, Hyun Myung Son, and Kwang Deog Jung. "Thermochemical Hydrogen Production Using Ni-Ferrite and CH4." In ASME 2003 International Solar Energy Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/isec2003-44084.
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Hydrogen production by a 2-step water-splitting thermochemical cycle using metal oxides (ferrites) redox pairs and CH4 have been studied in this experiment. Reactions were performed in a two-step redox cycle in which the ferrites were reacted with CH4 at 700°C–800°C to produce CO, H2, and various reduced phases (reduction step); these were then reoxidized with water vapor to generate H2 in water-splitting step (oxidation step) at 600°C–700°C. The reduced forms of Ni-Fe2O3, Ni-FeO and Ni-Fe alloy from XRD, showed respectively different reactivity for H2 formation from H2O. These were oxidized to the ferrite phase to produce H2 in the water-splitting step at 600°C–700°C. In reduction reaction at 800°C, carbon deposition arise on surface of Ni-ferrite due to CH4 decomposition. This reduced phase containing carbon, which reacts with H2O at 600°C, produce H2, CO, and CO2. The amount of H2 evolved using reduced phase containing carbon was much than that of other phase.
Reports on the topic "CH4 oxidation"
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I. A. Parshikov, Igor A. OXIDATION OF GERANYL-N-PHENYLCARBAMATE BY FUNGUS BEAUVERIA BASSIANA WITH AIM TO OBTANING OF NEW ANTI-CANCER DRUGS. Intellectual Archive, October 2020. http://dx.doi.org/10.32370/iaj.2427.
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The microbial oxidation of geranyl-N-phenylcarbamate by fungus Beauveria bassiana was investigated. Oxidation of the C3 – C4 double bond of the parent molecule leads to regioselective formation of O-3,4-epoxyheranyl-N-phenylcarbamate in 30 % yield
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Cook, B., S. Letts, and E. Fearon. Rate Of Oxidation Of Plasma Polymer (GDP or CH). Office of Scientific and Technical Information (OSTI), October 2005. http://dx.doi.org/10.2172/877933.
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Droby, Samir, Michael Wisniewski, Ron Porat, and Dumitru Macarisin. Role of Reactive Oxygen Species (ROS) in Tritrophic Interactions in Postharvest Biocontrol Systems. United States Department of Agriculture, December 2012. http://dx.doi.org/10.32747/2012.7594390.bard.
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To elucidate the role of ROS in the tri-trophic interactions in postharvest biocontrol systems a detailed molecular and biochemical investigation was undertaken. The application of the yeast biocontrol agent Metschnikowia fructicola, microarray analysis was performed on grapefruit surface wounds using an Affymetrix Citrus GeneChip. the data indicated that 1007 putative unigenes showed significant expression changes following wounding and yeast application relative to wounded controls. The expression of the genes encoding Respiratory burst oxidase (Rbo), mitogen-activated protein kinase (MAPK) and mitogen-activated protein kinase kinase (MAPKK), G-proteins, chitinase (CHI), phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS) and 4-coumarate-CoA ligase (4CL). In contrast, three genes, peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT), were down-regulated in grapefruit peel tissue treated with yeast cells. The yeast antagonists, Metschnikowia fructicola (strain 277) and Candida oleophila (strain 182) generate relatively high levels of super oxide anion (O2−) following its interaction with wounded fruit surface. Using laser scanning confocal microscopy we observed that the application of M. fructicola and C. oleophila into citrus and apple fruit wounds correlated with an increase in H2O2 accumulation in host tissue. The present data, together with our earlier discovery of the importance of H₂O₂ production in the defense response of citrus flavedo to postharvest pathogens, indicate that the yeast-induced oxidative response in fruit exocarp may be associated with the ability of specific yeast species to serve as biocontrol agents for the management of postharvest diseases. Effect of ROS on yeast cells was also studied. Pretreatment of the yeast, Candida oleophila, with 5 mM H₂O₂ for 30 min (sublethal) increased yeast tolerance to subsequent lethal levels of oxidative stress (50 mM H₂O₂), high temperature (40 °C), and low pH (pH 4). Suppression subtractive hybridization analysis was used to identify genes expressed in yeast in response to sublethal oxidative stress. Transcript levels were confirmed using semi quantitative reverse transcription-PCR. Seven antioxidant genes were up regulated. Pretreatment of the yeast antagonist Candida oleophila with glycine betaine (GB) increases oxidative stress tolerance in the microenvironment of apple wounds. ROS production is greater when yeast antagonists used as biocontrol agents are applied in the wounds. Compared to untreated control yeast cells, GB-treated cells recovered from the oxidative stress environment of apple wounds exhibited less accumulation of ROS and lower levels of oxidative damage to cellular proteins and lipids. Additionally, GB-treated yeast exhibited greater biocontrol activity against Penicillium expansum and Botrytis cinerea, and faster growth in wounds of apple fruits compared to untreated yeast. The expression of major antioxidant genes, including peroxisomal catalase, peroxiredoxin TSA1, and glutathione peroxidase was elevated in the yeast by GB treatment. A mild heat shock (HS) pretreatment (30 min at 40 1C) improved the tolerance of M. fructicola to subsequent high temperature (45 1C, 20–30 min) and oxidative stress (0.4 mol-¹) hydrogen peroxide, 20–60 min). HS-treated yeast cells showed less accumulation of reactive oxygen species (ROS) than non-treated cells in response to both stresses. Additionally, HS-treated yeast exhibited significantly greater (P≥0.0001) biocontrol activity against Penicillium expansum and a significantly faster (Po0.0001) growth rate in wounds of apple fruits stored at 25 1C compared with the performance of untreated yeast cells. Transcription of a trehalose-6-phosphate synthase gene (TPS1) was up regulated in response to HS and trehalose content also increased.