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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Surface Methane Concentrations Along the Mid-Atlantic Bight Driven by Aerobic Subsurface Production Rather Than Seafloor Gas Seeps

Relatively minor amounts of methane, a potent greenhouse gas, are currently emitted from the oceans to the atmosphere, but such methane emissions have been hypothesized to increase as oceans warm. Here, we investigate the source, distribution, and fate of methane released from the upper continental slope of the U.S. Mid-Atlantic Bight, where hundreds of gas seeps have been discovered between the shelf break and ~1,600 m water depth. Using physical, chemical, and isotopic analyses, we identify two main sources of methane in the water column: seafloor gas seeps and in situ aerobic methanogenesis which primarily occurs at 100–200 m depth in the water column. Stable isotopic analyses reveal that water samples collected at all depths were significantly impacted by aerobic methane oxidation, the dominant methane sink in this region, with the average fraction of methane oxidized being 50%. Due to methane oxidation in the deeper water column, below 200 m depth, surface concentrations of methane are influenced more by methane sources found near the surface (0–10 m depth) and in the subsurface (10–200 m depth), rather than seafloor emissions at greater depths.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Zeolite supported Pd catalysts for the complete oxidation of methane: A critical review

This review summarizes the recent literature reports on the development of zeolite supported Pd catalysts for the complete oxidation of methane. In-depth analysis reveals that different types of zeolite framework structures, regardless of the dimensionality, pore opening structure, and channel size, have little influence on the methane oxidation activity or the on-stream stability of the supported Pd catalysts. In contrast, the Si/Al ratio of a zeolite support plays a critical role. Both the catalytic activity and the on-stream stability of a Pd/zeolite catalyst increase with the increase of the Si/Al ratio. Catalysts supported on siliceous zeolites consistently show excellent light-off activity and remarkable on-stream stability whether in a dry or wet feed. Silanol nest defect sites in a siliceous zeolite are proposed to be the anchoring sites promoting the formation and minimizing the sintering of finely dispersed Pd nanoparticles. Remaining challenges in overcoming the sulfur poisoning effect are discussed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1974

Kinetics of oxygen atom formation during the oxidation of methane behind shock waves

An experimental and analytical study of the formation of oxygen atoms during the oxidation of methane and methane-hydrogen mixtures behind incident shock waves was carried out over the temperature range 1790-2584 K at reaction pressures between 1.2 and 1.7 atm. Oxygen atom levels were determined indirectly by measurement of emission from reaction of O with CO. On the basis of these data and ignition-delay data reported in the literature, a kinetic scheme for methane oxidation was assembled. The proposed kinetic mechanism, in general, predicts higher peak oxygen atom levels than the current oxidation mechanisms proposed by Bowman and Seery and by Skinner and his co-workers.

Jachimowski, C. J.↗
DOE OSTI2021

Role of catalytic nitrile decomposition in tricopper complex mediated direct partial oxidation of methane to methanol

Synthetic homogeneous system known to date performing methane to methanol conversion using O 2 as terminal oxidant is unique and based on copper complex with piperazine-based ligand (Cu 3 L in Fig. 1) in a medium of acetonitrile. Prior work have shown that in order to achieve catalytic turnover, hydrogen peroxide is needed to regenerate the active site. We show in this paper that reaction solvent based on organic nitrile decompose concurrently with methane activation and that in the absence of either acetonitrile, Cu complex or hydrogen peroxide, the catalytic turnover does not happen. We show in this manuscript that the direct methane oxidation to methanol might have been mediated by catalytic Radziszewski oxidation between acetonitrile and H 2 O 2 . Additionally we have discovered that in the absence of methane, peroxide mediated acetonitrile decomposition also makes methanol via a background reaction which was hitherto unknown.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1989

Proposed reference models for nitrous oxide and methane in the middle atmosphere

Data from the Stratospheric and Mesospheric Sounder (SAMS) on the Nimbus 7 satellite, for the period from Jan. 1979 - Dec. 1981, are used to prepare a reference model for the long-lived trace gases, methane and nitrous oxide, in the stratosphere. The model is presented in tabular form on seventeen pressure surfaces from 20 to 0.1 mb, in 10 degree latitude bins from 50S to 70N, and for each month of the year. The means by which the data quality and interannual variability, and some of the more interesting globally and seasonally variable features of the data are discussed briefly.

Taylor, F. W.↗
DOE OSTI2023

Continuous partial oxidation of methane to methanol over Cu-SSZ-39 catalysts

Here, the direct conversion of methane to methanol using molecular oxygen as the oxidant is a grand challenge in the chemical sciences. Here we describe our efforts in using copper-exchanged SSZ-39 for this chemistry and show it is a promising material for this reaction. Testing in a continuous flow reactor at 225 °C, Cu-SSZ-39 showed superior activity for methane partial oxidation compared to Cu-SSZ-13 (site time yields of 26.9 ± 0.8 mol CH3OH ·mol Cu -1 ·h -1 *10 -3 versus 13.2 mol CH3OH ·mol Cu -1 ·h -1 *10 -3 respectively). A clear maximum in methanol productivity, both in terms of a mass catalyst basis and copper atom basis is observed for Cu-SSZ-39 at a Cu/Al ~ 0.2. Running this reaction in the absence of oxygen over samples with a Cu/Al > 0.1 the reactivity is markedly lower than that in the presence of oxygen unlike what is observed in SSZ-13.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Plasma-Assisted Chemical-Looping Combustion: Low-Temperature Methane and Ethylene Oxidation with Nickel Oxide

The chemical reaction network of low-temperature plasma-assisted oxidation of methane (CH 4 ) and ethylene (C 2 H 4 ) with nickel oxide (NiO) was investigated in a heated plasma reactor through time-dependent species measurements by electron-ionization molecular beam mass spectrometry (EI-MBMS). Methane (ethylene) oxidation by NiO was explored in temperature ranges from 300-700 °C (300-500 °C) and 300-800 °C (300-600°C) for the plasma and non-plasma conditions, respectively. Significant enhancement of methane oxidation was observed with plasma between 400 and 500 °C, where no oxidation was observed under non-plasma conditions. For the oxidation of methane at higher temperatures three different oxidation stages were observed: I) a period of complete oxidation, II) a period of incomplete CO oxidation, and III) a period of carbon buildup. For the C 2 H 4 experiments, and unlike the CH 4 experiments, the plasma resulted in a significant amount of new intermediate oxygenated species, such as CH 2 O, CH 3 OH, C 2 H 4 O, and C 2 H 6 O. Carbon deposits were observed under both methane and ethylene conditions and verified by X-ray photoelectron spectroscopy (XPS). ReaxFF simulations were performed for the oxidation of CH 4 and C 2 H 4 in a non-plasma environment. The simulated intermediates and products largely agree with the species measured in the experiments, though the predicted intermediate oxygenated species such as CH 2 O and C 2 H 6 O were not observed in experiments under non-plasma conditions. A reaction pathway analysis for CH 4 and C 2 H 4 reacting with NiO was created based on the observed species from the MBMS spectra, along with ReaxFF simulations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1993

Factors that control the stable carbon isotopic composition of methane produced in an anoxic marine sediment

The carbon isotopic composition of methane produced in anoxic marine sediment is controlled by four factors: (1) the pathway of methane formation, (2) the isotopic composition of the methanogenic precursors, (3) the isotope fractionation factors for methane production, and (4) the isotope fractionation associated with methane oxidation. The importance of each factor was evaluated by monitoring stable carbon isotope ratios in methane produced by a sediment microcosm. Methane did not accumulate during the initial 42-day period when sediment contained sulfate, indicating little methane production from 'noncompetitive' substrates. Following sulfate depletion, methane accumulation proceeded in three distinct phases. First, CO2 reduction was the dominant methanogenic pathway and the isotopic composition of the methane produced ranged from -80 to -94 per thousand. The acetate concentration increased during this phase, suggesting that acetoclastic methanogenic bacteria were unable to keep pace with acetate production. Second, acetate fermentation became the dominant methanogenic pathway as bacteria responded to elevated acetate concentrations. The methane produced during this phase was progressively enriched in C-13, reaching a maximum delta(C-13) value of -42 per thousand. Third, the acetate pool experienced a precipitous decline from greater than 5 mM to less than 20 micro-M and methane production was again dominated by CO2 reduction. The delta(C-13) of methane produced during this final phase ranged from -46 to -58 per thousand. Methane oxidation concurrent with methane production was detected throughout the period of methane accumulation, at rates equivalent to 1 to 8 percent of the gross methane production rate. Thus methane oxidation was too slow to have significantly modified the isotopic signature of methane. A comparison of microcosm and field data suggests that similar microbial interactions may control seasonal variability in the isotopic composition of methane emitted from undisturbed Cape Lookout Bight sediment.

Alperin, M. J.↗
DOE OSTI2022

A Reduced F 420 -Dependent Nitrite Reductase in an Anaerobic Methanotrophic Archaeon

Coenzyme F 420 -dependent sulfite reductase (Fsr) protects methanogenic archaea inhabiting deep-sea hydrothermal vents from the inactivation of methyl coenzyme M reductase (Mcr), one of their essential energy production enzymes. Anaerobic methanotrophic archaea (ANME) that oxidize methane and rely on Mcr, carry Fsr homologs that form a distinct clade.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1994

Survival and Recovery of Methanotrophic Bacteria Starved Under Oxic and Anoxic Conditions

The effects of carbon deprivation on survival of methanotrophic bacteria were compared in cultures incubated in the presence and absence of oxygen in the starvation medium. Survival and recovery of the examined methanotrophs were generally highest for cultures starved under anoxic conditions as indicated by poststarvation measurements of methane oxidation, tetrazolium salt reduction, plate counts, and protein synthesis. Methylosinus trichosporium OB3b survived up to 6 weeks of carbon deprivation under anoxic conditions while maintaining a physiological state that allowed relatively rapid (hours) methane oxidation after substrate addition. A small fraction of cells starved under oxic and anoxic conditions (4 and 10%, respectively) survived more than 10 weeks but required several days for recovery on plates and in liquid medium. A non-spore-forming methanotroph, strain WP 12, displayed 36 to 118% of its initial methane oxidation capacity after 5 days of carbon deprivation. Oxidation rates varied with growth history prior to the experiments as well as with starvation conditions. Strain WP 12 starved under anoxic conditions showed up to 90% higher methane oxidation activity and 46% higher protein production after starvation than did cultures starved under oxic conditions. Only minor changes in biomass and niorpholow were seen for methanotrophic bacteria starved tinder anoxic conditions. In contrast, starvation under oxic conditions resulted in morphology changes and an initial 28 to 35% loss of cell protein. These data suggest that methanotrophic bacteria can survin,e carbon deprivation under anoxic conditions by using maintenance energy derived Solelyr from an anaerobic endogenous metabolism. This capability could partly explain a significant potential for methane oxidation in environments not continuously, supporting aerobic methanotrophic growth.

Roslev, Peter↗
DOE OSTI2024

Methane partial oxidation under periodic reaction conditions on Pt/Al 2 O 3

The increasing interest in utilizing methane, the primary component of natural gas, for chemical production has spurred research into methane partial oxidation (MPO) as an alternative to traditional steam methane reforming (SMR). MPO has lower energy requirements and potential for carbon capture, making it an attractive option for hydrogen production. Challenges remain, however, such as carbon deposition leading to degradation and achieving high hydrogen selectivity. Here, the impact of periodic reactor operation on MPO over a Pt/Al 2 O 3 catalyst was studied, primarily via varying reactor inlet compositions. Experiments were conducted using periodic operation strategies to assess the influence of changing reactant inlet concentrations on hydrogen formation during MPO. The results suggest that cycling between mixtures with low and high oxygen content can lead to transient hydrogen formation rates that surpass those achieved at steady state. Control experiments and density functional theory (DFT) calculations show that enhanced hydrogen formation can be attributed to the reaction between CO with hydroxyl groups at the metal and alumina support interface. Furthermore, this work underscores the critical role of surface coverages at the metal–support interface and suggests avenues for future exploration, including alternative support materials with higher OH mobility and changes in the cycling scheme to enhance catalyst performance under periodic conditions.

03 NATURAL GAS↗
DOE OSTI2021

Nickel–Sulfonate Mode of Substrate Binding for Forward and Reverse Reactions of Methyl-SCoM Reductase Suggest a Radical Mechanism Involving Long-Range Electron Transfer

Methyl-coenzyme M reductase (MCR) catalyzes both the synthesis and the anaerobic oxidation of methane (AOM). Its catalytic site contains Ni at the core of cofactor F 430 . The Ni ion, in its low-valent Ni(I) state, lights the fuse leading to homolysis of the C–S bond of methyl-coenzyme M (methyl-SCoM) to generate a methyl radical, which abstracts a hydrogen atom from coenzyme B (HSCoB) to generate methane and the mixed disulfide CoMSSCoB. Direct reversal of this reaction activates methane to initiate anaerobic methane oxidation. On the basis of the crystal structures, which reveal a Ni–thiol interaction between Ni(II)–MCR and inhibitor CoMSH, a Ni(I)–thioether complex with substrate methyl-SCoM has been transposed to canonical MCR mechanisms. Similarly, a Ni(I)–disulfide with CoMSSCoB is proposed for the reverse reaction. However, this Ni(I)–sulfur interaction poses a conundrum for the proposed hydrogen-atom abstraction reaction because the >6 Å distance between the thiol group of SCoB and the thiol of SCoM observed in the structures appears to be too long for such a reaction. The spectroscopic, kinetic, structural, and computational studies described here establish that both methyl-SCoM and CoMSSCoB bind to the active Ni(I) state of MCR through their sulfonate groups, forming a hexacoordinate Ni(I)–N/O complex, not Ni(I)–S. These studies rule out direct Ni(I)–sulfur interactions in both substrate-bound states. As a solution to the mechanistic conundrum, we propose that both the forward and the reverse MCR reactions emanate through long-range electron transfer from the Ni(I)–sulfonate complexes with methyl-SCoM and CoMSSCoB, respectively.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2004

Hydrocarbon Biomarker Stratigraphy of C-Isotopic Excursions Marking Chemical Changes in the Ocean with Contemporanious Biotic Extinction-Radiation Events

One paper recording progress in this topic has been accepted for publication. We report a method for the rigorous identification of biomarkers (crocetane and PMI) that may be specific for methanotrophic and methanogenic archaea and, perhaps, the process of anaerobic oxidation of methane. If catastrophic methane efflux from sub-sea methane hydrate is responsible for extinction events, as has been hypothesized by many workers, then we might expect to find biomarkers for methane oxidation in sediments marking some extinction boundaries. Unfortunately, identifying crocetane and PMI with certainty is not a trivial exercise and these biomarkers appear to have been mis-identified in a recent publication by workers from Curtin University. Barber et al. (2001) identified crocetane and PMI in sediments deposited in the basal Triassic of the Perth Basin, Australia. However, Barber et al. (2001) also found crocetane and PMI in many other sediments and oils in a way that was inconsistent with our knowledge of these systems.

Summons, Roger E.↗
DOE OSTI2020

A Perspective on the Electrochemical Oxidation of Methane to Methanol in Membrane Electrode Assemblies

Direct conversion of methane to methanol has been a long-sought objective. Partial oxidation by thermal catalysis is possible but suffers from a rapid loss in methanol selectivity with increasing methane conversion. More recently, the electrochemical oxidation of methane, using water, rather than oxygen, as the oxidizing agent has been considered in both aqueous electrolyte systems and membrane-electrode assemblies (MEAs). While promising results have been demonstrated using MEAs, the absence of key metrics of system performance make it hard to compare and contrast the results of different investigators. Overall, this Perspective examines why MEAs are well-suited for the electrochemical oxidation of methane, defines the metrics for assessing MEA performance, and reviews the progress in the field. An analysis of the challenges to finding suitable electrocatalysts is included with the aim of guiding the search for electrocatalysts that would be both active and selective for the conversion of methane to methanol.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Ru-promoted perovskites as effective redox catalysts for CO2 splitting and methane partial oxidation in a cyclic redox scheme

The current study reports AxA’1-xByB’1-yO3- perovskite redox catalysts (RCs) for CO2-splitting and methane partial oxidation (POx) in a cyclic redox scheme. Strontium (Sr) and iron (Fe) were chosen as A and B site elements with A’ being lanthanum (La), samarium (Sm) or yttrium (Y), and B’ being manganese (Mn), or titanium (Ti) to tailor their equilibrium oxygen partial pressures (P_(O_2 ) s) for CO2-splitting and methane partial oxidation. DFT calculations were performed for predictive optimization of the oxide materials whereas experimental investigation confirmed the DFT predicted redox performance. The redox kinetics of the RCs improved significantly by 1 wt.% ruthenium (Ru) impregnation without affecting their redox thermodynamics. Ru impregnated LaFe0.375Mn0.625O3 (A=0, A’=La, B=Mn, and B’=0) was the most promising RC in terms of its superior redox performance (CH4/CO2 conversion >90% and CO selectivity~ 95%) at 800oC. Long-term redox testing over Ru impregnated LaFe0.375Mn0.625O3 indicated stable performance during the first 30 cycles following with a ~25% decrease in the activity during the last 70 cycles. Air treatment was effective to reactivate the redox catalyst. Detailed characterizations revealed the underlying mechanism for redox catalyst deactivation and reactivation. Furthermore, this study not only validated a DFT guided mixed oxide design strategy for CO2 utilization but also provides potentially effective approaches to enhance redox kinetics as well as long-term redox catalyst performance.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

SPRUCE Anaerobic oxidation of methane mitigates net methane production and responds to long-term experimental warming in a northern bog: Supporting data

This data set contains measurements of anaerobic oxidation of methane (AOM), net methane (CH4) production, carbon dioxide (CO2) production, and gross CH4 production measurements from the SPRUCE experiment (Hanson et al. 2017). CH4 is greenhouse gas with 45 times the sustained global warming potential of CO2 over 100 years, which may have significant implications on global climate change. The process of AOM plays a large role in the extent of CH4 emissions from wetland environments like those at the SPRUCE experiment site. This study conducted two on different dates. In experiment 1, net CH4 and CO2 production were measured with a gas chromatograph through the peat profile at in situ temperatures of the SPRUCE plots four times from May to October, 2016 (2016-05 to 2016-10). Two treatments were examined, a Porewater Treatment that was a 1:1 volumetric peat:porewater slurry and a No Porewater Treatment that was field-moist peat with no porewater added. Additionally, net CH4 production were measured at frequent intervals (from 4 hr to 9 d) in peat from selected SPRUCE plots from soil collected on October 16, 2016 (2016-10-16). Samples were collected from the SPRUCE plots, immediately made anaerobic, and transported to the University of Oregon for rate measurements within several days of collection. In experiment 2, AOM, net CH4 production, CO2 production, and gross CH4 production were measured through the peat profile at in situ field temperatures once from samples collected in July, 2021 (2021-07). The same two porewater treatments were examined. AOM was measured with a 13CH4 tracer method using a Picarro G2201-i analyzer for isotopic CO2/CH4 quantification with a small stable isotope module attached. This data set contains three data files in comma separate (*.csv) format. This data set is associated with the following publication: Barney, M, AM Hopple, LL Gregory, JK Keller, and SD Bridgham. 2024. Anaerobic oxidation of methane mitigates net methane production and responds to long-term experimental warming in a northern bog. Soil Biology and Biochemistry, 190, 109316. https://doi.org/10.1016/j.soilbio.2024.109316.

SPRUCE Experiment, Marcell Experimental Forest, Me↗