Showing papers on "Methane published in 1985"
TL;DR: In this paper, the in situ rates of sulfate reduction and anaerobic methane oxidation in 2-3m-long sediment cores were made, with a broad maximum below the sediment surface and a smaller, narrow maximum at the sulfate-methane transition.
Abstract: Concomitant radiotracer measurements were made of in situ rates of sulfate reduction and anaerobic methane oxidation in 2-3-m-long sediment cores. Methane accumulated to high concentrations (> 1 mM CH/sub 4/) only below the sulfate zone, at 1 m or deeper in the sediment. Sulfate reduction showed a broad maximum below the sediment surface and a smaller, narrow maximum at the sulfate-methane transition. Methane oxidation was low (0.002-0.1 nmol CH/sub 4/ cm/sup -3/ d/sup -1/) throughout the sulfate zone and showed a sharp maximum at the sulfate-methane transition, coinciding with the sulfate reduction maximum. Total anaerobic methane oxidation at two stations was 0.83 and 1.16 mmol CH/sub 4/ m/sup -2/ d/sup -1/, of which 96% was confined to the sulfate-methane transition. All the methane that was calculated to diffuse up into the sulfate-methane transition was oxidized in this zone. The methane oxidation was equivalent to 10% of the electron donor requirement for the total measured sulfate reduction. A third station showed high sulfate concentrations at all depths sampled and the total methane oxidation was only 0.013 mmol m/sup -2/ d/sup -1/. From direct measurements of rates, concentration gradients, and diffusion coefficients, simple calculations were made of sulfate and methane fluxes andmore » of methane production rates.« less
546 citations
TL;DR: In this article, the EPR spectroscopy was used to analyze the initial activity of MgO at temperatures of approximately 500/sup 0/C and showed that methyl radicals were produced on the surface, released into the gas phase, and trapped downstream in a solid argon matrix.
Abstract: When methane was passed over MgO at temperatures of approximately 500/sup 0/C, methyl radicals were produced on the surface, released into the gas phase, and trapped downstream in a solid argon matrix where they were analyzed by EPR spectroscopy. Significant differences in initial activity were observed, depending on whether the MgO was pretreated under vacuum or a flow of oxygen. Vacuum conditioning led to essentially no activity while oxygen conditioning resulted in substantial radical production. The oxidant of choice was also critical. Nitrous oxide resulted in a continuous decline of activity while in the presence of oxygen the formation of radicals was at a steady state. Doping of MgO with lithium, sodium, or iron was also examined. Lithium was found to greatly increase the activity up to a doping level of approximately 15.0 wt%. Two pathways are believed to be responsible for the radical formation. Over pure MgO, intrinsic cattion vacancies react with molecular oxygen to given an O/sup -/ center which can abstract a hydrogen atom from methane to produce the methyl radical. For the lithium-doped samples, substitutional Li/sup +/ ions react with molecular oxygen to form a (Li/sup +/O/sup -/) center which is also capable of abstracting amore » hydrogen atom from methane. 28 references, 5 figures, 3 tables.« less
518 citations
TL;DR: In this paper, the thermodynamic stability of clathrate hydrate is calculated under a wide range of temperature and pressure conditions applicable to solar system problems, using a statistical mechanical theory developed by van der Waals and Platteeuw (1959) and existing experimental data on properties of Clathrate hydrates and their components.
Abstract: The thermodynamic stability of clathrate hydrate is calculated under a wide range of temperature and pressure conditions applicable to solar system problems, using a statistical mechanical theory developed by van der Waals and Platteeuw (1959) and existing experimental data on properties of clathrate hydrates and their components. At low pressure, dissociation pressures and partition functions (Langmuir constants) for CO clathrate (hydrate) have been predicted, using the properties of clathrate containing, as guests, molecules similar to CO. The comparable or higher propensity of CO to incorporate in clathrate relative to N_2 is used to argue for high CO-to-N_2 ratios in primordial Titan if N_2 was accreted as clathrate. The relative incorporation of noble gases in clathrate from a solar composition gas at low temperatures is calculated and applied to the case of giant-planet atmospheres and icy satellites. It is argued that nonsolar but well-constrained noble gas abundances will be measured by Galileo in the Jovian atmosphere if the observed carbon enhancement is due to bombardment of the atmosphere by clathrate-bearing planetesimals sometime after planetary formation. The noble gas abundances in Titan's atmosphere are also predicted under the hypothesis that much of the satellite's methane accreted as clathrate. Double occupancy of clathrate cages by H_2 and CH_4 in contact with a solar composition gas is examined, and it is concluded that potentially important amounts of H_2 may have incorporated in satellites as clathrate. The kinetics of clathrate formation is also examined, and it is suggested that, under thermodynamically appropriate conditions, essentially complete clathration of water ice could have occurred in high-pressure nebulae around giant planets but probably not in the outer solar nebula; comets probably did not aggregate as clathrate. At moderate pressures, the phase diagram for methane clathrate hydrate in the presence of 15% ammonia (relative to water) is constructed, and application to the early Titan atmospheric composition is described. The high-pressure stability of CH_4, N_2, and mixed CH_4-N_2 clathrate hydrate is calculated; conversion back to water and CH_4 and/ or N_2 fluids or solids is predicted for pressures ≳ 12 kilobars (independent of temperature) and temperatures ≳ 320 K (independent of pressure). The effect of ammonia is to shrink the T-P stability field of clathrate with increasing ammonia concentration. These results imply that (1) clathrate is stable throughout the interior of Oberon- and Rhea-sized icy satellites, and (2) clathrate incorporated in the innermost icy regions of Titan would have decomposed, perhaps allowing buoyant methane to rise. Brief speculation on the implications of this conclusion for the origin of surficial methane on Titan is given. A list of suggested experiments and observations to test the theory and its predictions is presented.
355 citations
Patent•
ARCO1
TL;DR: In this article, a method of synthesizing hydrocarbons from a methane source is described, which includes the steps of separating a mixture of lower alkanes to form a first fraction contain-ing predominately methane and at least one second fraction containing predominately C2+ alkanes; de-hydrogenizing the second fraction to form an effluent comprising C 2+ olefins; contacting the methane fraction with an oxide of a metal which oxide when contacted with methane at between about 500° and 1000°C. is reduced and produces higher hydrocarbon products and water
Abstract: OF THE DISCLOSURE A method of synthesizing hydrocarbons from a methane source which includes the steps of separating a mixture of lower alkanes to form a first fraction contain-ing predominately methane and at least one second fraction containing predominately C2+ alkanes; dehydrogenating the second C2+ fraction to form an effluent comprising C2+ olefins; contacting the methane fraction with an oxide of a metal which oxide when contacted with methane at between about 500° and 1000°C. is reduced and produces higher hydrocarbon products and water; and oligomerizing the C2+ olefin fraction and the methane contacting effluent to produce higher hydrocarbon products. Also disclosed is a method of synthesizing hydrocarbons from a methane source which includes the steps of contacting a methane with a reducible metal oxide, recovering ethylene from the effluent of the contacting and oligomerizing the ethylene to produce higher hydrocarbon products.
325 citations
303 citations
TL;DR: In this paper, experimental measurements have been made on the initial hydrate formation temperatures and pressures in systems containing methane, ethane, propane, carbon dioxide or hydrogen sulfide in the presence of methanol solutions.
284 citations
TL;DR: In this paper, detailed species concentration profiles have been measured using optical and mass spectrometric methods in an atmospheric pressure methane air diffusion flame burning on a Wolfhard-Parker slot burner.
269 citations
TL;DR: The movement of methane (CH4) from anaerobic sediments through the leaves, stems, and flowers of aquatic plants and into the atmosphere was found to provide a significant pathway for the emission of CH4 from the aquatic substrates of flooded wetlands as discussed by the authors.
Abstract: The movement of methane (CH4) from anaerobic sediments through the leaves, stems, and flowers of aquatic plants and into the atmosphere was found to provide a significant pathway for the emission of CH4 from the aquatic substrates of flooded wetlands. Methane concentrations well above the surrounding ambient air levels were found in the mesophyll of 16 varies of aquatic plants and are attributed to transpiration, diffusion, and pressure-induced flow of gaseous CH4 from the roots when they are embedded in CH4-saturated anaerobic sediments. Methane emissions from the emergent parts of aquatic plants were measured using floating chamber techniques and by enclosing the plants in polyethylene bags of known volume. Concentration changes were monitored in the trapped air using syringes and gas chromatographic techniques. Vertical profiles of dissolved CH4 in sediment pore water surrounding the aquatic plants' rhizomes were obtained using an interstitial sampling technique. Methane emissions from the aquatic plants studied varied from 14.8 mg CH4/d to levels too low to be detectable. Rooted and unrooted freshwater aquatic plants were studied as well as saltwater and brackish water plants. Included in the experiment is detailed set of measurements on CH4 emissions from the common cattail (Typha latifolia). This paper illustrates that aquatic plants play an important gas exchange role in the C cycle between wetlands and the atmosphere.
259 citations
TL;DR: In this article, the authors studied the production and emission of methane from submerged paddy soil in laboratory rice cultures and in Italian paddy fields and found that up to 80% of the CH4 produced in the paddy soils did not reach the atmosphere but was apparently oxidized in the rhizosphere.
Abstract: Production and emission of methane from submerged paddy soil was studied in laboratory rice cultures and in Italian paddy fields. Up to 80% of the CH4 produced in the paddy soil did not reach the atmosphere but was apparently oxidized in the rhizosphere. CH4 emission through the rice plants was inhibited by an atmosphere of pure O2 but was stimulated by an atmosphere of pure N2 or an atmosphere containing 5% acetylene. Gas bubbles taken from the submerged soil contained up to 60% CH4, but only 0.15% sea salt (0.01% sulfate) resulted in a strong inhibition of the rates of methanogenesis and a decrease in the rates of CH4 emission. This result explains the observation of relatively low CH4 emission rates in rice paddy areas flooded with brackish water.
254 citations
TL;DR: In this article, the authors studied the trapping and release of H2, CO, CO2, CH4, Ar, and N2 by amorphous water ice under dynamic conditions, at low temperatures starting at 16°K, with gas pressure of 5 × 10−8−10−6 Torr.
238 citations
TL;DR: The inhibition experiment results suggest that methane oxidation in anoxic marine sediments is not directly mediated by sulfate-reducing bacteria or methanogenic bacteria, which is consistent with two possibilities: anaerobic methane oxidation may be mediated by an unknown organism or a consortium involving an unknown methane oxidizer and sulfATE-red reducing bacteria.
Abstract: Anaerobic methane oxidation is a general process important in controlling fluxes of methane from anoxic marine sediments. The responsible organism has not been isolated, and little is known about the electron acceptors and substrates involved in the process. Laboratory evidence indicates that sulfate reducers and methanogens are able to oxidize small quantities of methane. Field evidence suggests anaerobic methane oxidation may be linked to sulfate reduction. Experiments with specific inhibitors for sulfate reduction (molybdate), methanogenesis (2-bromoethanesulfonic acid), and acetate utilization (fluoroacetate) were performed on marine sediments from the zone of methane oxidation to determine whether sulfate-reducing bacteria or methanogenic bacteria are responsible for methane oxidation. The inhibition experiment results suggest that methane oxidation in anoxic marine sediments is not directly mediated by sulfate-reducing bacteria or methanogenic bacteria. Our results are consistent with two possibilities: anaerobic methane oxidation may be mediated by an unknown organism or a consortium involving an unknown methane oxidizer and sulfate-reducing bacteria.
Patent•
22 Mar 1985TL;DR: In this article, a method of controlling temperature during a pyrolysis reaction was proposed, where a fuel and oxidizer are combusted in a combustion zone to produce a hot gas stream at a superatmospheric pressure.
Abstract: A method of controlling temperature during a pyrolysis reaction wherein the predominant pyrolysis reactions are endothermic. A fuel and oxidizer are combusted in a combustion zone to produce a hot gas stream at a superatmospheric pressure. The hot gas stream is then passed through a converging-diverging nozzle to accelerate the hot gas stream to a velocity of at least about mach 2. The reactant to be pyrolyzed is injected into the supersonic hot gas stream to produce a reaction mixture flowing at supersonic velocity and initiate the endothermic pyrolysis reactions. Substantially immediately thereafter the velocity of the reaction mixture is reduced over a predetermined reaction time to convert the kinetic energy of the reaction mixture to thermal energy in an amount sufficient to substantially offset the endothermic reactions taking place while maintaining supersonic flow. At the end of the predertermined reaction time the velocity of the reaction mixture is reduced to subsonic flow and the reaction quenched. The present invention is particularly adapted to the pyrolysis of methane to produce acetylene and ethylene by contacting the methane with hot gases resulting from the reaction of hydrogen with oxygen.
TL;DR: Measurements of the methane concentration in air extracted by two different methods from ice samples from Siple Station in western Antarcitica allow the reconstruction of the history of the increase of the atmospheric methane during the past 200 years.
Abstract: Air entrapped in bubbles of cold ice has essentially the same composition as that of the atmosphere at the time of bubble formation. Measurements of the methane concentration in air extracted by two different methods from ice samples from Siple Station in western Antarcitica allow the reconstruction of the history of the increase of the atmospheric methane during the past 200 years.
TL;DR: In this article, the direct catalytic partial oxidation (CPO) of natural gas to methanol has been demonstrated to give commercially viable per pass conversion and selectivity has not yet been developed.
TL;DR: A combination of anthropogenic activities and a possible decline of global concentrations for the hydroxyl radicals that formerly removed methane from the atmosphere are cited as potential causes for the 1.3 percent/year rise of atmospheric methane levels.
TL;DR: In this paper, the results of a study of direct measurements of methane fluxes to the atmosphere from salt marsh soils and of indirect determinations of fluxes from tidal creek waters are presented.
Abstract: It is thought that biological methanogenesis in natural and agricultural wetlands and enteric fermentation in animals are the dominant sources of global tropospheric methane. It is pointed out that the anaerobic soils and sediments, where methanogenesis occurs, predominate in coastal marine wetlands. Coastal marine wetlands are generally believed to be approximately equal in area to freshwater wetlands. For this reason, coastal marine wetlands may be a globally significant source of atmospheric methane. The present investigation is concerned with the results of a study of direct measurements of methane fluxes to the atmosphere from salt marsh soils and of indirect determinations of fluxes from tidal creek waters. In addition, measurements of methane distributions in coastal marine wetland sediments and water are presented. The results of the investigation suggest that marine wetlands provide only a minor contribution to atmospheric methane on a global scale.
TL;DR: In this article, it was shown that silica-supported molybdena has the ability to catalyze the partial oxidation of methane to methanol and formaldehyde at the temperature range of 480-590 °C and a total pressure of 1 atm.
TL;DR: In this article, the authors show that the rate of carbon deposition depends on the chemical potential of the carbon in the gas mixtures irrespective of their nature, CO-CO2 or CH4-H2.
Patent•
ARCO1
TL;DR: In this paper, a method for converting methane to higher hydrocarbon products and coproduct water was proposed, where a gas comprising methane and a gaseous oxidant are contacted with a nonacidic catalyst at temperatures within the range of about 700° to 1200° C. in the presence of a halogen promoter, the contacting being conducted in the substantial absence of alkali metals or compounds thereof.
Abstract: A method for converting methane to higher hydrocarbon products and coproduct water wherein a gas comprising methane and a gaseous oxidant are contacted with a nonacidic catalyst at temperatures within the range of about 700° to 1200° C. in the presence of a halogen promoter, the contacting being conducted in the substantial absence of alkali metals or compounds thereof.
TL;DR: In this paper, the authors compared experimental results compiled from the literature to thermodynamic calculations of the most stable proportion of condensed phases to deposit from gas mixtures of Si-C-Cl-H and found that the predominant gas molecules participating in a deposition process are chlorides and chlorosilanes for silicon and methane and acetylene for carbon.
Abstract: Experimental results compiled from the literature were compared to thermodynamic calculations of the most stable proportion of condensed phases to deposit from gas mixtures of Si-C-Cl-H. The calculations indicated that the predominant gas molecules participating in a deposition process are chlorides and chlorosilanes for silicon and methane and acetylene for carbon. The mismatch of the calculated and experimentally determined phase boundaries at 1473 and 1600 K led to the conclusion that silicon deposition occurs faster than carbon deposition in proportion to their partial pressures. The probable reason is that silicon-bearing gas molecules have a greater sticking probability on polar Si and SiC surfaces because of their asymmetric geometries. 18 references, 8 figures, 3 tables.
TL;DR: The 1-2 percent increase in tropospheric methane determined from gas chromatographic measurements since 1977 has important implications for atmospheric photochemistry and climate, as reported in this paper.
Abstract: The 1-2 percent increase in tropospheric methane determined from gas chromatographic measurements since 1977 has important implications for atmospheric photochemistry and climate. To extend the measurement baseline, solar absorption spectra have been analyzed and mean troposphere CH4 mixing ratios for the years 1951 and 1981, and an average rate of CH4 increase of 1.1 + or - 0.2 percent per year is found for this period.
TL;DR: In this paper, graphite fibers are grown on a suitably nucleated ceramic surface by passing a methane gas stream over the surface at an elevated temperature, where the methane concentration in the gas stream is adjusted to between 5 and 15 volume percent to form microscopic carbon filaments.
TL;DR: The roughly 1 percent/year increase in tropospheric methane and roughly 2 percent/ year increase in carbon monoxide deduced from recent analyses of ground-based solar infrared spectra recorded in 1950 and 1951 have very important implications for the photochemistry and chemistry of the troposphere as discussed by the authors.
Abstract: The roughly 1 percent/year increase in tropospheric methane and roughly 2 percent/year increase in tropospheric carbon monoxide deduced from recent analyses of ground-based solar infrared spectra recorded in 1950 and 1951 have very important implications for the photochemistry and chemistry of the troposphere. Photochemical calculations indicate that as a result of the increase of methane and carbon monoxide since 1950-51, levels of the hydroxyl radical, the key species in the photochemistry of the troposphere, may have decreased by about 25 percent.
Patent•
15 Feb 1985TL;DR: In this article, a process for treating a landfill for recovering methane therefrom is described, wherein a mixture of methane and carbon dioxide is withdrawn from a central portion of the landfill and the carbon dioxide and methane are separated.
Abstract: A process for treating a landfill for recovering methane therefrom wherein a mixture of methane and carbon dioxide is withdrawn from a central portion of the landfill and the carbon dioxide and methane are separated. The methane is fed to a pipeline and a portion of the carbon dioxide is fed to wells spaced around the periphery of the landfill at a pressure of 7 to 170 kPa to prevent air from entering the landfill around the periphery thereof.
TL;DR: Results indicated that the smaller the size of the molecular weight fraction, the more extensive the degradation of low-molecular-weight, polyaromatic lignin derivatives during anaerobic degradation.
Abstract: [14C-lignin]lignocellulose was solubilized by alkaline heat treatment and separated into different molecular size fractions for use as the sole source of carbon in anaerobic enrichment cultures. This study is aimed at determining the fate of low-molecular-weight, polyaromatic lignin derivatives during anaerobic degradation. Gel permeation chromatography was used to preparatively separate the original 14C-lignin substrate into three component molecular size fractions, each of which was then fed to separate enrichment cultures. Biodegradability was assessed by monitoring total carbon dioxide and methane production, evolution of labeled gases, loss of 14C-activity from solution, and changes in gel permeation chromatographic elution patterns. Results indicated that the smaller the size of the molecular weight fraction, the more extensive the degradation to gaseous end products. In addition, up to 30% of the entire soluble lignin-derived carbon was anaerobically mineralized to carbon dioxide and methane.
TL;DR: In this paper, an oxidative coupling of methane over Ag and Bi2O3-Ag was carried out by electrochemically pumped oxygen through yttria-stabilized zirconia at 973 K.
Abstract: Oxidative coupling of methane over Ag and Bi2O3–Ag were carried out by the electrochemically pumped oxygen through yttria-stabilized zirconia at 973 K. The oxygen pumped to the Bi2O3–Ag catalyst showed higher catalytic activity and selectivity for the production of C2-compounds (C2H4+C2H6) compared to the surface oxygen from gas phase.
TL;DR: In this paper, the authors evaluated the technical and economic feasibility of producing specific gas products via the catalytic gasification of biomass, and the results of research conducted from October 1980 to November 1982 are presented.
Abstract: The purpose of the project is to evaluate the technical and economic feasibility of producing specific gas products via the catalytic gasification of biomass. The results of research conducted from October 1980 to November 1982 are presented. The project was comprised of laboratory studies, process development, and economic analyses. The laboratory studies were conducted to develop operating conditions and catalyst systems for generating methane-rich gas, synthesis gases, hydrogen, and carbon monoxide. The process development unit (PDU), previously used for tests at atmospheric pressure, was modified for operation at absolute pressures of up to 10 atm (1000 kPa). A program for use on a microcomputer was written to determine the effect of yield changes at elevated pressures on process economics.
TL;DR: In this article, a fully optical remote monitoring of low-level CH4 gas with a wide area coverage of 10 km in diameter realized by utilizing ultralowloss silica optical fiber link and a compact absorption cell in conjunction with highly radiant InGaAsP and InGaA light emitting diodes (LEDs) in the near infrared region.
Abstract: This paper reports for the first time the fully optical remote monitoring of low-level CH4 gas with a wide area coverage of 10 km in diameter realized by utilizing ultralowloss silica optical fibre link and a compact absorption cell in conjunction with highly radiant InGaAsP and InGaAs light emitting diodes (LEDs) in the near infrared region. For this novel application, the near-infrared absorption spectra of CH4 molecules were measured and studied involving the ν2+2ν3 combination band around 1.33 μm and the 2ν3 overtone band around 1.66 μm. This fibre-optic system was demonstrated to be feasible and sufficiently sensitive and safe as being a practical CH4 gas remote sensor whose detection sensitivity is normally required to be 25% of the lower explosion limit (LEL) of CH4 gas in air. This result verifies a large potential for applying extensively to various strategic points within the environment, such as industrial and mining complexes as well as urban and residential areas, with considerably increased reability, safety and marketability over the presently available techniques.
TL;DR: The behavior of two mixtures of CH 4, CO 2, H 2 S and H 2 O was studied over a temperature range from ≈37.8° to 204°C at pressures in the 0.4-18.5 MPa range as mentioned in this paper.