Showing papers on "Methane published in 1986"
TL;DR: In this paper, the carbon and hydrogen stable isotope composition of the methane as a function of the coexisting carbon dioxide and formation water precursors is used to distinguish two primary methanogenic pathways.
1,756 citations
TL;DR: In this paper, catalytic oxidation of methane was carried out over various perovskite-type oxides and compared with Pt/alumina catalyst at a conversion level below 80%.
487 citations
TL;DR: Partial oxidation is a widely used process to convert hydrocarbons and alcohols to valuable oxygen-containing chemicals as discussed by the authors, however, the direct utilization of these reactions for the manufacture of formaldehyde and methanol has remained extremely difficult.
Abstract: Partial oxidation is a widely used process to convert hydrocarbons and alcohols to valuable oxygen-containing chemicals. Although methane is the simplest hydrocarbon which gives formaldehyde and methanol as partial oxidation products, the direct utilization of these reactions for the manufacture of formaldehyde and methanol has remained extremely difficult. During the 1940s, two processes for the conversion of methane to formaldehyde were developed in Germany [l]. The first process used NO as a catalyst, and a commercial plant using this process was known to have been in operation in Copsa Mica in Romania. The second process used a combination of ozone and barium peroxide as the catalyst. In the current industrial practice, however, methane is converted to HCHO through a three-step process involving high temperature steam reforming, low pressure methanol synthesis, and oxidative dehydrogenation of methanol to formaldehyde, as shown by Unlike steam reforming, direct oxidation does not require ener...
410 citations
TL;DR: In this paper, three models: % residual methane, higher hydrocarbon enrichment, and CO2-CH4 coexisting pairs are used to independently calculate fractionation factors (αc) in the range of 1.002-1.014.
404 citations
TL;DR: In this article, the presence of rice plants stimulated the emission of CH4 both in the laboratory and in the field, and more than 90% of the CH4 emission was due to plant-mediated transport.
Abstract: Methane emission rates from rice-vegetated paddy fields followed a seasonal pattern different to that of weed-covered or unvegetated fields. Presence of rice plants stimulated the emission of CH4 both in the laboratory and in the field. In unvegetated paddy fields CH4 was emitted almost exclusively by ebullition. By contrast, in rice-vegetated fields more than 90% of the CH4 emission was due to plant-mediated transport. Rice plants stimulated methanogenesis in the submerged soil, but also enhanced the CH4 oxidation rates within the rhizosphere so that only 23% of the produced CH4 was emitted. Gas bubbles in vegetated paddy soils contained lower CH4 mixing ratios than in unvegetated fiels. Weed plants were also efficient in mediating gas exchnage between submerged soil and atmosphere, but did not stimulate methanogenesis. Weed plants caused a relatively high redox potential in the submerged soil so that 95% of the produced CH4 was oxidized and did not reach the atmosphere. The emission of CH4 was stimulated, however, when the cultures were incubated under gas atmospheres containing acetylene or consisting of O2-free nitrogen.
378 citations
TL;DR: An undescribed mussel (family Mytilidae), which lives in the vicinity of hydrocarbon seeps in the Gulf of Mexico, consumes methane (the principal component of natural gas) at a high rate, demonstrating a methane-based symbiosis between an animal and intracellular bacteria.
Abstract: An undescribed mussel (family Mytilidae), which lives in the vicinity of hydrocarbon seeps in the Gulf of Mexico, consumes methane (the principal component of natural gas) at a high rate. The methane consumption is limited to the gills of these animals and is apparently due to the abundant intracellular bacteria found there. This demonstrates a methane-based symbiosis between an animal and intracellular bacteria. Methane consumption is dependent on the availability of oxygen and is inhibited by acetylene. The consumption of methane by these mussels is associated with a dramatic increase in oxygen consumption and carbon dioxide production. As the methane consumption of the bivalve can exceed its carbon dioxide production, the symbiosis may be able to entirely satisfy its carbon needs from methane uptake. The very light (delta(13)C = -51 to -57 per mil) stable carbon isotope ratios found in this animal support methane (delta(13)C = -45 per mil at this site) as the primary carbon source for both the mussels and their symbionts.
370 citations
TL;DR: This chapter focuses on the enzymes involved in the bacterial oxidation of methane and methanol to formaldehyde and the energy transduction systems involved in coupling these oxidations to ATP synthesis by way of electron transport chains, proton translocation, and the proton motive force.
Abstract: Publisher Summary Methylotrophs are defined as microorganisms that are able to grow at the expense of reduced carbon compounds containing one or more carbon atoms but containing no carbon-carbon bonds. These bacteria oxidize methane and methanol and use the energy for growth. The methylotrophs can be divided into two well-defined groups: those able to use methane and those unable to do so. Methylotrophic bacteria that grow on methane are also called “methanotrophs.” This chapter focuses on the enzymes involved in the bacterial oxidation of methane and methanol to formaldehyde and the energy transduction systems involved in coupling these oxidations to ATP synthesis by way of electron transport chains, proton translocation, and the proton motive force. The first reaction in methane oxidation is hydroxlyation catalyzed by a very unusual mono-oxygenase; this requires a reductant that is probably always NADH. Methanol oxidation to formaldehyde is always catalyzed by methanol dehydrogenase (MDH) having pyrrolo–quinoline quinone (PQQ) as its prosthetic group.
299 citations
TL;DR: In this paper, the authors used static open chamber technique to measure emissions of nitrous oxide, methane, and carbon dioxide from tropical forests of Brazil, Ecuador, and Puerto Rico.
Abstract: Emissions of nitrous oxide, methane, and carbon dioxide were measured at diverse locations in tropical forests of Brazil, Ecuador, and Puerto Rico using a static open chamber technique. Mean fluxes to the atmosphere were 1.7 x 10 to the 10th, -0.7 x 10 to the 10th, and 1.5 x 10 to the 14th molecules/sq cm per s for N2O, CH4, and CO2, respectively. The data indicate that tropical forests contribute a significant fraction of the global source for atmospheric N2O, about 40 percent of the current source, and possibly 75 percent of the preindustrial source. Methane is consumed by soils on average, but the sink is an insignificant part (less than 5 percent) of the atmospheric cycle for the gas. Emissions of CO2 from forest soils are higher at equatorial sites than at middle or high latitudes, as expected from ecological considerations. Soils emit CO2 at rates more than twice as large as the rate of carbon infall in litter; hence much of the emitted CO2 must arise from root metabolism.
282 citations
TL;DR: In this paper, an apparatus to measure mixed gas permeation through polymer films is described, based on a combination of manometric and gas chromatography techniques, allowing straightforward determination of film permeabilities and selectivities over a wide range of feed pressures and compositions.
243 citations
TL;DR: In this paper, solid-state carbon-13 nuclear magnetic resonance with magic-angle spinning gave resolved lines from ethane, propane and isobutane and apparently from methane in the two sizes of cage in the hydrate lattice.
204 citations
TL;DR: In this article, the authors report similar results, using Antarctic ice, for the CO2 levels during the seventeenth and eighteenth centuries, which suggest an average concentration of 281 (standard deviation σ = 7) p.p.m.v.
Abstract: Atmospheric carbon dioxide (CO2) levels before the industrial revolution were ∼ 260–280 p.p.m.v. (parts per 106 by volume) as determined from studies of air trapped in ice1,2. We report here similar results, using Antarctic ice, for the CO2 levels during the seventeenth and eighteenth centuries, which suggest an average concentration of 281 (standard deviation σ = 7) p.p.m.v. The data constrain the net release of biospheric carbon to the atmosphere over the past 200 yr, to ∼5 × 1010 tonnes of carbon, mostly during 1850–1900. Measurements of two other ‘greenhouse’ gases, methane (CH4) and nitrous oxide (N2O), show increases of about 90 and 8% respectively since 1600. This CH4 increase is similar to the recently reported3–6 doubling over the same period, and the N2O increase, the first direct evidence of historical changes in N2O, is consistent with releases due to expanding anthropogenic combustion processes7.
TL;DR: In this article, the extinction limits of counterflow diffusion flames burning methane and propane were investigated using activation energy asymptotic theories developed previously, and the theoretical predictions were compared with experimental results, and overall chemical kinetic rate parameters characterizing the gas phase oxidation of a diffusion flame were derived.
TL;DR: The model allowed to simulate satisfactorily the methane production under very different operational conditions and there is not a direct relationship between the growth and the energy production related to metabolite formation.
TL;DR: The 3He/4He vs. CH4/3He ratio of the magmatic end-member remains poorly constrained (0 to 3 × 109) and one cannot rule out the possibility that a significant proportion of the methane in some fields may be of deep-earth origin this paper.
TL;DR: The growth yield of methylococcus capsulatus (Bath) on methane was dependent on the availability of copper in the growth medium and the carbon conversion efficiency from methanol with nitrate as nitrogen source was as high as theoretically predicted.
Abstract: The growth yield ofMethylococcus capsulatus (Bath) on methane was dependent on the availability of copper in the growth medium In nitrate mineral salts medium the carbon conversion efficiency increased by 38%, concomitant with the transition from soluble to particulate methane monooxygenase, after transfer from low to high copper medium An increase in growth efficiency was also observed with ammonia as nitrogen source but not when methanol replaced methane as carbon source The high growth efficiency is attributed to a reduced NADH requirement for methane oxidation This could only arise if methanol dehydrogenase was capable of electron transfer, either directly or indirectly to the particulate methane monooxygenase (MMO) The carbon conversion efficiency from methanol with nitrate as nitrogen source was as high as theoretically predicted It is suggested that the previously low yields of methanotrophs grown on methanol resulted from the use, as nitrogen source, of ammonia which was oxidised by the MMO still present under these growth conditions
TL;DR: Systematic seasonal variations in the stable carbon isotopic signature of methane gas occur in the anoxic sediments of Cape Lookout Bight, a lagoonal basin on North Carolina's Outer Banks, and appears to require seasonally averaged data from individual sites.
Abstract: Systematic seasonal variations in the stable carbon isotopic signature of methane gas occur in the anoxic sediments of Cape Lookout Bight, a lagoonal basin on North Carolina's Outer Banks Values for the carbon isotope ratio (delta 13C) of methane range from -573 per mil during summer to -685 per mil during winter in gas bubbles with an average methane content of 95% The variations are hypothesized to result from changes in the pathways of microbial methane production and cycling of key substrates including acetate and hydrogen The use of stable isotopic signatures to investigate the global methane cycle through mass balance calculations, involving various sediment and soil biogenic sources, appears to require seasonally averaged data from individual sites
TL;DR: In this paper, chemical and isotopic compositions have been measured on 62 microbial gases from Tertiary hemipelagic sediments in the Middle America Trench off Guatemala and from decaying kelp and surf grass currently accumulating in Scripps Submarine Canyon off southern California.
Patent•
24 Jan 1986
TL;DR: In this article, a recycle process for the separation of landfill gas containing a wide variety of impurities into a carbon dioxide product stream and a fuel-grade-pressurized methane product stream was proposed.
Abstract: A recycle process for the separation of landfill gas containing a wide variety of impurities into a carbon dioxide product stream and a fuel-grade-pressurized methane product stream, the process providing for the removal of both the impurities and the carbon dioxide in a cryogenic column as a bottom stream, the separation of the methane from the overhead product stream by a membrane process, and, optionally, the removal of impurities from the carbon dioxide bottom stream in a separate purification column, to recover a high-quality, liquid, carbon dioxide stream.
TL;DR: In this article, the authors measured C-14 labeled bicarbonate and acetate over the top 28 cm of anoxic Cape Lookout Bight sediments during the summer of 1983.
TL;DR: In this paper, a measurement method was developed for the thermal conductivity of thin films in the direction parallel to the surface, which is made between 100°C and 130°C for diannond films from 7 µm to 30 µm thick that are synthesized from a gas phase of methane/hydrogen mixture by microwave plasma chemical vapor deposition.
Abstract: A measurement method is developed for the thermal conductivity of thin films in the direction parallel to the surface. Measurements are made between 100°C and 130°C for diannond films from 7 µm to 30 µm thick that are synthesized from a gas phase of methane/hydrogen mixture by microwave plasma chemical vapor deposition, The thermal conductivity of diamond films increases rapidly with decreasing concentration of methane. The highest thermal conductivity ever obtained in this experiment is about 1000 Wm-1 K-1. The thermal conductivity and Raman spectrum are compared under different synthesis conditions.
TL;DR: In this article, the experimental rate equation observed could be well explained in terms of the reaction mechanism proposed, which is initiated by abstracting hydrogen atom from the methane adsorbed by the diatomic oxygen on the surface.
Patent•
24 Jul 1986TL;DR: In this paper, a method of treating CO 2 rich gas for injection into a petroleum reservoir is described, where the presence of ethane and propane in the overhead vapors overcomes the effect of nitrogen and methane on minimum miscibility pressure in the reservoir, and the problems created by CO 2 freezing and the CO 2 /ethane azeotrope are avoided.
Abstract: A method of treating CO 2 rich gas for injection into a petroleum reservoir is described. CO 2 rich gas containing methane, nitrogen, ethane, propane, butanes, and heavier components is distilled such that substantially all of the heavier components are produced as a bottoms product and substantially all of the CO 2 , ethane, and propane are produced as an overhead vapor. The presence of ethane and propane in the overhead vapors overcomes the effect of nitrogen and methane on minimum miscibility pressure in the reservoir, and the problems created by CO 2 freezing and the CO 2 /ethane azeotrope are avoided, furthermore, a readily marketable liquid product is produced.
TL;DR: In this article, the experimental kinetic rate data for acetate decarboxylation were integrated with the thermal-temporal-spatial relationships of sediment and fluid in the upper portions of actively forming sedimentary basins.
TL;DR: In this article, the mass-weighted average isotopic composition of all sources should equal the mean C-13 of atmospheric methane, corrected for a kinetic isotope effect in the OH attack of CH4.
Abstract: Ratios of C-13/C-12 have been measured in atmospheric methane and in methane collected from sites and biota that represent potentially large sources of atmospheric methane. These include temperate marshes (about -48 percent to about -54 percent), landfills (about -51 percent to about -55 percent), and the first reported values for any species of termite (-72.8 + or - 3.1 percent for Reticulitermes tibialis and -57.3 + or - 1.6 percent for Zootermopsis angusticollis). Numbers in parentheses are delta C-13 values with respect to PDB (Peedee belemnite) carbonate. Most methane sources reported thus far are depleted in C-13 with respect to atmospheric methane (-47.0 + or - 0.3 percent). Individual sources of methane should have C-13/C-12 ratios characteristic of mechanisms of CH4 formation and consumption prior to release to the atmosphere. The mass-weighted average isotopic composition of all sources should equal the mean C-13 of atmospheric methane, corrected for a kinetic isotope effect in the OH attack of CH4. Assuming the kinetic isotope effect to be small (about -3.0 percent correction to -47.0), as in the literature, the new values given here for termite methane do not help to explain the apparent discrepancy between C-13/C-12 ratios of the known CH4 sources and that of atmospheric CH4.
TL;DR: In this article, the authors determined the heat capacity of solution of methane into water by direct calorimetric measurement over a range of temperature from 0 to 50/sup 0/C.
Abstract: Heats of solution of methane into water have been determined by direct calorimetric measurement over a range of temperature from 0 to 50/sup 0/C The results allow the determination of the heat capacity change and the temperature dependence of the heat capacity change A favorable comparison is found with the high-precision van't Hoff study of Rettich et al The observed temperature dependence of the solute heat capacity supports the predictions of Gill et al based on a simple two-state model of water molecules in the first solvation shell
Patent•
27 Jun 1986TL;DR: In this paper, a catalytic process for the conversion of methane to C2 + hydrocarbons, particularly rich in ethylene or benzene, or both, is described.
Abstract: Disclosed is a catalytic process for the production of higher molecular weight hydrocarbons from lower molecular weight hydrocarbons. More particularly, disclosed is a catalytic process for the conversion of methane to C2 + hydrocarbons, particularly hydrocarbons rich in ethylene or benzene, or both. The process utilizes a metal-containing catalyst, high reaction temperature of greater than 1000° C., and a high gas hourly space velocity of greater than 3200 hr-1.
TL;DR: In this paper, the adsorption kinetics of propylene, propane and methane at 120 K on Si (100)−(2 × 1) are compared. And the difference in sticking is shown in two ways.
TL;DR: In this article, a mathematical model which simulates the flow of methane and water through a coal seam was developed, where partial differential equations governing the flow were derived from mass balances applied to an elemental volume of the reservoir.
Abstract: A mathematical model which simulates the flow of methane and water through a coal seam was developed. Partial differential equations governing the flow of methane and brine were derived from mass balances applied to an elemental volume of the reservoir. A two-dimensional cartesian coordinate system was superimposed on the coal seam and was utilized to transform the continuous flow equations to discrete form by application of finite differences.
TL;DR: Soot formation in pyrolysis of chlorinated methanes, their mixtures with methane, and chlorinated ethylenes were studied behind reflected shock waves by monitoring the attenuation of an He-Ne laser beam.