Showing papers on "Methane published in 1973"

High-temperature oxidation of CO and CH4

Abstract: The oxidation of moist carbon monoxide and the post-induction-phase oxidation of methane were studied in a turbulent flow reactor. Reactants, stable intermediates, and products were determined spatially by chemical sampling and gas-chromatographic analysis. The carbon monoxide-oxygen reaction in the presence of water was studied at atmosphericpressure, and over the following ranges: temperature, 1030°–1230°K; equivalence ratio, 0.04–0.5; and water concentration, 0.1%–3.0%. The over-all rate expression found was − d [CO]/ dt =10 14.6±0.25 exp[(−40,000±1200)/ RT ][CO] 1.0 [H 2 O] 0.5 [O 2 ] 0.25 mole cm −3 sec −1 . The data support the fact that hydroxyl radical concentration in the reaction exceeds that at thermal equilibrium by as much as 2 orders of magnitude. The post-induction-phase reaction of methane and oxygen was studied at atmospheric pressure, over the temperature range of 1100°–1400°K and equivalence ratio range of 0.05–0.5. The over-all methane disappearance-rate expression was found to be − d [CH 4 ]/ dt =10 13.2±0.20 exp[(−48,400±1200)/ RT ][CH 4 ] 0.7 [O 2 ] 0.8 , mole cm −3 sec −1 . The rate was shown to be independent of water concentrations added initially or produced in the reaction. The over-all appearance rate of carbon dioxide in the methane-oxygen reaction is described by d [CO 2 ]/ dt =10 14.75±0.40 exp[(−43,000±2200)/ RT ][CO] 1.0 [H 2 O] 0.5 [O 2 ] 0.25 mole cm −3 sec −1 . This correlation represents rates of carbon dioxide formation 3.5 times slower than those found in the independent study of the moist carbon monoxide reaction. From these and other experiments it was possible to deduce thatCH 4 +OH→CH 3 +H 2 O (3) is not the only mechanism contributing to the observed rate of disappearance of methane. It was concluded that the reaction CH 4 +O→CH 3 +OH (4) is of major importance in both oxygen-and fuel-rich systems at high temperatures. Furthermore, the experimental data support that these two reactions, as well as CH 3 +H 2 →CH 4 +H (−5) contribute to the methane results reported here.

Methane in lake kivu: new data bearing on its origin.

Abstract: Lake Kivu, an African rift lake, contains about 50 cubic kilometers of methane (at standard temperature and pressure) in its deep water. Data resulting from two recent expeditions to the lake and a reevaluation of earlier data suggest that most of the methane was formed by bacteria from abiogenetic carbon dioxide and hydrogen, rather than being of volcanic origin or having formed from decomposing organic matter.

Production of methane

Abstract: Continuous process for the production of a gaseous stream comprising about 50 to 97 mole % methane (dry basis) or higher from a sulfur containing hydrocarbonaceous fuel without polluting the environment A gaseous stream comprising H2 and CO produced by the partial oxidation of a hydrocarbonaceous fuel is subjected to water gas shift reaction to produce a gaseous stream rich in H2 and CO2 Acid gases ie CO2 and H2S are separately removed leaving a hydrogen-rich gas stream At least a portion of the CO2 previously recovered is recombined with the hydrogen-rich stream to produce a gaseous mixture having a mole ratio H2/CO2 of about 4 to 10 This gas mixture is subjected to conventional catalytic methanation to produce a fuel gas comprising in mole % (dry basis) H2 45 to 1, and CH4 50 to 99 By using the reaction of CO2 and H2 rather than the reaction of CO and H2, a reduction of about 25% in the very large heat release encountered with the methanation reaction may be achieved Optionally, substantially pure methane may be produced by adding a second portion of CO2 to the aforesaid fuel gas to produce a gaseous mixture having a mole ratio H2/CO2 of about 4, subjecting said gas mixture to conventional catalytic methanation to produce CH4 and H2O, and separating H2O from the process gas stream to produce substantially pure methane Thus, the normally vigorous exothermic methanation reaction may be controlled better by the stepwise addition of CO2 to react with the hydrogen in the process gas stream

Mechanism of the steam reforming of methane over a coprecipitated nickel-alumina catalyst

Abstract: The kinetics of the steam reforming of methane over a coprecipitated Ni/Al2O3 catalyst have been examined in the temperature range 773 to 953 K and in the pressure range 0–10 Torr. Examination of the stoichiometry of the reaction showed that a catalyst freshly reduced in hydrogen at 873 K was further reduced by the reaction mixture. This is taken to imply that reduction of some phase such as NiAl2O4 was occurring. The rate determining step of the reaction on the fully reduced catalyst under reducing conditions was found to be the rate of adsorption of methane and competition for the adsorption sites by water occurred. The water–gas shift reaction did not proceed appreciably, and this implies that significant CO and CO2 adsorption does not occur on the catalyst surface; this is in agreement with the kinetic results. Experiments involving D2O or D2 helped to confirm these conclusions.

Catalytic coal hydrogasification process

Abstract: Methane is produced by the thermoneutral reaction of steam with coal or other carbonaceous material in a hydrogasification zone containing an alkali metal catalyst and sufficient hydrogen to suppress competing endothermic reactions. The gas taken overhead from the gasifier is subjected to steam reforming and then processed for the removal of acid constituents, hydrogen which is recycled to the hydrogasification zone, and carbon monoxide which is used as fuel for the steam reformer.

Inhibition of methane formation in soil by various nitrogen-containing compounds

Abstract: The evolution of methane from soil samples under anaerobic conditions was suppressed by adding nitrogen-containing chemicals. Nitrate caused the strongest inhibition of CH4 formation followed with decreasing efficiency by nitrite, nitric oxide and nitrous oxide; ammonium sulfate and hydroxylamine did not have an influence. It was also observed that organic substances in relation to their structure and concentration influence the evolution of CH4.

Sources, sinks, and concentrations of light hydrocarbons in the Gulf of Mexico

Abstract: A survey of the concentrations of light hydrocarbons in the Gulf of Mexico has been made aboard the R.V. Alaminos of Texas A&M University. The hydrocarbon analyzer consists of a modified Beckman process gas chromatograph with a flame ionization detector. For surface profiling, gases are ‘stripped’ from seawater taken 3 meters below the sea surface by vacuum extraction with a 12-stage booster pump. These gases are injected periodically into the gas stream of the chromatograph for analysis. The system also has the capability of analyzing discrete seawater samples either by the method of McAullife or by the method of Swinnerton and his co-workers. Coastal waters of the Gulf of Mexico are not in equilibrium with the atmosphere insofar as low molecular weight hydrocarbons are concerned, even though methane in most of the open Gulf of Mexico is in fairly close equilibrium with the atmosphere. The coastal waters of the gulf act both as a source and as a sink for atmospheric methane. The important man-derived sources of methane in the gulf are ports with their associated shipping and industrial activity, offshore petroleum drilling and production operations, and open ocean shipping activity. High light hydrocarbon concentrations have been found in the vicinity of a tanker discharging ‘clean ballast water.’ The important natural sources include seepage from oil and gas reservoirs and anaerobic production of methane. The main sink for atmospheric methane in the Gulf of Mexico is in the Yucatan area, where there is major upwelling of deep water with low hydrocarbon concentrations.

Method for establishing communication path in viscous petroleum-containing formations including tar sand deposits for use in oil recovery operations

Abstract: Many oil recovery techniques for viscous oil recovery such as recovery of bitumen from tar sand deposits, including steam injection and in situ combustion, require establishment of a high permeability interwell fluid flow path in the formation. The method of the present invention comprises forming an initial entry zone into the formation by means such as noncondensible gas sweep or hydraulic fracturing and propping, or utilizing high permeability streaks naturally occurring within the formation, and expanding the zone by injecting steam and a noncondensible gas into the gas swept zone, propped fracture zone or high permeability streak. The mixture of steam and noncondensible gas is injected into the formation at a pressure in pounds per square inch not exceeding numerically the overburden thickness in feet, and the steam-noncondensible gas-bitumen mixture is produced either from the same or a remotely located well. The operation may be repeated through several cycles in order to enlarge the flow channel. Suitable noncondensible gases include nitrogen, air, carbon dioxide, flue gas, exhaust gas, methane, natural gas, ethane, propane, butane and mixtures thereof. Saturated or supersaturated steam may be used.

Greenhouse Models of the Atmosphere of Titan

Abstract: The greenhouse effect is calculated for a series of Titanian atmosphere models with different proportions of methane, hydrogen, helium, and ammonia. A computer program is used in temperature-structure calculations based on radiative-convective thermal transfer considerations. A brightness temperature spectrum is derived for Titan and is compared with available observational data. It is concluded that the greenhouse effect on Titan is generated by pressure-induced transitions of methane and hydrogen. The helium-to-hydrogen ratio is found to have a maximum of about 1.5. The surface pressure is estimated to be at least 0.4 atm, with a daytime temperature of about 155 K at the surface. The presence of methane clouds in the upper troposphere is indicated. The clouds have a significant optical depth in the visible, but not in the thermal, infrared.

Studies on the affinity of methanol--and methane--utilizing bacteria for their carbon substrates.

Abstract: . Methanol- and methane-utilizing organisms were grown in chemostat culture and the response of respiration rate to different concentrations of substrate was measured. Cells of Pseudomonas extorquens NCIB 9399 grown on methanol demonstrated a high affinity for methanol (Km=20·4 μM). The affinities for formaldehyde and formate were 104 μM and 228 μM, respectively. The maximum respiration rate was similar for all 3 substrates. Methanol concentrations of 100 times the Km for formaldehyde so that inhibition by formaldehyde formed as an intermediate in methanol oxidation would be very unlikely. The Km for methane of a culture of a pseudomonad grown on methane was very low, 26 μM; that of the same organism for methanol was 50 μM. The maximum respiration on methanol was c. twice that on methane so that no methanol accumulation would be expected in a methane limited chemostat culture of this organism.

Methane in the atmosphere.

Abstract: Methane is present in the troposphere with a volume concentration of about 1.5 ppm. Estimates of Koyama indicate a predominantly biological origin with a total production rate of about 2.7 x 10/sup 14/ g CH/sub 4//yr. From that the author estimated the atmospheric lifetime of methane to be around 20 years. Measurements of the C-14 in methane by Libby and later by Bainbridge, et al. gave a C-14 content of 75% of recent wood and, therefore, confirm the predominant biological origin, the addition of inactive CH; from industrial sources being only about 25%. Much less is known about sinks of CH/sub 4/. Cadle reported fairly high destruction rates by atomic O, a reaction which should be important at high altitude. Bainbridge reports a decrease in the measured methane concentration above the tropopause. He, however, considers this decrease too small to account for the destruction rate of 20 years estimated by Koyama. Measurements on air samples collected on aircraft flights at various altitudes show a high variability of the CH/sub 4/ content both with time and altitude.

Analysis of ancient atmospheres

Abstract: In 1967 and 1968, ice samples were taken from various depths in the ice caps of Greenland and Antarctica and transported to the Stanford Research Institute laboratories in the frozen state. These samples ranged in age from 100 to 2500 years. After the ice samples had been melted in the laboratory, the air trapped as compressed bubbles in the glacial ice during the transition from firn to ice was collected and removed by a novel technique developed for this specific purpose. Carbon monoxide and methane analyses were made on a large number of samples by using gas chromatography. Major components were also measured in a few samples by mass spectrometry. The measured methane concentration appear to be about half of present-day concentrations. The measured CO concentrations were high in value by severalfold, and initially the validity of the approach was doubted. However, in the light of recent evidence suggesting that the largest global source of CO is oxidized methane, our CO and CH4 measurements can be reinterpreted. They suggest that the background CO concentration in the atmosphere has been near current concentrations of about 0.1 ppm for many centuries. It can be inferred, therefore, that no large increase in CO concentration accompanied the advent of the Industrial Revolution.

Methane Formation by Lake Sediments during in Vitro Incubation

Abstract: Renewed (de novo) synthesis of methane gas was shown to occur when samples of lake sediment were dispersed on glass beads and incubated in a helium atmosphere at 23°C. Under the above conditions, sediment samples from hardwater and softwater lakes generated up to 440 nanomoles and 80 nanomoles per ml of sediment per two days, respectively. At the time of collection, sediment samples possessed approximately similar amounts of “native” methane. Nitrate, sulfate, and acetylene were shown to suppress methane synthesis by sediment incubated as described.

Tropospheric budgets for methane, carbon monoxide, and related species

Abstract: A tropospheric photochemical model is presented that provides a homogeneous gas phase radical chain mechanism for the removal of tropospheric methane, carbon monoxide, molecular hydrogen, and formaldehyde. The chain reaction that destroys methane serves as the tropospheric source for formaldehyde, which in turn serves as the major source of tropospheric carbon monoxide and molecular hydrogen. Simple relationships between methane and its destruction products are derived that give a surface mixing ratio for carbon monoxide of 0.1 ppm, independent of the radical number densities, and an upper limit for formaldehyde mixing ratio of 1 ppb. Detailed calculations of total column production and loss rates based on earlier calculated altitude profiles for the number densities of the hydroxyl radical and formaldehyde yield the following: For methane, a total column loss rate of 4.5 × 1011 molecules/cm2 sec and a tropospheric residence time of 2 years; for carbon monoxide, a total column production of 4.5 × 1011 molecules/cm2 sec, a tropospheric residence time of 0.1 year (assuming the measured value of 0.12 ppm for the carbon monoxide mixing ratio), and a uniform mixing ratio of 0.07 ppm based solely on atmospheric destruction and production; for molecular hydrogen, a column production rate of 1.6 × 1011 molecules/cm2 sec, a uniform mixing ratio of 0.7 ppm, and a tropospheric residence time of 2 years.

Absorption and separation of normally liquid gas contaminants

Abstract: Treatment of gas mixtures containing combustible gas such as methane, hydrogen and carbon monoxide and containing as contaminants acid gas, i.e., hydrogen sulfide and carbon dioxide, and normally liquid contaminants embracing aromatic hydrocarbons, non-acidic sulfur compounds and hydrogen cyanide to separate the normally liquid gas contaminants and the acid gas.

Solid/liquid phase equilibria in the mixtures methane + n-hexane and methane + n-pentane

Abstract: Experimental phase diagrams have been obtained for the mixtures methane + n-hexane and methane + n-pentane from an analysis of their cooling curves. Both systems exhibit large positive deviations from ideality, and for methane + n-hexane a distinct flatness in the temperature against composition diagram at high methane concentrations is indicative of the close proximity of liquid/liquid immiscibility. A thermodynamic treatment of the data using an analytic equation of state confirms more quantitatively the position of this hypothetical upper critical solution point.

Method for establishing communication path in viscous petroleum-containing formations including tar sands for oil recovery operations

Abstract: Many oil recovery techniques for viscous oil recovery including steam injection and in situ combustion require establishment of a high permeability fluid flow path in the formation. The method of the present invention comprises forming an initial entry zone into the formation by means such as hydraulic fracturing and propping, or utilizing high permeability streaks naturally occurring within the formation, and injecting into the propped fracture zone or high permeability streak a solvent for the petroleum contained in the formation, said solvent being saturated with a gas or containing appreciable quantities of gas dissolved therein. The solvent-gas solution is injected into the formation at a pressure up to a value equal in pounds per square inch to the overburden thickness in feet, until the formation in the exposed area has been pressurized to the desired pressure and thereafter terminating injection and producing the gas and solvent-bitumen mixture by solution gas pressure depletion. The operation may be repeated through several cycles in order to enlarge the flow channel, and in the instance of a multi-well throughput operation adjacent injection and production wells are both treated in a cyclical fashion until communication between injection wells and production wells is established. Suitable solvents include aromatic hydrocarbons such as benzene, toluene, and xylene as well as carbon disulfide. Suitable gases include carbon dioxide, methane, nitrogen and air.