Showing papers on "Methane published in 1975"

Process for preparing methane rich gases

Abstract: Hydrogen and carbon oxides are reacted to form methane by passing an inlet stream of preheated methanation synthesis gas together with a recycle stream of product gas through a catalyst bed in an adiabatic methanation reactor. The inlet temperature is between 250° and 350° C, the outlet temperature between 500° and 700° C. The recycle stream is withdrawn from the outlet stream after the latter has been cooled to a temperature between 250° and 350° C and being, however, at least 50° C above the dew point. A preferred means for withdrawing the recycle stream is an ejector driven by the inlet stream or by added steam.

Measurement of atomic oxygen and nitrogen oxides in jet-stirred combustion

Abstract: Direct spectroscopic measurement of continuum chemiluminescence at 3500 A, due presumably to the reaction CO+O→CO 2 + hv , was used to determine super-equilibrium atomic oxygen concentrations in situ for near-homogeneous, continuous-combustion of either carbon monoxide or methane with 133% theoretical air in a jet-stirred reactor operated near blowout, at atmospheric pressure. Reactor CO and NO x concentrations were measured by gas sampling. The motivation for this initial optical spectroscopic examination of the jet-stirred reactor was the elucidation of NO x formation in high-intensity, backmixed combustion. Measured gas temperatures were in the ranges T =1350 to 1500°K for carbon monoxide combustion, and T =1400° to 1800°K for methane combustion. Peak atom oxygen concentrations occurred just prior to reactor blowout. Partial equilibrium was indicated for the reactions CO+OH⇆CO 2 +H and O 2 +H⇆O+OH, at throughput rates sufficiently less than reactor blowout. Atomic oxygen measurements were used to compare NO x measurements with values predicted for plausible NO x kinetic formation mechanisms, considering only O, OH, and H as reaction radical intermediates. Agreement between the comparisons was obtained only for carbon monoxide combustion, indicating that nitrous oxide probably acts as an intermediate in NO x formation in the presence of super-equilibrium concentrations of atomic oxygen.

Growth yields of microorganisms on methanol and methane - theoretical-study

Abstract: An attempt was made to calculate growth yields of microorganisms on methanol and methane on the basis of known biochemical pathways of C1 metabolism. Since 3‐phosphoglycerate is a key intermediate in the assimilation pathways of C1 compounds, the calculations were based on the assumption that the synthesis of cell material from C1 substrates can be regarded as a two step process. When YATP on 3‐phosphoglycerate was taken as 10.5, a maximal cell yield of organisms of the composition C4H8O2N on methanol was found to be 0.73 g cells/g substrate. For growth on methane a value of 0.91 g cells/g substrate was calculated when a mixed function oxidase was implicated in methane oxidation. These yields were calculated on the basis of the ribulose phosphate pathway of formaldehyde fixation as the major pathway of C1 assimilation. Yields calculated on the basis of the serine pathway were on an average 20% lower. The calculations disclosed that for growth on methane, at least for Methylococcus capsulatus, a reversed electron transport system is required when methane is oxidized by a mixed function oxidase. The theoretical cell yields on methanol and methane have been compared with experimentally obtained yields and the validity of the estimations of growth yields on the basis of the present calculations is discussed.

The Thermal Decomposition of Methane. I. Kinetics of the Primary Decompositionto C2H6 + H2; Rate Constant for the Homogeneous Unimolecular Dissociation of Methane and its Pressure Dependence

Abstract: The pyrolysis of methane has been studied in a static system at temperatures of 995, 1038, 1068, and 1103 K and pressures from 25 to 700 Torr. It was concluded that the initial stages of the reacti...

Dynamics of activated chemisorption: Methane on rhodium

Abstract: Chemisorption of methane has been examined on highly perfect rhodium surfaces by a combination of field emission and molecular beam techniques in order to explore the mechanism of activation. It has been found that dissociative adsorption can be initiated on rhodium at 245 K just by excitation of the gas. Quantitative rate studies as a function of gas temperature have established that the CH4 molecule must overcome an activation barrier of 7 kcal mole−1 for reaction to occur. For gas temperatures 600 < TG < 710 K, the efficiency of chemisorption per impact is at least an order of magnitude smaller for CD4 than for CH4 and a factor of ? 3 smaller for CH2D2. This suggests that translational and rotational motion are not directly involved in passing over the barrier. Vibrational excitation of methane molecules appears to be the significant step in the reaction at the surface. Transition state theory fails to account for the significantly smaller rates observed for CD4 than for CH4. However, Slater’s dynamica...

GASP: A computer code for calculating the thermodynamic and transport properties for ten fluids: Parahydrogen, helium, neon, methane, nitrogen, carbon monoxide, oxygen, fluorine, argon, and carbon dioxide. [enthalpy, entropy, thermal conductivity, and specific heat

Abstract: A FORTRAN IV subprogram called GASP is discussed which calculates the thermodynamic and transport properties for 10 pure fluids: parahydrogen, helium, neon, methane, nitrogen, carbon monoxide, oxygen, fluorine, argon, and carbon dioxide. The pressure range is generally from 0.1 to 400 atmospheres (to 100 atm for helium and to 1000 atm for hydrogen). The temperature ranges are from the triple point to 300 K for neon; to 500 K for carbon monoxide, oxygen, and fluorine; to 600 K for methane and nitrogen; to 1000 K for argon and carbon dioxide; to 2000 K for hydrogen; and from 6 to 500 K for helium. GASP accepts any two of pressure, temperature and density as input conditions along with pressure, and either entropy or enthalpy. The properties available in any combination as output include temperature, density, pressure, entropy, enthalpy, specific heats, sonic velocity, viscosity, thermal conductivity, and surface tension. The subprogram design is modular so that the user can choose only those subroutines necessary to the calculations.

Fuel gas production

Abstract: A process is described for the production of methane from methanol by catalytic dehydration and dehydrogenation providing a high initial methane yield and a final substitute natural gas product of high calorific value. The catalytic dehydration and dehydrogenation steps may be effected simultaneously or in sequence. High efficiency in usage of raw materials and thermal requirements of the process are secured. A preferred catalyst containing both dehydration and dehydrogenation functions consists essentially of a major amount of iron oxide and minor amounts of chromium oxide and phosphate or tungstate ions.

Oxidation of C1 Compounds by Particulate fractions from Methylococcus capsulatus: distribution and properties of methane-dependent reduced nicotinamide adenine dinucleotide oxidase (methane hydroxylase).

Abstract: Cell-free particulate fractions of extracts from the obligate methylotroph Methylococcus capsulatus catalyze the reduced nicotinamide adenine dinucleotide (NADH) and O2-dependent oxidation of methane (methane hydroxylase). The only oxidation product detected was formate. These preparations also catalyze the oxidation of methanol and formaldehyde to formate in the presence or absence of phenazine methosulphate with oxygen as the terminal electron acceptor. Methane hydroxylase activity cannot be reproducibly obtained from disintegrated cell suspensions even though the whole cells actively respired when methane was presented as a substrate. Varying the disintegration method or extraction medium had no significant effect on the activities obtained. When active particles were obtained, hydroxylase activity was stable at 0 C for days. Methane hydroxylase assays were made by measuring the methane-dependent oxidation of NADH by O2. In separate experiments, methane consumption and the accumulation of formate were also demonstrated. Formate is not oxidized by these particulate fractions. The effects of particle concentration, temperature, pH, and phosphate concentration on enzymic activity are described. Ethane is utilized in the presence of NADH and O2. The stoichiometric relationships of the reaction(s) with methane as substrate were not established since (i) the presumed initial product, methanol, is also oxidized to formate, and (ii) the contribution that NADH oxidase activity makes to the observed consumption of reactants could not be assessed in the presence of methane. Studies with known inhibitors of electron transport systems indicate that the path of electron flow from NADH to oxygen is different for the NADH oxidase, methane hydroxylase, and methanol oxidase activities.

The reduction of nitric oxide in simulated combustion effluents by hydrocarbon-oxygen mixtures

Abstract: A study has been made of the chemistry of a gas-phase process for the reduction of nitric oxide in a flowing system of simulated combustion effluents (CO and CO2 in N2, H2O being inert with respect to this reaction). The reductant consists of mixtures of hydrocarbons (e.g., isobutane or gasoline) and carefully controlled amounts of oxygen. The latter brings the rate and nature of the products of the otherwise slow reaction between hydrocarbon and NO close to the requirements of practicability. The reactions were carried out in a ceramic flow reactor at temperatures in the range of approximately 1200°K to 1700°K and with residence times of 50 to several hundred milliseconds. In addition to temperature, the most critical parameters are the molar ratios R1=[HC]/[NO] and R3=[O2]/[HC] where HC is any one of the hydrocarbons used (methane, ethane, isobutane, isobutylene and gasoline). When the fraction of the initial NO remaining, is plotted as a function of R3 (for a given R1), a characteristic minimum is formed, along with a maximum for HCN. Increasing R1 results in greater reduction of NO but tends to increase HCN production. For a ratio of R1=1 at an initial NO concentration of 1000 ppm, total fixed nitrogen (TFN) remaining after reduction (NO+HCN) may range from 10% to 45% of the original concentration at the minimum of the TFN-R3 curve, depending on temperature, residence time and stoichiometry. The HCN can be oxidized to residual NO. Various aspects of the basic chemical mechanism are examined and it is suggested that O2 provides effective reducing free radicals, e.g., CH and CH2, by hydrogen abstraction of the hydrocarbon. They can then reduce NO through reactions typified by the exothermic step, CH+NO=HCO+N.

Molecular gas species in the lunar atmosphere

Abstract: Evidence is presented from the data obtained by the Apollo 17 lunar mass spectrometer which indicates the presence of methane and perhaps very small amounts of ammonia and carbon dioxide in the lunar atmosphere. This evidence is based on predawn enhancement of the concentrations of the mass peaks at the parent position for these molecular gas compounds. Methane is shown to be the most abundant molecular gas, although its exceedingly low concentration (1000 mol/cu cm) is slightly less than that of Ar-36. Several reasons are considered for the very low concentration of methane in the lunar atmosphere.

Effect of leaking natural gas on soil and vegetation in urban areas

Abstract: Leakage of natural gas from the gas distribution system affects the physical, chemical and biological processes in the soil. Particularly the microbial oxidation of methane is then of predominant importance for the composition of the soil gas phase. The rate of methane oxidation was measured under varying conditions of gas phase composition, temperature and nutrient supply. Computation models were evolved with which it is possible to calculate the effect of these and other factors on the distribution of methane, oxygen and carbon dioxide around a leak. Experiments with actual and artificial leaks as well as the calculations showed that the extent of the gas zone largely depends on the leakage rate, the depth of the groundwater table, the soil moisture content and the extent of the pavement. The soil temperature also proved to have a significant influence by its effect on the microbial methane oxidation. At low temperatures this microbial process is limited and consequently the anaerobic zone, which is invariably present in summer, may then disappear completely, thus making the probability of injury to vegetation negligible in winter. After repair of the leak the poor aeration conditions in the soil may persist for quite a long time. This is caused by the high consumption rate of oxygen required for the oxidation of organic substances and reduced anorganic compounds accumulated in the soil during gas leakage. The oxygen overdemand and the oxidation rate were determined for various gassed soils. Measures can be taken to accellerate soil recovery processes and to improve conditions for regeneration of injured trees and before planting new trees. Both experiments and calculations with computation models proved that installation of open ventilation channels is very effective, even if the leak cannot be immediately repaired. So ventilation channels can also be installed as preventive measure.

Process and apparatus for the manufacture of a gas mixture containing acetylene, ethylene, methane and hydrogen, by thermal cracking of liquid hydrocarbons

Abstract: A process for the manufacture of a gas mixture containing acetylene, ethylene, methane and hydrogen by cracking a liquid hydrocarbon by means of a plurality of arcs burning under the surface of the liquid hydrocarbon and limited, in their electrical effect, by current-limiting elements, wherein the total energy acting on the system is distributed by an arrangement of the electrical components, which is responsible for the stability of the arcs, over a plurality of localized burning points, the current-limiting components being matched to the voltage so that the output of each individual arc on average does not exceed 1.2 kW.

GASP: A computer code for calculating the thermodynamic and transport properties for ten fluids: Parahydrogen, helium, neon, methane, nitrogen, carbon monoxide, oxygen, fluorine, argon, and carbon dioxide

Abstract: A FORTRAN IV subprogram called GASP is discussed which calculates the thermodynamic and transport properties for 10 pure fluids: parahydrogen, helium, neon, methane, nitrogen, carbon monoxide, oxygen, fluorine, argon, and carbon dioxide. The pressure range is generally from 0.1 to 400 atmospheres (to 100 atm for helium and to 1000 atm for hydrogen). The temperature ranges are from the triple point to 300 K for neon; to 500 K for carbon monoxide, oxygen, and fluorine; to 600 K for methane and nitrogen; to 1000 K for argon and carbon dioxide; to 2000 K for hydrogen; and from 6 to 500 K for helium. GASP accepts any two of pressure, temperature and density as input conditions along with pressure, and either entropy or enthalpy. The properties available in any combination as output include temperature, density, pressure, entropy, enthalpy, specific heats, sonic velocity, viscosity, thermal conductivity, and surface tension. The subprogram design is modular so that the user can choose only those subroutines necessary to the calculations.

Method for controlling the carbon content of directly reduced iron

Abstract: This invention relates to a method for controlling the carbon content of metallized iron pellets produced by the continuous direct reduction of iron oxide in a vertical shaft furnace with a reducing gas having a high hydrogen and carbon monoxide content According to the method, in addition to the standard reducing gases introduced to the reducing zone, methane or methane-containing gas is introduced to the shaft furnace at specified locations beneath the reducing zone and, by controlling the conditions in the furnace, a proportion of the injected gas is reformed in the furnace to reducing gases

Relationships between sulfate-reducing and methane-producing bacteria

Abstract: Sulfate ions in the muddy sediments of Lake Vechten are consumed by sulfate-reducing bacteria of which the abundance is limited by the concentration of these ions. Methane producers are found deeper in the mud at lower concentrations of hydrogen sulphide.