Methane natural occurrence

Irradiation of ethyleneimine (341,342) with light of short wavelength ia the gas phase has been carried out direcdy and with sensitization (343—349). Photolysis products found were hydrogen, nitrogen, ethylene, ammonium, saturated hydrocarbons (methane, ethane, propane, / -butane), and the dimer of the ethyleneimino radical. The nature and the amount of the reaction products is highly dependent on the conditions used. For example, the photoproducts identified ia a fast flow photoreactor iacluded hydrocyanic acid and acetonitrile (345), ia addition to those found ia a steady state system. The reaction of hydrogen radicals with ethyleneimine results ia the formation of hydrocyanic acid ia addition to methane (350). Important processes ia the photolysis of ethyleneimine are nitrene extmsion and homolysis of the N—H bond, as suggested and simulated by ab initio SCF calculations (351). The occurrence of ethyleneimine as an iatermediate ia the photolytic formation of hydrocyanic acid from acetylene and ammonia ia the atmosphere of the planet Jupiter has been postulated (352), but is disputed (353). 

Non-conventional gas is natural gas found in unusual underground conditions, such as very impermeable reservoirs which require massive stimulation in order to be recovered, or in underground occurrences of gas hydrates, or dissolved in formation water, or coal-bed methane, or gas from in-situ gasification of coal. 

Now in its Second Edition, this highly acclaimed text fully equips readers with the skills and knowledge needed to analyze soil and correctly interpret the results. Due to the highly complex nature of soil, the author carefully explains why unusual results are routinely obtained during soil analyses, including the occurrence of methane in soil under oxidative conditions. The text also assists readers in developing their own analytical techniques in order to analyze particular samples or test for particular compounds or properties. 

Just as oil, natural gas is also categorised as conventional and unconventional. Unlike crude oil, however, natural gas deposits are normally classified according to the economic or technical approach, i.e., all occurrences that are currently extract-able under economic conditions are considered conventional, whereas the rest are termed unconventional. Conventional natural gas includes non-associated gas from gas reservoirs in which there is little or no crude oil, as well as associated gas , which is produced from oil wells the latter can exist separately from oil in the formation (free gas, also known as cap gas, as it lies above the oil), or dissolved in the crude oil (dissolved gas). Unconventional gas is the same substance as conventional natural gas, and only the reservoir characteristics are different and make it usually more difficult to produce. Unconventional gas comprises natural gas from coal (also known as coal-bed methane), tight gas, gas in aquifers and gas hydrates (see Fig. 3.17). It is important to mention in this context so-called stranded gas , a term which is applied to occurrences whose extraction would be technically feasible, but which are located in remote areas that at the moment cannot (yet) be economically developed (see Section 3.4.3.1). 

For the measurement of the hydrocarbon precursors of photochemical oxidants, the naturally occurring methane must be separated from the other so-called nonmethane hydrocarbons. Only one procedure, gas chromatography coupled with flame ionization detection, is available for this separation and measurement. Although instrumentation for routinely accomplishing this process is commercially available, its maintenance (continued operation) requires a degree of operational know-how that may be too costly for most public agencies in the United States to support. Consequently, the data currently are insufficient to relate the occurrence of photochemical oxidants and ozone accurately to some of their most important precursors, the nonmethane hydrocarbons. 

Only since 1965 has mankind recognized that the formation of in situ hydrates in the geosphere predated their artificial formation (ca. 1800) by millions of years. In addition to their age, it appears that hydrates in nature are ubiquitous, with some probability of occurrence wherever methane and water are in close proximity at low temperature and elevated pressures. 

There are four requirements for generation of natural gas hydrates (1) low temperature, (2) high pressure, (3) the availability of methane or other small nonpolar molecules, and (4) the availability of water. Without any one of these four criteria, hydrates will not be stable. As indicated in both the previous section and in Section 7.4.3, the third criteria for hydrate stability—namely methane availability—is the most critical issue controlling the occurrence of natural gas hydrates. Water is ubiquitous in nature so it seldom limits hydrate formation. However, the first two criteria are considered here as an initial means of determining the extent of a hydrated reservoir. 

Methane. (Marsh Gas, Fire Damp), Methan, Sumpfgas, or Grubengas (Ger) Methane or Grisou (Fr) Metan (Russ) CH4 mw 16.04 a colorl, odorless, and tasteless gas mp —182.5°, bp —161.5°, crit temp —82.1°, crit p 672 psi (Ref 1) CA Registry No 74-82-8 Occurrence. It is the chief constituent of natural gas, which is from 60—98% methane. It occurs to some extent in all coal mines where mixts with air are called by the miners fire damp as it is the cause of almost all coal mine fires and explns (Ref 3). It also occurs in the gases evolved when organic matter decomposes anaerobically as in the bottoms of swamps and marshes, hence the name marsh gas ... 

Coal Gas, Natural Gas, Petroleum.—From its natural formation and occurrence as marsh gas and as fire damp it is not surprising to find that methane occurs also as a constituent of three related sub-... 

Occurrence.—The members of this series of acids are derived from the methane series of hydrocarbons and occur very commonly in nature. In a few cases they are found free as formic acid in ants and nettles and valeric acid in the root of Valeriana. In most cases the acids are combined with alcohols as esters and as such are found in ethereal oils, fats and waxes. This has given them the name fatty acids. 

Occurrence natural gas. Preparation, bum methane in limited oxygen ... 

A common feature associated with cold seeps is the presence of gas hydrates, which are naturally occurring solids comprised essentially of natural gas, mainly methane, trapped in frozen, crystalline water (see reviews by Kvenvolden, 1993 and Buffet, 2000). The occurrence of gas hydrates is controlled by an interrelation among temperature, pressure and composition, and they are stable in solid form only in a narrow range of these conditions (Kvenvolden, 1993). Because of these restrictions, gas hydrates are common mainly in polar and deep... 

Locating deposits of bitumens on the basis of geomicrobiological methods — for example the occurrence of methane bacteria can indicate natural gas, propane bacteria indicate the presence of petroleum, and similarly for bacteria utilizing butane, pentane and hexane. 

Tullo, Alexander H. Methane on Ice. Chemical En neering News 83 (August 22, 2005) 16-17. This brief article describes the nature and occurrence of methane hydrate crystals and the prospects of their use as a future source of fuel. 

Commercial natural gas occurrence can be broadly classified into two categories, conventional and unconventional. The conventional category includes natural gas found as associated and non-associated or free gases, including dissolved or solution. The unconventional natural gas resource includes, (1) deep gas, (2) coal bed methane, (3) gas hydrates and (4) gas In shales, (5)... 

The occurrence of some of the important petrochemical reactions, such as the water gas shift reaction, methane steam reforming, partial oxidation of natural gas to syngas, dry reforming of methane, etc., has been mentioned in detail in previous chapters in this book, but the application of membrane reactors in other industrial important reactions is briefly mentioned. 

With these examples, the notion of sonochemical switching was introduced, which means that for the first time it was evidenced that the interaction of ultrasound with a reactive system is able to change the nature of the reaction products, not only to increase a rate or a yield. An application of this reaction was mentioned in a patent. It seems that a change in the mechanisms was not examined. The observation that electron acceptors such as nitroaromatics in catalytic amounts increase the yield of cyanide at the expense of the diphenyl-methane product was not exploited in this respect. The simultaneous occurrence of the destruction of acidic catalytic sites and the enhancement of a non-polar mechanism would constitute an interesting general interpretation. 

The carbon dioxide reforming of methane has attracted academic and industrial interest, since it produces synthesis gas with a H2/CO ratio closed to 1, which is more suitable for methanol and Fischer-Tropsch synthesis compared to the steam reforming of methane providing synthesis gas with a H2/CO ratio = 3. This reaction is of particular importance for the valorization of C02-rich fossil natural gas but also for the transformation of biogas extensively produced by various anaerobic waste treatments [1]. The production of synthesis gas from CH4 and CO2 is highly endothermic (Eq. (22.1)), the reaction equilibrium is influenced by the simultaneous occurrence of the reverse water-gas shift reaction (RWGS) (Eq. (22.2)). 

Carburization damage is mainly associated with high-temperature exposure to carbon dioxide, methane, and other hydrocarbons. Heat-treating equipment used for gas carburization (surface hardening) of steels is also vulnerable. An insidious aspect of carburization is its nonuniform nature. Just as for other forms of localized corrosion, it is extremely difficult to predict and model localized carburization damage. As a rule of thumb, carburization problems only occur at temperatures above 815°C, because of unfavorable kinetics at lower temperatures. Carburization is therefore not a common occurrence in most refining operations because of the relatively low tube temperatures of most refinery-fired heaters. 

In the U.S., active coalbed methane extraction has been carried out since the 1950s, and its annual output currently stands at 55 billion m, accounting for about 8% of the total natural gas production. The production of coalbed methane is also underway in Canada, Australia, China, India, and other countries. Most of the coalfields in Russia (Kuznetsk, Pechora, Donetsk, Taimyr, Tunguska, etc.) contain gas. The methane content in such highly metamorphosed coal seams increases with the depth of their occurrence, reaching 40—50 rv /ton. The preliminary degassing of coal seams is a necessary condition for safe operation of the miners and an additional source of methane. The use of coalbed-methane wells is complicated by a low flow rate and its large spread, which can vary from 2 to more than 200 thousand m /day, with t5 ical values of 5—15 thousand m /day [304]. 

---