МЕТАН

Описание

Methane is a colorless, odorless, flammable hydrocarbon gas that is the simplest alkane. The root word, met, in methane is derived from the Greek root word methe meaning wine. Methylene was used in the early 19th century as the name for methanol, which is wood alcohol, CH3OH. Methylene comes from methe + hydē, the latter being the Greek word for wood, so methylene would mean wine from wood. Methanol got the names methylene and wood alcohol because it was discovered by Robert Boyle (1627–1691) in the 17th century by the destruction distillation of wood. Destructive distillation involves heating in the absence of air.

Methane is the first alkane and carries the suffix“ane” denoting an alkane, thus methe z + ane = methane. The carbon is at the center of the tetrahedron, which can be assumed to be an equilateral pyramid, with a hydrogen atom at each of the four corners of the tetrahedron.
Methane is the principal component of natural gas, with most sources containing at least 75% methane. Methane production occurs naturally through a process called methanogenesis. Methanogenesis involves anaerobic respiration by single-cell microbes collectively called methanogens.

Химические свойства

Methane is a natural, colorless, odorless, and tasteless gas. It is used primarily as fuel to make heat and light. It is also used to manufacture organic chemicals. Methane can be formed by the decay of natural materials and is common in landfi lls, marshes, septic systems, and sewers. It is soluble in alcohol, ether, benzene, and organic solvents. Methane is incompatible with halogens, oxidizing materials, and combustible materials. Methane evaporates quickly. Methane gas is present in coal mines, marsh gas, and in sludge degradations. Methane can also be found in coal gas. Pockets of methane exist naturally underground. In homes, methane may be used to fuel a water heater, stove, and clothes dryer. Incomplete combustion of gas also produces carbon monoxide. Methane gas is flammable and may cause fl ash fi re. Methane forms an explosive mixture in air at levels as low as 5%. Electrostatic charges may be generated by fl ow and agitation.

История

Methane has been used as a fossilfuel for thousands of years. The discovery of methane is attributed to the Italian physicist Alessandro Volta (1745–1827). Volta, known primarily for his discoveries in electricity, investigated reports of a flammable gas found in marshes. In November 1776, Volta, while visiting the Lake Maggiore region of northern Italy, noticed that gas bubbles emanated from disturbed sediments in marshes. Volta collected the gas and began investigations on its nature. He discovered that the gas was highly flammable when mixed with air. He developed an instrument termed Volta’s pistol (also called a spark eudiometer) that fired metal balls like a miniature cannon to conduct combustion experiments with methane. He also developed a lamp fueled by methane.

Использование

Methane is used primarily as a fuel to make heat and light. It is also used to manufacture organic chemicals. Methane can be formed by the decay of natural materials and is common in landfills, marshes, septic systems, and sewers. It is soluble in alcohol, ether, benzene, and organic solvents. Methane is incompatible with halogens, oxidising materials, and combustible materials. Methane evaporates quickly. Methane gas is present in coal mines, marsh gas, and sludge degradations. Methane can also be found in coal gas. Pockets of methane exist naturally underground. In homes, methane may be used to fuel a water heater, stove, and clothes dryer. Also, incomplete combustion of gas also produces carbon monoxide. Methane gas is flammable and may cause flash fire. Methane forms an explosive mixture in air at levels as low as 5%. Electrostatic charges may be generated by flow and agitation.

Определение

A gaseous alkane. Natural gas is about 99% methane and this provides an important starting material for the organic-chemicals industry. Methane can be chlorinated directly to produce the more reactive chloromethanes, or it can be ‘reformed’ by partial oxidation or using steam to give mixtures of carbon oxides and hydrogen. Methane is the first member of the homologous series of alkanes.

Методы производства

Methane is the end product of anaerobic decay. It is the major constituent of natural gas, present at concentrations between 600,000 and 800,000 ppm 60 to 80% of natural gas. Methane collects in coal mines or geologically similar earth deposit sites, evolves as marsh gas, and forms during certain fermentation and sludge degradation processes. Methane is also produced by decomposition in municipal landfills; concentrations can be as high as 250,000 ppm. It is often accompanied by other low molecular weight hydrocarbons.

Общее описание

METHANE is a colorless odorless gas. METHANE is also known as marsh gas or methyl hydride. METHANE is easily ignited. The vapors are lighter than air. Under prolonged exposure to fire or intense heat the containers may rupture violently and rocket. METHANE is used in making other chemicals and as a constituent of the fuel, natural gas.

Реакции воздуха и воды

Highly flammable.

Профиль реактивности

METHANE is a reducing agent, METHANE is involved in many explosions when combined with especially powerful oxidizers such as bromine pentafluoride, chlorine trifluoride, chlorine, iodine, heptafluoride, dioxygenyl tetrafluoroborate, dioxygen difluoride, trioxygen difluoride and liquid oxygen. Other violent reactions include, chlorine dioxide and nitrogen trifluoride. Liquid oxygen gives an explosive mixture when combined with liquid METHANE [NFPA 1991]. Contact of very cold liquefied gas with water may result in vigorous or violent boiling of the product and extremely rapid vaporization due to the large temperature differences involved. If the water is hot, there is the possibility that a liquid "superheat" explosion may occur. Pressures may build to dangerous levels if liquid gas contacts water in a closed container [Handling Chemicals Safely 1980].

Опасность

Severe fire and explosion hazard, forms explosive mixture with air (5–15% by volume). An asphyxiant gas.

Угроза здоровью

Methane is a relatively potent gas. It is the simplest alkane and the principal component of natural gas. Exposures to methane gas cause toxicity and adverse health effects. The signs and symptoms of toxicity include, but are not limited to, nausea, vomiting, diffi culty breathing, irregular heart beat, headache, drowsiness, fatigue, dizziness, disorientation, mood swings, tingling sensation, loss of coordination, suffocation, convulsions, unconsciousness, and coma. While at low concentrations methane causes no toxicity, high doses lead to asphyxiation in animals and humans. Displacement of air by methane gas is known to cause shortness of breath, unconsciousness, and death from hypoxemia. Methane gas does not pass readily through intact skin. However, in its extremely cold liquefi ed form, methane can cause burns to the skin and eyes. No long-term health effects are currently associated with exposure to methane.

Пожароопасность

Special Hazards of Combustion Products: None

Сельскохозяйственное использование

Biogas, a gaseous fuel, is produced by the fermentation of organic matter by methane-forming bacteria (methanogens). Biogas consists of a mixture of methane, carbon dioxide and hydrogen.
A mixture of methane and carbon dioxide, or even methane alone, formed in the deep layers of organic material in swamp bottoms or landfills, is sometimes called swamp gas or marsh gas.
Acetoclastic bacteria form methane exclusively from acetic acid in anaerobic digestion. They grow slowly and have a doubling time of several days, which is the rate-limiting step in biogas production. Bacteria that ferment fatty acids (mainly propionic acid and butyric acid) to acetic acid are called acetogenic bacteria.
Animal dung and plant residues are used to produce biogas in a fermenter. The residual biogas slurry containing 1.4 to 1.8 % nitrogen, 1.1 to 1.7 % phosphorus (as P₂O₅)an d 0.8 to 1.3 % potassium (as K₂O) is used as organic manure. Animal manure used for biogas production does not lose its fertilizer nutrient value. Biogas is usually made by the decomposition of domestic, industrial and agricultural sewage wastes. Methane, its major component, can be harvested and used as a pollution-free renewable resource and a derived source of domestic energy. Biogas, produced in special biogas digesters, is widely used in China and India.

Использование в материалах

Methane is noncorrosive and may be contained by any common, commercially available metals, with the exception of cryogenic liquid applications. Handling equipment must, however, be designed to safely withstand the temperatures and pressures to be encountered.
At the temperature of liquid methane, ordinary carbon steels and most alloy steels lose their ductility and are considered unsafe for liquid methane service. Satisfactory materials for use with liquid methane include Type 18-8 stainless steel and other austenitic nickel-chromium alloys, copper, Monel, brass, and aluminum.

Профиль безопасности

A simple asphyxiant. Very dangerous fire and explosion hazard when exposed to heat or flame. Reacts violently with powerful oxidzers (e.g., bromine pentafluoride, chlorine trifluoride, chlorine, fluorine, iodine heptafluoride, dioxygenyl tetrafluoroborate, dioxygen difluoride, trioxygen difluoride, liquid oxygen, ClO2, NF3,OF2). Incompatible with halogens or interhalogens in air (forms explosive mixtures). Explosive in the form of vapor when exposed to heat or flame. To fight fire, stop flow of gas. See also ARGON for a description of asphyxiants.

Возможный контакт

Methane is used as a fuel and in the manufacture of organic chemicals, acetylene, hydrogen cyanide, and hydrogen. It may also be a cold liquid. Natural gas is used principally as a heating fuel. It is transported as a liquid under pressure. It is also used in the manufacture of various chemicals including acetaldehyde, acetylene, ammonia, carbon black; ethyl alcohol; formaldehyde, hydrocarbon fuels; hydrogenated oils; methyl alcohol; nitric acid; synthesis gas; and vinyl chloride. Helium can be extracted from certain types of natural gas.

хранилище

Occupational workers should store methane gas containers away from incompatible substances and handle in accordance with standard set regulations and grounding and bonding if required.

Перевозки

UN1971 Methane, compressed or Natural gas, compressed (with high methane content), Hazard Class: 2.1; Labels: 2.1-Flammable gas. UN1972 Methane, refrigerated liquid (cryogenic liquid) or Natural gas, refrigerated liquid (cryogenic liquid), with high methane content), Hazard Class: 2.1; Labels: 2.1-Flammable gas. Cylinders must be transported in a secure upright position, in a wellventilated truck. Protect cylinder and labels from physical damage. The owner of the compressed gas cylinder is the only entity allowed by federal law (49CFR) to transport and refill them. It is a violation of transportation regulations to refill compressed gas cylinders without the express written permission of the owner

Методы очистки

Dry methane by passing over CaCl2 and P2O5, then through a Dry-ice trap and fractionally distil it from a liquid-nitrogen trap. Oxygen can be removed by prior passage in a stream of hydrogen over reduced copper oxide at 500o, and higher hydrocarbons can be removed by chlorinating about 10% of the sample: the hydrocarbons, chlorides and HCl are readily separated from the methane by condensing the sample in the liquid-nitrogen trap and fractionally distilling it. Methane has also been washed with conc H2SO4, then solid NaOH and then 30% NaOH solution. It is dried with CaCl2, then P2O5, and condensed in a trap at liquid air temperature, then transferred to another trap cooled in liquid nitrogen. CO2, O2, N2 and higher hydrocarbons can be removed from methane by adsorption on charcoal. [Eiseman & Potter J Res Nat Bur Stand 58 213 1957, Beilstein 1 IV 3.] HIGHLY FLAMMABLE.

Несовместимости

May form explosive mixture with air. A strong reducing agent. Incompatible with oxidizers (chlorates, nitrates, peroxides, permanganates, perchlorates, chlorine, bromine, fluorine, etc.); contact may cause fires or explosions. Keep away from alkaline materials, strong bases, strong acids, oxoacids, epoxides. Reacts violently with bromine pentafluoride, chlorine dioxide, nitrogen trifluoride, oxygen difluoride and liquid oxygen. In general, avoid contact with all oxidizers

Утилизация отходов

Return refillable compressed gas cylinders to supplier. Incineration (flaring)

Меры предосторожности

Occupational workers should be careful during handling and management of methane gas because of its severe fi re and explosion hazard, particularly with pressurized containers. The containers may rupture or explode if exposed to suffi cient heat. Workers should avoid heat, flames, sparks, and other sources of ignition, and stop any leak if possible without personal risk. Workers should wear appropriate chemical-resistant gloves. Also, vapors should be reduced with water spray and keep unnecessary workers/people away from the place of chemical hazard. The closed spaces should be well ventilated before the workers enter. Methane is not toxic; however, it is highly flammable and may form explosive mixtures with air. Methane is violently reactive with oxidizers, halogens, and some halogen-containing compounds. Methane is also an asphyxiant and in enclosed areas displaces oxygen. Septic tanks, cesspools, and drywells present serious hazards, including septic cave-in or collapse, methane gas explosion hazards, and asphyxiation hazards. Occupational workers/work area supervisor should note the indications of methane gas poisoning: Soon after exposure to oxygen levels of less than 15% in air, if the workers feel symptoms of dizziness, headache, and tiredness, medical advice should be provided.