Uses
As a constituent in cooking and illuminating gas; in the production of ammonia, methanol, and chlorohydrocarbons; it occurs in natural gas and is produced by the decomposition of organic matter.
Description
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.
Chemical Properties
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.
History
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.
Uses
Methane is widely distributed in nature. As adeep earth gas, it is outgassing from earth’scrust. It is also present in the atmosphere(0.00022% by volume). It is the prime constituentof natural gas (85–95% concentration).It is formed from petroleum crackingand decay of animal and plant remains. It isfound in marshy pools and muds. Methaneis used as a common heating fuel in naturalgas; in the production of hydrogen, acetylene,ammonia, and formaldehyde; and as acarrier gas in GC analysis.
Uses
Methane is an important starting material for numerous other chemicals. The most important of these are ammonia, methanol, acetylene, synthesis gas, formaldehyde, chlorinated methanes, and chlorofl uorocarbons. Methane is used in the petrochemical industry to produce synthesis gas or syn gas, which is then used as a feedstock in other reactions. Synthesis gas is a mixture of hydrogen and carbon monoxide. It is produced through steam-methane reforming by reacting methane with steam at approximately 900 C in the presence of a metal catalyst: CH4 + H2O→CO + 3H2. Alternately, methane is partially oxidized and the energy from its partial combustion is used to produce syn gas:
CH4 + 2O2→ CO2 + 2H2O
CH4 + CO2→2CO + 2H2
CH4 + H2O→CO + 3H
Hydrogen from syn gas reacts with nitrogen to produce ammonia: N2 + 3H2→2NH3. Carbon monoxide and hydrogen from syn gas can be combined to produce methanol: CO + 2H2→CH3OH.
Methanol is primarily used for the production of formaldehyde through an oxidation process: 2CH3OH + O2→CH2O + H2O or an oxidation-dehydrogenation process: CH3OH CH2O + H2.
Chlorination of methane, in which chlorine is substituted for one to all four of the hydrogens in methane, produces methyl chloride (CH3Cl), methylene chloride (CH2Cl2), chloroform (CHCl3), and carbon tetrachloride (CCl4). The substitution of chlorines and fluorines in methane results in chlorofl uorocarbons. Methane is a fossil fuel that acts as a greenhouse gas, making it a subject of widespread interest in global warming research.
Uses
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.
Definition
methane: A colourless odourless gas, CH
4; m.p.–182.5°C; b.p.–164°C.Methane is the simplest hydrocarbon,being the first member of thealkane series. It is the main constituentof natural gas (～99%) and as such is an important raw material forproducing other organic compounds.It can be converted into methanol by catalytic oxidation.
Definition
The first member of the paraffin (alkane) hydrocarbon series.
Definition
natural gas: A naturally occurringmixture of gaseous hydrocarbonsthat is found in porous sedimentaryrocks in the earth’s crust, usually inassociation with petroleum deposits.It consists chiefly of methane(about 85%), ethane (up to about10%), propane (about 3%), and butane.Carbon dioxide, nitrogen, oxygen,hydrogen sulphide, and sometimeshelium may also be present. Naturalgas, like petroleum, originates in thedecomposition of organic matter. It iswidely used as a fuel and also to producecarbon black and some organicchemicals. Natural gas occurs onevery continent, the major reservesoccurring in the USA, Russia, Kazakhstan,Turkmenistan, Ukraine, Algeria,Canada, and the Middle East. Seealso liquefied petroleum gas.
Definition
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.
Production Methods
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.
General Description
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.
Air & Water Reactions
Highly flammable.
Reactivity Profile
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].
Hazard
Severe fire and explosion hazard, forms
explosive mixture with air (5–15% by volume). An
asphyxiant gas.
Health Hazard
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.
Health Hazard
Methane is a nonpoisonous gas. It is anasphyxiate. Thus exposure to its atmospherecan cause suffocation.
Fire Hazard
Special Hazards of Combustion Products: None
Agricultural Uses
Methane (CH
4) is a colorless gas produced from a highly
reduced paddy field. This odorless gas is also produced
by decomposing organic matter in sewage and marshes.
It is the chief constituent of natural gas. It occurs in
coal gas and water gas and is produced in petroleum
refining.
There is now enough evidence to suggest that rice
cultivation results in increased methane emission to the
atmosphere.
The reasons for interest in methane are that it is an
important energy source, which has a global warming
potential of about 24.5% (carbon dioxide being loo%),
and is responsible for approximately 25% of the
anticipated warming.
Atmospheric methane originates mainly from
biogenic sources, such as rice paddies and natural
wetlands. Rice paddies account for 15 to 20% of the
world's total anthropogenic methane emission. In
addition to the role of rice plant in methane emission, it
also plays a significant role in methane oxidation because
oxygen transported below the ground by plants, leaks out of the rhizosphere into the sediments, stimulating the
methane oxidizing activity. Most of the methane emitted
from rice fields is expected to be from the Asian region as
it has 90% of the total world rice harvested area.
Several investigations have demonstrated that
methane flux in rice fields is dependent on the variety of
rice [dryland, imgated or deep ponded water], water
level, fertilizer application and crop phenology
Strategies to mitigate methane emission from paddy soils
of the world have been identified, which include (a) a
form and dose of nitrogen and other chemical fertilizers,
(b) the mode of fertilizer application, (c) water
management, and (d) cultivation practices. Recent
studies have indicated that methane emission decreased
by about 50% after the application of an ammonium
based fertilizer, due to oxidation of methane. The various
options to mitigate methane emission are (a) direct
seediig of paddy crop, (b) intermittent irrigation, (c) soil
amendment with sulphate containing fertilizers, and (d)
compost addition in place of fresh organic matter.
Agricultural Uses
Natural gas is the feedstock for 78% of the world's
ammonia produced. It is a naturally occurring mixture of
gaseous hydrocarbons found in porous sedimentary rocks
in the earth's crust, usually in association with petroleum
deposits. It is a colorless, odorless, flammable gas or
liquid.
Natural gas contains methane (about 85%), hydrogen
sulphide and carbon dioxide in varying percentages, and
a small percentage of ethane and higher hydrocarbons.
Agricultural Uses
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 P
2O
5)an d 0.8 to 1.3 % potassium (as K
2O) 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.
Materials Uses
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.
Safety Profile
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.
Potential Exposure
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.
Physiological effects
Methane is generally considered nontoxic. Exposures
to concentrations of up to 9 percent
methane have been reported without apparent ill
effects; inhalation of higher concentrations
eventually causes a feeling of pressure on the
forehead and eyes, but the sensation ends after
returning to fresh air. Methane is a simple asphyxiant.
First aid
If this chemical gets into the eyes, remove any contact lenses at once and irrigate immediately for at least 15 min, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts the skin, remove contaminated clothing and wash immediately with soap and water. Seek medical attention immediately. If this chemical has been inhaled, remove from exposure, begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR if heart action has stopped. Transfer promptly to a medical Methane 1725 facility. When this chemical has been swallowed, get medical attention. Give large quantities of water and induce vomiting. Do not make an unconscious person vomit. If frostbite has occurred, seek medical attention immediately; do NOT rub the affected areas or flush them with water. In order to prevent further tissue damage, do NOT attempt to remove frozen clothing from frostbitten areas. If frostbite has NOT occurred, immediately and thoroughly wash contaminated skin with soap and water.
Environmental Fate
Methane is a relatively potent greenhouse gas. The concentration
of methane in the Earth’s atmosphere in 1998, expressed
as a mole fraction, was 1745 ppb, up from 700 ppb in 1750.
By 2008, however, global methane levels, which had stayed
mostly flat since 1998, had risen to 1800 ppb.
Methane has a molecular weight of 16.04 gmol
-1.
At 25 ℃, methane has solubility in water of 22 mg l
-1, an
estimated vapor pressure of 466 000 mmHg, and a Henry’s law
constant of 0.66 atm-m
3 mol
-1 (HSDB, 2011). The log octanol/
water partition coefficient is 1.09. Conversion factors for
methane in air are as follows: 1mgm
-3 = 1.52 ppm; and
1 ppm= 0.66 mgm
-3.
If released into air, the very low boiling point (
-161 ℃)
and high vapor pressure predict that methane will exist
solely as a vapor in the ambient atmosphere. Vapor-phase
methane will be degraded in the atmosphere by a reaction
with photochemically produced hydroxyl radicals; the halflife
for this reaction in air is estimated to be 6 years
(HSDB, 2011).
If released into water, liquid methane would boil off. Any
residual methane would only moderately adsorb to suspended
solids and sediment based on an estimated Koc (organic carbon
partition coefficient) of 90. Volatilization from water surfaces is
expected to be the dominant fate process based on the estimated
Henry’s law constant. Estimated volatilization half-lives for both
a model river and a model lake are 2 h (US EPA, 2011). Utilization
of methane by soil microorganisms has been detected from
five soil samples collected from sites near Adelaide, South
Australia. The biodegradation half-life of methane was estimated
to be 70 days to infinity based on gas exchange biodegradation
experiments conducted in model estuarine ecosystems (HSDB,
2011).
If released to soil, methane would be expected to rapidly
volatilize. Anymethane thatmigrated to the subsurface would
have high to moderate mobility in the subsurface based on
the relatively low Koc value. Volatilization of methane from
moist soil surfaces is expected to be an important fate process
(HSDB, 2011).
Using a measured log Kow (octanol water partition coefficient)
of 1.09, the US Environmental Protection Agency’s
(USEPA) EPI Suite computer program estimates both a bioconcentration
factor (BCF) and a bioaccumulation factor
(BAF) of 2. This predicts that bioaccumulation and/or biomagnification
would be insignificant. Methane would therefore
not be expected to be found in the tissues of fish or wildlife as
methane contains no persistent functional groups (e.g., chlorine,
bromine) and exposure would be expected to be low.
storage
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.
Shipping
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
Purification Methods
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.
Toxicity evaluation
Methane acts as an asphyxiant at concentrations that are high
enough to displace oxygen.
Incompatibilities
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
Waste Disposal
Return refillable compressed
gas cylinders to supplier. Incineration (flaring)
Precautions
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.
GRADES AVAILABLE
Methane is typically available for commercial
and industrial purposes in a c.P. Grade
(minimum purity of 99 mole percent), a technical
grade (minimum purity of 98.0 mole percent),
and a commercial grade that is actually
natural gas as it is received from the pipeline.
(There is no guaranteed purity, but methane
content usually runs about 93 percent or better.)
