Natural Sources of Methane Emission
Methane or marsh gas is the simplest hydrocarbon of paraffin that occurs in natural gas sources and emission from the oil-wells having molecular formula CH4 with regular tetrahedral chemical structure. A methane molecule is the principal chemical product of organic decay in swamps and marshes. Therefore, methane production by the action of bacteria on swamps and marshes in our environment and called the marsh gas. Sewage sludge fermented by catalyst bacteria yields methane gas about 70 percent and also formes 40 percent by volume in coal gases and this gas uses as a liquid fuel in our everyday life. Methane gas also responsible for global warming and acts as greenhouse gases.
Structural Formula of Methane Molecule
Methane is the simplest natural unsaturated hydrocarbon in an olefin series with the molecular formula CH4 and molecular weight 16 gm mol-1. If we assuming the quadrivalence of carbon atom it shows the following structure in chemical science. The carbon atom in methane has 2s1 2px1 2py1 2pz1 electronic configuration. On mixing these four atomic orbitals give four equivalent sp3-hybrid orbitals. These hybridized orbitals directed towards the corner of the regular tetrahedron showing on the above picture. Each of these half-filled hybrid orbitals of carbon atom bonding with half-filled atomic orbitals of the hydrogen atom. Therefore, CH4 molecule has a tetrahedral shape with the C-H-C bond angle of 109.5°.
Properties of hydrogen atom in four H-C-H bonds are equivalent with no dipole moment. Therefore, the bond angle, bond energy, and bond length of all carbon hydrogen bond are equivalent in CH4 molecule.
Chemical Production Process of Methane
Methane is the main part of learning chemistry of natural marsh gas synthesized by striking electric between carbon electrodes in atmosphere hydrogen or by heating carbon mixture with element nickel at 475°C in the presence of hydrogen.
- Sabatier and Senderens in 1897 invented the process of methane production by passing a mixture of hydrogen and carbon monoxide or carbon dioxide over finely divided nickel at about 300°C.
CO + 3H2 → CH4 + H2O
CO2 + 4H2 → CH4 + 2H2O
- Methane may conventionally be prepared by heating 1:3 mixture of sodium acetate and soda-lime or reduction of methyl iodide with dissolving metals or by strong base lithium aluminum hydride.
CH3COONa + (NaOH + CaO) → CH4 + Na2CO3
- Other methods for the preparation of CH4 done by water on aluminum carbide or Grignard reagent methyl magnesium iodide.
Al4C3 + 12H2O → 3CH4 + 4Al(OH)3
CH3MgI + H2O → CH4 + MgI(OH)
Physical and Chemical Properties
At normal temperature, methane is a colorless, orderless, non-poisonous gaseous substances with boiling point = -164°C and melting point -184°C in 760 mmHg. This gas is less soluble in water but more soluble in organic solvents (alcohol and ether). Therefore, 100 ml of water used to dissolve about 5 ml of CH4 gas at 20°C. Thermodynamics combustion of CH4 gives non- luminous flame in air or oxygen by forming carbon dioxide and water.
This natural gas explodes violently when mixed with air (oxygen) which causes the explosion in coal mines, where methane is known as fire-damp. On catalytic oxidation, it produces methanol and formaldehyde with decreasing the oxidation number of the carbon atom. But when a mixture of methane and oxygen passing through a copper tube at 100 atm pressure and 200°C temperature. The gas mixture produced methanol.
Uses of Methane Gas in Everyday Life
Uses of finely divided carbon going through incomplete combustion of methane gas at 1000°C.
- Methane on heating to 1000°C or by incomplete combustion produces carbon in a very finely divided state known as caron black. This carbon black is uses in paint, printer ink, and rubber industry for making motor tires.
- Methane gas uses as an organic fuel in our everyday life.
- Methyl chloride, acetylene, formaldehyde, and methanol which obtained from methane, use largely in the chemical plants.
- It used as a source of synthesis gas. Hence a mixture of this gas and steam passed over the heated nickel supported on alumina to produce synthesis gas. Methane gas largely used as the natural source of hydrogen gas in the chemical industry.
CH4 + H2O → CO + 3H2
CH4 + 2H2O → CO2 + 4H2
Methane in Greenhouse Gases
Now a serious concern about the increase in the use of methane, carbon dioxide, CFC, ozone, nitrous oxide gases, and water vapor of the atmosphere causes to raise the global temperature and the effect is known as the greenhouse effect. But the greenhouse used to maintain in winter counties by artificial heating. The contribution to global warming of CH4 gas is about 16 to 20 percent. Therefore, CH4 heating the earth’s atmosphere by trapping electromagnetic infrared particles or heat reflected from the earth’s surface. Recently due to many global activities like the industrial revolution and uses natural gas, the concentration of greenhouse gases increases.
The average temperature of the earth’s atmosphere rises about 2.5°C in the next 30 years which resulting in a major climate change in the world. Hence the polar ice caps will melt indirectly by greenhouse gases methane. These consequently increase in sea level. Therefore, many seaside localities including some big Iceland completely submerged. Therefore, to save our civilization use non-fossil fuel like wind energy, nuclear power, and decreasing the uses of fossil fuels like natural gas (sources of methane), coal, etc.