Methane

Article

May 22, 2022

Methane is a simple hydrocarbon (alkane) made up of one carbon atom and four hydrogen atom; its chemical formula is CH4, and it occurs naturally in the form of gas.

History

The discovery

In the autumn of 1776 Alessandro Volta studied a phenomenon known even in more distant times, reported to him by Carlo Giuseppe Campi: in a stagnant bend of the Lambro river, when a flame approached the surface, celestial flames were lit. This phenomenon had already been studied separately by Lavoisier, Franklin and Priestley a few years earlier and was classified simply as an exhalation of flammable air, of mineral origin. Volta wanted to go deeper into the matter. While he was a guest in Angera in the house of his friend Teresa Castiglioni (Angera 1750 - Como 1821), Alessandro Volta discovered the flammable air in the marsh of the Partegora island, in the locality of Bruschera (province of Varese). Trying to move the bottom with the help of a stick, he saw bubbles of gas rising and collected them in bottles. He gave this gas the name of flammable marsh air and discovered that it could be ignited, either by means of a lit candle or by an electric discharge; he deduced that the gas was formed in the decomposition of animal and vegetable substances. Thinking immediately of its practical use, he first built an electrophlogopneumatic gun in wood, metal and glass, the purpose of which would be the transmission of a signal at a distance, and later made a flammable air lamp and perfected the eudiometer for measuring and gas analysis. For further confirmation of his thesis, he went in 1780 to Pietramala, on the Tuscan Apennines, where there were famous wisps. The correct composition of the gas was determined by William Henry in 1805.

Methane extraction in Italy

In June 1958 in Italy, near Lodi, an Eni drilling, then chaired by Enrico Mattei, discovered the first deep deposit in Western Europe. Subsequently, the surveys in the Adriatic Sea began, but the first two drillings gave negative results, so Eni abandoned the idea preferring to allocate the resources to drillings in the Red Sea. Pending the authorizations from the Egyptian government, Eni decided to carry out a third drilling off the coast of Ravenna, which gave a positive result. In 1959 the first methane platform went into operation. Off the coast of Crotone, Eni's platforms currently extract about 15% of the national consumption of methane, for both civil and industrial use.

Physico-chemical properties

The methane molecule has a tetrahedral shape; the carbon atom is at the center of a regular tetrahedron at the vertices of which are the hydrogen atoms. The bond angles are 109.5 °. The methane molecule has sp3 hybrid atomic orbitals, like all the carbons of the molecules of the alkane class, of which it is the shortest member; therefore it has 4 equivalent C-H bonds. At ambient temperature and pressure it occurs as a colorless, odorless and highly flammable gas. Liquid methane, on the other hand, is obtained by cooling the gas to a temperature of –162 ° C, again at atmospheric pressure.

Abundance and availability in the world

Underground

Methane is the result of the decomposition of some organic substances in the absence of oxygen. Most of the methane is obtained by extraction from its underground deposits, where it is often combined with other hydrocarbons, the result of the decomposition of organic substances buried deep in prehistoric times. Methane is normally present in oil fields but there are also huge fields of methane only. Methane derives from the source rocks, from which all hydrocarbons (from solids - bitumen, to liquids - petroleum, up to gaseous, such as methane itself) gradually derive through the cracking of the kerogen.