Ethane is a hydrocarbon gas made from petroleum. It is the second (first is methane) in a series of simple hydrocarbon petrochemical compounds in a family of related compounds named ‘Alkanes’, all of which have the feature of containing only single bonds between carbon atoms. Alkanes (also known as paraffins or saturated hydrocarbons) are chemical compounds that consist only of the elements carbon (C) and hydrogen (H). The first four primary alkanes are methane, ethane, propane, and butane. After methane, ethane is the second-largest component of natural gas. Natural gas from different gas fields varies in ethane content from less than 1% to over 6% by volume.
Prior to the 1960s, ethane and larger molecules were typically not separated from the methane component of natural gas, but simply burnt along with the methane as a fuel. Today, however, ethane is an important petrochemical feedstock, and it is separated from the other components of natural gas in most well-developed gas fields. Natural gas, crude oil, and coal are collectively known as hydrocarbons. Also called petroleum compounds, hydrocarbons are made up of the elements hydrogen and carbon, plus impurities.
Who discovered Ethane?
Ethane was first discovered by Michael Faraday, an English chemist and physicist in 1834, by the electrolysis (a method of using a direct electric current (DC) to drive an otherwise non-spontaneous chemical reaction) of a solution of potassium aceatate. He mistook the hydrocarbon product of this reaction for methane, and did not investigate it further. This error was corrected in 1864 by Carl Schorlemmer, a German chemist who showed that the product was in fact Ethane. The name "ethane" is derived from the Greek name “aither”, meaning "upper air."
What are the Properties of Ethane?
The chemical formula for ethane gas is C2H6.
Ethane is a hydrocarbon that exists in nature as an odorless and colorless gas at standard temperature and pressure.
It is a stable compound and shows resistance to reactivity.
It has a molar mass of 30.07 grams per mole (g/mol).
The melting point of ethane is -181.76 °C (89.34 °K) and its boiling point stands at -88.6° C (184.5 °K).
Ethane is soluble in polar solvents like water due to its non-polar nature. Basically, the solubility of ethane is quite low for the formation of a homogeneous solution.
At room temperature, it is also highly combustible. The complete combustion of the gas produces carbon dioxide and water along with the release of 1561 kilo joules per mole (kJ/mol). The chemical reaction is given as:
2 C2H6 + 7 O2 --> 4 CO2 + 6 H2O + 3,170 kJ.
How is Ethane prepared?
Ethane may be easily prepared in the laboratory by a method called “Kolbe electrolysis”. In this method, an aqueous solution of an acetate (CH3COO-) salt, a derivative of acetic acid is electrolysed. At the anode, acetate is oxidized to produce carbon dioxide and methyl (CH3.) radicals, and the highly reactive methyl radicals combine to produce ethane. The chemical reaction is:
CH3COO- --> CH3• + CO2 + e-
CH3• + •CH3 --> C2H6
By Turbo expansion:Ethane is most efficiently separated from methane by liquefying it at cryogenic temperatures. A variety of refrigeration strategies are there: the most economical process presently in wide use employs turbo expansion, and can recover over 90% of the ethane in natural gas. In this process, chilled gas expands through a turbine; as it expands, its temperature drops to about -100 °C. A turbine is a rotary engine that extracts energy from a fluid flow and converts it into useful work. At this low temperature, gaseous methane can be separated from the liquefied ethane and heavier hydrocarbons by distillation. Further distillation then separates ethane from the propane and heavier hydrocarbons
Ethane can also be separated from petroleum gas, a mixture of gaseous hydrocarbons that arises as a byproduct of petroleum refining.
What are the free radical reactions of Ethane?
The chemistry of ethane also primarily involves free radical reactions. Free radicals are atoms, molecules, or ions with unpaired electrons on an open shell (not completely filled with electrons) configuration. Free radicals may have positive, negative, or zero charge. Free radical reaction is any chemical reaction involving free radicals. Ethane can react with the halogens (a series of nonmetal elements from Group 17 of the periodic table), especially chlorine and bromine, by free radical halogenation. Halogenation is a chemical reaction that incorporates a halogen atom into a molecule. This reaction proceeds through the propagation of the ethyl (C2H5.) radical to form ethyl chloride and chlorine radical. The chlorine radical reacts with ethane in the next step to form ethyl radical and Hydrochloric acid. In the chemical industry, more selective chemical reactions are used for the production of any particular two-carbon halocarbon. The reaction is as follows:
C2H5• + Cl2 --> C2H5Cl + Cl•
Cl• + C2H6 --> C2H5• + HCl
What are the Uses of Ethane?
Production of Ethene: The main use of ethane is in the chemical industry in the production of ethene (ethylene) by steam cracking. Steam cracking is a petrochemical process in which saturated hydrocarbons are broken down into smaller, often unsaturated, hydrocarbons. It is the principal industrial method for producing the lighter alkenes (double bonds between carbon atoms), including ethene (or ethylene) and propene (or propylene). Ethane is favored for ethene production because the steam cracking of ethane is fairly selective for ethene, while the steam cracking of heavier hydrocarbons yields a product mixture poorer in ethene.
Ethane can be used as a refrigerant in cryogenic refrigeration systems. In a scientific research, liquid ethane is used to vitrify water-rich samples for electron microscopy. Vitrification of water is promoted by rapid cooling. A thin film of water quickly immersed in liquid ethane at -150 °C or colder, freezes too quickly for water to crystallize. This rapid freezing does not disrupt the structure of soft objects present in the liquid state, as the formation of ice crystals can do.
The Saudi Arabian firm SABIC has announced construction of a 30,000 plants to produce acetic acid by ethane oxidation.
Commercial use: Ethylene is a major commercial product, widely used for quickening the process of food ripening, the manufacture of welding gas, and a primary component in the production of “Levinstein sulfurmustard”, a toxic chemical weapon gas.
What are the Safety measures to be taken while handling Ethane?
At room temperature, ethane is a flammable gas. When mixed with air at 3.0% – 12.5% by volume, it forms an explosive mixture.
Extra precautions are required where ethane is stored as a cryogenic liquid. Direct contact with liquid ethane can result in severe frostbite.