What is Ethanol?

Technical Properties

Chemical and physical properties of ethanol:

Molecular Formula: C₂H₆O / CH₃−CH₂−OH / C₂H₅OH

Synonyms: ethyl alcohol, grain alcohol, methylcarbinol, TSDA, Ethos, absolute alcohol, drinking alcohol, ethylic alcohol, hydroxyethane

Cas Number: 64-17-5

Molecular Mass: 46.041 g·mol⁻¹ 

Exact Mass: 46.041865 g/mol

Flashpoint: 55°F / 12.8°C

Boiling Point: 173.3°F / 78.5°C at 760 mm Hg 

Melting Point: -173.4°F / -114.1°C

Vapour Pressure: 59.3 mm Hg at 25 °C

Water Solubility: Miscible

Density: 0.7893 g/cu (at 20 °C)

Ethanol occurs naturally in many areas such as in corn, safflower, in urine, faeces, blood and sweat, emissions from fires, volcanoes, insects, fermentation of sugars and also fruit (when overripe). Ethanol is a byproduct of the metabolism of yeast, indicating that it is present in most yeast habitats and is also produced during the germination of plants.

Production

Ethanol has been produced for thousands of years and is one of the oldest organic processes utilized by humankind with people throughout history appreciating its intoxicating properties. 

Historically, it was produced via ethanol fermentation which is the process of converting sugars, such as glucose, into cellular energy which produces ethanol as a result:

C₆H₁₂O₆ → 2 CH₃CH₂OH + 2 CO₂

Large volumes of ethanol are still produced by fermentation and are mainly used for alcoholic and fuel uses of ethanol. Raw materials can be used in replacement of sugars, including starch and sugar-based feedstocks, such as corn grain or sugar cane, or cellulosic feedstocks such as grass, wood, crop residues, or agricultural waste.

Carbon dioxide can also be used to replace the sugars or raw materials using electrochemical reactions. However, this method tends to produce smaller amounts of ethanol.

Another method of producing ethanol is through the acid-catalysed hydration of ethylene in the presence of a catalyst such as phosphoric acid:

C₂H₄ + H₂O → CH₃CH₂OH

This method is typically used for producing ethanol for solvent uses.

Ethanol is also produced through the enzymatic hydrolysis of cellulose, wet milling of corn and the oxidation of methane.

It is produced for use in a wide range of industries with demand increasing most rapidly in the fuel industry where government changes in legislation are requiring fuel manufacturers to increase the percentage of ethanol in their fuel.  The global production of ethanol is rising with approximately 52 million tonnes produced in 2008 alone.

Reactions

Ethanol is highly flammable and soluble in water. It reacts violently with acetyl bromide and chloride and explosive mixtures can be formed if ethanol is mixed with highly concentrated hydrogen peroxide.

Several enzyme reactions use ethanol, one of which being the oxidisation of ethanol to acetaldehyde with nicotinamide-adenine dinucleotide, in the presence of an alcohol dehydrogenase catalyst:

Ethanol + NAD⁺ → acetaldehyde + NADH + H⁺

Other reactions include hypochlorous acid or chlorine to form ethyl hypochlorite.

Ethanol reacts with carboxylic acids such as amino or fatty acids to produce ethyl esters in the presence of an acid catalyst such as hydrofluoric and phosphoric acid.

RCOOH + HOCH₂CH₃ → RCOOCH₂CH₃ + H₂O

Other reactions include the combustion of ethanol forming CO₂ and water, reacting with alkali metals or strong bases and the dehydration of ethanol with an acid catalyst.

Handing, storage & distribution

Hazards & toxicity

Ethanol has an NFPA rating of 2 and can cause temporary incapacitation or residual injury. Ethanol (in vapour form only) will irritate the eyes, nose and throat. It has a fire rating of 3  and can be ignited under almost all ambient temperature conditions.

Safety & procedures 

Personal protective equipment should be warn at all times to prevent possible contact with your skin and eyes.  If contact is made with your skin, immediately wash the contaminated area. Wet clothing should be removed immediately and replaced.

In the case of spillage, attempt to isolate the leak to a minimum of 50 metres. The leak should be absorbed using dry earth or non-combustible materials. Access to sewers, basements and waterways should be blocked. Alcohol-resistant foam, CO₂ or water spray extinguishers should be used. Ignition sources should be removed to prevent a fire or further fires developing.

Storage & distribution

Ethanol is stored in storage tanks and/or stainless-steel drums and can be transported by bulk vessels or tank trucks.  For transportation purposes, ethanol is classed as packing group II and hazard class 3 as it has a flashpoint of 14 °C (closed cup) and is highly flammable.  It should be kept in a cool, dry, well-ventilated area that is free from all fire hazards.  It has a specific gravity of 0.789.

Uses

Industrial uses of ethanol

The primary use of ethanol is in the manufacturing of alcoholic beverages. Other manufacturing uses include in the production of acetaldehyde, ethyl chloride, ethyl acetate,  ethylene dibromide, acetic acid, glycol ethers, ethylamines and also in explosives, dyes, detergents, fillers, lubricants, lacquers, additives, coatings, cosmetics, perfumes, food extracts flavourings, gasoline and pharmaceuticals.

Pharmaceutical uses of ethanol include as an antiseptic in wipes and anti-bacterial spray. It is also used occasionally as an antidote to methanol poisoning and as a neurotoxin, teratogenic agent and a human metabolite. Ethanol can relieve chronic pain for inoperable cancer patients through the neurolysis of nerves.

Another primary use of ethanol is as an engine cleaner burner fuel additive. The majority of gasoline produced in the U.S. contains 10% ethanol which oxygenates the fuel reducing its pollution.

Uses of ethanol as a solvent

Ethanol has many uses as a solvent including for resins, fatty acids, hydrocarbons, fats, oils and waxes. It is also present in personal care products, air care products, paints and markers. Ethanol’s structure enables for the dissolving into polar compounds such as water, non-polar and hydrophilic such as hexane and hydrophobic.

Ethanol is also used as a medicinal solvent due to its low toxicity and non-polar capabilities. It is seen in drugs for pain relief and medicines for coughs and colds.

Commercial uses of ethanol

Ethanol is found in many cosmetic, beauty and personal care products, antibacterial gels and sanitisers due to its cleaning properties and helps to separate sprays into the air and keep lotions and jells from splitting.

It is also present in paints, varnishes, oils, vanilla extracts, fuel, alcoholic beverages, anti-freezes, inks, adhesives.