Before we look at how ethanol is made, let’s explore what it is and what it’s used for.
We’re probably all familiar with ethanol as the main ingredient in alcoholic drinks (although it should never be consumed on its own as it isn’t fit for human consumption in its pure form). Its pure form is a clear, colourless, flammable liquid which has a distinctive smell. Ethanol is also called pure alcohol, absolute ethanol, ethanol absolute, ethyl alcohol, and just plain alcohol.
Ethanol has many uses, both for consumers in perfumes, fragrances and medicines, and in a laboratory or industrial context.
3 Ways Ethanol is Made
Over 90% of ethanol produced globally is made from the fermentation of crops, with the remainder produced by the hydration of ethene. Experiments have also been conducted to produce ethanol from carbon dioxide.
How Ethanol Is Made From Fermentation
Plant or crop-based fermentation produces the ethanol that alcoholic drinks are made from. Examples of the types of crops (also called feedstock) used are barley, rice, corn, and wheat. Basically, any crop or plant containing large quantities of sugar like starch or cellulose can be used, with ethanol produced in a four-step process:
- The crops or plants are ground down so it’s easier to process them
- Sugar is either dissolved from the ground-down crops or plants, or the starch or cellulose produced is converted into sugar through a cooking process
- Microbes including yeast and bacteria feed on the sugar, producing ethanol. This process is called fermentation. A by-product of fermentation is carbon dioxide
- The ethanol is distilled to achieve a high concentration. Additives are added to ‘denature’ the ethanol, meaning it is made unfit for human consumption (and avoids the alcoholic beverage tax!)
This fermentation process is also how bioethanol for biofuels is made. Additionally, it is used as a solvent in the manufacture of cosmetics, pharmaceuticals, coatings, and detergents. The waste plant products are used as feed for livestock.
How Ethanol Is Made From The Hydration Of Ethene
Ethanol can also be made by reacting ethene with steam in the acid-catalyzed hydration of ethylene from petrochemical feedstocks. The most common catalyst used is phosphoric acid.
In this process, phosphoric acid is adsorbed onto a surface such as silica in a fixed bed reactor in the presence of high-pressure steam at 300°C, meaning the formation of ethanol is exothermic. The reaction can also be reversed.
How Ethanol Is Made From Carbon Dioxide
Carbon dioxide (CO2) can also be used as the raw material to make ethanol at room temperature and pressure. Hydrogen can be used to reduce CO2 to produce ethanol as well as other acids such as acetic acid.
In this process, a copper nanowire array used as a cathode adsorbs molecules of carbon dioxide. However, only around half the current goes into producing hydrogen so only a small quantity of ethanol is produced. That means it’s not a viable process for producing large quantities of ethanol quickly.
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