In this section we’re going to look at how alcohol, or ethanol, is produced. We’re also going to look at some of its uses – here’s a clue – people don’t just drink it!
Ethanol is produced on an industrial scale using hydration of ethene. Ethanol is produced in such large quantities as it is a useful intermediate in the manufacturing of organic compounds.
However, worth mentioning that industrially produced ethanol would not be put into drinks as the impurities within it can be very harmful.
In the industrial process of turning ethene into ethanol an acid catalyst is required, such as phosphoric acid, plus high temperatures and high pressures even though the reaction is exothermic.
Methane can also be used to produce the alcohol methanol. And similarly to ethanol it is a commonly used starting block in the synthesis of complex organic molecules.
Alcohol can also be produced by the fermentation of sugars and starch using yeast (the basis for brewing and baking).
The fermentation process uses yeast and sugars. The concentration of ethanol produced by the fermentation process reaches a maximum of about 12-15% by volume.
This is because the yeast can only respire anaerobically for a certain amount of time before they have produced too much ethanol which stops them respiring any further.
During the fermentation process the temperature must be kept at 35 degrees centigrade. This is because, like our own bodies, the yeast enzymes cease to function much above 40 degrees centigrade.
We must keep it reasonably warm however, as the warmer the reaction vessel the faster the yeast works until this breaking point.
Interestingly ethanol is both renewable and nonrenewable, how? It depends on the source.
Currently we produce ethanol from ethene, which comes from crude oil (nonrenewable), and by fermentation (renewable).
So why do we keep producing ethanol from crude oil? Simple, it’s cheaper, faster and produces a higher purity.
Producing from crude oil is a continuous process rather than a batch one, and this in part leads to it being a faster and cheaper method of producing ethanol.
There is also the added benefit of high purity, which is desirable in making other organic molecules, whereas it is hard to make 100% pure ethanol by fermentation.
However, it is hoped that in the future we might use ethanol from fermentation to produce ethene by dehydration.
This is because crude oil is nonrenewable, and is the current major source of ethene. But it will run out and without crude oil we would no longer have plastics like polyethene.