Comparing the two methods of producing ethanol
4 marks · NormalThe table below gives some information about two industrial methods for making ethanol.
| Fermentation | Hydration of Ethene |
|---|---|
| Batch process | Continuous process |
| Sugar beet or corn used | Ethene from crude oil used |
| Slower (days) | Faster (hours) |
| Low temperature and pressure | High temperature and pressure |
Give one reason why some countries prefer making ethanol by fermentation.
State one process feature that makes hydration of ethene more efficient than fermentation.
Explain why ethanol from fermentation needs further processing before it can be used as a chemical feedstock.
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(a) They may not have access to crude oil / have abundant crops / renewable resources are available / crude oil is not available.
(b) Continuous process / no need to restart for each batch / reactants can be continuously supplied.
(c) The ethanol produced from fermentation is impure and contains water and other impurities. It must be purified (e.g. by distillation) before it can be used as a chemical feedstock.
Common mistakes: Describing general advantages of ethanol rather than process-specific features
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Marking points
B1 (a) · 1 mark · Correctly states a reason: e.g. lack of oil resources / renewable resources available.
B2 (b) · 1 mark · States a process feature of hydration making it more efficient (continuous process, flow process).
M1 (c) · 1 mark · Recognises fermentation ethanol is impure/contains water/needs purification.
A1 (c) · 1 mark · Describes a correct reason: e.g. needs distillation, not suitable for chemical use until purified.
Worked solution
(a) Countries without crude oil or with plentiful crops may prefer fermentation.
(b) Hydration can be carried out as a continuous process, making it more efficient.
(c) Fermentation produces ethanol mixed with water and other impurities, so further processing such as distillation is required to obtain pure ethanol.