Manufacture of ethanol (Edexcel GCSE Chemistry): Revision Notes

Manufacture of ethanol

Ethanol ($C₂H₅OH$) can be produced using two main methods: hydration of ethene and fermentation of sugars. Each method has different raw materials, conditions, and advantages.

1. Hydration of Ethene

Equation: $CH₂=CH₂ + H₂O → C₂H₅OH$

(Ethene + Water → Ethanol)

Conditions:

• Temperature: 300°C

• Pressure: 60-70 atm

• Catalyst: Phosphoric acid (H₃PO₄) Process:

• Ethene, which is obtained from cracking crude oil, reacts with steam in the presence of a phosphoric acid catalyst to produce ethanol.

2. Fermentation of Yeast

Equation: $C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂$

(Glucose → Ethanol + Carbon dioxide)

Conditions:

• Temperature: 30-40°C

• Anaerobic conditions (no oxygen present)

• Yeast acts as a natural catalyst. Process:

• Yeast is mixed with a sugar solution (e.g., glucose) in the absence of oxygen.

• Yeast breaks down the sugar into ethanol and carbon dioxide.
• The reaction stops when the ethanol concentration reaches about 15%, as it kills the yeast.

Comparison of the Two Methods:

Method	Raw Materials	Conditions	Advantages	Disadvantages
Hydration of Ethene	Ethene (from crude oil)	300°C, 60-70 atm, Phosphoric acid	Continuous process, pure ethanol	Non-renewable, high energy input
Fermentation of Yeast	Sugars (e.g., glucose)	30-40°C, anaerobic, yeast	Renewable, low energy input	Batch process, produces dilute ethanol

---