Describe the preparation of Ethyl alcohol from molasses.

The preparation of ethyl alcohol (ethanol) from molasses is a widely used industrial process, especially in countries with abundant sugarcane production. Molasses, a byproduct of sugar refining, contains fermentable sugars that can be converted into ethanol through microbial fermentation.

🧪 Steps in the Preparation of Ethyl Alcohol from Molasses

1. Dilution of Molasses
– Molasses is thick and viscous, so it’s diluted with water to create a sugar solution.
– The sugar concentration is adjusted to around 10–15% for optimal fermentation.

2. Sterilization
– The diluted molasses is sterilized to eliminate unwanted microbes.
– This ensures that only the desired yeast strain will act during fermentation.

3. Fermentation
– Yeast (Saccharomyces cerevisiae) is added to the diluted molasses.
– Enzymes like invertase convert sucrose into glucose and fructose.
– Then zymase converts glucose/fructose into ethanol and carbon dioxide:

C12H22O11 + H2O → C6H12O6 + C6H12O6
C6H12O6 → 2 C2H5OH + 2 CO2

– Fermentation is carried out anaerobically at 28–32°C for 30–70 hours.

4. Distillation
– The fermented mash (called “beer”) contains about 8–10% ethanol.
– It’s distilled to separate ethanol from water and other impurities.
– Fractional distillation yields rectified spirit (~95% ethanol).

5. Dehydration (Optional)
– If absolute alcohol (100% ethanol) is needed, further dehydration is done using agents like benzene or molecular sieves.

⚙️ By-products and Uses
– Carbon dioxide: Captured and used in beverages or dry ice production.
– Fusel oil: Contains higher alcohols like amyl alcohol, used in chemical industries.
– Slops: Residual mash rich in nutrients, often used as cattle feed.