Alcohol Production

Full Notes

Hydration of Alkenes (Industrial Process)

Equation (Ethanol Production): C₂H₄ + H₂O → C₂H₅OH

Conditions:

• Reagent: Steam (H₂O)
• Catalyst: Phosphoric acid (H₃PO₄)
• Temperature: ~300 °C
• Pressure: ~60–70 atm
• Mechanism: Electrophilic addition (steam adds across the double bond).

Advantages:

• Fast, continuous process.
• Pure ethanol produced (no need for purification).

Disadvantages:

• Non-renewable (uses crude-oil-derived ethene).

Fermentation of Glucose (Biological Process)

Equation: C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂

Conditions:

• Yeast (contains enzymes).
• Temperature: 30–40 °C.
• Anaerobic conditions (prevents oxidation to CO₂ + H₂O).

Process:
Yeast converts glucose into ethanol and carbon dioxide. The ethanol solution is purified by fractional distillation.

Advantages:

• Renewable (uses plant-based glucose).
• Requires simple equipment.

Disadvantages:

• Batch process (slow, inefficient).
• Ethanol must be purified (energy-intensive).

Ethanol as a Biofuel

Biofuel: A fuel derived from biological material (e.g., plants).

Bioethanol is often described as “carbon neutral” because:

• Plants absorb CO₂ during photosynthesis: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
• Ethanol fermentation releases CO₂: C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂
• Combustion of ethanol releases CO₂: C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O

Why this claim is not valid:

• Farming, transport, and processing use fossil fuels (producing extra CO₂).
• Deforestation for biofuel crops may reduce CO₂ absorption.

Environmental and Ethical Issues of Biofuel Use

Pros:

• Renewable alternative to fossil fuels.
• Potential to reduce greenhouse gas emissions.
• Creates jobs in agriculture and biofuel production.

Cons:

• Uses large amounts of land → reduces food crop production.
• May increase food prices in poorer regions.
• Energy-intensive processing reduces environmental benefits.

Summary