3.12 describe the dehydration of ethanol to ethene, using aluminium oxide.

C2H5OH > C2H4 + H2O

ethanol > ethene + water

aluminium oxide is the catalyst for this reaction.

3.11 evaluate the factors relevant to the choice of method used in the manufacture of ethanol, for example the relative availability of sugar cane and crude oil

Fermentation

• Cane sugar widely avalible/ cheap/ renewable
• Slow process
• Impurities in the product
• Done in batches

Hydrating (ethene and steam)

• Crude oil (cracked to make ethene) expensive/ non-renewable
• Fast process
• Pure product
• Continuous reaction

3.10 describe the manufacture of ethanol by the fermentation of sugars, for example glucose, at a temperature of about 30°C

Ethanol can be made by the anaerobic respiration of microorganisms.

glucose > ethanol + carbon dioxide

This happens at 30 degrees.

3.9 describe the manufacture of ethanol by passing ethene and steam over a phosphoric acid catalyst at a temperature of about 300°C and a pressure of about 60–70 atm

C2H4 (ethene) + H2O (steam) > C2H5OH (ethanol)

This reaction takes place at a high pressure (60-70 atm) and a high temperature (300) to make the reaction happen very quickly. Phosphoric acid also speeds up the reaction as it is a catalyst.