Ethanol Production

Question 1

What are the uses of ethanol?

Answer 1

• solvent in cosmetics + perfumes
• in manufacture of drugs, detergents and inks
• alcohol in alcoholic drinks
• intermediate in synthesis of other organic chemicals

Question 2

What are the two methods to produce ethanol?

Answer 2

Crude oil and fermentation

Question 3

Describe process of producing ethanol from crude oil

Answer 3

• ethene is made when crude oil fractions are cracked to form an alkane and alkene
• ethene is then hydrated by adding water with a concentrated (phosphoric) catalyst to produce ethanol

Contains double bond
Conditions : conc H3PO4 catalyst, steam, 450 celsius temp, 50 - 100 atm pressure

Ethene + water = ethanol
CH2 = CH2 + H2O (g) = CH3CH2OH

Question 4

Describe process of producing ethanol from fermentation

Answer 4

• carbohydrates in plants are converted to sugars
• then fermented into ethanol using enzymes found in yeast

Conditions : yeast enzymes, 35 celsius temp, no oxygen

C6 H12 O6 (aq) = 2CH3 CH2 OH (aq) + 2CO2 (g)

Question 5

Why is getting temp correct important in producing ethanol by fermentation?

Answer 5

• too cold = ROR is slow
• too high = enzymes denature + stop working

Question 6

Why should no oxygen be present when producing ethanol by fermentation?

Answer 6

Ethanol may oxidise to ethanoic acid

Question 7

Ethanol stops being produced when conc is at 15%, why?
How can this be fixed?

Answer 7

• enzymes can no longer function, fermentation stops
• to get a greater conc, mixture has to be distilled as ethanol has a lower bp than water

Question 8

Compare the advantages and disadvantages of hydration of ethene (crude oil)

Answer 8

Advantages

• large scale is produced using this method
• high purity of ethanol is produced
• easily accessible raw material
• high ROR - quicker
• continous production method

Disadvantages

• high temp + pressure needed, lot of energy, higher costs
• expensive + high tech equipment needed
• crude oil is non renewable, will run out soon

Question 9

Compare the advantages and disadvantages of fermentation

Answer 9

Advantages

• uses renewable resources, wont run out
• low tech method, can be done in developing countries as little expensive equipment is needed
• readily available and renewable raw materials from plants
• low cost

Disadvantages

• slow ROR
• causes food prices to rise if crops are used to produce alcohol instead of food
• produces less, less efficient
• not as pure ethanol, has to be distilled
• enzyme could be denatured due to high temp