Alcohols
Making Ethanol
Found in alcoholic drinks and used as a solvent to make many common substances such as
detergents and pharmaceuticals – can also be used as a fuel
Is a biofuel as made from plants that are renewable
Over 90% is produced from crops such as sugar cane, sugar beet, corn, rice and maize by
fermentation – renewable raw materials
o Not pure, also contains water
o Fractional distillation used to make pure ethanol from mixture
Other main method is reaction of ethene with steam
Fermentation of Carbohydrates
C6H12O6 -> 2C2H5OH + 2CO2
36°C temperature
Normal atmospheric pressure
Enzyme in yeast catalyst (zymase)
Aqueous
Anaerobic (stops ethanol being turned into ethanoic acid)
Carbohydrate crops raw materials – renewable
Batch process (stop-start)
Slow reaction rate
Impure ethanol – yeast poisoned over 15% ethanol
Reaction of ethene with steam
C2H4 + H2O -> C2H5OH
300°C temperature
70 atm pressure
Concentrated phosphoric acid catalyst
Crude oil raw materials – finite
Continuous process
Fast reaction rate
Pure ethanol – not for human consumption
Mechanism:
,
H+ is regenerated – acts as catalyst
Carbon Neutrality
Ethanol is regarded as being ‘carbon neutral’ as it releases the same amount of CO 2 when
burned as taken in from atmosphere in photosynthesis
However, in the process from crop to fuel, there are other processes to consider such as fuel for
machinery and transport so it is not 100% carbon neutral, and there are growing concerns that
too much agricultural land is used to grow crops for biofuel rather than food
Introduction to Alcohols
General formula: CnH2n+1OH
Alcohols have the suffix -ol or the prefix hydroxy-
Classified as primary, secondary or tertiary depending on the number of alkyl groups attached to
the carbon carrying the OH group
Primary Alcohols
Making Ethanol
Found in alcoholic drinks and used as a solvent to make many common substances such as
detergents and pharmaceuticals – can also be used as a fuel
Is a biofuel as made from plants that are renewable
Over 90% is produced from crops such as sugar cane, sugar beet, corn, rice and maize by
fermentation – renewable raw materials
o Not pure, also contains water
o Fractional distillation used to make pure ethanol from mixture
Other main method is reaction of ethene with steam
Fermentation of Carbohydrates
C6H12O6 -> 2C2H5OH + 2CO2
36°C temperature
Normal atmospheric pressure
Enzyme in yeast catalyst (zymase)
Aqueous
Anaerobic (stops ethanol being turned into ethanoic acid)
Carbohydrate crops raw materials – renewable
Batch process (stop-start)
Slow reaction rate
Impure ethanol – yeast poisoned over 15% ethanol
Reaction of ethene with steam
C2H4 + H2O -> C2H5OH
300°C temperature
70 atm pressure
Concentrated phosphoric acid catalyst
Crude oil raw materials – finite
Continuous process
Fast reaction rate
Pure ethanol – not for human consumption
Mechanism:
,
H+ is regenerated – acts as catalyst
Carbon Neutrality
Ethanol is regarded as being ‘carbon neutral’ as it releases the same amount of CO 2 when
burned as taken in from atmosphere in photosynthesis
However, in the process from crop to fuel, there are other processes to consider such as fuel for
machinery and transport so it is not 100% carbon neutral, and there are growing concerns that
too much agricultural land is used to grow crops for biofuel rather than food
Introduction to Alcohols
General formula: CnH2n+1OH
Alcohols have the suffix -ol or the prefix hydroxy-
Classified as primary, secondary or tertiary depending on the number of alkyl groups attached to
the carbon carrying the OH group
Primary Alcohols
