Industrial Processes

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We want:

• High yield (large percentage of products)
  • (100% yield is not possible for reversible processes)
• Fast rates
• Get as much as we can as quickly as we can

"Time is money" - Mr Norrie

• SAFETY AND PRODUCTION CONSIDERATIONS

To get a high Rate:

• High temperature
• High pressure (gas, for a higher rate of reaction)
• Catalyst (not consumed)

To get a high Yield

• Le Chatelier’s Principle
  • E.g. exothermic reactions favoured by low temperature

Contact process and Haber process explicit in objective Probably won’t be asked for a blueprint of the factory BUT - Remember key details

• E.g. Temp, pressure, catalyst

Haber Process

$N_2+3H_2\rightleftharpoons 2N{H}_3+\text{heat},\Delta \text{H= -92 kJ}$

High rate requires:

• High pressure
• High temperature

High Yield requires

• high pressure
• Low temperature

Conditions

• High pressure (100 - 250 atm)
  • Not to high
    • safety
    • Expensive
• Compromise: Medium temperature (350˚C - 550˚C)
  • Reasonable rate AND yield
  • If it is too low, the rate is slow, but the yield is high

$N{H}_3$ is removed as reaction proceeds $N_2\text{ and }{H}_2$ is added Doesn’t reach equilibrium, but the yield argument still applies

Contact Process

• Manufacture of sulfuric acid
• Get $S{O}_2$
  • This is a by-product - greenhouse gas + acidic, from many industrial processes
• This process used to capture $S{O}_2$ and fix in solution

$2S{O}_2+O_2\rightleftharpoons 2S{O}_3+\text{heat}$

Factors increasing rate:

• High temperature
• High pressure
• Catalyst

Increase yield

• Favoured by lower temperature
• Favoured by high pressure

Conditions

• Compromise: Medium temperature (450˚C)
• Catalyst $V_2{O}_5$
• Pressure: 1-2 atmospheres
• ECONOMIC COMPROMISE
  • Benefits of higher pressures are outweighed by associated costs