A batch process is operated with the following sequence. The feed to the batch process consists of a solution of 500 L of ethanol with 120 mole of A and 120 mole of B. If the temperature of the solution is sufficient, A and B will react to form P (the desired product): A (eth) + B (eth) → P (s) DHreact = − 250 kJ/mol (1) product P is sparingly soluble in ethanol, which helps facilitate its removal from the reaction solution. It can be assumed that the reaction rate is first-order in both the concentration of A (cA ) and B (cB ), and so second-order overall: -r A = k c A cB (2) The batch process consists of the following FOUR steps: Initially, the tank is empty. 1. Fill tank with solution (ethanol/A/B). 50°C (1 hour) Increase temperature of the feed from 20°C to 2. Reaction takes place isothermally at 50°C (4 hours, to give conversion of 50%) 3. Filtration of reaction solution to give product P (2 hours) 4. Drying with hot nitrogen gas followed by the removal of powder product (3 hours) product P is sparingly soluble in ethanol, which helps facilitate its removal from the reaction solution. It can be assumed that the reaction rate is first-order in both the concentration of A (cA ) and B (cB ), and so second-order overall: -r A = k c A cB (2) The batch process consists of the following FOUR steps: Initially, the tank is empty. 1. Fill tank with solution (ethanol/A/B). 50°C (1 hour) Increase temperature of the feed from 20°C to 2. Reaction takes place isothermally at 50°C (4 hours, to give conversion of 50%) 3. Filtration of reaction solution to give product P (2 hours) 4. Drying with hot nitrogen gas followed by the removal of powder product (3 hours) it is later discovered that a side reaction is taking place forming soluble product Q, with zero value. This unwanted side reaction has the following kinetics: zero- order in both components A and B. The selectivity for this reaction is low: only about 0.1% of A is converted to Q, with the stoichiometry given by: A (eth) + 2B (eth) = Q (eth). A. What are the two main problems associated with this side reaction? B. How would you rank these problems in order of severity? C. Consider how to apply semi-batch operation to reduce the amount of Q being produced while trying to maintain the production rate of P.
A batch process is operated with the following sequence. The feed to the batch process consists of a solution of 500 L of ethanol with 120 mole of A and 120 mole of B. If the temperature of the solution is sufficient, A and B will react to form P (the desired product):
A (eth) + B (eth) → P (s)
DHreact
=
−
250
kJ/mol
(1)
product P is sparingly soluble in ethanol, which helps facilitate its removal from the reaction solution. It can be assumed that the reaction rate is first-order in both the concentration of A (cA ) and B (cB ), and so second-order overall:
-r A = k c A cB
(2)
The batch process consists of the following FOUR steps:
Initially, the tank is empty.
1. Fill tank with solution (ethanol/A/B). 50°C (1 hour)
Increase temperature of the feed from 20°C to
2. Reaction takes place isothermally at 50°C (4 hours, to give conversion of 50%)
3. Filtration of reaction solution to give product P (2 hours)
4. Drying with hot nitrogen gas followed by the removal of powder product (3 hours)
product P is sparingly soluble in ethanol, which helps facilitate its removal from the reaction solution. It can be assumed that the reaction rate is first-order in both the concentration of A (cA ) and B (cB ), and so second-order overall:
-r A = k c A cB
(2)
The batch process consists of the following FOUR steps:
Initially, the tank is empty.
1. Fill tank with solution (ethanol/A/B). 50°C (1 hour)
Increase temperature of the feed from 20°C to
2. Reaction takes place isothermally at 50°C (4 hours, to give conversion of 50%)
3. Filtration of reaction solution to give product P (2 hours)
4. Drying with hot nitrogen gas followed by the removal of powder product (3 hours)
it is later discovered that a side reaction is taking place forming soluble
product Q, with zero value.
This unwanted side reaction has the following kinetics: zero-
order in both components A and B. The selectivity for this reaction is low: only about 0.1%
of A is converted to Q, with the stoichiometry given by: A (eth) + 2B (eth) = Q (eth).
A. What are the two main problems associated with this side reaction?
B. How would you rank these problems in order of severity?
C. Consider how to apply semi-batch operation to reduce the amount of Q being produced while trying to maintain the production rate of P.
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