INDUSTRIAL PRODUCTION OF ISOPYLBENZENE
Isopropylbenzene is an organic compound that is a colourless liquid at room temperature with an aromatic odour. It is in insoluble in water but soluble in alcohol and many other organic solvents. The main use of this organic compound is to manufacture other chemicals such as acetone, phenol, acetone and methyl styrene. It can also be used as a thinner in paints, enamels and lacquers. The production of Cumene involves a reaction between benzene and propylene in a high temperature, high pressure gas phase reactor C6H6 + C3H6 → C9H12 There is also another sequential chemical reaction of cumene and propylene to form an undesirable product: p-diisopropylenebenzene as per the below chemical reaction: C9H12 + C3H6 → C12H18 Figure 1: Industrial production of Isopropylbenzene from propylene and benzene About 3-6 % of the produced Isopropylbenzene reacts in reaction
2. Process description
Fresh feed streams of propylene and benzene from their respective tanks are fed into the reactor as liquids at room temperature. The fresh feed benzene stream is mixed with a recycle stream that consists of benzene in a fresh feed benzene: recycled benzene ratio of 1:3. This stream is passed through a heat exchanger where the temperature is raised to 230C before being fed to the reactor. The reactor effluent enters the heat exchanger at 400C and leaves at 200C. The pressure of the reactor is sufficient and is able to maintain the reactor effluent stream as a liquid. Upon being cooled in the heat exchanger, the reactor effluent is fed to a distillation column (T1). The stream that is fed into the first distillation column (T1) has isopropylbenzene: benzene ratio of 1:7.
Questions
SECTION 1: 15 MARKS
ANSWERS WITH EXPLANATION
1.1 Assumptions Based on Literature:
The reaction between benzene and propylene to produce isopropylbenzene (cumene) is a single-stage, irreversible reaction with no side reactions other than the undesired reaction to form p-diisopropylenebenzene.
The reactor operates at high temperature and high pressure, maintaining the reactor effluent as a liquid.
There is no loss of material in the process.
1.2 Flow Chart of Isopropylbenzene Production Process:
Here is a simplified flow chart of the isopropylbenzene production process:
+---------------------------------+
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+------------+
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| |
+------------+
| Column (T1)|
+------------+
| Column (T2)|
+------------+
| |
+------------+
1.3 Degree of Freedom Analysis:
Mass flow rate of isopropylbenzene leaving T1 (F_IPB_out)
Mass flow rate of unreacted propylene leaving T1 (F_unreacted_propylene_out)
Energy balance (enthalpy balance): Energy in = Energy out
Equilibrium relationships for vapor-liquid equilibrium inside the column.
