19.1 Introduction

• • In this lecture, we study the process technology associated to the production of cumene and acrylonitrile from propylene.

• Both Cumene and Acrylonitrile are very important compounds that are required for the manufacture of other downstream petrochemicals.

• We first present the process technology associated to the Cumene.

19.2 Cumene

19.2.1 Reactions

• • C₆ H₆ + .

• The reaction is exothermic.

• Side reaction:

•  C₆ H₆ + C₃ H₆ → nC₉ H₁₂

• Catalyst: H₃ PO₄ impregnated catalyst on porous carrier.

• Operating conditions: 25 atms pressure and 250°C temperature.

19.2.2 Process technology (Figure 19.1)

Figure 19.1 Flow sheet of Cumene production

• • Propylene obtained from refinery processes as a mixture of propylene and propane.

• The mixture along with benzene is compressed to 25 atms.

• Eventually the mixture enters a heat integrated exchanger to heat the pre-heat the feed   mixture.

• The feed mixture enters a packed bed reactor.

• The stream distribution in the packed bed reactor corresponds to cold shot arrangement i.e., cold propane from the distillation column in the process is added after every reactor with the product stream so that the temperature of the stream is controlled.

• Here, propylene is the limiting reactant and therefore, presumably all propylene undergoes conversion.

• Here, propane does not react but is a diluents or inert in the system. In that way it controls the reaction temperature.

• The reactor units are maintained at about 250^oC.

• The product vapors are cooled using the heat integrated exchanger.

• The vapors then pass to a depropanizer which separates propane from the product mixture.

• The bottom product consisting of benzene, cumene and polyalkyl benzenes enters another distillation column which separates benzene from the mixture of cumene and polyalkyl benzene. The benzene stream is recycled to enter the compressor.

• The bottom product from the benzene column is sent to a cumene column which produces cumene as top product and poly alkyl benzene as bottom product.

• Therefore, the entire process technology is nothing but a simple reactor separator recycle arrangement.