Polyisopropyl benzene

Benzene was alkylated with crude propylene, using H2SO4 of strength from 75 to 97%. The spent acid was recycled in part. With equal moles of benzene and propylene, 25% by weight of acid based on benzene gave 35% isopropyl and 35% polyisopropyl benzene, while 100% acid gave 40% isopropyl and 50% polyisopropyl benzene. With 0.5 mole propylene per mole benzene, all the propylene was consumed and the ratio of mono- to polypropyl benzenes was independent of the acid ratio. 

Cumene Processes. Current processes now used to produce cumene are similar to those that produce ethylbenzene. Monsanto found that its ethylbenzene process was also applicable to produce cumene but with slightly different operating condition. The modified conditions are temperatures less than 135°C and pressure of about 50 psig (46). Monsanto-type processes are used at several plants. Unreacted benzene and poly-isopropyl benzenes are separated from the reaction products and then recycled to the reactor. Eventually, all of polyisopropyl benzenes react to give cumene, so overall yields are typically 97-98%. 

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