Cumene or isopropylbenzene, is manufactured exclusively by alkylation of benzene with propene. In the most important industrialized countries, propene used for production of cumene accounts for 7-8% of the total propene consumption:

The reaction takes dace either in the liauid or gas Dhase. As in the ethylation of benzene, Friedel-Crafts systems or proton donors are used as catalysts. Reaction conditions for the alkylation with propene are generally milder than with ethylene, since propene is more easily protonated.

In the liquid-phase process, H₂SO₄ or AlCl₃ is used at 35-40 °C (e. g., Kellogg/Monsanto), or alternatively HF at 50-70°C (Hüls process), with a low propene pressure of up to 7 bar.

The gas-phase alkylation, e.g., UOP process, is done with H₃PO₄/SiO₂ catalysts promoted with BF₃ at 200-250 °C and 20-40 bar, using propene/ mixtures with only a very small concentration of ethylene or other olefins, since these would also lead to alkylation. Propane and any other saturated constituents do not affect the reaction as they are removed unaltered. Steam is simultaneously passed over the catalyst so that:
1. The exothermic reaction is controlled via heat absorbed by the water
2. The phosphoric acid is better attached to the support due to hydrate formation

Moreover, an excess of benzene is normally used to minimize the facile further propylation of cumene. The selectivities are 96-97'70 (based on C₆H₆) and 91 -92% (based on C₃H₆). Di- and triisopropyl benzene and n-propylbenzene are the main by-products. After distillation, cumene is obtained with a purity of more than 99.5%. Process improvements from, e. g., Monsanto/Lummus include downstream transalkylation in order to use the more highly propylated products to increase the cumene yield.

The majority of the currently operating processes use the UOP route, which in 1991 accounted for about 90% of cumene production worldwide.
 
More recent process developments concern the use of zeolite catalysts (e. g., ABB Lummus Crest/Nova, Enichem, etc.), which have the advantages of a noncorrosive system without the release of acidic catalyst components. In addition, yields of nearly 100% can be attained, thereby increasing the capacity of the plant.