In cumene production, what byproduct is typically generated alongside cumene?

In cumene production, the primary byproduct typically generated alongside cumene is polyisopropylbenzenes, mainly diisopropylbenzene (DIPB) and triisopropylbenzene (TIPB). Cumene is produced by the alkylation of benzene with propylene, where propylene adds to the benzene ring. While the desired reaction is the addition of one propylene molecule to form cumene (monoisopropylbenzene), further alkylation can occur, leading to the formation of DIPB and TIPB. These polyalkylated benzenes are less valuable than cumene. To minimize their formation, the reaction conditions, such as the benzene-to-propylene ratio and catalyst activity, are carefully controlled. The DIPB and TIPB can be transalkylated with benzene to produce more cumene, increasing the overall yield of the desired product. Transalkylation involves the transfer of an isopropyl group from DIPB or TIPB to benzene, resulting in the formation of two cumene molecules. This transalkylation reaction is often carried out in the same reactor or in a separate reactor using a similar catalyst.