The Polimeri/Lummus process is used to produce high-purity cumene from propylene and benzene using a proprietary zeolite catalyst provided by Polimeri Europa. The process can handle a variety of propylene feedstocks, ranging from polymer grade to refinery grade.
Alkylation and transalkylation reactions take place in the liquid phase in fixed-bed reactors. Propylene is completely reacted with benzene in the alkylator (1), producing an effluent of unconverted benzene, cumene and PIPB (diisopropylbenzene and small amounts of polyisopropylbenzenes). The specially formulated zeolite catalyst allows production of high-purity cumene while operating at reactor temperatures high enough for the reaction heat to be recovered as useful steam. PIPB is converted to cumene by reaction with benzene in the transalkylator (2). The process operates with relatively small amounts of excess benzene in the reactors.
Alkylator and transalkylator effluent is processed in the benzene column (3) to recover unreacted benzene, which is recycled to the reactors. On-specification cumene product is produced as the overhead of the cumene column (4). The PIPB column (5) recovers polyalkylate material for feed to the transalkylator and rejects a very small amount of heavy, non-transalkylatable byproduct. The PIPB column can also reject cymenes when the benzene feedstock contains an excessive amount of toluene. Propane contained in the propylene feedstock can be recovered as a byproduct, as can non-aromatic components in the benzene feedstock.
The PBE-1 zeolite catalyst has a unique morphology in terms of its small and uniform crystal size and the number and distribution of the Bronsted and Lewis acid sites, leading to high activity and selectivity to cumene in both the alkylation and transalkylation reactions. The catalyst is very stable because it tolerates water and oxygenates and does not require drying of the fresh benzene feed. Run lengths are long due to the catalyst’s tolerance to trace poisons normally present in benzene and propylene feedstocks, and the extremely low rate of coke formation in the catalyst as a result of its unique extrazeolite pore size distribution. Regeneration is simple and inexpensive.
Equipment is constructed of carbon steel, thereby reducing investment.
Licensor: Lummus Technology