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Material Balances Design Problem Cumene Production

Background Cumene (isopropyl benzene) is produced by reacting propylene and benzene over an acid catalyst. Cumene may be used to increase theoctane in gasoline, but its primary use is as a feedstock for manufacturing phenol and acetone. The plant where you are employed has been buying cumene to produce phenol. Management is consideringmanufacturing cumene rather than purchasing it to increase profits. Someone has made a preliminary sketch for such a process and has submitted to the engineering department for consideration. Your group isassigned the problem of evaluating the sketch and recommending improvements in the preliminary design. Cumene Production Reactions The reactions for cumene production from benzene and propylene are asfollows: C3H6 + propylene C6H6 → benzene C6H5-C3H7 cumene →

C3H6 + propylene

C6H5-C3H7 cumene

C3H7-C6H4-C3H7 diisopropyl benzene (DIPB)

The best technology for cumene production is acatalytic process that is optimized at 350°C and 25 atm. pressure. The benzene is kept in excess to limit the amount of DIPB product. Process Description The reactants are fed as liquids from theirrespective storage tanks. After being pumped up to the required pressure dictated by catalyst operating conditions, the reactants are mixed, vaporized and heated up to the reactor operating temperature. Thecatalyst converts the reactants to the desired and undesired products according to the reactions listed above. The molar feed ratio is 2:1 benzene to propylene; propylene conversion is 99%; theproduct molar selectivity ratio is 31:1 cumene to DIPB. The product gases are cooled to 40°C at 25 atm. pressure to condense essentially all of the cumene, DIPB, and unreacted benzene to a liquid. Theunreacted propylene and a propane impurity are separated from the liquid and are used as fuel gas. The liquid stream is sent to two distillation towers. The first distillation tower separates benzene...