Alkylation of Benzene Using Batch and Continuous Fixed-Bed Reactors

Abstract

Alkylation reactions of benzene with propylene using heterogeneous catalysts H þ -b zeolite, MCM-22, and ZSM-5 were studied for their affinity for cumene production. This work focused on the gas-phase reaction using different crystalline catalysts at several temperatures and amounts of reactants using both batch and continuous fixed-bed reactors. The properties of baseline commercial H þ -b catalysts versus versions modified with Ga, La, and Pt were studied. Quantitative analysis of product mixture was performed by gas chromatography. For the batch reactor, b-zeolite produced the highest cumene yield and selectivity of 72% and 92%, respectively, at 225 C. At this temperature, a benzene:propylene dilution of 7:1 molar ratio was the optimum. For the continuous system, cumene production is favored at lower space velocities, higher benzene-to-propylene ratio, and temperatures close to 225 C. Ga modification of the H þ -b zeolite significantly enhanced cumene yield in the continuous fixed-bed reactor at 225 C, from 27% of the unmodified b-zeolite to 36% for the Ga-modified one. The life span of modified b-catalysts was studied in the fixed-bed reactor for the first eight hours of reaction.

A one-step catalytic separation process for the production of cumene

“…Even in this preliminary stage, the selectivity obtained with our catalytic separation reactions stayed in the 85 percentile at the relatively low reaction temperature of Table 1 Results of reactive separation of cumene, with reactor at 115°C and 1 atm, feeding 3.5 ccm 14.5% propylene/N 2 and 2.7 ml liquid benzene, after 3 h reaction 115°C and at only 1 atmosphere. To obtain the same selectivity in a conventional batch or fixed-bed reactor system would require a higher reaction temperature (above 150°C) [13,14]. It is not clear the effect that a high benzene:propylene molar ratio, such as the one used in the reactive separation, (22:1) would have in a conventional batch or fixed bed system.…”

“…It is not clear the effect that a high benzene:propylene molar ratio, such as the one used in the reactive separation, (22:1) would have in a conventional batch or fixed bed system. The stability of the catalyst with reaction time remains to be studied, as the main drawback of the use of highly active zeolites in cumene production is their quick deactivation [13].…”