✦ LIBER ✦

Dramatic innovation of propene epoxidation efficiency derived from a forced flow membrane reactor

✍ Scribed by Masayoshi Kobayashi; Junya Togawa; Tohru Kanno; Jun-ichi Horiuchi; Kiyosi Tada

Publisher: Wiley (John Wiley & Sons)
Year: 2003
Tongue: English
Weight: 126 KB
Volume: 78
Category: Article
ISSN: 0268-2575
DOI: 10.1002/jctb.775

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✦ Synopsis

Abstract

It is possible to develop a selective epoxidation process for propene using heterogeneous catalysis in a forced‐flow membrane reactor. The most innovative processes required two catalysts, Cs–Ag and Re–Ag, which were immobilized in the membrane pores of a micro‐porous glassy (MPG) substance, and three different reactor systems for reaction gas flows in the membrane pores. The systems included a convection‐flow reactor (CFR), a diffusion‐flow reactor (DFR), and a packed‐bed‐flow reactor (PFR). The three types were examined over temperatures ranges from 420 to 525 K, while keeping the total conversion of propene to less than 10%. The membrane reactor systems followed two common Langmuir‐type equations of reaction rates for CO~2~ and propylene oxide (PO) formation under steady state operations at atmospheric pressure. The amount of the intermediate for CO~2~ formation, whose structure retained the CCC bond of a propene molecule, was sensitively controlled by the types of catalysts and reactor systems used. Comparing the three immobilized catalysts, Cs–Ag, Re–Ag, and Ag~2~O, the larger the amount of intermediate formed on the catalysts the higher was the propylene oxide (PO) selectivity and thus the PO selectivity followed the order of Re–Ag > Cs–Ag > Ag~2~O. The CFR with Re–Ag/MPG clearly demonstrated hysteresis kinetics depending on the increase (C‐up) or decrease (C‐down) in the propene concentration. The PO selectivity was separately evaluated as 73–35% for the C‐up and 35–21% for the C‐down. The convection flow rate of reactants in the pores effectively contributed to an enhancement of the PO production rate from 18 to 41% of PO selectivity, for the reactant flow rate of 70–130 cm^3^ min^−1^ at 483 K.