Study of mass transfer characteristics of a cocurrent downflow bubble column reactor using hydrogenation of itaconic acid

Abstract

The performance of a cocurrent downflow contactor (CDC) bubble column reactor has been examined using a first order reaction involving the palladium catalyzed hydrogenation of itaconic acid. The reaction was carried out at ambient temperature and in the pressure range 110–290 kPa using 5% and 10% w/w Pd/charcoal catalysts in two solvents (water and 2-propanol). The quantitative evaluation of the mass transfer and kinetic parameters was achieved using the classical film model for a first-order reaction. Because of the large specific gas-liquid interfacial area generated in the CDC, k L a, the volumetric gas-liquid mass transfer coefficient, was large (0.4–6 s −1) and was comparable with that of a much smaller stirred reactor ( ∼1 10 in size) with only ∼10% limiting step for this type of reaction, the relative contribution of the gas-liquid mass transfer resistance in the CDC was low (1–50% of the total resistance) compared with the liquid-solid mass transfer and surface reaction resistances for the three-phase catalytic hydrogenation of itaconic acid. The liquid-solid mass transfer coefficient ( k s ) and first-order reaction rate constant ( k 1) in the CDC were similar to those obtained in the stirred reactor with both the liquid-solid mass transfer and surface reaction being important rate steps. However, the magnitude of k s and k 1 depends critically on the method of calculating k s and an independent evaluation of k s should be carried out to obtain more accurate k 1 values. These initial studies indicate that the CDC has good potential as a three phase catalytic reactor and unlike some bubble columns can be used for relatively fast reactions.