Yield optimization in a cycled trickle-bed reactor: ethanol catalytic oxidation as a case study

Abstract

The effect of slow ON-OFF liquid flow modulation on the yield of consecutive reactions is investigated for oxidation of aqueous ethanol solutions using a 0.5% Pd/Al 2O 3 commercial catalyst in a laboratory trickle-bed reactor. Experiments with modulated liquid flow rate (MLFR) were performed under the same hydrodynamic conditions (degree of wetting, liquid holdup) as experiments with constant liquid flow rate (CLFR). Thus, the impact of the duration of wet and dry cycles as well as the period can be independently investigated. Depending on cycling conditions, acetaldehyde or acetic acid production is favored with MLFR compared to CLFR. Results suggest both the opportunity and challenge of finding a way to tune the cycling parameters for producing the most appropriate product. ON-OFF liquid flow modulation in a trickle-bed reactor and its impact on the yield of ethanol oxidation in presence of a Pd/Al 2O 3 catalyst is studied. High cycling frequencies benefit the yield toward the intermediate product, while intermediate frequencies significantly increase the final product yield. As demonstrated, product distribution can be considerably modified through frequency tuning.