Characterizing Lactic Acid Hydrogenolysis Rates in Laboratory Trickle Bed Reactors

Abstract

Representative reaction kinetics are difficult to obtain in multiphase laboratory trickle bed reactors, particularly when the gaseous reactant is rate-limiting, because of mass transport resistances and reactor hydrodynamics in the trickle bed regime. The ruthenium-catalyzed hydrogenolysis of lactic acid to propylene glycol has been examined in trickle bed and batch reactors to better understand the influence of mass transfer and partial wetting and to identify operating conditions where intrinsic kinetic rates can be obtained. At high liquid flow rates and low conversions in the trickle bed reactor, propylene glycol formation rates agree well with intrinsic rates obtained in a stirred batch reactor, with rate independent of feed flow rate or bed configuration in the trickle bed reactor. Application of a mass transport model to the trickle bed reactor at lower flow rates allows rates to be predicted outside the intrinsic kinetic regime. These results provide guidance for proper operation of laboratory trickle bed reactors and make it possible to predict performance in a trickle-bed reactor based on experiments conducted in bench-scale batch reactors.