A Hydrodynamic Study of Benzyl Alcohol Oxidation in a Micro-Packed Bed Reactor

Abstract

The various flow regimes prevalent during gold-palladium catalyzed benzyl alcohol oxidation in a micro-packed bed reactor and their influence on reaction performance are identified. The reaction is studied in a 300μm deep x 600μm wide silicon-glass micro-structured reactor packed with 65μm catalyst particles at a temperature of 120°C, pressure of 1 bar (g), using pure oxygen and neat benzyl alcohol as the feed. Significant improvement in the conversion and selectivity to the main product, benzaldehyde, is observed with increasing gas flowrate and decreasing liquid flowrate, which coincides with a change in the flow pattern from “liquid-dominated slug” (segregated regions of liquid and gas slugs) to “gas-continuous trickle” (thin film coated catalyst particles with gas flowing through the voids). The latter flow regime results in enhanced external mass transfer due to an increase in the available interfacial area and shorter diffusional distances. Results show selectivity up to 81% at a catalyst space time of 76 gcatgalc(-1).s, outperforming a conventional batch laboratory reactor.