Packed bed reactor technology in sugar oxidation

Abstract

Packed beds are among the most used reactors in many sectors of chemical industries. In this work, the aim was to develop a general dynamic heterogeneous multiscale model for continuous packed bed reactors, by using experimental data to improve the accuracy of mass transfer modelling. Arabinose oxidation to arabinoic acid with molecular oxygen was used as a case study. Experiments were performed in a continuous reactor system composed of a packed bed connected with a buffer tank for allowing recycling of the liquid phase and precise pH control. The packed bed was filled with laboratory prepared gold on alumina (3 %) catalyst extrudates. Various liquid flowrates were screened (150 mL/min, 200 mL/min and 250 mL/min). The obtained experimental results were used to estimate more accurately the gas–liquid mass transfer coefficient, which was implemented in the model by using the gPROMS Model Builder. The effect of different liquid flowrates on the reactor performance was evaluated. The results showed that complete arabinose conversion can be obtained in all the cases. However, a high conversion was achieved faster in case of higher liquid flowrates (9.9 h for the 250 mL/min, 10.4 h for the 200 mL/min and 10.95 h for 150 mL/min), which agreed with our experimental discoveries: the reason is that the high flow rate suppresses the external mass transfer resistances at the gas–liquid interface and around the catalyst extrudates.