Monolithic Stirrer Reactors for the Sustainable Production of Dihydroxybenzenes over 3D Printed Fe/γ-Al2O3 Monoliths: Kinetic Modeling and CFD Simulation

The aim of this work is to evaluate the performance of the stirring 3D Fe/Al2O3 monolithic reactor in batch operation applied to the liquid-phase hydroxylation of phenol by hydrogen peroxide (H2O2). An experimental and numerical investigation was carried out at the following operating conditions: CPHENOL,0 = 0.33 M, CH2O2,0 = 0.33 M, T = 75-95 degrees C, P = 1 atm, omega = 200-500 rpm and WCAT ~ 1.1 g. The kinetic model described the consumption of the H2O2 by a zero-order power-law equation, while the phenol hydroxylation and catechol and hydroquinone production by Eley-Rideal model; the rate determining step was the reaction between the adsorbed H2O2, phenol in solution with two active sites involved. The 3D CFD model, coupling the conservation of mass, momentum and species together with the reaction kinetic equations, was experimentally validated. It demonstrated a laminar flow characterized by the presence of an annular zone located inside and surrounding the monoliths (u = 40-80 mm s-1) and a central vortex with very low velocities (u = 3.5-8 mm s-1). The simulation study showed the increasing phenol selectivity to dihydroxybenzenes by the reaction temperature, while the initial H2O2 concentration mainly affects the phenol conversion.

Automated summary

This study evaluates the performance of a stirring 3D Fe/Al2O3 monolithic reactor in the liquid-phase hydroxylation of phenol using hydrogen peroxide. Both experimental and numerical investigations were conducted to validate the kinetic and CFD models. The results show that the reaction temperature affects the selectivity of phenol conversion to dihydroxybenzenes, while the initial H2O2 concentration mainly affects the conversion rate of phenol.