Dechlorination of p-chlorophenol in a microreactor with bimetallic Pd/Fe catalyst

Dechlorination of p-chlorophenol was investigated in a single-pass, continuous-flow microreactor system made of two parallel palladized iron plates. The plates formed a microscale channel 27 mm wide, 70 mm long, and 0.2 mm high. The bimetallic catalyst was prepared by electroless deposition of Pd on the reactor plate surfaces. Experiments were performed under steady-state conditions at different temperatures between 293 and 333 K and at a variety of flow conditions in the range from 1.5 x 10(-9) to 1 x 10(-8) m(3)/s. A two-dimensional mathematical model, containing convection, diffusion, and pseudo-first-order catalytic reaction terms, was developed to analyze the experimental data and to forecast reactor performance. Depending on the prevailing kinetic and convection/diffusion phenomena, the developed model can be reduced to the ideal plug-flow model or can depict reactor performance that is close to or even worse than the performance of an ideal mixed-flow reactor. Under operating conditions typical to this study, the model and the experimental data indicate plug-flow behavior of the microreactor. Analysis of the obtained chemical kinetic rate constants provides an estimate of the activation energy for this reaction (E-a = 48.43 +/- 6.13 kJ/mol), which remains unchanged despite observed deactivation of the catalyst. The deactivation of the catalyst is caused by reversible catalyst passivity, and it is modeled by second-order kinetics. Analysis of the experimental data shows that the observed deactivation influences only the preexponential factor in the Arrhenius law for the investigated reaction.