Catalytic deactivation of typical rigid heterogeneous catalysts becomes noticeable in a continuous flow reactor; however, it has been addressed inadequately and in an isolated manner.
We have developed a cost-effective non-lithographic method for the fabrication of a PDMS-based microchannel-coupled mill reactor. Immobilized nickel particles are resistant to leaching in the flow process. It is observed that during continuous operation, milli reactors show a strong catalytic activity for the reduction of resazurin and p-nitrophenol with a conversion rate of almost 100 %. Catalytic poisoning is ubiquitous and gets gradually prominent whereas complete catalytic deactivation of magnetic Ni-microparticles is found to be an instantaneous process. Relatively large-sized resorufin binds predominantly to the surface and thereby blocks the access of the substrate to the Ni-particles. The dissociations of product molecules - resorufin and p-aminophenol are the rate-limiting steps that caused the abrupt deactivation of Ni-microparticle. The kinetic mechanism of heterogeneous derived from the Langmuir-Hinshelwood mechanism satisfactorily explains the catalytic poisoning and deactivation of nickel microparticles.
Our work sheds light on the intricacies of catalytic activity and poisoning of magnetic nickel microparticles.