Continuous flow reduction of 4-nitrophenol by “water soluble” palladium nanoparticles: from batch to continuous flow system

Process intensification research is concentrated on the use of the continuous flow microreactor over the conventional batch reactors due to the various advantages that bring this latter in terms of efficient micromixing and enhanced heat and mass transfer in small residence time. The continuous flow process has been successfully developed for many common reactions in the pharmaceutical and chemical industries. This paper explores the catalytic performance of Pd nanoparticles (NPs) in a continuous flow mode and studies different microreactors configuration, and their applications on the benchmark reaction model of 4-nitrophenol reduction in aqueous media by using sodium borohydride as a reducer. A PTFE Spiral Capillary Microreactor (SCM) was designed and compared to a Continuous Vessel Microreactor (CVM) for the reduction of 4-Nip into 4-Amp. Multiple equations were obtained from different microreactor configurations that can be used for the calculation of theoretical mean conversion and 4-nitrophenol concentration at the outlet of the microreactor. The kinetics studies of this reaction model already determined in batch reactor were confirmed by using pseudo-first order in continuous flow microreactor. The real microreactor (SCM) is acting as a plug flow reactor (PFR). The engineering aspects such as reaction conditions and microreactor model are discussed. This work studies the kinetics of the 4-Nip reduction for the first time with nanoparticles non supported in continuous flow. This work showed that the kinetic study of the reaction can be carried out successfully in SCM and advantageously in particular for short reaction times.