A New Multistage Consecutive Stirred-tank Microreactor Applied For Liquid-solid Separation And Reaction

Recently,environmental problems and resource problems of reaction and separation process caused by traditional macro-scale reactors with poor repeatability,low efficiency and productivity,have become more and more serious.Such macro-scale batch reactors are not suitable for experimental studies with trial and error and industrial production with differentiated demands.With the aim of reducing resource consumption in fundamental research and industrial production,the continuous production process in microreactors is currently being applied to the efficient and safe synthesis of fine chemicals.With its characteristic micro dimensions,microreactors have lots of advantages like high mass and heat transfer efficiency,good controllability and intrinsic safety.When transferring chemical synthesis and separation processes from conventional macroreactors to microreactors,researchers often encounter blockage of microreactors caused by the solids occurring in reaction separation processes.In this work,a new multistage continuous stirred-tank microreactor,i.e.multistage micro-CSTR reactor,made of quartz glass with high transparency and good chemical stability was developed.The reactor consists of 16 miniaturized cylindrical tanks in series,each of which is fully agitated by a micro magnetic stir bar.The residence time distribution test shows that near-plug flow was achieved in the multistage micro-CSTR reactor for both homogeneous liquid flow and solid suspension flow.Typical separation and reaction processes were applied in the new multistage micro-CSTR reactor:continuous drug crystallization and solid-containing photochemical reactions.First,the continuous crystallization of carbamazepine was implemented without blockage problems in the multistage micro-reactor,even with 5.4 w.t.%solid content in the flow.Different crystal forms of carbamazepine were obtained under different conditions.Compared with the batch reactor,the multistage micro-CSTR reactor exhibited higher controllability in crystal quality and yield.Then a continuous and stable feeding unit for solid suspensions was built for heterogeneous photocatalytic reactions in the multistage micro-CSTR reactor.The photocatalytic degradation of methylene blue and chloramphenicol by TiO2 particles were conducted,respectively,with no clogging in the multistage micro-CSTR reactor for 10 h.Moreover,the reaction rate was accelerated to nearly 25～45 times as compared to the batch photoreactions in the flask.Last,cyclobutane tetraformic acid dianhydride,as a solid product in the reaction,was obtained directly by photodimerization of maleic anhydride in the multistage micro-CSTR reactor without blockage.This work proposes a feasible solution for solid manipulation for chemical reactions and separation processes conducted in microreactors.The multistage micro-CSTR reactor not only solves solid blockage problem in the microchannel,but also shows higher efficiency than the batch reactor.This work pushes forward application range of microreactors in continuous drug crystallization and fine photochemical synthesis.