The microreactor confers many advantages over conventional scale chemistry, including enhancement in heat and mass transfer, high surface to volume ratio, ease control of concentration gradients, and reduced exposure to toxic and hazardous materials, which inherently make microreactor green the analytical chemistry.
Although to date the majority of microreactor systems are built up on a chip platform, they are impractical for slower reactions. We have devised a parallel approach in which many boluses of reactants are injected serially into a capillary-based microreactor. The reactions, which may take hours, occur in parallel. This system allows us to conduct the research on screening for catalysts and reaction conditions with high-throughput.
A mathematical model has been established in order to predict the maximum throughput via adjusting the process parameters, such as capillary dimension, flowrate, and reaction time. Lanthanide triflate-catalyzed allylation reactions of benzaldehyde with tetraallytin were used as the model reactions. Common Lewis acids are very sensitive to the presence of water, however, lanthanide triflates can function as Lewis acids in aqueous solutions. In addition, lanthanide triflates can be easily recovered after the reaction and reused without losing activity. These unique properties have made lanthanide triflates extremely attractive using as catalysts in green chemistry. The calculation showed that high flowrate and small inner diameter of capillary reactor favor higher throughput. Using a continuous flow, the maximum throughput of the microreactor is able to reach 16 reactions per hour for a two-hour reaction using a 75ėm ID capillary and 20ėL/hr flowrate.
Keywords: microreactor, green analytical chemistry, high-throughput, screening