(97c) A Multiphase Semi-Flow Microreactor to Study the Influence of Water on Organometalic Catalysis

Water is a potential solvent in homogeneous organometallic catalysis, such as Pd-catalyzed Cu-free sonogashira reaction (a.k.a., heck alkynylation) [typically done in organic medium]^1â??3. This unconventional solvent is cheap, easily accessible and non-toxic, but what makes it attractive is its ability to dissolve polar salts and products formed during the reaction. By having a device with simultaneous reaction and separation, it is expected to reduce the chemical waste produced per product formed, also known as E-factor¹. Although water is an interesting complementary solvent, only a few efforts were placed on understanding its influence. To better understand its impact in the reaction and separation, a microfluidic semi-flow reactor has been designed and coupled with in-situ Raman and online GC.

In the present study, the role of water was analyzed using a 3D Raman spectrum chemical map of the reaction progression and species transfer. Regarding the reaction progression, the microreactor was divided in several points, and the reaction yield was acquired and treated using MatLab. For the mass transfer, both phases were trapped in a semi-flow reactor, and the species transfer were measured using image analysis tools, such as ImageJ, and Raman spectroscopy. The mass transfer measurements were validated using benchmark cases: gas-liquid and liquid-liquid.

The reaction experimental results obtained were compared with batch and flow experiments from literature (also performed in aqueous medium). In one hand, microfluidic reaction intensification experiments have shown that the reaction is often limited by mass transfer at the mili-scale. In the other hand, mass transfer experiments (indirect measurement of the molecular diffusivity) have allowed us to understand were the reaction is performed and to define the role of water in a reaction/separation process.

Bibliography

(1) Hu, C.; Shaughnessy, K. H.; Hartman, R. L. React. Chem. Eng. 2016, 36.

(2) Sabio, J. C.; Domier, R. C.; Moore, J. N.; Shaughnessy, K. H.; Hartman, R. L. Chem. Eng. Technol. 2015, 38, 1717â??1725.

(3) Domier, R. C.; Moore, J. N.; Shaughnessy, K. H.; Hartman, R. L. Org. Process Res. Dev. 2013, 17, 1262â??1271.