Flow Chemistry

The Hii research group first started to work on flow chemistry in 2008, with a collaboration with Prof. Klaus Hellgardt (Department of Chemical Engineering). This has turned out to be an extremely fruitful areas of research. We apply continuous flow for developing sustainable multiphasic processes, as well as a reaction understanding tool to study reaction kinetics, including catalyst leaching.

Utilizing alcohol feedstocks in continuous flow

Alcohols are readily available with great structural diversity from renewal sources, making them attractive feedstocks for the production of high-value chemicals, such as selective oxidation to aldehydes/ketones, acids/esters. Alcohols can also be used to selectively alkylate amines (including ammonia), without extraneous reagents, generating only water as a benign byproduct. Commercially-available Ru, Au and Ni catalysts were utilised in these reactions and we demonstrated that better selectivity can be achieved in continuous flow.

Catalyst leaching

Catalyst leaching is often under-reported and overlooked in the development of heterogeneous catalysts. We designed and constructed a tandem flow reactor system to determine the leaching of Pd catalysts under operando conditions, in a quantifiable manner. The work combines concepts of heterogeneous/homogeneous catalysis, reaction engineering and multiscale modelling.

Catalyst deactivation (time-on-stream)

Similarly, understanding how a catalyst deactivates is critical in designing more robust and, eventually, commercially viable systems. Mechanistic and kinetic studies are best performed under Operando conditions using in situ analytical methods to monitor the performance of a catalyst in real time. In this work, we delineated two catalyst deactivation pathways associated with the Ru-catalysed aerobic oxidation reaction.

Redox chemistry with (just) electrons and water

Redox reactions can be achieved most sustainably by using electrons and water, and electrochemical reactions are undoubtedly best performed in flow. Projects in this area included the chemoselective reduction of C=C bonds, and the generation of peroxosulfate oxidants for the dihydroxylation of alkenes.

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