(523f) In-Situ Chemical Composition Sensing Using IR Adsorption in Micro-Structured Flow Reactors

Flow reactors are attractive options for moving beyond small-scale batch synthesis for some high-value chemicals, particularly in the fine chemical industry. One major limitation at the present is the lack of online sensors, for example it is challenging to design a reactor to carry out a complex organic chemical reaction, since most available analytics require sampling and relatively slow, offline analysis, making the results of limited use for process control.

In our DFG-funded Research Unit called Promise (https://promise.kit.edu) we explore multiple options for the in-situ sensing and control of a range of different physical and chemical processes. One project in particular explores the possibility for using relatively low-cost, solid-state IR sensors embedded into a flow reactor along the flow path, to give real-time, spatially resolved measurements of chemical compositions, which can be correlated to the extent of the chemical reaction (and even more complex measures like product selectivity, by-products and so on). In this presentation we outline our latest reactor design, which features three distinct and individually temperature-controlled reaction zones, two IR sensing zones (with specific materials of construction that allow for IR-transmission over a very wide range of wavelengths, much greater than can be achieved using conventional glass materials), and unique flow paths allowing for full system sealing at the top and bottom of the reactor. This apparatus was constructed in the micro process engineering workshop and combined with unique and custom-built IR sensors, resulting in a system that can make real-time IR analysis and use the results for process monitoring and eventually process control.

The Figure shows exploded views (from the top and bottom), indicating the complexity of the device and the careful design decisions necessary to achieve optical transparency in all required regions, while meeting flow and sealing requirements. Initial results for several photochemical reactions will be presented.