New microreactor designs for practical applications realized by additive manufacturing
Continuous processing is playing an increasing role in the development and manufacturing of pharmaceuticals and fine chemicals. Linked to this development is the interest in flow chemistry that means milli- or even microstructured reactors and their use for continuous processing. These reactors enable a precise control over the chemical process due to their small internal structuring and with that the access to unusual process conditions (Novel Process Windows). Additionally, other more operational advantages of interest for chemical production purposes are linked to the flow chemistry approach - like addressing the need for flexible and modular production concepts, the straightforward scale-up approach and the amenability to automated operation and integration of process analytical technologies. Classic unit operations like mixing and heat exchange are thereby already addressed by a range of commercially available devices. With the advent or broader uptake of additive manufacturing techniques in general, these technologies are also increasingly applied for miniaturized chemical reactors. While current examples mainly stem from lab-scale investigations, there is a clear trend and ambition towards addressing industrial application and the related harsh process conditions and higher throughput ranges. This chapter briefly recaps central aspects of flow chemistry and the related reactor technology before introducing the main additive manufacturing techniques used for the realisation of microsystems and micro- and milli-structured reactors as well as describing corresponding examples. A special focus is given thereby on selective laser melting to realize finely structured 3D chemical reactors in metal since this technique is seen as most promising for realising structured reactors against the background of industrial chemical production.