Heterocat, homocat and biocat : what does better flow?

Abstract: Flow chemistry meanwhile has become almost regular branch of (synthetic) chemistry. Catalytic microreactors have also caught some attention; most prominently for small auxiliary power units driven by fuel processing. Under this umbrella, a kind of flow catalysis has emerged. Point is now is this "just" catalysis in flow or does the term justify – likewise Flow Chemistry – an own consideration? This sheds light in more general terms on the question how to treat the term Flow Catalysis emerging "interdisciplines" in a time having "Technology Convergence" as a megatrend. Who is responsible for nanotechnology and who might be for flow catalysis (e.g. for the teaching curriculum)? Moreover, the question is approach if flow will impact the balance within the trinity of heterogeneous-, homogeneous- and biocatalysts. Flow chemistry is more than microreactors Flow chemistry is the chemists taking up and interpreting microreactor technology developed by the engineers. While so simplifying the equipment on the one side (towards capillaries, T mixers, and so on), flow chemistry gave emphasis on new aspects not covered so much by the previous microreactor development. This is, among others, the focus on online and inline process analytics finally leading to process-analytical technology or even complex process automation, e.g. for computer-assisted kinetic model development. The chemists have also much contributed to the development of proper flow separations. Most importantly, flow extractions (typical done in segmented flow mode) with integrated phase separation by wetting of slits or solubility-driven (hydrophobic) membranes. Yet, also distillation and membrane-separation exploration has been started and solid-scavenger based adsorption (‘filtration’) is state of the art. Chemistry and catalysis With most industrial processes being catalyzed, chemistry and catalysis are closely linked since ever. Not surprisingly thus, the flow chemists have also become flow catalyst researchers and have widely introduced that topic. Since there is obviously a difference and added value in flow chemistry to the field of chemistry, it stands to reason to pose the same theorem to flow catalysis and catalysis (1). This essay gives some thoughts on this, based on the authors’ own experience and findings reported in literature.