Flow chemistry

[2] Choosing to run a chemical reaction using flow chemistry, either in a microreactor or other mixing device offers a variety of pros and cons.

The drawbacks have been discussed in view of establishing small scale continuous production processes by Pashkova and Greiner.

[7] Continuous reactors are typically tube-like and manufactured from non-reactive materials such as stainless steel, glass, and polymers.

Mixing methods include diffusion alone (if the diameter of the reactor is small e.g. <1 mm, such as in microreactors) and static mixers.

Continuous flow reactors allow good control over reaction conditions including heat transfer, time, and mixing.

The smaller scale of microflow reactors or microreactors can make them ideal for process development experiments.

The gas reactions that have been most successfully adapted to flow are hydrogenation and carbonylation,[9][10] although work has also been performed using other gases, e.g. ethylene and ozone.

The large surface area to volume ratio of a microreactor maximizes the illumination, and at the same time allows for efficient cooling, which decreases the thermal side products.

In flow chemistry this changes to a parallel approach, where chemist and chemical engineer work interactively.

However, due to the extremes of temperature and pressure reached in a microwave it is often difficult to transfer these reactions to conventional non-microwave apparatus for subsequent development, leading to difficulties with scaling studies.

[20] The very rapid mixing and excellent temperature control of microreactors are able to give consistent and narrow particle size distribution of nanoparticles.

As discussed above, running experiments in continuous flow systems is difficult, especially when one is developing new chemical reactions, which requires screening of multiple components, varying stoichiometry, temperature, and residence time.