Chemical reactors, the modular approach

Chemical reactors, the modular approach
03 July 2013 - Design

This blog first learned about Leroy Cronin from a TED talk he presented on printing molecules here. This talk was flawed because the impression was given that you can actually print molecules. A recent article from the Cronin lab in Chemical Science here should give a nice opportunity to find out what really gets printed in the Cronin lab.

In it Kitson et al. describe performing a series of consecutive conventional organic reactions (DA cyclisation, imine formation and hydrogenation) not done in the classical way of batch production (glass or steel reactors) or even via flow chemistry (plastic or steel tubing).

The "reactionware" that is central to the innovation are collections of reaction chamber cubicles designed by computer and 3D-printed. Each cubicle encloses a custom designed reactor optionally with a custom catalytic surface or custom chromatographic channel. Tandem reaction are made possible by locking cubicles together with the inlet and outlet ports and letting gravity do all the work. The process is more complicated though than it sounds: the printing process has to be interrupted (take 12 hours for curing to finish) when it comes to filling the reactor with chemicals or even adding a stirring bar. Nevertheless, yields from the reactionware sequence compare well with yields from the conventional methods.

There are some annoyances. What type of material is a cube made of? The article is not at all clear: it says it is printed from polypropylene, but how? The supplementary info mentions extrusion. But is extrusion also 3D printing? Think not. The raw material list mentions an acetoxy-silicone polymer (LOCTITE 5366), a material that can be UV cured but is certainly not polypropylene. Is it a polypropylene-like material? The description acetone-silicone polymer is not at all scientific. This blog eventually had to give up, the reactor walls are fuzzy.
Another annoyance. A 2012 article from the same group in Nature Chemistry (DOI) and another 2012 article (DOI) all describe a similar experiment but with a different chemical reaction. If we consider everything mankind have come up with in terms of organic reactions and their combinations we are going to enjoy a long string of Cronin reactionware articles.

By the way, the novel concept is sold as an opportunity "where chemistry can be performed (...) in places where there is no laboratory apparatus and by people who have no detailed knowledge of liquid handling in chemistry". We can be certain the Jesse Pinkmans of this world have taken notice.