The greenhouse gas we most commonly talk about is carbon dioxide, with methane probably coming in a close second. A gas that’s 11,700 times more potent than carbon dioxide, however, is fluoroform, which, while non-toxic and ozone-friendly, is still harmful to the environment. One suggested way of dealing with the greenhouse gas problem is to capture those gases and put them to other uses, and that’s what researchers at Austria’s University of Graz did with fluoroform, which is a waste product from the production of fluoropolymers such as Teflon. By 3D printing a stainless steel flow reactor, they were able to harness fluoroform and turn it into a synthetic building block.
The research is published in a paper entitled “Design and 3D printing of a stainless steel reactor for continuous difluoromethylations using fluoroform,” which you can access here. The team, led by C. Oliver Kappe, designed the reactor to convert a known batch reaction – the difluoromethylation of a lithiated nitrile – to a scalable continuous process. The team discusses the merits of 3D printing for the creation of such reactors:
“These manufacturing techniques provide virtually full design freedom and allow fabrication of microreactors with complete control over mixing structures, mixing points, flow paths, and residence volumes. The 3D CAD file is easily shared with collaborators for examination and, additionally, can form the basis for finite element analysis and computer-assisted design optimization. Despite the many advantages of 3D printing, applications for the construction of microreactors are still surprisingly rare.”
Most of the microreactors that have been 3D printed have been fabricated using FDM and SLA technology, which are relatively cheap but, since they use plastic, aren’t often suitable for the purposes of microreactors. Polymer-based materials exhibit low stability against many reagents and common organic solvents, such as aromatic solvents, ethers and chloroform.
“Moreover, the low thermal conductivity limits applications to reactions which proceed at room temperature and do not release a lot of heat,” the team continues.
The University of Graz researchers, however, turned to selective laser melting (SLM), which, because it utilizes metal, was able to produce a reactor with the required thermal conductivity as well as the chemical, mechanical and thermal stability required for applications in organic synthesis. 3D printing allowed them to create a reactor with a highly precise and controlled design suited to the work it would be carrying out.
“The reactor features four inlets to combine the substrate feed with two reagent feeds and a final quench solution,” the researchers state. “The reaction was performed at a reaction temperature of −65 °C to generate the desired product in excellent yields after a total reaction time of less than 2 min.”
Another benefit of using 3D printing was that the researchers were able to use the CAD file itself to run computational fluid dynamics simulations. The reactor was then printed from stainless steel using an EOSINT M 280 3D printer from EOS, in a process that took about 14 hours. The reaction was then carried out and, as stated above, produced the desired results extremely quickly.
“It can be expected that additive manufacturing and related direct digital manufacturing technologies, in combination with computational chemical reaction and fluid dynamics simulation, will play a fundamental role in the design of next-generation, continuous flow microreactors,” the researchers conclude. “Further work is planned in our laboratories to integrate in-line analysis into the reactor and to further explore difluroromethylation chemistry with fluoroform and other multiphase (g/l) reactions.”
Authors of the paper include Bernhard Gutmann, Manuel Köckinger, Gabriel Glotz, Tania Ciaglia, Eyke Slama, Matej Zadravec, Stefan Pfanner, Manuel C. Maier, Heidrun Gruber-Wölfler, and C. Oliver Kappe.
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