Setup for real-time monitoring of the extrusion process by Raman spectroscopy.
Source: BAM, Process Analytical Technology Division
Solvents play a crucial role in traditional chemical synthesis, often comprising around 80% of the total volume of chemicals used. It results in millions of tons of harmful organic solvents released into the environment each year. Mechanochemical reactions, in contrast, require only catalytic amounts of solvent or no solvent at all and offer an environmentally friendly alternative. To bring mechanochemical reactions to the industrial scale, the challenging upscaling problem must be overcome. Enter extrusion, a technique that emerged as a continuous production alternative to traditional ball mills and has proved to be effective for up-scaling syntheses.
In our study, we focused on the metal-organic framework ZIF-8 known for its large surface area, and high thermal, chemical, and mechanical stability. ZIF-8 has gained significant attention in materials science due to its potential to tackle energy, environmental, and technological challenges. Building on a previous study, where we explored a simple “batch“ method to create ZIF-8, we are moving forward by adapting it to a continuous extrusion process.
Here is how the process works: solid basic zinc carbonate and 2-methylimidazole were mixed in the extruder, along with a small amount of ethanol or water. The process parameters were optimized using Raman spectroscopy with a specially designed setup to monitor the conversion of reagents in real time. Under optimized conditions, we successfully produced pure and highly crystalline ZIF-8 at 40°C, using only a tiny amount of ethanol and a small excess of the linker. The resulting ZIF-8 material displayed properties on par with the commercially available reference Basolite Z1200, showing the surface area of ~1800 m2 g–1. The reaction could yield ∼ 3 kg d−1 assuming a continuous operation, with a space-time yield of ca. 67,000 kg m−3 d−1. Finally, we have compared our method to other large-scale ZIF-8 productions and concluded that the proposed approach has the highest potential for large-scale production of ZIF-8.
Optimizing the Green Synthesis of ZIF-8 by Reactive Extrusion Using In Situ Raman Spectroscopy
Nikita Gugin, Jose Villajos, O. Dautain, Michael Maiwald, Franziska Emmerling
published in ACS Sustainable Chemistry & Engineering, Volume 11, Issue 13, pages 5175 bis 5183
BAM Materials