How to Track Mechanochemical Reactions in Resonant Acoustic Mixers by in Situ Raman Spectroscopy

Area of Science:

• Chemical Engineering
• Materials Science
• Spectroscopy

Background:

• Mechanochemical synthesis traditionally uses ball mills, but resonant acoustic mixers (RAM) offer solvent-free, scalable alternatives.
• Optimizing reaction conditions for RAM is challenging due to differences from ball milling.

Purpose of the Study:

• To systematically define an operational window for effective in situ Raman monitoring within resonant acoustic mixers (RAM).
• To ensure high-quality spectral acquisition by assessing critical parameters for RAM-based synthesis.

Main Methods:

• Investigated parameters including vessel material, gravitational force, filling degree, substrate rheology, and reaction time.
• Employed a sapphire-glass window and precisely aligned laser for spectral acquisition.
• Validated the framework across various mechanochemical reactions: Knoevenagel, quinoxaline, ZIF, and Glaser reactions.

Main Results:

• Established an optimal operational window for in situ Raman monitoring in RAM.
• Identified a minimum filling degree of 10% and applied g-forces between 20-70 g as crucial parameters.
• Achieved strong, reproducible Raman signals under controlled conditions, demonstrating robustness.

Conclusions:

• The developed framework enables robust and versatile in situ Raman spectroscopy for RAM-based mechanochemical synthesis.
• This optimization is key for advancing solvent-free, scalable chemical production using RAM technology.