Monitoring Heterogeneously Catalyzed Hydrogenation Reactions at Elevated Pressures Using In-Line Flow NMR.

Area of Science:

• Chemical Engineering
• Analytical Chemistry
• Reaction Engineering

Background:

• Monitoring solid-catalyzed gas-liquid reactions often requires offline analysis, limiting real-time kinetic studies.
• Traditional methods struggle with in-line analysis of reactions involving dissolved gases under pressure.
• Microfluidic systems offer controlled environments for catalytic reactions but integrating sensitive detection can be challenging.

Purpose of the Study:

• To develop and validate a novel in-line monitoring system for solid-catalyzed gas-liquid reactions.
• To integrate a high-sensitivity stripline Nuclear Magnetic Resonance (NMR) detector with a high-pressure microfluidic network.
• To demonstrate the system's capability for quantitative analysis, gas solubility determination, and reaction kinetics studies.

Main Methods:

• A microfluidic system was designed to dissolve hydrogen gas in a solvent and mix it with a substrate.
• The reaction mixture was passed through a catalyst cartridge and then directly into a stripline NMR detector.
• The system was validated by monitoring palladium-catalyzed hydrogenation reactions of various unsaturated compounds.

Main Results:

• The developed setup allows for quantitative in-line monitoring of gas-liquid reactions.
• The system accurately determined the solubility of hydrogen gas in different solvents.
• Reaction kinetics for several palladium-catalyzed hydrogenation reactions were successfully determined in a microfluidic context.

Conclusions:

• The combined microfluidic and stripline NMR approach provides a powerful tool for in-line reaction monitoring.
• This method facilitates the optimization and kinetic analysis of hydrogenation reactions.
• The system demonstrates versatility for studying various gas-liquid catalytic processes.