Temperature-dependent complex dielectric permittivity: a simple measurement strategy for liquid-phase samples

Area of Science:

• Chemical Engineering
• Materials Science
• Physical Chemistry

Background:

• Microwave (MW) heating is crucial for intensified and electrified chemical manufacturing.
• Accurate dielectric permittivity data, essential for MW heating, is often unavailable due to limitations in current measurement techniques.
• Temperature and pressure significantly influence dielectric properties, necessitating accessible measurement methods.

Purpose of the Study:

• To develop a simple, benchtop approach for measuring temperature-dependent dielectric permittivity of liquid samples.
• To provide accurate dielectric data near the 2.45 GHz industrial, medical, and scientific (ISM) frequency.
• To facilitate the optimization of microwave-assisted chemical processes by providing accessible material property datasets.

Main Methods:

• Utilized a modified bireentrant microwave measurement cavity.
• Incorporated larger pressure- and temperature-capable vials for liquid sample analysis.
• Measured dielectric permittivity for vapor pressures up to 7 bar across a range of temperatures.

Main Results:

• Successfully deduced temperature-dependent permittivity for various liquids, including water, organic solvents, and hydrochloric acid solutions.
• Validated the methodology against existing literature data, confirming its accuracy for materials with dielectric constants from 1 to 100.
• Provided simple data-fitting models for practical application in chemical process design.

Conclusions:

• The developed benchtop method offers a rapid and accurate way to obtain critical dielectric permittivity data for liquids.
• This advancement addresses the lack of accessible datasets, supporting the broader adoption of microwave technology in chemical manufacturing.
• The generated data and fitting models will aid researchers and engineers in designing and optimizing MW-assisted processes.