Binary Diffusion Coefficients for Methane and Fluoromethanes in Nitrogen

Area of Science:

• Physical Chemistry
• Chemical Engineering
• Atmospheric Science

Background:

• Binary gas-phase diffusion coefficients are vital for atmospheric and combustion chemistry models.
• Refrigerant-related fluoromethanes are increasingly important in various industrial applications.

Purpose of the Study:

• To measure binary gas-phase diffusion coefficients for methane, fluoromethane, difluoromethane, and trifluoromethane in nitrogen.
• To investigate the temperature dependence of these diffusion coefficients over extended temperature ranges.
• To compare experimental results with existing literature data and provide new insights.

Main Methods:

• Reverse-flow gas chromatography was employed to determine diffusion coefficients.
• Measurements were conducted across a wide temperature range (250 K to 723 K) for different species.
• Diffusion coefficients for methane in air were also measured and compared to nitrogen.

Main Results:

• Accurate diffusion coefficients were obtained for the homologous series of (fluoro)methanes.
• New data extends the temperature range for difluoromethane and trifluoromethane diffusion measurements.
• Measurements in air for methane showed excellent agreement with those in nitrogen.

Conclusions:

• The study provides the first diffusion coefficient measurements for fluoromethane.
• Results broadly agree with previous studies, but highlight differences in temperature dependence due to extended temperature ranges.
• Findings support the use of reverse-flow gas chromatography for accurate diffusion coefficient determination.