Binary gas-phase diffusion coefficients, of interest in physical models of atmospheric and combustion chemistry, have been measured in N₂ for the homologous series of refrigerant-related (fluoro)methanes: methane (CH₄), fluoromethane (CH₃F), difluoromethane (CH₂F₂), and trifluoromethane (CHF₃). Values have been determined by reverse-flow gas chromatography, which has been previously demonstrated to provide accurate results over a wide range of temperatures. Coefficients were measured at temperatures of (300–550) K for all species and extending up to 650 and 723 K for CH₂F₂ and CHF₃, respectively, and down to 250 K for CH₄. We also performed measurements for CH₄ in air at temperatures of (250–350) K, obtaining values the same as in N₂ within 0.3%, well within our experimental uncertainty. We report the first measurements for CH₃F and compare with the limited literature data for the other compounds. Our results agree broadly with earlier measurements in both N₂ and air. The greater temperature ranges reported in this work lead to temperature dependences that differ from most previous experiments, although they are consistent with several literature estimates and are similar to temperature exponents found for small hydrocarbons in N₂. Comparison of the present work with a recent study that found different diffusion coefficients for methane when determined in a typical arrested flow apparatus and a novel “twin tube” method unaffected by sample adsorption shows a much better agreement with the arrested flow results over all common temperatures.

中文翻译：

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甲烷和氟甲烷在氮气中的二元扩散系数

在大气和燃烧化学的物理模型中感兴趣的二元气相扩散系数已在 N _{2 中}测量，用于制冷剂相关（氟）甲烷的同系系列：甲烷 (CH ₄ )、氟甲烷 (CH ₃ F)、二氟甲烷（CH ₂ F ₂）和三氟甲烷（CHF ₃）。数值是通过逆流气相色谱法确定的，之前已经证明它可以在很宽的温度范围内提供准确的结果。所有物种的系数在 (300–550) K 的温度下测量，CH ₂ F ₂和 CHF _{3 的}系数可扩展至 650 和 723 K分别和降低至250 K中CH ₄。我们还在(250–350) K 的温度下对空气中的CH ₄进行了测量，获得与 N ₂相同的值，误差在 0.3% 以内，完全在我们的实验不确定性范围内。我们报告了 CH ₃ F的第一次测量，并与其他化合物的有限文献数据进行了比较。我们的结果与早期在 N ₂和空气中的测量结果大体一致。在这项工作中报告的更大的温度范围导致温度依赖性与大多数以前的实验不同，尽管它们与一些文献估计一致，并且类似于 N ₂中小烃的温度指数. 将目前的工作与最近的一项研究进行比较，该研究发现在典型的滞流装置和不受样品吸附影响的新型“双管”方法中确定甲烷的不同扩散系数，表明在所有常见温度下与滞流结果的一致性要好得多.