Investigating the Determination of Diffusion Coefficients of Butane in Hydrogen, by Reversed-Flow Inverse Gas Chromatography

Reversed-flow inverse gas chromatography (RF-IGC) combined with a flame ionization detector (FID) was used to determine diffusion coefficients of butane in hydrogen over a wide temperature range 287.7–518.2 K, at atmospheric pressure. These results provide the first experimental diffusivities for C₄H₁₀ in H₂. Hydrogen served both as carrier gas and as FID fuel gas, which required modification of the flow arrangement. Digitization of the chromatographic signal allowed two mathematical models, based on short-time and long-time analysis of the concentration–time response, to be applied and compared. The accuracy of the short-time and long-time methods was 99.3% and 99.4%, respectively. The short-time diffusivities deviated slightly from the Fuller–Schettler–Giddings (FSG), Gilliland and Huang et al. equations by 6.2%, 4.6% and 6.1%, respectively. The long-time analysis provides smaller diffusivities, from 6.1 to 13 %, than those determined by long time model, with bigger deviations of 16%, 15% and 13% from the FSG, Huang et al. and Gilliland equations, respectively. The temperature exponents were: 1.72 ± 0.02 for the short-time analysis and 1.59 ± 0.03 for the long-time analysis models, respectively. Long-time analysis model is simpler, slightly more accurate at higher temperatures, but in the case of the studied C₄H₁₀ in H₂ system provides smaller diffusivities and more deviating from the predicted values than those determined in the case of short-time model, which is accurate but more complicated in terms of estimations procedure.