Silver(I) ions have the propensity of undergoing reduction
to form
metallic silver within olefin/paraffin separation systems when they
are subjected to hydrogen at elevated temperatures. Ionic liquids
(ILs) are versatile solvents known for their low vapor pressure, high
thermal stability, and structural tunability and have been shown to
minimize hydrogen-induced reduction of silver(I) ions when employed
as solvents. In the development of robust separation platforms that
employ silver(I) ions, it is essential to deploy reliable approaches
capable of measuring and assessing the factors that lower the overall
separation performance. In this study, silver(I) ions dissolved in
an imidazolium-based IL are subjected to mixed gas streams composed
of hydrogen, nitrogen, and methane under varying temperatures. Using
inverse gas chromatography, a total of 44 columns with stationary
phases containing four different concentrations of silver(I) bis[(trifluoromethyl)sulfonyl]imide
([Ag+][NTf2
–]) dissolved in
the 1-decyl-3-methylimidazolium ([C10MIM+])
[NTf2
–] IL were used to measure partition
coefficients of olefins and paraffins, as well as aromatics, esters,
and ketones. Upon exposing the stationary phases to mixed gases at
elevated temperatures, olefin partitioning between the silver(I) ion
pseudophase and the two other phases (i.e., carrier gas and IL stationary
phase) was observed to decrease over time, while partitioning between
the IL stationary phase and carrier gas remained unchanged. It was
found that exposure gases composed of 5.0 to 85.0 mol % hydrogen and
temperatures ranging from 95 to 130 °C resulted in a remarkable
acceleration of silver(I) ion reduction and an approximate 36.4–61.3%
decrease in olefin partitioning between the silver(I) ion pseudophase
and both the carrier gas and IL stationary phase after 60 h. While
binary mixtures of hydrogen and nitrogen resulted in a continuous
decrease in silver(I) ion–olefin complexation capability, a
ternary gas mixture produced varied silver(I) ion reduction kinetics.
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