Measurement of adsorption energies on heterogeneous surfaces by inverse gas chromatography

Properties of materials as determined by inverse gas chromatography

“…Charmas et al indicated the following advantages of IGC method in comparison to the traditional adsorption techniques: (i) no need to pump out the preliminary sample under vacuum, (ii) the possibility to study the temperature effects, (iii) measurements are accurate at low surface concentrations, (iv) physical and chemical adsorption can be studied, (v) commercially available gas chromatographs could be used. The use of FC-IGC is often reported in literature [10][11][12][13][14].…”

Interrelations between Adsorption Energies and Local Isotherms, Local Monolayer Capacities, and Energy Distribution Functions, as Determined for Heterogeneous Surfaces by Inverse Gas Chromatography

“…From all the above and other searches of the literature, one may easily come to the conclusion that nobody so far has tried a solution for f (ε) other than through the integral equation [1]. This is not true, however, since in four recent papers of ours (8)(9)(10)(11) we have done exactly that, employing an inverse gas chromatographic tool known as reversed-flow gas chromatography (RF-GC). A recent review on that is worth mentioning (12).…”

“…A recent review on that is worth mentioning (12). All determinations by us concerning adsorption onto heterogeneous surfaces (8)(9)(10)(11)(12) are based on experimental chromatographic data, under one single assumption, namely, that the local isotherm θ( p, T, ε) obeys the Jovanovic isotherm model (13). It is well known that this goes over to the Langmuir isotherm in middle pressures and to a linear form at low pressures.…”

“…The values of the preexponential factors A i above and the corresponding coefficients of time B i are easily and fairly accurately determined from the chromatogram by a simple PC program of nonlinear least-squares regression (12). Based on the experimental equation [4] and the Jovanovic model (13), a new inverse gas chromatography methodology was developed to measure directly local (homogeneous) adsorption energies, ε, local monolayer capacities, c * max , local adsorption isotherms, θ ( p, T, ε), and adsorption energy distribution functions, f (ε), on heterogeneous surfaces (8)(9)(10), all as functions of experimental time, circumventing altogether the integral equation [1].…”

“…(10) or in the review (12). They have been applied to several gaseous/solid systems and the results are collected either in tables or in figures (8)(9)(10)(11)(12), giving the time t, the gaseous concentration of the adsorbate c y , the adsorption energy ε, the local monolayer capacities c * max , the local adsorption isotherm values θ, and the probability density function f (ε), i.e., the adsorption energy distribution. The appearance of the graphical representation of all the above quantities with the time in the abscissa, as plotted with the PC program MATHEMATICA 3 with 3000 plot points, shows some interesting maxima and minima.…”