Generalization of gas‐liquid partition chromatography to study high pressure vapor‐liquid equilibria of multicomponent systems

Abstract

The use of chromatographic retention volume data to obtain vapor-liquid equilibrium coefficients has been extended to a ternary system with all components present at finite concentrations in the liquid phase and essentially a light binary gas comprising the vapor phase. The data are obtained by observing the retention time of the solute of interest when that solute is eluted by a flowing gas stream through a column packed with an inert porous firebrick on which is impregnated a fixed, relatively nonvolatile liquid. The retention times are used to compute retention volumes which may be related t o the K values of the solute.A previous mathematical description of the elution process is modified to include the case of an N component elution gas, all constituents of which are soluble in the fixed liquid phase. A general solution is derived for the multicomponent elution gas from which K values for each component may be calculated i f retention volume data are taken for each, provided molecules of the solute samples used are distinguishable from others of the same species present in the eloution gas. For the case of indistinguishable sample molecules, the rate theory development of Stalkup and Deans is verified for a binary elution gas.Sufficient retention data were taken to completely define the concentration dependence of the K value for propane in the system methane-propane-n-decane at -20", 0", 40°, and 70°F. from 20 to 1,OOO Ib/sq.in.abs. Six methane-propane binary mixtures were used as elution gases, consisting of 2.08, 4.31, 6.90, 9.44, 13.09, 16.27 mole % propane. Retention data were also taken for methane under the same conditions. Distinguishability of sample molecules was achieved by using radioactive solute samples tagged with carbon-14. Propane retention data were also obtained for the system methane-propane-n-heptane at In this paper the application of gas-liquid partition chromatography ( GLPC) to the study of vapor-liquid equilibria is generalized to include multicomponent systems. Establishing the validity of such application greatly increases the spectrum of systems subject to study by GLPC. The rapidity and simplicity of the elution process compared with conventional methods for studying phase behavior make such an increase in applicability desirable.In the GLPC process a vapor-liquid system is established by passing a gas through a column packed with an inert, porous solid material on the surface and in the pores of which an immobile liquid phase is fixed. A small perturbation with the solute of interest is eluted through the column by the carrier gas. The time required for the perturbation to travel the length of the column is determined by and related to the manner in which the solute distributes itself between the two phases. GLPC was first introduced by Martin and James (21 ) .It was quickly recognized by Martin (20) technique represented potentially the easiest method of measuring the physical properties of solutes in solvent systems. His suggestion was verified by Porter, Deal, and Stross ...

Direct chromatographic equilibrium studies in chemically reactive gas‐solid systems

“…The use of a radioactively tagged component in the perturbation sample furnishes a direct measure of the p for that component, as has been reported by a number of authors (5,8,9,11 ) . The theoretical rationale for this observation follows from considering the tagged species to be a distinct component with physical properties identical to one of the untagged components.…”

“…The theory and practice of using a multicomponent carrier gas have been discussed by several of these authors (8,11,13,16); in each case the simplification produced by the use of radioactive tracers was noted.…”

Determination of multicomponent sorption equilibria using perturbation gas chromatography

“…Isotopic tracers have been used for some determinations at finite concentration (Stalkup and Deans, 1963;Gilmer and Kobayashi, 1964; Koonce et al, 1965) and can be used for multicomponent systems with any number of species but the method is not always feasible for lack of the needed tracers. The objective of this work was to develop perturbation gas chromatography equations for sorption in multicomponent, finite concentration systems that are not limited to stoichiometric exchange.…”

Chromatographic investigation of the oxygen exchange reaction between carbon monoxide and carbon dioxide

“…In recent years chromatography has emerged as a useful tool for direct measurement of many physicochemical phenomena. By relating the moments of the eluted chro-matographic peaks to the processes occurring within the column, investigators have been able to determine gasliquid K-values (Stalkup and Kobayashi, 1963;Koonce et al, 1965), adsorption isotherms (Eberly, 1961 and Peterson, 1963), intraparticle diffusion coefficients (Schneider and Smith, 1968), and axial dispersion coefficients (Taylor, 1953;Schneider and Smith, 1968). Recently, a generalized theory of direct chromatography (Deans et al, 1970), which includes nonlinear and coupling effects, was published.…”