(338d) Adsorption of Organics ON MSC5A IN Supercritical CO2

Chromatographic measurements were made for the adsorption of benzene, toluene and m-xylene on molecular sieving carbon (MSC) in supercritical fluid CO2 mixed with organics. Supercritical chromatograph packed with MSC was used to detect pulse responses of organics. Adsorption equilibria and adsorption dynamics parameters for organics were obtained by moment analysis of the response peaks. Figure.1 shows adsorption isotherm of benzene at 333K. According to Fig.1, the amount adsorbed increased with increases of benzene partial pressure, and reached to saturation.Dependences of adsorption equilibrium constants, K*, and micropore diffusivity, D, on the amount adsorbed were examined. The dependencies of adsorption equilibrium constants, K*, and micropore diffusivity, D, of toluene, benzene and m-xylene, on molarity of toluene with each parameters of temperature or pressure were obtained. It was found that the values of K* and D for an organic substance depended on the amount adsorbed of other organics strongly. Figure.2 shows dependency of adsorption equilibrium constants, K*, for benzene, toluene, and m-xylene on amount adsorbed of benzene at 20MPa. Figure.3 shows dependency of micropore diffusivity, D/ā2exp(σ2), for benzene, toluene, and m-xylene on the amount adsorbed of benzene at 20MPa. And Stop & Go method was used as simulation method of perturbation chromatography for investigating adsorption equilibrium and rate. Numerical solution for multicomponent chromatogram in time domain could be obtained by appropriate model equations with experimental conditions. This simulated chromatogram can be compared with experimental chromatogram to determine the adsorption equilibrium and rate parameters. Figure 4.shows adsorption isotherm of Stop & Go method simulations. In addition, molecular simulation of multicomponent adsorption equilibria was performed, and potential parameters were determined by comparing the simulation with experimental results. Simulation soft ware is Cerius2 (Version4.2) made by MSI. The purpose of performing simulation is to elucidate an adsorption mechanism on the molecule level. We see from Figure 5 that benzene adsorbs into the adsorption space, which simulates micropore. Here, benzene adsorbed in parallel to layer in model.