Adsorption Equilibria of Carbon Dioxide and Ethane on Graphitized Carbon Black

Adsorption of gases on carbonaceous materials has always been an attractive research project because of the different structures and surface properties of various carbonaceous materials. Among these materials, graphitized carbon black (GCB) plays an important role because it could be regarded as having a homogeneous surface. Therefore, graphitized carbon black has often been chosen as a reference material in characterizing the interaction between a molecule and surface carbon atoms. 1 Studies in this field can provide fundamental information on the adsorption potential for other carbonaceous materials. In addition, the adsorption equilibrium prediction models are based on the effects of adsorbate-adsorbent interactions for practical purposes. An efficient method that is able to predict the adsorption equilibria would be very convenient for adsorption engineering research and applications. The adsorption potential theory developed by Dubinin 2 put forward the concept of the characteristic curve, which could be used to evaluate gas adsorption equilibria using a single experimental adsorption isotherm. Many experimental vapor adsorption equilibrium data on microporous materials, especially on activated carbons, have proved that this method is valid. Attempts to extend the adsorption potential theory to make it applicable to supercritical conditions need more investigation and substantiation. Ruthven 3 provided a similar method, the generalized equilibrium isotherm K ·p ∼ n, to make adsorption predictions. It uses the Henry’s law constant K to express the interaction between an adsorbed molecule and the adsorption sites on the surface. This opinion is reasonable for nonpolar systems, experimental data over a wide temperature range are needed for calculation of the Henry’s law constant. Molecular simulation is another important prediction approach with assumptions about the solid-fluid interaction, the surface properties, and the pore structure. This method has obtained great success for spherical molecules on carbonaceous materials. The development of molecular simulation requires more support from equilibrium data over a wide experimental range and more improvement in the calculations on nonspherical molecules. 4,5 In this paper, adsorption equilibrium data for pure carbon dioxide and ethane on graphitized carbon black over a wide temperature and pressure range are presented. Also, a generalized adsorption isotherm for predicting the adsorption equilibria is proposed.