Thermodynamic Modeling of Adsorption of Pure Gases and Binary and Ternary Mixturesof Gases with Simplified Local Density Model

In this work, the SLD model is used to investigate the adsorption of pure gases and binary and ternary mixtures of them on solids. The volumetric properties of the fluid phase are described by PR and EDS equations of state. Three different procedures are used to estimate the parameters of the model. In the first and second procedures, the model is considered to have 2 and 1 adjustable parameters respectively. However, in the third procedure, none of the parameters are adjusted. In all the three cases, only the data of the pure compounds are used. The results show that although the adjustment of the parameters improves the results for pure compounds, it does not necessarily improve the prediction of the model for the mixture of gases, and even in some cases, less reliable results are observed. As a result, good predictions are observed without fitting the parameters of the model. The average absolute percentage of deviation for the calculation of excess adsorption for pure gases with PR EOS is 6.6%, 10.0%, and 11.6% for procedures 1, 2, and 3 respectively. The corresponding values for ESD EOS are 8.1, 10.4, and 15.9. For binary gas mixtures, the errors are 2.7%, 3.9%, and 4.2% for procedures 1, 2, and 3 respectively in case of using PR EOS; ESD EOS results in errors of 4.7%, 3.5%, and 4.8% for procedures 1, 2, and 3 respectively. A ternary gas mixture composed of methane, ethane, and ethylene is also examined; the average absolute percentages of deviations are 5, 4, and 15.6 in case of PR EOS and 6.9, 8.9, and 17.4 with ESD EOS for procedures 1, 2, and 3 respectively. The comparison of the equations of state used show that PR equations of state generally produce better results.