Inverse ideal adsorbed solution theory for calculation of single-component adsorption equilibria from mixture isotherms supported by adsorption equilibrium distribution

Abstract

Adsorption isotherm data of methanol, ethanol, and dimethyl carbonate were determined via headspace experiments on two activated carbons (RB 4 from CABOT Norit and SC 40 from SilCarbon) at different temperatures. However, dimethyl carbonate (DMC) showed a significant decomposition to methanol and CO2 during the adsorption experiments. Hence, the measured isotherm data for DMC were always two-component isotherm data assuming CO2 as non-adsorbing component. Thus, ideal adsorbed solution theory (IAST) was inverted to determine the single-component isotherm of DMC using two-component isotherm data and the known single component isotherm of methanol. The inverse IAST was supported by the calculation of the adsorption equilibrium distribution. This calculation was done with the expectation maximization method and results were used to determine the most probable isotherm equations to initialize the inverse IAST calculation. The methodology was validated for mixtures of methanol and ethanol where both single-component isotherms were known. Finally, single-component isotherms were calculated for DMC on RB 4 and SC 40 at different temperatures.