Adsorption Thermodynamics and Kinetics of Light Hydrocarbons on Microporous Activated Carbon at Low Temperatures

The removal of light hydrocarbons from exhaust air and process gas is important for a variety of applications, e.g., in natural-gas treatment. However, particularly at lower concentrations, the removal of C-1 and C-2 hydrocarbons is either very expensive or unfeasible with standard technology. Adsorption processes at temperatures below 0 degrees C may provide a technical solution, but until today, no systematic study on the dynamics of trace adsorption at low temperatures is available. Therefore, in this work, we present breakthrough curve experiments of ethane, propane, and n-butane over a temperature range from +20 to -80 degrees C and a concentration range from 5 to 1000 Pa on microporous activated carbon. Equilibrium loadings are calculated and modeled with the temperature dependent Toth equation. From dynamic simulations of the experimental breakthrough curves, kinetic parameters are determined. The lowering of temperature results in the slowdown of kinetics, which, however, simultaneous capacity gain.