(502g) Measurement of the Selective Solubilities of Ch4/C2H6/Co2-Mixtures on Alkylsulphate Ionic Liquids for Natural- and Biogas Cleaning

Ionic liquids are very suitable substances for separation processes and have been more and more the focus of research during the recent years [1]. Especially the high solubility of CO₂ [2,3] offers many interesting applications. Natural- and biogas contain a variety of impurities including also carbon dioxide, which decreases its calorific value and increases environmental pollution. The cleaning of this gases by means of ionic liquids seems to be very promising.

Investigations of pure gas solubilities in ionic liquids can be performed using comercially available high pressure sorption measuring instruments. In case of selective solubilities in gas mixtures containing two or more components, measurements are much more complex. This presentation deals with a newly developed sorption measuring apparatus to determine the selective sorption of complex gas mixtures up to 200°C and 200 bar. The apparatus is based on a combined volumetric-gravimetric principle including a highly precise gravimetric sorptive gas density measurement. In addition the sorptive gas concentration is measured by means of a gas chromatograph.

The experimental results contain mono gas sorption measurements of CH₄, C₂H₆, CO₂,  binary gas sorption measurements of CH₄/C₂H₆, CH₄/CO₂, C₂H₆/CO₂–mixtures and ternary gas sorption measurement of CH₄/C₂H₆/CO₂–mixtures on alkylsulphate ionic liquids. The results show the selective sorption behaviour of the gases in the respective ionic liquid depending on the different conditions (temperature, pressure, concentration). 

Selective Sorption behaviour of Ecoeng 212 and BMIM [PF6] in a 90wt% CH4/10wt% CO2–mixture at 50°C

[1]       P. Wasserscheid, T. Welton (Eds.), Ionic Liquids in Synthesis 2003, Wiley-VCH, 81-93

[2]       Lynnette A. Blanchard, Zhiyong Gu, and Joan F Brennecke, High-Pressure Phase Behavior of Ionic Liquid/CO₂ Systems, J. Phys. Chem. B 2001, 105, 2437-2444

[3]       Cesar Cadena, Jennifer L. Anthony, Jindal K. Shah, Timothy I. Morrow, Joan F. Brennecke and Edward J. Maginn, Why Is CO₂ So Soluble in Imidazolium-Based Ionic Liquids?, J. Am. Chem. Soc., 126 (2004) 16 , S. 5300-5308