Toward greener solutions for gas separation
Sorption, or separation via sorbents/solvents (dissolving the gases in a solvent that facilitates adsorption or absorption and thus removal), is employed in numerous processes from purification to hydrogen production to carbon dioxide (CO2) capture and sequestration. Studies have shown that improved solvents could reduce energy requirements substantially while nearly eliminating harmful waste. Among the prime candidates are ionic solvents, ionic liquids that are salts with melting points near room temperature. Room temperature ionic liquids (RTILs) have a number of attractive properties in addition to their ‘eco-friendliness’. They do not evaporate to produce airborne contaminants (non-volatility) and do not catch fire (non-flammability). In addition, they are chemically and thermally stable and, given their tremendous variety, they can be tailored to individual mixtures depending on required solubility characteristics. Despite their attractiveness, RTILs have not achieved their potential largely due to a dearth of standards defining the selective sorption characteristics for multigas applications. European researchers initiated the S-SCIL project to fill the knowledge gap and facilitate widespread and effective application of RTILs in multigas separation processes. The S-SCIL consortium successfully developed standards and instrumentation for measuring selective sorption in multigas applications. Included were methods for characterising the behaviour of substances such as porous solids and nanoparticles used in the sorption process. Important existing single gas and newly developed multigas sorption standards were adapted for characterisation of gas separation using RTILs. Novel gravimetric measurement instrumentation for sorptive gas analysis enhanced the potential market for gravimetric methods. In addition, a number of instruments for monogas and multigas measurements were developed that were easy to use and maintain, facilitated remote data analysis via the Internet and included detailed explanatory software. Commercialisation of S-SCIL technologies should facilitate more widespread use of RTILs in gas separation processes of vital importance to the environment.
