CO2-philic Oligomers as Novel Solvents for CO2 Absorption

Desirable properties for an oligomeric CO2-capture solvent in an integrated gasification combined cycle (IGCC) plant include high selectivity for CO2 over H2 and water, low viscosity, low vapor pressure, low cost, and minimal environmental, health, and safety impacts. The neat solvent viscosity and solubility of CO2, measured via bubble-point loci and presented on a pressure−composition diagram (weight basis), and water miscibility in CO2-philic solvents have been determined and compared to results obtained with Selexol, a commercial oligomeric CO2 solvent. The solvents tested include polyethyleneglycol dimethylether (PEGDME), polypropyleneglycol dimethylether (PPGDME), polypropyleneglycol diacetate (PPGDAc), polybutyleneglycol diacetate (PBGDAc), polytetramethyleneetherglycol diacetate (PTMEGDAc), glyceryl triacetate (GTA), polydimethyl siloxane (PDMS), and perfluorpolyether (PFPE) that has a perfluorinated propyleneglycol monomer unit. Overall, PDMS and PPGDME are the best oligomeric solvents tested and exhibit properties that make them very promising alternatives for the selective absorption of CO2 from a mixed gas stream, especially if the absorption of water is undesirable.