Energy & Fuels, Vol.27, No.11, 6913-6920, 2013
Hydrophobic Polymeric Solvents for the Selective Absorption of CO2 from Warm Gas Streams that also Contain H-2 and H2O
The hydrophobic polymers polydimethyl siloxane (PDMS) and polypropyleneglycol dimethylether (PPGDME) may provide an alternative to physical solvents based on the hydrophilic polymer polyethyleneglycol dimethylether (PEGDME) for the precombustion capture of CO2 from the warm, high pressure stream that also contains H2O and H-2. PPGDME can be made with a linear repeat unit (PPGDME(1), poly(1,3-propanediol) dimethylether) or a branched repeat unit (PPGDME(b), poly(1,2-propanediol) dimethylether). The solubility of CO2 and H-2 in each of the four solvents of specified average molecular weight (PEGDME 250, PDMS 550, PPGDME(1) 678 and PPGDME(b) 430) is determined between 25 and 120 degrees C at pressures to 10 MPa. CO2 is much more soluble in each solvent than H-2; however, the solubility of CO2 decreases as the solubility of H-2 increases with increasing temperature. PPGDME(1) 678 and PPGDME(b) 430 are comparable CO2 solvents. PPGDME(1) 678 absorbs less H-2 than all the other solvents, while PPGDME(b) 430 absorbs significantly more H-2. PDMS 550 is a very good CO2 solvent, absorbing more CO2 than all of the other solvents at all temperatures except for PEGDME 250 at 25 degrees C. PDMS 550 absorbs more H-2 than all of the other solvents.