Hydrophobic Polymeric Solvents for the Selective Absorption of CO_2 from Warm Gas Streams that also Contain H_2 and H_2O

摘要

The hydrophobic polymers polydimethyl siloxane (PDMS) and polypropyieneglycol dimethvlether (PPGDME) may provide an alternative to physical solvents based on the hydrophilic polymer polyethylenegjycol dimethylether (PEGDME) for the precombustion capture of CO_2 from the warm, high pressure stream that also contains H_2O and H_2. PPGDME can be made with a linear repeat unit (PPGDME_v poty( 1,3-propanediol) dimethylether) or a branched repeat unit (PPGDME_b, poly(1,2-propanediol) dimethylether). The solubility of CO_2 and H_2 in each of the four solvents of specified average molecular weight (PEGDME 250, PDMS 550, PPGDME_l 678 and PPGDME_b 430) is determined between 25 and 120 ℃ at pressures to 10 MPa. CO_2 is much more soluble in each solvent than H_2; however, the solubility of CO_2 decreases as the solubility of H_2 increases with increasing temperature. PPGDME, 678 and PPGDME_b 430 are comparable CO_2 solvents. PPGDME, 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 CO_2 solvent, absorbing more CO_2 than all of the other solvents at all temperatures except for PEGDME 250 at 25 ℃. PDMS 550 absorbs more H_2 than all of the other solvents.