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 H2. PPGDME can be made with a linear repeat unit (PPGDMEl, poly(1,3-propanediol) dimethylether) or a branched repeat unit (PPGDMEb, poly(1,2-propanediol) dimethylether). The solubility of CO2 and H2 in each of the four solvents of specified average molecular weight (PEGDME 250, PDMS 550, PPGDMEl 678 and PPGDMEb 430) is determined between 25 and 120 °C at pressures to 10 MPa. CO2 is much more soluble in each solvent than H2; however, the solubility of CO2 decreases as the solubility of H2 increases with increasing temperature. PPGDMEl 678 and PPGDMEb 430 are comparable CO2 solvents. PPGDMEl 678 absorbs less H2 than all the other solvents, while PPGDMEb 430 absorbs significantly more H2. 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 °C. PDMS 550 absorbs more H2 than all of the other solvents.

The addition of CO 2 -soluble, brine-soluble, surfactants to the high pressure CO 2 may facilitate the in-situ generation of CO 2in-brine foams for conformance and/or mobility control. Most of these non-ionic surfactants dissolve in CO 2 to concentrations of roughly 0.05 -0.10wt% at CO 2 EOR conditions and stabilize CO 2 -in-brine foams in high pressure windowed cells. Huntsman SURFONIC® N series surfactants, branched nonylphenol ethoxylates, containing an average of 12 (N-120) or 15 (N-150) ethylene oxide repeat units were selected for mobility and CT studies detailed in this paper.Transient mobility measurements were conducted using a water-wet Berea core (104 mD), a water-wet Bentheimer sandstone core (~1500 mD), and several mixed wettability SACROC carbonate cores (3.6 and 8.9 mD). The CO 2 was injected into a brine-saturated core at a superficial velocity of 10 ft/day, and the surfactant was either not used, dissolved only in the brine at 0.06wt%, dissolved only in the CO 2 at 0.06wt%, or dissolved in both the brine and the CO 2 at 0.06wt. Regardless of what phase the surfactant was dissolved in, in-situ foam generation in the relatively high permeability sandstone was evidenced by total pressure drop values that were 2 -3 times greater than the test with no surfactant. The mobility reduction was more modest (20 -50% increases in pressure drop) in the lower permeability SACROC cores (3.6 and 8.9 mD) when the surfactant was dissolved in the CO 2 . When the surfactant was dissolved in the brine, the pressure drops increased by a factor of 1.5 -3 for the 8.9 mD core.CT scanning of in-situ foam generation was then conducted by injecting high pressure CO 2 into a 5wt% KI brinesaturated water-wet Berea sandstone (3 -8 mD). Tests were done with no surfactant or with the surfactant dissolved either in the brine at 0.03wt% or in the CO 2 at 0.06wt%. At a low and high superficial velocity values of 0.47 ft/day and 4.7 ft/day, insitu foam generation occurred when surfactant was dissolved in the brine or the CO 2 , but the core was swept more effectively by the foam generated with the surfactant present in the brine.

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A series of studies on the acidity of AlCl 3 -1-ethyl-3-methylimidazolium chloride (EMIC) melts buffered with alkali metal chlorides were carried out. The solubility of HCl, a strong Brønsted acid in these melts, was measured in melts buffered with LiCl, NaCl, and KCl. The solubility of HCl in all three melts is 450-475 mM under 1 atm of HCl, approximately the same as that in the acidic (AlCl 3 -rich) melts. The relative solubility products of LiCl, NaCl, and KCl were measured, and it was found that K sp (NaCl)/K sp (LiCl) ) 72 ( 6 and K sp (KCl)/K sp -(NaCl) ) 1000 ( 400. It is likely that the differences in the acidity of HCl in the various melts are due to the differences in the solubility product of the relevant alkali metal chlorides. These ratios are consistent with the results of previous studies on the acidity of HCl in the melts. The concentrations of the strongly Lewis acidic Al 2 Cl 7ion in melts buffered with LiCl were measured using an aluminum electrode. The results of the potentiometric work indicate that a melt containing 1 M Li + (approximately n AlCl3 /n EMIC ) R ) 1.25:1 prior to buffering) would contain about 200 µM Al 2 Cl 7 -. This corresponds to a solubility product of about (1.5 ( 0.5) × 10 -12 M 2 . The liquid junction potentials between unbuffered and buffered melts were found to be about 49 mV × ([Li + ]/M). These results are related to previous work on the acidity of HCl in these melts, and it is shown that it is possible to explain many of the acidity and latent acidity results on the basis of the solubility products of the alkali metal chlorides.