In Situ Infrared Spectroscopic Study of Forsterite Carbonation in Wet Supercritical CO2

• Published in: Environmental science & technology 2011-07, Vol.45 (14), p.6204-6210
• Main Authors: Loring, John S, Thompson, Christopher J, Wang, Zheming, Joly, Alan G, Sklarew, Deborah S, Schaef, H. Todd, Ilton, Eugene S, Rosso, Kevin M, Felmy, Andrew R
• Format: Article
• Language: English
• Subjects: CARBON DIOXIDE; Carbon Dioxide - chemistry; Carbon Sequestration; Climatology. Bioclimatology. Climate change; Earth, ocean, space; Energy and the Environment; Environmental Molecular Sciences Laboratory; ENVIRONMENTAL SCIENCES; Exact sciences and technology; External geophysics; Kinetics; Meteorology; MINERALIZATION; Pressure; REACTION KINETICS; SATURATION; SILICATE MINERALS; Silicon Compounds - chemistry; Spectrophotometry, Infrared; SPECTROSCOPY; Temperature; TRAPPING; WATER; Water - chemistry; WATER SATURATION
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es201284e

Carbonation reactions are central to the prospect of CO2 trapping by mineralization in geologic reservoirs. In contrast to the relevant aqueous-mediated reactions, little is known about the propensity for carbonation in the key partner fluid: supercritical carbon dioxide containing dissolved water (“wet” scCO2). We employed in situ mid-infrared spectroscopy to follow the reaction of a model silicate mineral (forsterite, Mg2SiO4) for 24 h with wet scCO2 at 50 °C and 180 atm. The results show a dramatic dependence of reactivity on water concentration and the presence of liquid water on the forsterite particles. Exposure to neat scCO2 showed no detectable carbonation reaction. At 47% and 81% water saturation, an Ångstrom-thick liquid-like water film was detected on the forsterite particles and less than 1% of the forsterite transformed. Most of the reaction occurred within the first 3 h of exposure to the fluid. In experiments at 95% saturation and with an excess of water (36% above water saturation), a nanometer-thick water film was detected, and the carbonation reaction proceeded continuously with approximately 2% and 10% conversion, respectively. Our collective results suggest constitutive links between water concentration, water film formation, reaction rate and extent, and reaction products in wet scCO2.