Conductivity Measurements on H2O-Bearing CO2-Rich Fluids

Abstract

Recent studies report rapid corrosion of metals and carbonation of minerals in contact with carbon dioxide containing trace amounts of dissolved water. One explanation for this behavior is that addition of small amounts of H 2 O to CO 2 leads to significant ionization within the fluid, thus promoting reactions at the fluid-solid interface analogous to corrosion associated with aqueous fluids. The extent of ionization in the bulk CO 2 fluid was determined using a flow-through conductivity cell capable of detecting very low conductivities. Experiments were conducted from 298 to 473 K and 7.39 to 20 MPa with H 2 O concentrations up to *1,600 ppmw (mole fraction of water, x H 2 O &3.9 9 10 -3 ), corresponding to the H 2 O solubility limit in liquid CO 2 at ambient temperature. All solutions showed conductivities \10 nSÁcm -1 , indicating that the bulk solutions were essentially ion-free. This observation suggests that the observed corrosion and carbonation reactions are not the result of ionization in CO 2 -rich bulk phase, but does not preclude ionization in the fluid at the fluid-solid interface.

Quantitative Review of Olivine Carbonation Kinetics: Reactivity Trends, Mechanistic Insights, and Research Frontiers

“…The increased water activity and clustering 158,159 at elevated temperatures will also likely induce ion formation, which has not yet been detected in wet scCO 2 . 160 Organic ligands and metal−organic complexes, ubiquitous in diverse geologic settings, 147 can be stable at >200 °C and may contribute to reactions in the bulk CO 2 fluid in addition to those in adsorbed nanoscale water films. 26,27 These nonaqueous reactions will lead to carbon cycling among organics, carbonate minerals, and CO 2 fluids.…”

Phase Equilibria of Water/CO2 and Water/n-Alkane Mixtures from Polarizable Models

“…Thermodynamic properties of water/CO 2 mixtures have been extensively measured, mostly at temperatures lower than 373 K, but important discrepancies remain in the phase equilibrium data at higher temperatures . For phase equilibria at elevated temperatures (>473 K) and pressures (>200 bar), which are of particular interest for geochemical applications, there are mainly three sets of experimental measurements from Takenouchi and Kennedy, Todheide and Frank, and Capobianco et al Although these show consistent results for CO 2 solubility in water, the reported equilibrium compositions of the CO 2 -rich phase are in disagreement. A comprehensive review of experimental data for the water/CO 2 mixture is available .…”

Electrochemical characterisation of ionic dynamics resulting from spin conversion of water isomers

“…that dissociates to H 3 O + and HCO 3 -. The ion OHis required for dissociation of H 2 CO 3 that is delivered by the autoionization process [26]. The equilibrium reaction (1) is obeying Le Chatelier's principle; the forward reaction is exothermic, an increase in temperature causes reverse reaction.…”

“…The equilibrium reaction (1) is obeying Le Chatelier's principle; the forward reaction is exothermic, an increase in temperature causes reverse reaction. Following [26], the ionic dynamics of…”

“…hypothetical reactions CO 2 + p-H 2 O and CO 2 + o-H 2 O in pure water are expected to demonstrate different electrochemical reactivity. Kinetics of CO 2 dissolving is well investigated [25], [26] that leads to accumulation of H 3 O + , HCO 3 and CO 3 2ions in six different time scales, and continuous increasing of conductivity up to the saturation level. Additionally, we also test the pathway of reactive oxygen species (ROS) under external excitation that forms, among others, singlet oxygen 1 O 2 and hydrogen peroxide H 2 O 2 with different free radicals and ions [27].…”