Using Active Learning to Rapidly Develop Machine Learned Diffusion Coefficients of CO2 Conversion Reagents in Metal–Organic Frameworks

Researches on thermophysical properties of CO₂ are needed because of its connection to global warming. The amount of CO₂ in the atmosphere is much affected by that of CO₂ contained in the ocean. The diffusion coefficient of CO₂ in high pressure seawater is an important parameter for its environmental estimation. In the present study an apparatus for the measurement of the mutual diffusion coefficient of high pressure liquid has been constructed based on the principle of the Taylor dispersion method. The mutual diffusion coefficients of the CO₂- water have been measured under high pressure. The main part of the apparatus consists a closed­circuit channel, a concentration detecting system and a pressure control system. A straight tube of 2104 mm was used as the diffusion tube. In order to cancel disturbance due to injection of the solute, the concentration change was observed optically at two positions along the diffusion tube.

An experimental approach for measuring carbon dioxide diffusion coefficient in water and oil under supercritical conditions

Simultaneous determination of sorption, heat of sorption, diffusion coefficient and glass transition depression in polymer–CO 2 systems

Apparent coefficient of diffusion of carbon dioxide through samples of cereals and rapeseed

Diffusion coefficients of CO2 molecule and bicarbonate ion in hemoglobin solution measured by fluorescence technique.

Electrochemical determination of the diffusion coefficient of cations into Chevrel phase-based electrochemical transfer junction by potential step chronoamperometry and impedance spectroscopy

The interfacial tension (IFT) and diffusion coefficient of CO 2 in a hydrocarbon in a carbonated water (CW) environment were estimated for pressures between 10-100 bar and at temperatures of 25 C, 35 C, and 45 C using axisymmetric pendant drop shape analysis (ADSA). We developed a dynamic numerical model accounting for the changes in properties at the CW-hydrocarbon interface owing to the swelling of the hydrocarbon drop (HD). This approach eliminates an error of about 36% arising from the assumption of a static boundary/volume in conventional methods. The results indicated that the IFT between CW and the hydrocarbon is a function of the CO 2 phase density and solubility. At low pressures (<60 bar, 25 C), IFT is directly proportional to the pressure, while at pressures larger than 60 bar, it is inversely proportional to the pressure. The physical behaviour of the CW-hydrocarbon system is driven mainly by a balance between CO 2 solubility and IFT, resulting in a constant CO 2 saturation. Despite the decrease in CO 2 solubility with temperature, the diffusion coefficient of CO 2 increases. The reduction in IFT with temperature counteracts the decrease in CO 2 solubility, leading to a higher diffusion coefficient as temperature increases. It is shown here that the CWhydrocarbon system induces more swelling and lower viscosity compared to similar systems but with pure CO 2 . As such, CW's potential for enhanced oil recovery (EOR) is realised.

Abstract

We perform dynamic Monte Carlo simulations to understand the kinetics of CO oxidation on Pt surface. Our simulations are performed on a model for CO electro-oxidation, where oxygen-containing species (adsorbed OH) formed on the Pt surface reacts with adsorbed CO by a Langmuir–Hinshelwood mechanism to form CO2. A systematic study of the model parameters shows that we obtain better electrocatalytic activity by increasing the surface diffusion coefficient of CO (kD) or the rate of reaction between adsorbed CO and adsorbed OH. We also show that if the initial state of adsorbed CO is a closely packed structure, increasing the surface coverage can result in negative voltammetry peak shifts because of the formation of weakly adsorbed states of CO. We have also modeled bulk CO voltammetry by introducing a CO adsorption rate, k4. We show that near-zero currents are obtained for the potentials (E) where the rate of OH adsorption, k1(E), is much smaller than k4. We also note that kD plays no significant role in CO oxidation when kD≪k4. Our results also show that bulk CO voltammetry peaks shift to more positive potentials compared to the stripping, as observed in experiments. Our potential step simulations show no difference in bulk and stripping current transients in the potential regions where k1(E)≫k4, whereas they vary significantly when k4≅k1(E).

Electrochemical studies on diffusion and redox behavior of various metal ions in some molten glasses

The general formulation of the classical kinetic theory, which is needed to predict transport properties of gases in situations where the hydrodynamic equations are valid, is reviewed. A rigid convex model of tetrahedral symmetry is used to predict the Senftleben-Beenakker effect of a static magnetic field on the thermal conductivity and viscosity of pure CH/sub 4/, CD/sub 4/ and CF/sub 4/. The parameters of the model are optimized and are found to assume physically reasonable values. The calculations agree with experiment to a degree comparable to that of similar work on diatomic molecules. A generalized scattering cross section, ..gamma.., is defined which can be evaluated exactly for the limiting cases of a spherical soft potential and rigid ovaloids. For a general soft nonspherical interaction of the Kihara type, a suitable approximation for the momentum dependence is made with the following attributes: ..gamma.. reduces to the form for soft sphere and rigid ovaloid in the limits and the resulting matrix elements of the collision operator can be written in terms of the familiar ..cap omega..* integrals. This formulation is used to investigate thermal diffusion in binary isotopic mixtures of CO. Calculations are made in an 80/sup 0/K to 300/sup 0/K range which includes the inversion temperatures for all mixtures studied. Thermal conductivity and diffusion coefficients of CO are also calculated. The parameters of the model can be adjusted to account for the major features of the experimental data. The physical significance of the parameters is discussed. (auth)

Microscopic experiments and simulations of CO2 huff-n-puff displacement mechanism considering heterogeneity and fractures

Diffusion coefficients are necessary to describe the mass transfer and adsorption rate of CO2 in formation fluids. However, data is scarcely reported for actual reservoir conditions of high pressure and temperature, which are normal in most scenarios of the CO2-enhanced oil recovery process in China's fractured-vuggy reservoirs and carbon storage process. Accordingly, this work employed the pressure decay method (PD) and relevant mathematical models to determine the CO2 diffusion coefficient in both liquids and cavern filling porous media at 50 MPa and 393 K. The effects of the type of reservoir fluids, the properties of carven filling porous media, and water saturation on CO2 diffusion coefficients were investigated. Results in bulk reservoir liquids showed that the CO2 diffusion coefficient in the oil sample was 4.1243 × 10−8 m2 s−1, much higher than those in the pure alkane phase, pure water and brine sample from reservoirs. Results of CO2 diffusion in carven filling porous media saturated with oil demonstrated a significant dependence on properties such as porosity and permeability, and a correlation in the CO2 diffusion coefficients between the bulk oil phase and cavern filling porous media in the form of touristy was documented. CO2 diffusion in the fractured cavern porous media was much higher than that without fracture. An increase in water saturation reduced CO2 diffusion coefficients in the carven filling porous medium studied, herein. Thus, the CO2 diffusion coefficient is essentially related to the type of liquid and properties of the filling media.

Experimental determination of solubility and diffusion coefficients of CO2 and N2 in poly(dimethyl, methylphenyl siloxane) (PMPS) for the pressure range 0–150 kPa and the temperature range of −10°C to 45°C is discussed. The absorption isotherms were measured by pressure decay equilibrium. Diffusion coefficients were determined by modeling the transient absorption data by Fickian diffusion. The value of solubility coefficient for CO2 at 35°C was 1.21 ± 0.02 cm3 CO2 (STP)/(cm3 polymer.atm) and it increased to 2.07 ± 0.01 cm3 CO2 (STP)/(cm3 polymer.atm) at 1°C. The absorption isotherms of CO2 obtained were linear for the pressure range 0–200 kPa and the enthalpy of sorption value was −10.82 kJ/mole for CO2. However, the diffusion coefficients of CO2 changed with feed pressure. The diffusion coefficient of CO2 in PMPS at 22°C and 128.6 kPa equilibrium pressure was 7.22 × 10−6 cm2/s and thus the permeability value at these conditions was 1392 Barrers. The diffusion coefficients of CO2 at 0°C and equilibrium pressures of 125.8 kPa and 10.5 kPa were 5.72 × 10−6 cm2/s and 4.31 × 10−6 cm2/s, respectively. Consequently, the CO2 permeability in PMPS decreases by about 20% when the pressure is reduced from 125.8 to 10.5 kPa at 0°C. © 2007 American Institute of Chemical Engineers AIChE J, 2008

CO2 diffusion coefficient plays a crucial part in saline aquifers for the CO2 storage and the safety of long-term sequestration. Therefore, it is particularly important to measure the diffusion coefficient accurately. As far as we know, there are currently no CO2 brine diffusion data in real cores under reservoir temperature and pressure conditions. In this paper, a study on the CO2 diffusion coefficient diffused in a brine-saturated Berea core along the radial direction was conducted at temperatures of 313.15 K to 373.15 K and pressures of 8 MPa to 30 MPa. On account of the experimental results, the effect of permeability, NaCl concentration, temperature and pressure on the CO2 diffusivity is analyzed. The results in this study indicate that the diffusion coefficient increases with increasing permeability, pressure and temperature and decreases with increasing NaCl concentration. However, the relationship between pressure and the diffusion coefficient is not linear. As the pressure gradually increases, the effect of pressure will become weak. In addition, an empirical correlation of the relationship between temperature–pressure and the CO2 diffusion coefficient could be obtained based on the experimental data. The data in this paper fill the blank on the study of the CO2 diffusivity in brine under reservoir conditions, which has positive significance for the study of supercritical CO2 diffusion in a brine-saturated core.