Diffusion Coefficient Of Carbon Dioxide Research Articles

Diffusion coefficients of zirconium (IV) acetylacetonate: Measurements and correlation in both pressurized liquid and supercritical fluid

Limited data exist on the diffusion coefficient of a solute in both pressurized and supercritical fluids, despite its crucial role as an essential transport property. In this study, we present the first-ever determined diffusion coefficients of zirconium acetylacetonate (Zr(acac)4) in two distinct fluids: pressurized ethanol and supercritical carbon dioxide. Using the Taylor dispersion method, we measured the diffusion coefficients in pressurized ethanol at temperatures between 298.15 and 333.15 K, reaching pressures up to 30.00 MPa. In supercritical carbon dioxide, we employed the chromatographic impulse response (CIR) method, conducting the experiments at temperatures from 308.15 to 343.15 K and pressures up to 35.00 MPa. Remarkably, predissolving Zr(acac)4 in supercritical carbon dioxide and injecting it into the diffusion column enabled the accurate determination of diffusion coefficients in supercritical carbon dioxide, which were approximately an order of magnitude higher than those in pressurized ethanol. Our investigation revealed diffusion activation energies, ranging from 26.7 to 10.2 kJ mol−1 at pressures between 10.00 and 30.00 MPa in supercritical carbon dioxide and from 20.4 to 19.6 kJ mol−1 at pressures between 20.00 and 30.00 MPa in pressurized ethanol. All diffusion data, in both liquid and supercritical states, can be effectively correlated using the equation Sc = ∑n=03(Cnηn) with 2 parameters and 4 adjustable coefficients. This correlation demonstrates high accuracy, with an average absolute relative deviation (AARD) of 3.7 % over a wide fluid viscosity range of 21.0 to 1305.0 μPa s. Additionally, it is observed that all diffusion data can also be well-fitted with the equation D12/T = αηβ with 2 parameters and 2 adjustable coefficients, achieving an AARD of 3.5 %.

A coupled model for the dynamics of gas exchanges in the human lung with Haldane and Bohr’s effects

We propose an integrated dynamical model for oxygen and carbon dioxide transfer from the lung into the blood, coupled with a lumped mechanical model for the ventilation process, for healthy patients as well as in pathological cases. In particular, we take into account the nonlinear interaction between oxygen and carbon dioxide in the blood volume, referred to as the Bohr and Haldane effects. We also propose a definition of the physiological dead space volume (the lung volume that does not contribute to gas exchange) which depends on the pathological state and the breathing scenario. This coupled ventilation-gas diffusion model is driven by the sole action of the respiratory muscles. We analyse its sensitivity with respect to characteristic parameters: the resistance of the bronchial tree, the elastance of the lung tissue and the oxygen and carbon dioxide diffusion coefficients of the alveolo-capillary membrane. Idealized pathological situations are also numerically investigated. We obtain realistic qualitative tendencies, which represent a first step towards classification of the pathological behaviours with respect to the considered input parameters.

Experimental Investigation on Carbonation due to Climate Change Impacts

<p>Various investigations have been carried out to evaluate the infrastructure’s augmented vulnerability owing to concrete carbonation persuaded by the changes in the environment during recent years. Due to global warming and its effect, carbon dioxide emission levels in the atmosphere get increased and this would further increase the probability of carbonation-induced corrosion in concrete structures. In this present study, an empirical model is used to identify the diffusion coefficient of carbon dioxide (CO2) in concrete. Water cement (w/c) ratio of 0.45, 0.5, and 0.55 has been considered with emission scenarios of Representative Concentration Pathway (RCP) 8.5 and 4.5 respectively. The research findings through empirical modeling proved that the depth of carbonation has a direct relationship with water cement ratio and it is also predicted that by the year 2100, considering 2000 as the base year, the carbonation depth may raise up to 78% for reinforced concrete structures subject to various climatic conditions such as temperature, humidity, etc.</p>

Diffusion Coefficient and Absorption of Carbonyl Sulfide in 1-Hexyl-3-methylimidazolium Bis (Trifluoromethyl) Sulfonylimide ([hmim][Tf2N

The solubility of carbonyl sulfide (COS) and also the diffusion coefficients of COS, carbon dioxide, and hydrogen sulfide were experimentally investigated in 1-hexyl-3-methylimidazolium bis(trifluoromethyl) sulfonylimide ([hmim][Tf2N]). The solubility was measured using a static apparatus, and the acid gas diffusivity was obtained by monitoring pressure drop with low initial pressure via the so-called semi-infinite volume method. All experimental absorption trials were carried out in the range of low and medium pressures and temperatures from (313.15 to 353.15) K. Furthermore, all diffusion coefficient experiments were determined at a temperature from (313.15 to 333.15) K and low pressure to some extent to be acceptable in the semi-infinite volume approach. The experimental results were correlated using the Shiflett and Yokozeki versions of the Redlich–Kwong equation of state. In addition, Henry’s law constants and the thermodynamic properties of dissolution at infinite dilution were calculated and discussed.

Determination of mass transfer coefficient of CO2 removal in water-in-oil emulsion

The removal of carbon dioxide is an important process in natural gas purification since its lower down the calorific value of the natural gas. In addition, carbon dioxide also capable of forming corrosion in the pipeline, thus its removal is crucial. Water-in-oil emulsion was proposed in this research since the absorption of carbon dioxide in emulsion would be an effective method to prevent corrosion. However, the absorption capability of the emulsion and the mass transfer coefficient of carbon dioxide during absorption process needs further investigation. The aim of this study is to determine the diffusivity and mass transfer coefficient of carbon dioxide in the emulsion and observed the correlation between mass transfer coefficient and the carbon dioxide absorption values obtained from experiment. In this study, water-in-oil emulsion was prepared by mixing the aqueous phase and organic phase solutions under two different formulation conditions. Firstly, the methyldiethanolamine (MDEA) and 2 amino-2-methyl-1-propanol (AMP) blending was mixed in different alkaline solution; sodium hydroxide (NaOH) solution, potassium hydroxide (KOH) solution and distilled water (H2O) to form aqueous phase solution. Secondly, MDEA was combined with different alkanolamines; dimethylethanolamine (DMEA), diethanolamine (DEA) and triethanolamine (TEA) in KOH solution to form another aqueous phase solution. The synthesized aqueous phase is then mixed with the organic phase consists of kerosene and Span-80 mixtures. Furthermore, viscosity and particle sizes of the emulsions at different emulsion formulations were measured and the diffusivity and mass transfer coefficients of carbon dioxide were calculated. This study showed that, by using suitable emulsion formulation containing MDEA/AMP in KOH solution, the estimated value of diffusivity and mass transfer coefficient of carbon dioxide was 1.0876 × 1010 m2/s and 1.15 × 103 m/s respectively, with viscosity of 261.03 mPa s and particle size of 189.71 nm was achieved. It was found the diffusion coefficient and mass transfer coefficient of carbon dioxide is highly influenced by the characteristics of emulsion such as viscosity and particles sizes.

Binary Diffusion Coefficients for Short Chain Alcohols in Supercritical Carbon Dioxide—Experimental and Predictive Correlations

Experimental binary diffusion coefficients for short-chain alcohols in supercritical carbon dioxide were measured using the Taylor dispersion technique in a temperature range of 306.15 K to 331.15 K and along the 10.5 MPa isobar. The obtained diffusion coefficients were in the order of 10-8 m2 s-1. The dependence of D on temperature and solvent density was examined together with the influence of molecular size. Some classic correlation models based on the hydrodynamic and free volume theory were used to estimate the diffusion coefficients in supercritical carbon dioxide. Predicted values were generally overestimated in comparison with experimental ones and correlations were shown to be valid only in high-density regions.

FTIR as a Powerful Tool for Measurements of Diffusion in Supercritical Carbon Dioxide Using Taylor Dispersion Method

A new experimental high-pressure setup for measuring diffusion coefficients in supercritical fluids, based on Taylor dispersion method, and using an FTIR detector to operate up to 25.0 MPa was designed and optimized. Tracer diffusivities, D12, of toluene and benzene in supercritical carbon dioxide were measured in the temperature range of 306.15–320.15 K, and pressure range of 7.5–17 MPa to evaluate the setup and experimental protocol. The effects of flow velocity, volume of the cell, absorbance at different wavenumbers on the diffusion coefficient as well as all parameters respecting the Taylor dispersion method have been analyzed. The obtained diffusion coefficients are in excellent agreement with the available literature data. The dependence of D12 on temperature, pressure, and solvent density were examined. Some correlation models based on the hydrodynamic theory were used to estimate the diffusion coefficients in supercritical carbon dioxide, which is the best agreement obtained for an improved version of the Wilke–Chang model.

Diffusion coefficient of carbon dioxide in relation to partial pressure of carbon dioxide as a marker for weaning from high-frequency oscillatory ventilation

Background Respiratory distress syndrome and transient tachypnea of newborn are common causes for admission to neonatal ICU. Measurement of diffusion coefficient of carbon dioxide (DCO2) and partial pressure of carbon dioxide in arterial blood (PaCO2) are useful to detect changes in alveolar ventilation, pulmonary perfusion, and CO2 production and help adjust ventilation settings. Aim Our study evaluated DCO2 in relation to PaCO2 as a maker for weaning from high-frequency oscillatory ventilation (HFOV). Patients and methods A total of 40 neonates were included in the study and were divided into two equal groups based on their gestational age (preterm vs. full term), and we measured DCO2 and PaCO2 in both groups at the time of shifting to HFOV and every 4 h till weaning from HFOV. Results The mean value of DCO2 was significantly higher in the full-term group, and there was no statistically significant difference between both studied groups regarding the mean value of PaCO2, except on the third day and at the time of weaning to conventional mechanical ventilation, where it was significantly higher in the preterm group. There was a significant negative correlation between mean value of DCO2 and mean value of PaCO2 on the first, second, and third day of HFOV and at the time of weaning to conventional mechanical ventilation. Conclusion DCO2 can be used roughly as a reflection for CO2 status but cannot be used alone as an indicator for weaning from HFOV but could be used in combination with other markers.

Analysis on the diffusion and mechanical properties of eucalyptus dried via supercritical carbon dioxide

Using the molecular dynamics software Materials Studio, a micro-level carbon dioxide – cellulose model was established to study the supercritical carbon dioxide drying of eucalyptus wood. The change of the primary components of the eucalyptus wood cellulose were also studied, by simulating various pressures, i.e., 10, 15, 20, 25, and 30 Pa, and simulating a temperature of 323 K. Results showed that the diffusion coefficient of carbon dioxide decreases as the pressure increases, and it reaches the maximum at 20 Pa, which was confirmed by the number of hydrogen bonds in the carbon dioxide cellulose model. Combined with the comprehensive analysis of the mechanical parameters, the Poisson’s ratio γ and the ratio of bulk modulus to shear modulus (K/G) values of cellulose first increased and then decreased as the pressure increased, and the Young’s modulus increased as the pressure increased. From a microscopic point of view, the study shows that eucalyptus cellulose has good mechanical properties when dried by supercritical carbon dioxide under a pressure of 20 Pa. The simulation results of the dynamic model agreed well with the measured results, and the simulation results support the previous experimental data and the practical application results in production.

Modeling and Experiment for the Diffusion Coefficient of Subcritical Carbon Dioxide in Poly(methyl methacrylate) to Predict Gas Sorption and Desorption.

Several researchers have investigated the phenomenon of polymer–gas mixtures, and a few have proposed diffusion coefficient values instead of a diffusion coefficient model. There is a paucity of studies focused on the continuous change in the diffusion coefficient corresponding to the overall pressure and temperature range of the mixture. In this study, the gas sorption and desorption experiments of poly(methyl methacrylate) (PMMA) were conducted via solid-state batch foaming, and the weight change was measured using the gravimetric method with a magnetic balance. The control parameters were temperature, which ranged from 290 to 370 K, and pressure, which ranged from 2 to 5 MPa in the subcritical regime. Based on the experimental data, the diffusion coefficient of the PMMA was calculated using Fick’s law. After calculating the diffusion coefficient in the range of the experiment, the diffusion coefficient model was employed using the least-squares method. Subsequently, the model was validated by comparing the obtained results with those in the literature, and the overall trend was found to be consistent. Therefore, it was confirmed that there were slight differences between the diffusion coefficient obtained using only Fick’s equation and the value using by a different method.

Simplified diffusion model of gas hydrate formation from ice

A kinetic model of gas hydrate formation from ice is presented. This model takes into account that the kinetics of gas hydrate formation from ice is limited only by the rate of diffusion of the gas through the gas hydrate layer. The problems of gas hydrate formation from a spherical ice particle, gas hydrate formation from a flat ice layer, and gas hydrate formation from cylindrical ice are considered separately. For each of these problems, a solution in the framework of a quasi-stationary approximation is obtained. The calculated data are compared with available experimental data on the kinetics of formation of methane hydrate and carbon dioxide hydrate from ice powder. From this comparison, the temperature dependence of the molecular diffusion coefficient of methane in methane hydrate and the temperature dependence of the molecular diffusion coefficient of carbon dioxide in carbon dioxide hydrate were determined: DCH4[m2s−1]=exp(−12.8−6242/T[K]) and DCO2[m2s−1]=exp(−30.0−1179/T[K]). In addition, from this comparison, it was found that the porous structure is absent in the volume of gas hydrate formed from ice. Taking into account the determined temperature dependence of the molecular diffusion coefficient of methane in methane hydrate, it is found that methane hydrate formation from ice proceeds more intensively the closer the temperature is to the quadruple point temperature and the higher the methane pressure is.

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

Several direct or indirect approaches have been proposed to measure diffusion coefficient of gases into liquids. The main complexity of indirect techniques such as pressure decay method is interpreting early pressure–time data which strongly affected by incubation period effect or convective instability. In the current approach, accurate apparatus and precise experimental setup including a high pressure and temperature PVT cell, a high precision Sanchez pump, heating and recording sub-system are implemented and a novel data analysis procedure is applied to modify pressure decay method. The effect of incubation period is reduced remarkably and diffusion coefficient of carbon dioxide in water in wide range of pressures and temperatures is determined and the effects of temperature, pressure and carbon dioxide phase alteration from gas to supercritical are investigated and the value of uncertainty is estimated. Furthermore, diffusion coefficient of CO 2 and methane in an oil sample from one of the Iranian southwest oil formations is determined precisely using the experimental approach while no incubation period is detected. The results showed that incubation period duration decreases with increasing diffusion coefficient. Additionally, when CO 2 state is gas, rate of increasing diffusion coefficient with pressure is decreased with temperature and when CO 2 state is supercritical, the rate of increasing diffusion coefficient with pressure is decreased significantly.

Carbonation reaction of strontium oxide for thermochemical energy storage and CO2 removal applications: Kinetic study and reactor performance prediction

CO2 removal in carbon capture and storage and potential of thermochemical energy storage are two main features of strontium oxide (SrO) carbonation reaction. To facilitate the simulation of a reactor for the energy storage and CO2 capture applications utilizing this reaction, it is critical to determine its kinetics. Thus, in this research, kinetic study of this non-catalytic gas-solid reaction considering bulk flow effect was investigated, for the first time, using the random pore model. In order to estimate the degree of the reaction and determine the reaction rate constant, activation energy, and diffusion coefficient of carbon dioxide in the product layer, a series of experiments was conducted within the temperature range of 800 °C–1000 °C and CO2 concentrations of 5 vol% to 40 vol% using a thermogravimeter analyzer. It was concluded that the order of the reaction was fractional (approximately first order). Further, the activation energy of inherent rate constants was estimated to be 64 kJ/mol. Furthermore, comparison of the predicted conversion-time profiles from the random pore model with experimental data revealed a good agreement. Besides, the diffusion coefficients of CO2 in the product layer were estimated at various temperatures using the best fit between experimental and simulation conversions. Also, prediction of a packed bed reactor performance for SrO carbonation was accomplished by the obtained kinetic parameters. Finally, the cycling study was performed and the residual conversions of SrO at 1000 and 1050 °C after 20 successive cycles were determined as 0.32 and 0.15, respectively.

Experimental study and modelling on diffusion coefficient of CO2 in water

One of the important ways to capture CO2 is to inject it into the (sub) surface water. This study focuses on laboratory measurements and modelling to find diffusion coefficient of CO2 into water and obtain dissolution rate during CO2 injection/flooding in the reservoir. Experiments were conducted in a precisionist Sanchez PVT-cell. Effective parameters on the diffusion coefficient were studied including temperature, injection pressure, and phase alteration of carbon dioxide. Diffusive transfers at pressures up to 18533 kPa and temperature range of 298 K–353 K were observed. The results revealed that at constant pressure of 5800 kPa, diffusion coefficient of carbon dioxide in water increases with increasing temperature. Likewise, at constant temperature of 298 K and 323 K, diffusion coefficient raised with growth of injection pressure. In addition, consideration of carbon dioxide phase alteration from gas to supercritical illustrated substantial drop of diffusion coefficient. Meanwhile, pressure decay method for finding the diffusion coefficient was modified which led to significant reduction of experiment duration and more accuracy of results by omitting source of errors.

Sorption and Diffusion of Methane and Carbon Dioxide in Amorphous Poly(alkyl acrylates): A Molecular Simulation Study.

Molecular simulations were carried out to understand the structural features and the sorption and diffusion behavior of methane and carbon dioxide in amorphous poly(alkyl acrylates) in the temperature range of 300-600 K. The hybrid Monte Carlo/molecular dynamics approach was employed to address the effects of polymer swelling and framework flexibility on the gas sorption. Simulations show that the glass-transition temperature decreases with the side-chain length of poly(alkyl acrylate), consistent with experiments. This is due to the fact that the shielding of the polar ester groups increases with the side-chain length. The simulated sorption isotherms for methane and carbon dioxide were in agreement with the experimental data. The polymer swelling becomes more pronounced, especially in the case of sorption of carbon dioxide. A significant swelling occurs, possibly because of the greater interaction between carbon dioxide and the polar ester groups in the polymers. The uptake of methane and carbon dioxide by poly(alkyl acrylates) generally increases with the side-chain length. Our simulations confirm the experimental findings that the diffusion coefficients of methane and carbon dioxide in poly(alkyl acrylates) increase with the side-chain length. Interestingly, the activation energies of gas diffusion decrease with the side-chain length. The diffusion coefficients of the penetrants have an exponential relationship with the void fraction, which is in agreement with the free volume theory.

Estimating CO2-Brine diffusivity using hybrid models of ANFIS and evolutionary algorithms

One of the important parameters illustrating the mass transfer process is the diffusion coefficient of carbon dioxide which has a great impact on carbon dioxide storage in marine ecosystems, saline aquifers, and depleted reservoirs. Due to the complex interpretation approaches and special laboratory equipment for measurement of carbon dioxide-brine system diffusivity, the computational and mathematical methods are preferred. In this paper, the adaptive neuro-fuzzy inference system (ANFIS) is coupled with five different evolutionary algorithms for predicting the diffusivity coefficient of carbon dioxide. The R2 values forthe testing phase are 0.9978, 0.9932, 0.9854, 0.9738 and 0.9514 for ANFIS optimized by particle swarm optimization (PSO), genetic algorithms (GA), ant colony optimization (ACO), backpropagation (BP), and differential evolution (DE), respectively. The hybrid machine learning model of ANFIS-PSO outperforms the other models.

Diffusion coefficients of carbon dioxide—ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) system at temperatures of 313 K and 323 K and pressures of 5 MPa and 8 MPa

This work reports the mutual diffusion coefficients of carbon dioxide - 1-Butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) system at different temperatures (313.15 and 323.15 K) and pressures (5 and 8 MPa). We have determined the time-dependent solubility of carbon dioxide in the ionic liquid and then, fit a computational fluid dynamics (CFD) model to the experimental data to obtain the diffusion coefficients. The increase in the molar density and the expansion of the liquid phase during the dissolution of carbon dioxide are taken into account in the transport model. The results show that the mutual diffusion coefficients increase with carbon dioxide mole fraction and the values obtained at thermodynamic phase equilibrium compare well with those calculated using different correlations.

Measurement and modeling of solubilities and diffusion coefficients of carbon dioxide in poly(ethylene-co-acrylic acid)

We measured and modeled the solubilities and diffusion coefficients of carbon dioxide (CO2) in poly(ethylene-co-acrylic acid) (PEAA) over temperatures of 373–473 K and pressures of up to 20 MPa. The measured solubilities of CO2 in PEAA obeyed Henry’s law and decreased with an increase in the acrylic acid content of the copolymer. The Sanchez-Lacombe equation of state could be applied to correlate the measured solubilities. The temperature dependence of the CO2 solubilities in PEAA was found to be similar to that in polyethylene with analysis using Henry’s law. Further, the gas solubility and acrylic acid content were the influential factors for determining the diffusivity of CO2, which could be modeled based on the free volume theory.

Solubilities and diffusion coefficients of carbon dioxide and nitrogen in poly(methyl methacrylate) at high temperatures and pressures

The solubilities and diffusion coefficients of carbon dioxide (CO2) and nitrogen (N2) in poly(methyl methacrylate) (PMMA) were studied at temperatures of 373 K–473 K and pressures of up to 20 MPa. The solubilities and diffusivities were measured by the gravimetric method using a magnetic suspension balance. The dissolution of CO2 and N2 in PMMA obeyed Henry’s law, with the solubilities of the two gases exhibiting different temperature dependences. Further, the solubility data could be fitted using the Sanchez–Lacombe equation of state. The Henry’s constants for the dissolution of the gases in PMMA indicated that their temperature dependences were similar to those of the gases in polystyrene. Finally, the diffusion coefficients of CO2 and N2 with model analysis suggested that, for both gases, the solubility has a determining effect on the diffusivity. The diffusion coefficients of both gases could be described using the free volume theory.

Mathematical modelling of pore formation in polymers using supercritical fluid media in the Ornstein-Zernike approximation

The paper studies the process of pore formation using supercritical fluid media. A mathematical model of pore formation in polymers in the process of supercritical carbon dioxide decompression has been developed, taking into account fluctuations in the Ornstein-Zernike approximation based on Patel-Teja cubic equation. Calculations and comparison with experimental data are given on the example of pore formation in polystyrene, which showed satisfactory agreement of the theory with experiment. Parameters of the Lennard-Jones pair interaction potential for carbon dioxide in the carbon dioxide-polystyrene system were obtained. The diffusion coefficient of supercritical carbon dioxide in a polymer takes on a different value than the coefficient of self-diffusion of pure carbon dioxide under the same thermodynamic conditions due to a change in the Lenard-Jones potential profile in a polymeric medium. The obtained values of the parameters of the Lennard-Jones equation, namely, the parameters of the intermolecular interaction potential and the maximum value of the attraction energy, make it possible to adequately estimate the value of the diffusion coefficient under given thermodynamic conditions.