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1.
A comprehensive two‐dimensional mathematical model based on surface renewal theory has been developed to analyze the CO 2 absorption into piperazine (PZ)‐activated aqueous N‐methyldiethanolamine (MDEA) solvent by taking into account the structured packed bed column hydraulics, mass transfer resistances, and chemical reactions. The modeling results have been validated with the experimental data reported in the literature, and they have been found to be in good agreement with the experimental results. The effects of amine concentration, liquid temperature, initial CO 2 partial pressure, liquid flow rate, and CO 2 loading on the mass transfer performance have been evaluated in terms of overall mass transfer coefficient ( K Ga v). The overall mass transfer coefficient and absorption flux of CO 2 into aqueous MDEA+PZ blended solution have been calculated over the CO 2 partial pressure range of 4–16 kPa, temperature range of 298–333 K, and solvent concentration of 1–3 M. To evaluate the performance of different solvents on separation process, some common industrial chemical absorbents including monoethanolamine (MEA), diethanolamine (DEA), triethylamine (TEA), MDEA and PZ were compared with a MDEA+PZ blended solution. The results indicate that CO 2 absorption reaction with PZ is faster than that with MDEA, but also adding small amounts of PZ as a promoter to MDEA solvents improves significantly the absorption rate. The results show that CO 2 absorption reaction with the MDEA+PZ blended solution is faster than that with TEA and MDEA, also comparable with DEA, but slower than those with MEA and PZ. The modeling results illustrate that the K Ga v enhances with increasing the solvent concentration, liquid temperature, and liquid flow rate, but reduces with increasing the CO 2 loading and initial CO 2 partial pressure. In addition, the reaction kinetics in terms of enhancement factor was found to decrease as the CO 2 loading enhances and increase as the operating temperature rises. 相似文献
2.
Carbon capture and storage is an important strategy for stabilizing the increasing concentration of atmospheric CO 2 and the global temperature. A possible approach toward reversing this trend and decreasing the atmospheric CO 2 concentration is to remove the CO 2 directly from air (direct air capture). Herein we report a simple aqueous guanidine sorbent that captures CO 2 from ambient air and binds it as a crystalline carbonate salt by guanidinium hydrogen bonding. The resulting solid has very low aqueous solubility ( K sp=1.0(4)×10 −8), which facilitates its separation from solution by filtration. The bound CO 2 can be released by relatively mild heating of the crystals at 80–120 °C, which regenerates the guanidine sorbent quantitatively. Thus, this crystallization‐based approach to CO 2 separation from air requires minimal energy and chemical input, and offers the prospect for low‐cost direct air capture technologies. 相似文献
3.
The dependent relation between temperature and pressure of supercritical CO 2+ ethanol binary system under the pressure range from 5 to 10 MPa with the variety of densities and mole fractions of ethanol
that range from 0 to 2% was investigated by the static visual method in a constant volume. The critical temperature and pressure
were experimentally determined simultaneously. The PTρ figures at different ethanol contents were described based on the determined pressure and temperature data, from which pressure
of supercritical CO 2 + ethanol binary system was found to increase linearly with the increasing temperature. P-T lines show certain convergent feature in a specific concentration of ethanol and the convergent points shift to the region
of higher temperature and pressure with the increasing ethanol compositions. Furthermore, the effect of density and ethanol
concentration on the critical point of CO 2 + ethanol binary system was discussed in details. Critical points increase linearly with the increasing mole fraction of
ethanol in specific density and critical points change at different densities. The critical compressibility factors Z c of supercritical CO 2 + ethanol binary systems at different compositions of ethanol were calculated and Z
c
-ρ figure was obtained accordingly. It was found from Z
c
-ρ figure that critical compressibility factors of supercritical CO 2 unitary or binary systems decline linearly with the increasing density, by which the critical point can be predicted precisely. 相似文献
4.
The effect of dissolved carbon dioxide on the glass transition temperature of a polymer, PMMA, has been investigated using molecular probe chromatography. The probe solute was iso-octane, and the specific retention volumes of this solute in pure PMMA and mixtures of PMMA with CO 2 were measured over a temperature range of 0 to 180°C and CO 2 pressures from 1 to 75 atm. The amount of CO 2 dissolved in the polymer was calculated from a model fit to previously published solubility data determined chromatographically. Classical van't Hoff-type plots were used to determine the glass transition temperature of CO 2-impregnated PMMA from low pressure up to 46 atm of CO 2. Solvent-induced plasticization was observed with the glass transition temperature decreasing by about 40°C. At some pressures, glass transitions at low temperatures could not be determined from the van't Hoff plots because of the proximity of the polymer glass transition temperature to the gas–liquid transition temperature for CO 2. For these pressures, a new method was developed to determine the glass transition composition. The glass transition pressure was then calculated from the measured composition and temperature using an isotherm model. In every case, the glass transition temperature decreased linearly with increasing concentration of CO 2 in the polymer. However, at higher compositions, the glass transition pressure decreased with increasing composition and decreasing temperature. The observed retention volume of iso-octane with PMMA in a glassy state was correlated with an adsorption model developed from a theory for liquid–solid chromatography derived by Martire. This model accurately described the observed decrease in retention of iso-octane by adsorption on the surface of glassy PMMA with increasing concentration of CO 2 dissolved in the polymer. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2537–2549, 1998 相似文献
5.
The new data for solubility of carbon dioxide are reported in mixed solvents containing (2.00 to 2.50 kmol/m 3) Diisopropanolamine (DIPA), (0.86 to 1.36) kmol/m 3) Piperazine (PZ), (0.86 to 1.36) kmol/m 3) N‐methyldiethanolamine (MDEA) and water, keeping the amine total concentration in the aqueous solution at 3.36 kmol/m 3 for temperatures from (40 to 70) °C and CO 2 partial pressures in the range of (30 to 5000) kPa. Experimental solubility results were represented by the mole ratio of CO 2 per total amine in the liquid mixture. Results show that at a given partial pressure of CO 2 the solubility of CO 2 in the DIPA solutions is lower than solubility in MDEA or PZ solutions and the CO 2 loading increased with decreasing temperature and increasing CO 2 partial pressure. 相似文献
6.
Here the authors developed a two-dimensional two-temperature chemical non-equilibrium (2T-NCE) model of Ar–CO 2–H 2 inductively coupled thermal plasmas (ICTP) around atmospheric pressure (760 torr). Assuming 22 different particles in this
model and by solving mass conservation equations for each particle, considering diffusion, convection and net production terms
resulting from 198 chemical reactions, chemical non-equilibrium effects were taken into account. Species density of each particle
or simply particle composition was also derived from the mass conservation equation of each one taking the non chemical equilibrium
effect into account. Transport and thermodynamic properties of Ar–CO 2–H 2 thermal plasmas were self-consistently calculated using the first order approximation of the Chapman–Enskog method at each
iteration point implementing the local particle composition and temperature. Calculations at reduced pressure (500 and 300 torr)
were also done to investigate the effect of pressure on non-equilibrium condition. Results obtained by the present model were
compared with results from one temperature chemical equilibrium (1T-CE) model, one-temperature chemically non equilibrium
(1T-NCE) model and finally with 2T-NCE model of Ar–N 2–H 2 plasmas. Investigation shows that consideration of non-chemical equilibrium causes the plasma volume radially wider than
CE model due to particle diffusion. At low pressure with same input power, presence of diffusion is relatively stronger than
at high pressure. Comparison of present reactive model with non-reactive Ar–N 2–H 2 plasmas shows that maximum temperature reaches higher in reactive C–H–O molecular system than non-reactive plasmas due to
extra contribution of reaction heat. 相似文献
7.
A four-armed anionic star-shaped block polymer, containing an anionic polymer poly(2-Acrylamido-2-methylpropanesulfonic acid) (PAMPS) as the core group and poly(2-(Dimethylamino)ethyl methacrylate) (PDM) as the terminal group, was synthesized by using the Atom Transfer Radical Polymerization (ATRP) method. The (PAMPS 50-PDM 50) 4 aqueous solution exhibited both polyelectrolyte and hydrophobic associative characteristics, that is, a low concentration of NaCl results in decreasing viscosity but a high concentration of NaCl results in increasing viscosity. The four-armed anionic block polymer shows a CO 2-reversible property at high concentrations of brine. Viscosity, pH, and ζ potential demonstrate the switchability jointly; the values could be switched from relatively low to high cyclically. These transitions could actually be attributed to the protonation of tertiary amine groups in PDM blocks, and the mechanism was proved by 1H NMR. 相似文献
8.
The density of the LiF-Li 2CO 3 melts system was measured using the Archimedean method. Using the quadratic regression orthogonal design with two factors, a regression equation for the density of LiF-Li 2CO 3 melts was obtained in which the concentration of LiF and temperature were considered. The results indicated that the density of the LiF-Li 2CO 3 melts decreased with either increasing the concentration of LiF or increasing temperature; a linear relation was observed between density and temperature. In addition, the influences of NaF, KF, NaCl, and KCl additives on the densities of the given systems were studied. The addition of NaF and KF increased the density of the melts, whereas NaCl and KCl resulted in an initial increase and subsequent decrease with an increasing additive concentration. The density attained a maximum at NaCl and KCl mass fraction of approximately 15%. 相似文献
9.
Adsorption separation of carbon dioxide from nitrogen at different system total pressures with silicalite as the adsorbent was studied by using concentration pulse chromatography. Improving the methodology for determining binary adsorption isotherms by concentration pulse method (CPM) was also the goal of this study. Binary adsorption isotherms, x–y phase diagrams and separation factor plots have been determined at 26 °C to look at the influence of pressure on the separation using concentration pulse chromatography. Available methods for determining binary adsorption isotherms using CPM have been reviewed and shown to be incapable of interpreting this particular binary system. An improved novel model has been proposed to interpret the data in this study. It has been referred to as the Kennedy-Tezel concentration pulse method (KT-CPM) and has been shown to be superior to other methods used in the literature. Results using this data were found to be consistent with the previous results in the literature. The binary isotherms for the CO 2–N 2 system show a decrease in CO 2 selectivity as total system pressure increases. The optimal separation factor for silicalite was found to increase with decreasing system pressure and decreasing mole fraction of CO 2 in the feed mixture. 相似文献
10.
Cross-linked poly(methyl methacrylate) particles were prepared via dispersion polymerization in supercritical carbon dioxide
(scCO 2) using poly(heptadecafluorodecyl methacrylate) (PHDFDMA) and 2,2′-azobisisobutyronitrile as the dispersant and the initiator,
respectively. The following chemicals were used as cross-linking agents: ethylene glycol dimethacrylate (EGDMA), 1,4-buthanediol
di(meth)acrylate (1,4-BD(M)A), and trimethylolpropane trimethacrylate. PHDFDMA was synthesized by solution polymerization
in scCO 2. We investigated the effect of the chemical structure, concentration of the cross-linking agents, reaction pressure, and
CO 2 density on the morphology, the polydispersity, and the cross-linking density of polymer particles. The resulting polymer
particle was characterized by field emission SEM, differential scanning calorimetry, and thermal gravimetric analysis. The
cross-linked PMMA particles is more agglomerate as the cross-linking agent concentration increased and as pressure decreased
at constant temperature. Glass-transition temperature ( T
g) of the resulting polymer increased as the cross-linking agent increased with temperature and pressure increasing at the
same CO 2 density. Decomposition temperature is slightly increased as 1,4-BDA concentration increased. From these results, we can confirm
that the thermal stability of the polymer increased as the cross-linking agent and EGDMA is the best cross-linking agent in
term of the thermal stability. 相似文献
11.
In this paper, ascorbic acid as a new carbon dioxide (CO 2) absorbent was investigated. The equilibrium solubility of CO 2 into 0.5, 1 and 1.5 mol dm −3 (M) aqueous ascorbic acid solutions were measured experimentally with a stirred batch reactor at total atmospheric pressure over the CO 2 partial pressure ranging from 0 to 45 kPa and temperatures between 298 and 313 K. The results of the gas solubility are presented as loading capacity (mol CO 2/mol ascorbic acid) as function of partial pressure of CO 2 for all experimental runs. Experimental results showed that solubility of CO 2 increases with increase in molar concentration of ascorbic acid solution at a given temperature and decreases with increase in temperature at a given concentration. The densities and viscosities of the ascorbic acid solutions were measured at the same conditions of the solubility measurement. Some corrosion rate tests were also performed on carbon steel at temperature of 308 K. It was observed that viscosity and corrosion rate increase when the molar concentration of ascorbic acid solution increases. 相似文献
12.
This paper investigated the solubility of carbon dioxide (CO 2) in an aqueous solution of monoethanolamine (MEA) and 1-butyl-3-methylimidazolium dibutylphosphate ((BMIM)(DBP)) ionic liquid (IL) hybrid solvents. Aqueous solutions of MEA-(BMIM)(DBP) hybrid solvents containing different concentrations of (BMIM)(DBP) were prepared to exploit the amine’s reactive nature, combined with the IL’s non-volatile nature for CO 2 absorption. Response surface methodology (RSM) based on central composite design (CCD) was used to design the CO 2 solubility experiments and to investigate the effects of three independent factors on the solubility of CO 2 in the aqueous MEA-(BMIM)(DBP) hybrid solvent. The three independent factors were the concentration of (BMIM)(DBP) (0–20 wt.%), temperature (30 °C–60 °C) and pressure of CO 2 (2–30 bar). The experimental data were fitted to a quadratic model with a coefficient of determination ( R2) value of 0.9791. The accuracy of the developed model was confirmed through additional experiments where the experimental values were found to be within the 95% confidence interval. From the RSM-generated model, the optimum conditions for CO 2 absorption in aqueous 30 wt% MEA-(BMIM)(DBP) were 20 wt% of (BMIM)(DBP), a temperature of 41.1 °C and a pressure of 30 bar. 相似文献
13.
The equilibrium of CO 2 and carbamate concentration data for the absorption of CO 2 in aqueous solutions of single and mixed amines was analyzed using the Deshmukh–Mather model. Data on CO 2 loading in aqueous solutions of DEA and MDEA and their mixtures at various temperature (303–323 K) and CO 2 partial pressure (0.09–100 kPa) together with carbamate concentrations in case of DEA and its mixtures with MDEA were fitted simultaneously to generate the different interaction parameters required to calculate the activity coefficients in the model. Using the generated interaction parameters, the model was applied to correlate the CO 2 loading in solutions of DEA and MDEA and their mixtures reported in the literature as well as those obtained in our laboratory and was found to be able to give a good estimation of CO 2 loading and carbamate concentration over a wide range of operating conditions in both single and mixed amine solutions. 相似文献
14.
The solubility and diffusion coefficient of carbon dioxide in intermediate‐moisture starch–water mixtures were determined both experimentally and theoretically at elevated pressures up to 16 MPa at 50 °C. A high‐pressure decay sorption system was assembled to measure the equilibrium CO 2 mass uptake by the starch–water system. The experimentally measured solubilities accounted for the estimated swollen volume by Sanchez–Lacombe equation of state (S‐L EOS) were found to increase almost linearly with pressure, yielding 4.0 g CO 2/g starch–water system at 16 MPa. Moreover, CO 2 solubilities above 5 MPa displayed a solubility increase, which was not contributed by the water fraction in the starch–water mixture. The solubilities, however, showed no dependence on the degree of gelatinization (DG) of starch. The diffusion coefficient of CO 2 was found to increase with concentration of dissolved CO 2, which is pressure‐dependent, and decrease with increasing DG in the range of 50–100%. A free‐volume‐based diffusion model proposed by Areerat was employed to predict the CO 2 diffusivity in terms of pressure, temperature, and the concentration of dissolved CO 2. S‐L EOS was once more used to determine the specific free volume of the mixture system. The predicted diffusion coefficients showed to correlate well with the measured values for all starch–water mixtures. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 607–621, 2006 相似文献
15.
The phase behavior of a system of importance for the hydroformylation reaction of 1-hexene in supercritical CO 2 has been studied in the range of 303.2–348.2 K with different CO 2 mole fractions. The conversion of 1-hexene varies from 0 to 1. The density of the reaction mixture at different conditions are also determined. It is demonstrated that the phase behavior changes with conversion of 1-hexene. At zero conversion, the phase separation pressure increases with increasing concentration of the reactants in the reaction system and decreases slightly with the increase of temperature. At other conversions, the phase separation pressure increases as temperature rises. The density of the reaction mixture at phase separation point is higher at the larger conversions. 相似文献
16.
Electrochemical reduction of CO 2 at metal- meso-tetraphenylporphyrin (TPP) supported gas diffusion electrodes (GDEs) under CO 2 at atmospheric pressure and 20 atm was carried out. At Co- and Fe-TPP supported GDEs that are comparatively active in the electrochemical reduction of CO 2 under atmospheric CO 2, the current efficiencies for the reduction of CO 2 increased up to 97.4 and 84.6%, respectively, by an increase in CO 2 pressure. At Cu- and Zn-TPP supported GDEs that showed low activity under atmospheric CO 2, the current efficiencies for CO 2 reduction increased up to 50.5 and 65.8%, respectively, under 20 atm CO 2. At these active metal-TPP supported GDEs, the potential of CO 2 reduction shifted positively by an increase in CO 2 pressure. These results indicate that the increase in concentration of CO 2 in the electrolyte solution caused by high pressure enhanced the electrocatalytic activity of metal-TPPs for CO 2 reduction. 相似文献
17.
CO 2 capture by aqueous alkanolamines treating is one of the prevalent methods to reduce carbon dioxide emissions and to help environmental problems. For realizing more the thermodynamics of the CO 2–MDEA–H 2O, the PC-SAFT equation of state was used to simulate the absorption of carbon dioxide by MDEA (methyldiethanolamine). A correlation for temperature-dependent binary interaction parameter were calculated by excess enthalpy data for aqueous MDEA at low temperatures (lower than 350 K), and then this binary interaction parameter used to predict phase equilibria of ternary aqueous mixtures of MDEA with carbon dioxide. Smith–Missen algorithm and PC-SAFT EOS have been used to determine concentration of species in chemical equilibrium and physical equilibrium, respectively. In addition, for determining parameter sets of MDEA, vapor pressure and saturated liquid density data were used and different and probable association schemes were considered in parameter estimations. Results show 4(2:2, 0:0) association scheme for MDEA and 4(2:2) association scheme for water have better agreement with binary and ternary VLE experimental data. 相似文献
18.
In this paper, experimental physical properties such as density, refractive index, and viscosity of aqueous potassium l-prolinate (KPr) as a solvent for CO 2 capture were investigated. Different concentrations of aqueous KPr in terms of mass fractions (0.05, 0.10, 0.20, 0.30, and 0.40) were studied over a temperature range 298.15–343.15 K. The obtained results showed that all physical properties increase with increasing the concentration of the solution (isothermally), and decrease as the solution temperature rises for any given concentration. The experimental data of density, refractive index, and viscosity were correlated using empirical correlations as a function of both, temperature and concentration. Coefficient of thermal expansion and activation energy were calculated from the experimental density and viscosity data, respectively, in the same temperature range. Thermal expansion coefficient slightly increases with increase in the temperature and concentration, while activation energy increases with the rise in concentration of amino acid salt. 相似文献
19.
This study aimed to investigate CO2 absorption using chemical solvent of amine H2O-TEA-CO2 in presence of activated carbon (AC) particles. The studied experimental range includes the temperature in range of 293–333 K, pressure in range of 3.5–9.5 bar, the concentration of solvents in range of 2.5–8.5 wt%, and amount of activated carbon in range of 0.3–0.9 kg/m3. The central composite design (CCD) with four parameters of temperature, pressure, amine concentration, and active carbon was applied in 5 levels. The physical solubility CO2 in amine solutions decreases with the increasing temperature that indicates the process is exothermic. The optimal values of temperature, pressure, concentration, and active carbon are 303.0 K, 8.00 bar, 7.00 M, 0.75 g, respectively, and 25.99% for the input variables and desirability index of 0.732. The CO2 loading, absorption capacity, and absorption percentage are obtained in the range of 0.572–1.180 molCO2/molTEA, 0.208–0.506 wt%, and 12.73–32.61% in Triethanolamine (TEA) solutions in activated carbon, respectively. All dependent variables had a p value of less than 0.05, indicating that models were significant and substantial. The result showed that the addition of solid particles to chemical solvents effectively enhances CO2 absorption. 相似文献
20.
In the literature, aqueous 2-((2-aminoethyl)amino) ethanol (AEEA) is identified as a promising solvent for postcombustion CO 2 capture. In this work, the kinetics of CO 2 absorption in the aqueous AEEA, containing a primary and a secondary amino group, is studied over a wide temperature range of 303.15-343.15 K and the amine concentration in the range of 0.47-2.89 M using the fall-in-pressure technique in a stirred cell reaction calorimeter setup with a horizontal gas-liquid interface. The overall rate constants for (AEEA + H 2O + CO 2) reaction system are estimated in the pseudo–first-order reaction regime. The kinetic models based on zwitterion and the termolecular reaction mechanisms are used to predict kinetic rate constants. The experimental kinetic data are better correlated using the zwitterion mechanism (AAD 9.18%) than that of the termolecular mechanism (AAD 10.4%). The density, viscosity, and physical solubility of pure components and aqueous binary mixtures of AEEA are also measured at the similar temperature and concentration ranges of rate kinetics. Empirical models are proposed to predict pure component density and viscosity data with AAD of 0.02% and 7.17%, respectively. The Redlich-Kister model, the Grunberg-Nissan model, and the O'Connell's model are used to correlate experimental density, viscosity, and physical solubility data of the binary mixtures with AAD of 0.034%, 4.92%, and 6.5%, respectively. The reaction activation energy ( Ea ∼ 32 kJ/mol) of the (AEEA + H 2O + CO 2) system is calculated from the Arrhenius power-law model using the zwitterion mechanism, which indicates lower energy barrier than that of the reported value for monoethanolamine (∼44 kJ/mol) in the literature. 相似文献
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