CO2 Absorption Properties Research Articles

Two Different Pathways from CO2 to HCO3− in Aqueous Solutions of Arginine Sodium Salt

AbstractAmino acids and their salts are amine compounds with great potential for the chemical absorption of CO2 via the amine method. The CO2 absorption properties of various amino acids and their salts have been previously reported. However, the detailed reaction mechanism of CO2 with basic amino acids in aqueous solutions has not yet been clarified. In this study, we focused on arginine (Arg), which has the highest basicity among the standard amino acids, and its monohydrochloride (ArgCl) and sodium (NaArg) salts for the dissolution of CO2 in the aqueous solutions of Arg, ArgCl, and NaArg. CO2 was chemically dissolved in aqueous Arg and NaArg solutions but not in the aqueous ArgCl solution. One‐dimensional 1H and 13C and two‐dimensional 1H‐13C heteronuclear multiple bond correlation nuclear magnetic resonance spectroscopy indicated that the final products in the aqueous Arg and NaArg solutions were protonated Arg and HCO3−. HCO3− was formed from both CO2‐bonded Arg/Arg− and CO32− intermediates in the aqueous NaArg solution but only from the CO2‐bonded Arg/Arg− intermediate in the aqueous Arg solution. In addition to their high environmental and biological compatibility, Arg and NaArg exhibit high CO2 absorption capacity, demonstrating their potential for practical use as naturally derived CO2 chemical absorbents.

Study on CO2 absorption by EmimCl-MEA deep eutectic solvent in microchannel

Carbon dioxide (CO2) is widely acknowledged as the primary contributor to the greenhouse effect. Microchannel reactors can be used for enhancing chemical processes, solving the problems of limited gas-liquid mass transfer, and have significant advantages in CO2 capture. In this study, the deep eutectic solvent (DES) prepared by mixing ionic liquid (1-ethyl-3-methylimidazolium chloride, EmimCl) and Ethanolamine (MEA) in a molar ratio of 1:1 was selected for CO2 capture in a microchannel. The structure and physical properties of the DES were investigated, and the effects of gas and liquid flow rates, water content, and CO2 concentration on the CO2 absorption properties were analyzed. The increase of the water content not only significantly reduces the viscosity of DES, but also improves the CO2 absorption performance. In addition, the CO2 absorption mechanism of this DES has been obtained by the NMR spectrum, showing that the absorption process is a rapid chemical absorption process between CO2 and MEA. The Cl- of EmimCl could stabilize the protonated amine and prevent it from further reacting with MEACO2-, furthermore increasing the CO2 absorption rate.

Excess properties and intermolecular interactions of 2-methoxyethanol + ethylenediamine binary system: Density, viscosity, spectral analyses, computational chemistry, and CO2 absorption property

To examine the fundamental physicochemical properties as well as intermolecular interactions for the 2-methoxyethanol (EGME) (1) + ethylenediamine (EDA) (2) binary system, this work systemically measured the density (ρ) and viscosity (η) values of the binary system with various mole ratios at P = 100.5 kPa and T = (298.15–318.15) K with the growth gap of 5 K. The as-measured values of the pure substances were compared with literature data. Multiple semi-empirical formulas were used to fit ρ and η values, and the absolute average deviations (AAD%) were calculated. After that, the excess molar volume (VmE), partial molar volume (V¯), apparent molar volume (Vφ), viscosity deviation (Δη), excess activation of Gibbs free energy (ΔG∗E), and several thermodynamic properties of the binary system were systemically analyzed. According to analysis results, it has been proven that the interaction exists between EGME and EDA molecules. And then, excess properties were fitted to the Redlich-Kister equation using multi-parametric nonlinear regression analyses, and standard deviations (σ) were calculated. In addition, based on various characterization methods including Raman, ultraviolet (UV), and nuclear magnetic resonance hydrogen (1H NMR) spectral analyses and density functional theory (DFT) calculation results, it is demonstrated that there is intermolecular hydrogen bonds in EGME (1) + EDA (2) binary system as the form of –OH⋯NH2–, which was consistent with the existence forms of intermolecular hydrogen bonds in different alcohol-amine systems from references. Finally, CO2 absorption capacity by pure EDA, pure EGME, and the EGME (1) + EDA (2) binary system were severally determined.

Theoretical insight into the chemo-absorption mechanism of amino acid ionic liquids on CO2

Amino acid ionic liquids (AAILs) are acknowledged as potential solvents for CO2 adsorption. However, the mechanism of AAILs adsorbing CO2 has not reached a consensus, which limited the development of high adsorption-performance AAILs. In this work, the mechanism of selected AAILs consisting of 1-Ethyl-3-methylimidazolium ([EMIM]+) cation and amino acids anions ([AA]−) adsorbing CO2 were investigated using density functional theory (DFT) calculations. The nature of the weak interactions between the ionic pairs was found to be hydrogen bonds. The amine group of [AA]− is highly likely to serve as the reactive site to adsorb CO2 with formation of zwitterions. The AAILs-CO2 were discovered to generate carbamic acid through proton transfer in zwitterions. In comparison, the generation of carbamic acid in [EMIM][Gly]-CO2 is a kinetically favorable reaction while in [EMIM][His]-CO2 it is the most thermodynamically favorable, which indicates faster adsorption of CO2 by [EMIM][Gly] and easier adsorption by [EMIM][His]. Furthermore, it was found that the presence of the cation [EMIM]+ weakens the interaction between the amino acid anion and CO2 at different reaction steps. This work revealed the fundamental chemo-absorption mechanism details of AAILs towards CO2, which contributes to rational development of AAILs with optimal CO2 absorption properties.

Excess properties, intermolecular interactions, and CO2 absorption property of ethylene glycol + diethylenetriamine binary solutions

In this work, the density (ρ) and viscosity (η) data of ethylene glycol (EG) + diethylenetriamine (DETA) binary solutions at T = 298.15 K–318.15 K and P = 100.5 kPa are reported. The basic physicochemical data of binary solutions were used to investigate their excess molar volume (VmE), viscosity deviation (Δη), and excess viscous flow activation Gibbs free energy (ΔG*E), which revealed that there was strong intermolecular interaction in the EG (1) + DETA (2) binary solutions. The density values, viscosity values, and excess properties of binary solutions were fitted by parametric models, such as Jouyban-Acree model, McAllister four-body model, and Redlich-Kister (R-K) equation. After that, the binary solutions were spectroscopically analyzed to further discuss their intermolecular interaction. Meanwhile, Raman, UV, and 1H NMR spectra jointly demonstrated the intermolecular hydrogen bonding of the binary solutions as the form of –OH···N(H2)–. Finally, CO2 absorption was carried out to investigate the CO2 absorption property of the binary solutions, which provided reference data for CO2 capture.

Effects of pressure and temperature on CO2 facilitation of amino acid salt-containing membranes for post-combustion carbon capture

Polymeric facilitated transport membranes (FTMs) that contain amino acid salts (AASs) provide a cost-effective option for reducing the CO2 emissions associated with burning fossil fuels. In the current work, we examined the effects of CO2 partial pressure and temperature on the CO2 absorption properties of three AAS mobile carriers, piperazine glycinate (PZ-Gly), 2-(1-piperazinyl)ethylamine glycinate (PZEA-Gly), and 2-(1-piperazinyl)ethylamine sarcosinate (PZEA-Sar), and their facilitation of CO2 transport by employing 13C NMR spectroscopy. The CO2 loading and the distribution of reaction products, i.e., carbamate and bicarbonate products, were analyzed and quantified for each AAS sample. The 13C NMR analysis revealed that PZEA-Sar had a greater CO2 loading and favored the more efficient bicarbonate pathway in comparison to PZ-Gly and PZEA-Gly. In addition, we noted marked differences in the formation of carbamate and bicarbonate products when the CO2 partial pressure and temperature were adjusted. The concentration gradient of the reaction products formed indicated that the diffusion of carbamate products was the most influential factor in CO2 transport under reduced CO2 partial pressure. However, as the partial pressure of CO2 increased, bicarbonate products began to play a more significant role. At elevated temperatures, a lower absorption of CO2 was observed, resulting in the reduced generation of both reaction products. This suggests that the enhanced CO2 permeance of FTMs is mainly attributed to the accelerated diffusion of the reaction products. The findings of this study contribute to a comprehensive understanding of the transport mechanism by which AAS carriers enhance CO2 facilitation, allowing for the refinement of more efficient FTM designs.

Magnetic and microwave absorption properties of Co2+ and Zn2+ co-doped barium hexaferrite nanoparticles

Magnetic and microwave absorption properties of Co2+ and Zn2+ co-doped barium hexaferrite nanoparticles

Enhancement of CO2 absorption and heat transfer properties using amine functionalized magnetic graphene oxide/MDEA nanofluid

Enhancement of CO2 absorption and heat transfer properties using amine functionalized magnetic graphene oxide/MDEA nanofluid

Effect of Low Nesquehonite Addition on the Hydration Product and Pore Structure of Reactive Magnesia Paste.

Reactive magnesia cement is considered an eco-efficient binder due to its low synthesis temperature and CO2 absorption properties. However, the hydration of pure MgO-H2O mixtures cannot produce strong Mg(OH)2 pastes. In this study, nesquehonite (Nes, MgCO3·3H2O) was added to the MgO-H2O system to improve its strength properties, and its hydration products and pore structure were analyzed. The experimental results showed that the hydration product changed from small plate-like Mg(OH)2 crystals to interlaced sheet-like crystals after the addition of a small amount of Nes. The porosity increased from 36.3% to 64.6%, and the total pore surface area increased from 4.6 to 118.5 m2/g. At the same time, most of the pores decreased in size from the micron scale to the nanometer scale, which indicated that Nes had a positive effect on improving the pore structure and enhancing the compressive strength. Combined with an X-ray diffractometer (XRD), a Fourier transform infrared spectrometer (FTIR), and a simultaneous thermal analyzer (TG/DSC), the hydration product of the sample after Nes addition could be described as xMgCO3·Mg(OH)2·yH2O. When Nes was added at 7.87 and 14.35 wt%, the x-values in the chemical formula of the hydration products were 0.025 and 0.048, respectively. These small x-values resulted in lattice and property parameters of the hydration products that were similar to those of Mg(OH)2.

Molecular simulations for improved process modeling of an acid gas removal unit

Reliable process modeling and simulation is required to optimize the design and performance of acid gas removal units, which play a key role in the H2S and CO2 removal from natural gas, and in the CO2 capture from flue gasses. Many physico-chemical properties that are key input parameters to the process models are obtained from time-consuming and sometimes dangerous experimental campaigns (H2S) or are not (easily) accessible experimentally and are currently estimated. In this work, we investigated which of these properties could quickly and reliably be obtained using molecular simulations, to improve the accuracy of the process models and to reduce the need for long or difficult experiments. The absorption properties of H2S, CO2, and CH4 in aqueous MethylDiEthanolAmine (MDEA) were computed using a combination of forcefield-based molecular dynamics, Monte Carlo methods, and quantum mechanical approaches. The results are compared to experimental data and/or currently used estimates in the AspenPlus process model. It was found that the key properties which might reliably and relatively easily be obtained by molecular simulations are physical: density, phase behavior, Henry coefficients, diffusion coefficients, viscosity, and surface tension. Quantum mechanical calculations based on the widely used density functional theory are instrumental in exploring reaction mechanisms and in determining the structure of transition states, but obtaining accurate free energies of reactions remains a challenge, especially when energy differences of less than 1 kJ mol−1 are necessary for quantitative predictions. Such an accuracy can only be reached if the solvent effects, which are detrimental, are correctly included in the model [1].

Improving the output characteristics of the Co2+:MgAl2O4/Er,Yb:glass passively Q-switched microchip laser

The saturable absorption properties of Co2 + : MgAl2O4 crystals in three different cutting directions were studied experimentally. The characteristic of the transmission of polarized incidence light through the [100], [110], and [111]-cut Co2 + : MgAl2O4 single crystal was investigated. The [110]-cut crystal had the maximum transmittance observed. We conclude that using a [110]-cut Co2 + : MgAl2O4 crystal to form a Co2 + : MgAl2O4 / Er,Yb:glass passive Q-switched microchip laser can improve the output characteristics of the laser, such as pulse energy and extinction ratio without changing any other parameters.

A polymeric suspension of amine functionalized silica nanoparticles derived from Moonj grass for the carbon capture and storage applications

Herewith, amine functionalization of low cost support from a novel and sustainable source has been entrenched to improve the carbon dioxide (CO2) capture efficiency. The support used is silica nanoparticles (SNPs), derived from a commonly available weed grass namely, Moonj (Saccharum munja L.). The amine functionality was anchored over the SNPs’s surface to obtain amine-functionalized SNPs (AFSNPs) using one step process. The SNPs and AFSNPs were characterized with FTIR, XRD, SEM, TEM, and BET to confirm the structural and textural properties. Subsequently, AFSNPs were suspended in a polymeric solution of 1000 ppm hydrolyzed polyacrylamide (HPAM) forming an AFSNP-HPAM nano-fluid. The nano-fluid remained stable for over 21 days and no sign of sedimentation was observed. Increasing the AFSNPs’s concentration in the nano-fluid increased the viscosity of the nano-fluid while increasing the amine loading over SNPs did not much affect the base viscosity. The nano-fluid showed improved CO2 absorption property for AFSNPs over SNPs. This improved CO2 absorption property can be attributed to the synergy between polymer and AFSNPs. The inclusion of the AFSNPs in the polymer matrix also enhanced thermal stability of polymer at high temperatures. Thus, the utilization of these AFSNPs is proposed in subsurface applications for effective carbon utilization and storage.

A green vapor suppressing agent for aqueous ammonia carbon dioxide capture solvent: Microcontactor mass transfer study

Aqueous ammonia is a promising carbon dioxide capture solvent and has recently attracted significant attention, but its main problem is high evaporation rate of ammonia in the absorber. Glycerol, which is a by-product of biodiesel, has hydroxyl groups that bind to ammonia molecules. Hence, it can reduce the vaporization of ammonia as an additive and improve the CO2 absorption properties. In this work, the mass transfer performance of glycerol, as an ammonia vaporization reduction additive, was investigated. Carbon dioxide absorption experiments using ammonia-glycerol hybrid solvent have been done in a T-shaped microchannel. The impact of process condition, including ammonia concentration (4–10 wt%), glycerol concentration (1–3 wt%), liquid flow rate (3–9 ml/min) and temperature (20–40 °C) was investigated on the volumetric overall mass transfer coefficient (KGaV), absorption percentage (AP) and volumetric molar flux (NAaV). According to the results, rising the glycerol concentration in the range of 2–3 wt% leads to an increase in KGaV by 4.8%. Hence, the addition of glycerol to aqueous ammonia not only increases the mass transfer coefficient but also reduces the vapor pressure of ammonia as a green vapor suppressing agent and diminishes the ammonia loss in the absorption tower.

Tuning the CO2 absorption and physicochemical properties of K+ chelated dual functional ionic liquids by changing the structure of primary alkanolamine ligands

To reveal the effects of the alkyl substitutions at alpha (α) or beta (β) position adjacent to amino group of primary alkanolamine ligands on CO2 absorption and physicochemical properties of metal chelated dual functional ionic liquids (DFILs), four DFILs were prepared by reacting potassium imidazole salt (KIm) with alkanolamine ligands, including 2-amino-2-methyl-1-propanol (AMP), 2-amino-1-butanol (AMB), DL-1-amino-2-propanol (DLAMP), and monoethanolamine (MEA). CO2 absorption behavior and mechanism of DFILs were studied, and density (ρ), speed of sound (u), and viscosity (η) of DFILs were measured to correlate with the CO2 absorption performance. DFT calculations were employed to explore the influence of the interactions between K+ and alkanolamine on the CO2 absorption and physicochemical properties of DFILs. The results show that CO2 capacity at 333.2 K is as follows: [K(AMP)2][Im] > [K(AMB)2][Im] > [K(DLAMP)2][Im] > [K(MEA)2][Im], indicating that the introduction of alkyl group at α or β position of alkanolamines can enhance CO2 capacity, and the effect of the α position is more significant than the β position. Both ρ and u follow the order: [K(AMP)2][Im] < [K(AMB)2][Im] < [K(DLAMP)2][Im] < [K(MEA)2][Im], while η is in the reverse order. Moreover, the saturated CO2 capacity of DFILs has an approximately linear relation with the thermal expansion coefficient. DFT calculations show that the presence of the alkyl group at α or β position of alkanolamines reduces the Mulliken charge of N and O atom, thereby weakening the cation coordination interaction between K+ with ligand, resulting in the decrease in ρ and u of DFILs. Moreover, the decrease in the Mulliken charge of N and O atom in alkanolamine leads to the increase of chelated cation-[Im]− interaction, thereby increasing η of DFILs. Consequently, [K(AMP)2][Im] exhibits higher CO2 capacity and good reversibility, due to the fact that CO2 can react with the chelated cation and [Im]– simultaneously. The present study provides a new method for effectively regulating the performance of DFILs.

A three dimensional cobalt-mixed ligands framework with selective adsorption of carbon dioxide

Selective adsorption of the CO2 in environment is an important research field of inorganic chemistry and coordination chemistry. A coordination polymer [Co2(tib)2(1,4-NDC)2]·7H2O (CTN) was composed by the reaction of 1,3,5-tris(1-imidazolyl) benzene (tib) and 1,4-naphthalenedicarboxylic acid (1,4-H2NDC) with Co2+ under solvothermal conditions. The result of X-ray single-crystal analysis shows that CTN is a twofold interpenetrating 3D framework with {42·65·83}{42·6} topology. CTN was further characterized by powder X-ray diffraction, IR spectroscopy, thermogravimetric analysis, and elemental analysis. Notably, CTN possesses an excellent CO2 absorption property.

High Performance of Fly Ash Derived Li &amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;SiO&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;-Based Sorbents for High Temperature CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; Capture

It is urgent to develop excellent solid CO2 sorbents with higher sorption capacity, simpler synthetic process, better thermal stability and lower costs of synthesis in CO2 capture and storage technologies. In this work, a number of Li4SiO4-based sorbents synthesized by lithium carbonate with three different kinds of fly ashes in various molar ratios were developed. The results indicate that the Li2CO3:SiO2 mole ratio used in the sorbents synthesis significantly affects the CO2 absorption properties. The sorption capacity increased with the excess of Li2CO3 first and then decreased when the excessive quantity was beyond a certain amount. The experiments found that FA-Li4SiO4_0.6, CFA-Li4SiO4_0.4, HCl/CFA-Li4SiO4_0.3 presented the best sorption ability among these fly ash derived Li4SiO4 samples, and the corresponding weight gain was 28.2 wt%, 25.1 wt% and 32.5 wt%, respectively. The three sorbents with the optimal molar ratio were characterized using various morphological characterization techniques and evaluated by thermogravimetric analysis for their capacity to chemisorb CO2 at 450&degC - 650&degC, diluted CO2 (10%, 20%) and in presence of water vapor (12%). The adsorption curve of FA- Li4SiO4_0.6 at different temperatures was simulated with the Jander-Zhang model to explore the influence of carbon dioxide diffusion on adsorption reaction. Further experiments showed that the adsorbent had a good sorption capacity in a lower partial pressure of CO2 and the presence of steam enhanced the mobility of Li+. What’s more, FA-Li4SiO4_0.6, CFA-Li4SiO4_0.4 and HCl/CFA-Li4SiO4_0.3 particles showed satisfactory sorption capacity in fixed-bed reactor and excellent cyclic sorption stability during 10 sorption/ desorption cycles.

Thermodynamics and kinetics analyses of high CO2 absorption properties of Li3NaSiO4 under various CO2 partial pressures.

The properties of Li3NaSiO4 as a CO2 absorbent were evaluated by thermogravimetry (TG) and X-ray diffraction, which revealed that the CO2 absorption and desorption reaction, Li3NaSiO4 + CO2 ↔ LiNaCO3 + Li2SiO3, is reversible. In scanning-type TG under various CO2 partial pressures (P(CO2)), mass gain ascribed to CO2 absorption started from approximately 400 °C, irrespective of P(CO2). CO2 desorption was observed at a higher temperature, which was considered the approximate equilibrium temperature of the above-mentioned reaction. A pseudo-Ellingham diagram of the reaction between Li3NaSiO4 and CO2, constructed using the obtained approximate equilibrium temperature under each P(CO2), showed similar behavior to that between Li4SiO4 and CO2, especially between 10-2 and 10-1 bar of P(CO2). Kinetics analysis by isothermal TG using the Jander model revealed that the reaction rate of CO2 absorption of Li3NaSiO4 was higher than that of Li4SiO4. The rate-determining step of CO2 absorption by Li3NaSiO4 was the diffusion process at the examined temperatures and P(CO2), which was different from the rate-determining step of the reaction between Li4SiO4 and CO2 under low P(CO2).

Understanding the interactions between the bis(trifluoromethylsulfonyl)imide anion and absorbed CO2 using X-ray diffraction analysis of a soft crystal surrogate

The selective carbon dioxide (CO2) absorption properties of ionic liquids (ILs) are highly pertinent to the development of methods to capture CO2. Although it has been reported that fluorinated components give ILs enhanced CO2 solubilities, it has been challenging to gain a deep understanding of the interactions occurring between ILs and CO2. In this investigation, we have utilized the soft crystalline material [Cu(NTf2)2(bpp)2] (NTf2‒ = bis(trifluoromethylsulfonyl)imide, bpp = 1,3-bis-(4-pyridyl)propane) as a surrogate for single-crystal X-ray diffraction analysis to visualize interactions occurring between CO2 and NTf2‒, the fluorinated IL component that is responsible for high CO2 solubility. Analysis of the structure of a CO2-loaded crystal reveals that CO2 interacts with both fluorine and oxygen atoms of NTf2‒ anions in a trans rather than cis conformation about the S–N bond. Theoretical analysis of the structure of the CO2-loaded crystal indicates that dispersion and electrostatic interactions exist between CO2 and the framework. The overall results provide important insight into understanding and improving the CO2 absorption properties of ILs.

Detailed Analysis of Water Vapor with All Isotopologues, Air Gas Mixtures and Air Molecules at Terahertz Range

The scarcity of radio spectrum led regulators to consider new frequency bands including Terahertz frequencies between 0.275 and 1 THz, which is previously reserved only for passive services such as satellite telemetry and radio astronomy. One of the major advantages of Terahertz bands is the available bandwidth. For example, future generation cellular networks would be able support extreme throughputs via Terahertz backhaul links. But the medium that the electromagnetic waves propagate need to be analyzed by this way theoretical results will turn to practical and commercially attractive results. This work will give the channel characteristics of detailed analyzes of CO2, H2O, O2, USA model (high latitude, winter)—USA model (tropics) between 0.275 and 10 THz range. The developed model in this paper evaluates the total absorption loss, path loss, SNR and capacity properties. The water vapor–H2O (which is the biggest enemy of high frequencies) with all isotopes is analyzed in this paper. This paper also presents the theoretical estimations of absorption properties of CO2, H2O, O2, USA model (high latitude, winter)—USA model (tropics) at the THz frequency band from 0.275 to 10 THz.

Energy Budgets for Terrestrial Extrasolar Planets

Abstract The pathways through which incoming energy is distributed between the surface and atmosphere have been analyzed for the Earth. However, the effect of the spectral energy distribution of a host star on the energy budget of an orbiting planet may be significant given the wavelength-dependent absorption properties of atmospheric CO2, water vapor, surface ice, and snow. We have quantified the flow of energy on aqua planets orbiting M-, G-, and F-dwarf stars, using a 3D Global Climate Model with a static ocean. The atmosphere and surface of an M-dwarf planet receiving an instellation equal to 88% of the modern solar constant at the top of the atmosphere absorb 12% more incoming stellar radiation than those of a G-dwarf planet receiving 100% of the modern solar constant, and 17% more radiation than an F-dwarf planet receiving 108% of the modern solar constant, resulting in climates similar to that of modern-day Earth on all three planets, assuming a 24 hr rotation period and fixed CO2. At 100% instellation, a synchronously rotating M-dwarf planet exhibits smaller flux absorption in the atmosphere and on the surface of the dayside, and a dayside mean surface temperature that is 37 K colder than its rapidly rotating counterpart. Energy budget diagrams are included to illustrate the variations in global energy budgets as a function of host star spectral class, and can contribute to habitability assessments of planets as they are discovered.