Absorption Of CO2 In Aqueous Solutions Research Articles

Experimental study on CO2 absorption in aqueous solutions and water–oil emulsions of TEA and blended MEA/DEA–TEA

ABSTRACT The CO2 absorptions in aqueous solutions and water-in-oil (W/O) emulsions of TEA, MEA–TEA, and DEA–TEA were investigated. By applying an experimental setup, the effects of reactant concentration (0.25–1 M for TEA, 0.1–0.3 M for MEA/DEA), temperature (15–35°C), volume fraction of the dispersed phase (0.4–0.6), and pressure (100–400 kPa) on capacity and rate of CO2 absorption were measured and compared. The CO2 absorption capacity in a TEA solution with a low/medium concentration (0.25–0.5 M) is more than the theoretical value while these values are approached to each other in the high concentration (1 M). The CO2 absorption capacity of blended solutions (MEA/DEA–TEA) is higher than that of the TEA solution. By increasing the temperature, the CO2 absorption capacities of the TEA and blended solutions are decreased by increasing the temperature. For the emulsion solutions, increasing the volume fraction of the dispersed phase causes a decrement in the capacity of absorption. In the low concentration of MEA/DEA (0.1 M), the aqueous solution has a higher absorption capacity than that of the emulsion while this trend is reverse in the high concentration of MEA/DEA (0.2–0.3 M). The CO2 absorption rates of emulsions are higher than the rates of their corresponding aqueous solutions. For the TEA solutions, the rate of CO2 absorption is controlled by the reaction rate while the shuttle mechanism enhances the absorption rate for the blended solutions. The CO2 absorption capacity and rate for the TEA and blended solutions are increased by pressure while this increment is more significant for the emulsions.

A mass transfer study of CO2 absorption in aqueous solutions of isomeric forms of sodium alaninate for direct air capture application

Direct air capture (DAC) of CO2 is a critical emerging technology required to achieve ambitious net-zero emissions. Aqueous amino acid absorbents are ideal candidates for DAC and this work describes the investigation of the CO2 absorption performance of sodium salts of β- and α-alaninate under relevant conditions for DAC by utilising synthetic CO2 gas streams at concentrations levels found in the atmosphere (200–600 ppm). The effects of solution concentration, temperature, gas flowrate, liquid flowrate, and dissolved CO2 concentration (i.e., CO2 loading) on CO2 mass transfer coefficients were investigated. The overall mass transfer coefficient was found to be independent of the gas and liquid flowrates, with larger values determined for β-alaninate solutions (0.75–1.16 mmol m−2 s−1 kPa−1) than that of α-alaninate (0.65–0.87 mmol m−2 s−1 kPa−1), under similar experimental conditions. The results showed that the overall mass transfer coefficient increases with increasing temperature, conversely decreasing steadily with increasing CO2 loading. The maximum CO2 loading capacity of the 5.0 M solutions was ∼10 % higher for β-alanine (0.651 mol CO2/mol alaninate) than α-alanine (0.607 mol CO2/mol alaninate) at 25.0 °C. Precipitation was found to play an important role in the CO2 absorption processes here. Interestingly, beyond CO2 loadings >0.12 mol CO2/mol α-alaninate, the 5.0 M solution of α-alaninate begins to develop precipitate(s) while precipitation in the β-alaninate solution is only initiated at much higher CO2 loadings >0.52 mol CO2/mol β-alaninate. This study provides valuable insights into the suitability of β-alanine and α-alanine for CO2 capture directly from the ambient air.

CO2 absorption kinetics and equilibrium solubility measurements in potassium salts of renewable amino acids from plant‐ and animal‐protein

AbstractAqueous solutions containing alkaline salts of natural amino acids, such as those from protein in plant seeds or high protein animal‐based waste, are green CO2‐separation solvents. In the present work, potassium salts of nine such amino acids were chosen for an in‐depth study: alanine, arginine, aspartic acid, glutamic acid, glycine, leucine, proline, serine, and valine. The kinetics of CO2 absorption in aqueous solutions of these salts was studied using a stirred cell. From the measurements of the absorption rate at different salt concentrations (molarity 0.1 and higher), CO2 partial pressures (5–25 kPa), and temperatures (298–308 K), values of the reaction order, rate constant, and activation energy were determined. Additionally, the liquid‐side mass transfer coefficient (0.005 cm/s) was also found. Potassium salts of proline, glycine, and arginine were most reactive and, hence, were chosen for equilibrium study. The loading capacity of these salts was measured at 308 K in a vapour–liquid equilibrium setup at near‐ambient pressure. On the contrary, the other chosen acids were comparatively less reactive with CO2.

Piperazine and methyldiethanolamine interrelationships in CO2 absorption by aqueous amine mixtures. Part II—Saturation rates of mixed reagent solutions

AbstractThis work is a companion to a previous article, Part I, published in The Canadian Journal of Chemical Engineering, dealing with CO2 absorption in aqueous solutions containing a single aminic reagent (specifically methyldiethanolamine (MDEA) or piperazine (PZ)). In this second part, different PZ/MDEA mixtures are experimentally studied and their performances are compared with that of the single reagents. It is indeed well known that small quantities of PZ added to MDEA aqueous solutions are sufficient to obtain a significant improvement in the kinetics of the process. PZ is considered an activator or promoter for MDEA, but the mechanism of this synergy has still not been clearly demonstrated. The aim of this study is an attempt to understand how PZ and MDEA can interact by experimentally analyzing this beneficial mutual effect and by explaining it with the help of a suitable yet not complex model. We believe that the involved chemistry is not more complex than that reported in Part I for the single reagents. According to our findings, it is MDEA that enhances the action of PZ, as opposed to what many authors claim. Moreover, our results seem to rule out the existence of any PZ shuttle effect.

Thermodynamic modeling of CO2 absorption in aqueous solutions of N,N-diethylethanolamine (DEEA) and N-methyl-1,3-propanediamine (MAPA) and their mixtures for carbon capture process simulation

Carbone capture by absorption–regeneration technology is a well-known process. However, the development and utilization of new solvents remains crucial to lower its energy consumption. Therefore, an accurate thermodynamic modeling is essential for the process simulation and optimization. This work focuses on the thermodynamic modeling of CO2 absorption in aqueous solutions of N,N-diethylethanolamine (DEEA), N-methyl-1,3-propanediamine (MAPA) and their mixtures using electrolyte NRTL model. A novel thermodynamic modeling of DEEA-H2O−CO2, MAPA-H2O−CO2 and DEEA-MAPA-H2O−CO2 systems was developed. The modeling was carried out by considering the pure vapor pressures, excess enthalpies, dielectric constants, physical solubilities of CO2, partial and total pressures experimental data. The predicted and correlated data such as vapor–liquid equilibrium (VLE) and heat of CO2 absorption were compared favorably to experimental data from the literature. Liquid–liquid phase separation of a specific mixture of these two amines was also highlighted. Subsequently, the developed model could be used for further simulations at large scale considering that successful validation was performed at pilot scale.

Experimental solubility of carbon dioxide in monoethanolamine, or diethanolamine or N-methyldiethanolamine (30 wt%) dissolved in deep eutectic solvent (choline chloride and ethylene glycol solution)

The success achieved by the COP21 in Paris in 2015 by committing 195 states to reduce the temperature of the planet, shows that it is urgent to find a solution to greenhouse gas emissions especially the CO2. Monoethanolamine (MEA) in aqueous solution is the reference solvent to capture CO2 emission based on chemical absorption. However, aqueous solutions present some drawbacks, such as equipment corrosion, loss of solvent and high energy consumption. New and green solvents could be a possible solution to this issue.As part of this study, new experimental data on the solubility of carbon dioxide in monoethanolamine, MEA or diethanolamine DEA or methyldiethanolamine MDEA 30 wt%, dissolved in greener and nontoxic deep eutectic solvent (DES) made of choline chloride (ChCl) and ethylene glycol (EG) with a molar ratio of 1:2 are reported. Measurements were performed at three different temperatures; 298.1, 313.1 and 333.1 K and pressures from 2 Pa up to 800 kPa using astatic apparatus with on-line analysis of the gas phase by GC to determine the partial pressure of CO2. The dissolved CO2 in the liquid was determined by volumetric method. In a first step, the apparatus and the entire CO2 isotherm determination protocol were validated by the study of CO2 absorption in aqueous solution of MEA (reference amine). As no literature data was available, the solubilities of CO2 in the DES/amine were compared with those obtained from the aqueous media. The two set of measurements are very close.Gabrielsen et al. (2005) model of correlation based on the equilibrium constant, initially used for aqueous amine solutions, has been successfully extended to CO2 capture by nonaqueous solutions.Comparison of heat of absorption values between aqueous amines and in the DES was also investigated.To the best of our knowledge, this is the first time CO2 isotherms of three classes of amine dissolved in the DES (choline chloride/ethylene glycol) was studied.

Thermodynamic Modelling of N, N-Diethylethanolamine Aqueous Solutions as a First Step to the Study of Demixing Mixture With N-Methyl-1,3-Propanediamine for CO2 Capture

This study focuses on the thermodynamic modeling of CO2 absorption in aqueous solutions of N,N-diethylethanolamine (DEEA) using electrolyte NRTL model. Thermodynamic modeling of DEEA-H2O-CO2 system was developed by considering the pure vapor pressures, excess enthalpies, dielectric constants, physical solubilities of CO2, partial and total pressures experimental data. The correlated results were compared favorably to experimental data from the literature. The thermodynamic model developed in this work can be used for CO2 absorption-regeneration process simulation of DEEA-based aqueous solutions.

Modeling CO2 absorption in aqueous solutions of DEA, MDEA, and DEA + MDEA based on intelligent methods

ABSTRACTRemoving CO2 as an acidic-potential component from different gaseous flows is a main topic in different industries producing green-house gases, especially in natural gas sweetening units. A group of well-known absorbents for CO2 are the amine solutions. The common amine compounds consisting di-ethanolamine (DEA), methyl-di-ethanolamine (MDEA), and their mixture in aqueous solution have been investigated in this study. The effort was to develop new models for estimation of CO2 loading capacity of the presented amine solutions using genetic programing (GP) and stochastic gradient boosting (SGB) trees as two advanced and novel machine learning approaches in this area. A total of 175 sets of experimental data of CO2 absorption including independent variables (temperature, CO2 partial pressure, concentrations of DEA and MDEA in water) and objective function (CO2 loading capacity) were collected from literature and fed to the mentioned algorithms (GP and SGB) as input dataset. Then, each algorithm was run over the dataset, separately and two new models were created. Finally, strict statistical evaluations were implemented to assess the estimating capability of the new models. The statistical parameters including correlation coefficients (R2 SGB = 0.99848 and R2 GP = 0.99087), root-mean-square deviations (RMSDSGB = 0.00903 mol/mol and RMSDGP = 0.02244 mol/mol) and average absolute relative deviations (AARDSGB = 0.95628% and AARDGP = 8.71909%) show that the utilized powerful algorithms have enhanced the applicability of the new developed models providing good` estimations in operational processes. Final results show superiority and more accuracy of the new SGB model for confident predictions in amine process.

Efficient hybrid modeling of CO2 absorption in aqueous solution of piperazine: Applications to energy and environment

Carbon dioxide (CO2) considerably contributes to the greenhouse effects and consequently, to the global warming. Thus, reduction of CO2 emissions/concentration in the atmosphere is an important goal for various industrial and environmental sectors. In this research work, we study CO2 capture by its absorption in mixtures of water and piperazine (PZ). Experimental techniques to obtain the equilibrium data are usually costly and time consuming. Thermodynamic modeling by Equations of State (EOSs) and connectionist tools leads to more reliable and accurate results, compared to the empirical models and analytical modeling strategies. This research work utilizes Genetic Programming (GP) and Genetic Algorithm-Adaptive Neuro Fuzzy Inference System (GA-ANFIS) to estimate the solubility of CO2 in mixtures of water and piperazine (PZ). In both methods, the input parameters are temperature, partial pressure of CO2, and concentration of PZ in the solution. A total number of 390 data points is collected from the literature and used to develop GP and GA-ANFIS models. Assessing the models by the statistical methods, both models are found to acceptably predict the CO2 solubility in water/PZ mixtures. However, the GP exhibits a superior performance, compared to GA-ANFIS; the values of Average Absolute Relative Error (AARD) are 5.3213% and 9.7143% for the GP and GA-ANFIS models, respectively. Such reliable predictive tools can assist engineers and researchers to effectively determine the key thermodynamic properties (e.g., solubility, vapor pressure, and compressibility factor) which are central to design and operation of the carbon capture processes in a variety of chemical plants such as power plants and refineries.

Equilibrium solubility and enthalpy of CO2 absorption in aqueous bis(3-aminopropyl) amine and its mixture with MEA, MDEA, AMP and K2CO3

Enthalpy and vapour-liquid equilibrium (VLE) characteristics of CO2 absorption in aqueous solution of a new polyamine, bis(3-aminopropyl) amine known as dipropylenetriamine (DPTA) and its aqueous mixture with monoethanolamine (MEA), N-methyldiethanolamine (MDEA), 2-amino-2-methyl-1-propanol (AMP) and potassium carbonate (K2CO3) is investigated in this work. The VLE and heat of CO2 absorption for 30% DPTA is studied in the range of temperature 30–50°C. In order to analyse the performance of DPTA as additive, mixed amine systems of (5wt% DPTA+25wt% MEA), (5wt% DPTA+25wt% AMP), (5wt% DPTA+25wt% MDEA), (5wt% DPTA+25wt% K2CO3) are studied and compared at 40°C temperature. Density, viscosity and heat capacity of single and mixed amine solvents are also measured in this work. Based on the properties explored in this work, aqueous (DPTA+K2CO3) appears to be better solvent compared to the other system studied.

A study of bovine and human carbonic anhydrases as a model enzyme system for CO2 hydration in post combustion capture

The Post Combustion Capture (PCC) process is currently the most applicable and effective approach to reduce emissions of CO2 from fossil fuel electricity generation. If the rate of CO2 hydration can be accelerated, the size of the absorber column can be reduced accordingly. Carbonic anhydrase type II (CAII), being one of the most active enzymes known for the reaction of CO2 with H2O, is a promising catalyst for CO2 absorption in aqueous solution for PCC application. In this study, the catalytic efficiencies of human (hCAII), wild type bovine (wtbCAII), and a series of wtbCAIIs (bCAM1–bCAM9) structurally modified in an attempt to improve thermal and salt stability were determined by stopped-flow spectrophotometry at 25°C. wtbCAII and hCAII were found to have the highest activity for the hydration of CO2 while bCAM9 was the least efficient catalyst (catalytic rate constants of 1.198(6)×108, 1.14(1)×108 and 0.77(2)×108M−1s−1, respectively). The remaining mutants have similar catalytic efficiencies for CO2 hydration and fall in the range of 8.63(6)×107–1.072(2)×108M−1s−1. In addition to these results, this study also verifies the analytical method developed for the study of enzymatic systems.

Catalysis of CO2 absorption in aqueous solution by vanadate and sulfate and their application to post combustion capture

A promising option to improve post combustion capture (PCC) is to use inorganic catalysts to accelerate the absorption process of CO2, in particular the reaction between CO2 and water to form carbonic acid. In this study, the efficiency of sulfate and vanadate on enhancing the hydration reaction of CO2 to form H2CO3 for PCC has been studied at 25°C by stopped-flow spectrophotometry. The catalytic rate constants were determined to be 14.2(2) and 277(6)M−1s−1 for sulfate and vanadate, respectively. Their application to PCC was further investigated by simulating the effect of these catalysts on the absorption process under PCC operating conditions. Vanadate was confirmed to have a greater efficiency toward CO2 hydration than sulfate and also a series of other inorganic catalysts reported earlier.

Measuring solubility of carbon dioxide in aqueous blends of N-methyldiethanolamine and 2-((2-aminoethyl)amino)ethanol at low CO2 loadings and modelling by electrolyte SAFT-HR EoS

In this work, new solubility values for CO2 absorption in aqueous solutions of N-methyldiethanolamine (MDEA) in the presence of different mole ratios of 2-((2-aminoethyl)amino)ethanol (AEEA) at low pressures are obtained. The total molar amine concentration of all the solutions has been fixed equal to 3.360mol·L−1 (5.370mol amine·kg−1 water). The mole ratio of AEEA/MDEA was set to 0.12500, 0.10000 and 0.05000. The experimental total pressure varied from (7.3 to 386.6)kPa and the experimental temperature was set to (313.15, 328.15, 343.15 and 358.15)K. The electrolyte SAFT-HR (eSAFT-HR) equation of state (EoS) (Najafloo et al., 2014) has been successfully applied to model the solubility of CO2 in aqueous mixtures of AEEA and MDEA. The overall average absolute relative per cent deviation (AAD%) in calculating the total pressure as a function of CO2 loading is 7.74 for (AEEA+MDEA+CO2+H2O) quaternary system at the four values of temperature. To verify the predictive ability of the model, the eSAFT-HR EoS was extrapolated to the Zoghi and Feyzi (2013) solubility results of the same quaternary system that were obtained at higher pressures or higher CO2 loadings at the same temperatures. The AAD of the present model is 11.39% lower.

Enhancement of Carbon Dioxide Mass Transfer Rate by (Ionic Liquid)-in-Water Emulsion

Effects of dispersed ionic liquid (IL) on physical absorption of CO2in aqueous solution were investigated in the study. IL-in-water emulsion had been prepared, whose continuous phase was surfactant aqueous solution, and dispersed phase was an ionic liquid, 1-octyl-3 methyl imidazole hexafluoride phosphate. The morphololgy of dispersion had been observed by visual method. The CO2concentrations in the bulk of the absorption solvent were calculated. Results show that the enhancement of carbon dioxide mass transfer was realized by IL-in-water emulsion. The reason for the increase of CO2mass transfer rates by dispersed ionic liquid has been attributed to the increase of mass transfer driving force depending on shuttle effect.

Absorption of CO2 in amino acid ionic liquid (AAIL) activated MDEA solutions

In order to discover the influence of temperature, solution composition and pressure on CO2 absorption in aqueous solutions of N-methyldiethanolamine (MDEA) and tetramethylammonium glycinate ([N1111][Gly]), this study carried out the equilibrium absorption under a wide range of pressure (0–300kPa) at three temperatures in a dual-vessel absorption equilibrium system. The impacts of MDEA or IL concentration on the physical properties and absorption performance of CO2 under three temperatures: 25°C, 35°C, and 45°C are compared in five aqueous solutions. It is found that with the increase of IL or MDEA concentration, the solution density grows slightly, while the viscosity rises dramatically. When the equilibrium pressure is less than 60kPa, CO2 loads increase greatly as the pressure grows while temperature has little influence on the absorption capacities for all the solutions. When the equilibrium pressure is over 100kPa, the absorption capacity increases gradually as the pressure grows and higher temperature leads to less CO2 load in the solution.

CO2 absorption in aqueous solutions of N-(2-hydroxyethyl)piperazine: Experimental characterization using interferometry and modeling

This work deals with the experimental characterization of carbon dioxide (CO2) absorption in an aqueous solution of N-(2-hydroxyethyl)piperazine, by using of digital holographic interferometry. This method enables visualizing the phenomena taking place in the vicinity of the gas–liquid interface. Thanks to a calibration, the obtained results yield the time evolution of the CO2 loading field in the aqueous solution and the gas–liquid absorption rate for various operating conditions. The processing method and the obtained results are detailed. A phenomenological model, highlighting the limiting steps of the gas–liquid CO2 absorption, is proposed. A set of experiments is realized and the parameters of this model are estimated for various initial amine concentrations and initial loadings. The results are discussed and correlations are proposed for the model parameters.

CO2 CAPTURE BY BIOMIMETIC ADSORPTION: ENZYME MEDIATED CO2 ABSORPTION FOR POST-COMBUSTION CARBON SEQUESTRATION AND STORAGE PROCESS

The huge emission of greenhouse gases from fossil-fuelled power plants is emphasizing the need for efficient Carbon Capture and Storage (CCS) technologies. The biomimetic CO2 absorption in aqueous solutions has been recently investigated as a promising innovative alternative for post-combustion CCS. The carbonic anhydrase (CA) - a broad group of ubiquitous enzymes - may catalyse the CO2 hydration reaction and then to promote CO2 absorption rate into aqueous solutions. Nevertheless the research on this issue is quite active, the reliable designing of absorption units still requires more details. The present study proposes the design of a random packing absorption column operated with alkaline solvents supplied with CA. The height of the packed bed to fulfil the 80% of CO2 abatement from a flue gas stream was as large as 15-20 m. A comprehensive discussion of effects of operating conditions and of CA features on unit performance is reported.

Carbamate Formation in Aqueous - diamine - CO2 Systems

Qualitative NMR spectroscopy was used to study the species formed during CO2 absorption in aqueous solution of diamines. Three different systems, consisting of primary (ethylenediamine), primary/secondary (3-(Methylamino) propylamine) and secondary (piperazine) diamines were studied by 13C NMR and the main products were identified based on various 1D and 2D NMR techniques. The main compounds were observed and assigned to (primary/ secondary) carbamate, dicarbamate and carbonate/bicarbonate. The highest concentration of carbonate/bicarbonate and dicarbamate were observed in the PZ/CO2/H2O followed by MAPA/CO2/H2O and EDA/CO2/H2O. Both 1H and 13C NMR spectroscopy was used to quantitatively determine the speciation of amines but 13C-NMR, although slower, has the potential of being more accurate than the 1H-NMR. The diamines studied in the present work were found to have high CO2 absorption capacity compared to other amines described in the literature. This indicates that they are interesting for the further investigation.

Kinetics of Carbon Dioxide absorption into aqueous MDEA + [bmim][BF4] solutions from 303 to 333 K

The kinetics of CO2 absorption in aqueous solutions of MDEA+[bmim][BF4] were investigated using a stirred cell reactor where the relevant parameters were evaluated. The rate equation of the absorption reaction was found to be close to first order with respect to CO2 at temperatures ranging from 303 to 333K and [bmim][BF4] concentration from 0 to 2.0molL−1. The activation energy decreased from 43.32kJmol−1 to 8.65kJmol−1 with increasing [bmim][BF4] concentration from 0 to 2.0molL−1 in aqueous 4molL−1 MDEA solution. Calculated results of the enhancement factor and Hatta number showed that the performance of CO2 absorption in the aqueous 4molL−1 MDEA+[bmim][BF4] solution almost obeyed the pseudo first order regime.

Measurement and Correlation of Solubility Data for CO2 in NaHCO3 Aqueous Solution

To investigate the influence of NaHCO3 on the CO2 absorption in aqueous solution, the solubility of CO2 in NaHCO3 aqueous solutions [(0, 0.05, 0.1, 0.5, and 1.0) mol·kg−1] was measured in the temperature range from (313 to 333) K with pressure range from (0.3 to 2.0) MPa by employing a new designed batch apparatus. The results showed that the solubility data for CO2 in NaHCO3 aqueous solutions agreed well with Henry's law, and the Henry constant appeared to be a function of temperature and the concentration of NaHCO3. Two thermodynamic models were proposed for correlating the experimental data, that is, the modified Setschenow and Peng−Robinson (PR)-Duan equations. It was proved that the models fitted well in with the experimental data, and the average relative deviations were (4.06 and 3.90) %, respectively. In addition, the Henry constant in pure water can be basically predicted at a certain temperature range. The influence of NaHCO3 on the solubility of CO2 is interpreted by “salting-out effect” which ...