Aqueous Solutions Of N-methyldiethanolamine Research Articles

Mass Transfer Characteristics of CO2 and Blended Aqueous Solutions of [C2OHmim][Lys]/MDEA in a Microchannel

In this paper, the two-phase flow and mass transfer process of CO2 and [C2OHmim][Lys]/MDEA mixed aqueous solution in a T-shaped microchannel were investigated systematically. By using a high-speed camera connected to a computer, the two-phase flow patterns were recorded online, including the Taylor flow and a small amount of Taylor-bubbly flow. And the effects of ionic liquid concentration and two-phase flow ratio (QG/QL) on bubble length, specific surface area, gas holdup, and mass transfer coefficient were studied experimentally. The results indicate that the blended solution of [C2OHmim][Lys]/MDEA could significantly enhance two-phase mass transfer compared to single N-methyldiethanolamine aqueous solution. The reaction mechanism between CO2 and ionic liquid/amine mixed aqueous solution was also analyzed. On the basis of experimental data, some new correlations for predicting the bubble initial length and the volumetric mass transfer coefficient were proposed, which matched well with the experimental data. This work is helpful to provide new ideas for the design of CO2 absorbents and further improve the data of gas–liquid mass transfer in microchannels.

Modeling and simulation of an enzymatic reactive absorption process in the internal zone of a rotating packed bed apparatus

A kinetic model of carbon dioxide absorption within an internal of a rotating packed bed (RPB) apparatus was developed using experimental data. Kinetics of the chemical reaction between carbon dioxide and aqueous solution of N-methyldiethanolamine with and without carbonic anhydrase additive were determined in a flat phase contact surface batch stirred reactor and implemented into the model. Overall pressure drop and absorption efficiency within a metal foam internal were modeled and compared with experimental measurements. The model's predictions of CO2 absorption and pressure drop fit mostly within 20% error range. Validated model served as a tool for further absorption process simulations and sensitivity analysis.

The performance and mechanism of CO2 desorption and corrosion in N-methyldiethanolamine aqueous solutions blended with amino acid ionic liquids

The CO2 desorption performance of N-methyldiethanolamine(MDEA)-Tetramethylammonium glycinate ([N1111][Gly]), MDEA-1-butyl-3-methylimidazolium lysinate ([Bmim][Lys]) aqueous solutions was investigated. The influences of amino acid ionic liquids (AAILs) type and AAILs concentration on CO2 desorption were demonstrated on the basis of experiments. The corrosion characteristics of 20# carbon steel in the MDEA-AAILs-CO2 aqueous solutions were also determined, and the effects of temperature, AAILs concentration, AAILs type, and CO2 loading on the corrosion rate were analyzed. Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance carbon spectroscopy (13C NMR) and scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) characterization were used to evaluate the CO2 desorption mechanism and corrosion mechanism, respectively. It is found that AAILs have a good performance in the desorption process and they can effectively reduce the corrosion rate of amine aqueous solution.

Experimental and numerical investigation of gas-side mass transfer in Taylor flow

Taylor flows are of great interest for industrial application where efficient gas absorption is needed. Literature however scarcely relates to the gas-side mass transfer coefficient kG in Taylor flows. In this work, the authors selected and developed an experimental method, based on bubble expansion record, to estimate kG value in a millimetric channel of circular section, fed with nitrogen gas and pure ethyl acetate (EA). The experiments provided an order of magnitude of a few mm.s−1 at least for kG, for a two-phase velocity UTP ∼ 0.1 m.s−1.CFD simulations completed the experimental investigation and further estimated the order of magnitude, with kG∼10-2 m.s−1 when 0.09<UTP<0.18 m.s−1. The transport of EA inside the bubble suggests a significant contribution of diffusion in regard with the convective effects. kG is found to be sensitive to UTP, and to the temperature via the gas diffusivity and also via the bubble expansion leading to an increase in bubble velocity. The dependence of the gas-side Sherwood number to the Péclet number is similar to previously reported observations concerning a spherical bubble freely rising in quiescent liquid.This study thus provides the means to evaluate the gas-side resistance for any gas–liquid system in Taylor flows, a resistance that was usually simply dismissed in previous works. As an example, the authors demonstrated that, in Taylor flows, for a gas–liquid system of industrial interest (diluted CO2 in 30 wt.% N-methyldiethanolamine aqueous solution), gas-side mass transfer resistance is lower than the liquid-side one by at least one order of magnitude.

The Performance and Mechanism of Co2 Desorption and Corrosion in N-Methyldiethanolamine Aqueous Solutions Blended with Amino Acid Ionic Liquids

The Performance and Mechanism of Co2 Desorption and Corrosion in N-Methyldiethanolamine Aqueous Solutions Blended with Amino Acid Ionic Liquids

Thermodynamic modeling of CO2 solubility into an aqueous solution of N-methyldiethanolamine using EoS/GE approach and different Alpha-functions

Carbon dioxide is among the most crucial impurity in natural gas and must be removed from the gas before any use to avoid environmental damage and problem. The CO2 absorption with the alkanolamine process is widely used for this purpose. This study has been dedicated to modeling the aqueous CO2+ N-methyldiethanolamine (MDEA) system's vapor-liquid equilibrium within the temperature range 297.7-413.15 K and gas loading in the range of 0.000249-1.507 CO2 mole/MDEA mole. In combination with the Wong-Sandler mixing rule and the NRTL activity coefficient model, the Peng-Robinson equation of state has been applied as an EOS/GE approach for modeling of vapor-liquid equilibrium of the CO2-MDEA-H2O system. For improving the performance of the model, five alpha,α, functions have been considered for the Peng-Robinson equation of state.Moreover, ions in the aqueous phase have been accounted for by contributions of the short-range, long-range interactions and the Born term in the Wong-Sandler mixing rule through the Peng-Robinson equation of state. Initially, the binary interactions of the CO2+H2O and MDEA+H2O systems are optimized. Using 283 experimental data of carbon dioxide solubility in the MDEA solution, one can calculate the other binary, and energy interaction parameters by applying simultaneous chemical and phase equilibrium computations. Consequently, to achieve the present modeling's predictability, the obtained parameters were used to predict the other 313 point data's phase equilibrium. The present model results showed that a good agreement is obtained between the calculated and experimental data. The Coquelet and Chapoy (C&C) and Twu alpha, α, functions present more accurate results than the others.

Surface Thermodynamics, Viscosity, Activation Energy of N-Methyldiethanolamine Aqueous Solutions Promoted by Tetramethylammonium Arginate

The surface tension and viscosity values of N-methyldiethanolamine (MDEA) aqueous solutions promoted by tetramethylammonium arginate ([N1111][Arg]) were measured and modeled. The experimental temperatures were 303.2 to 323.2 K. The mass fractions of MDEA (wMDEA) and [N1111][Arg] (w[N1111][Arg]) were 0.300 to 0.500 and 0.025 to 0.075, respectively. The measured surface tension and viscosity values were satisfactorily fitted to thermodynamic models. With the aid of experimentally viscosity data, the activation energy (Ea) and H2S diffusion coefficient (DH2S) of MDEA-[N1111][Arg] aqueous solution were deduced. The surface entropy and surface enthalpy of the solutions were calculated using the fitted model of the surface tension. The quantitative relationship between the calculated values (surface tension, surface entropy, surface enthalpy, viscosity, activation energy, and H2S diffusion coefficient) and the operation conditions (mass fraction and temperature) was demonstrated.

H2S solubility enhancement using ethylene diamine functionalized carbon nanotubes and the aqueous solution of N-methyldiethanolamine

Carbon Nanotubes (CNTs) were functionalized using Ethylene Diamine (EDA). To study surface morphology, identify the functional group and crystallography structure, the EDA-functionalized CNT was characterized using FESEM, FT-IR, and XRD, respectively. Synthesized EDA-CNTs were dispersed in 40 wt% MDEA solution and the stability of EDA-CNTs nanoparticles was assessed through zeta potential technique. While the pressure increased up to 8 bar, the solubility of H2S gas was then investigated in the nanofluid composed of 0.1 wt% EDA-CNTs and 40 wt% MDEA solution at 30, 45, and 60 °C. The results revealed that the solubility of the H2S gas could be enhanced to up to 13.65% when the 40 wt% MDEA solution was amended by 0.1 wt% EDA-CNTs nanoparticles.

Modeling H2S solubility in aqueous N-methyldiethanolamine solution using a new ePC_SAFT-MB equation of state

Perturbed chain statistical associating fluid theory (PC-SAFT) equation of state (EoS), mean spherical approximation (MSA) term and Born term are combined and proposed as a new electrolyte equation of state (ePC_SAFT-MB EoS) to model the solubility of H2S in aqueous N-methyldiethanolamine (MDEA) solutions in a wide range of temperature, pressure, MDEA concentration, and H2S loading. In order to find the best association schemes (2B, 3B and 4C) for H2O, MDEA and H2S in PC-SAFT EoS, different association schemes are considered for each one of the components in the wide range of temperature and pure parameters are determined. The binary interaction parameters (BIP) for H2O + H2S and MDEA + H2O binary systems are adjusted in the VLE calculation for different association schemes. The best result with minimum average absolute relative deviation percent (AAD%) of 2.21 and 2.72 are obtained with considering the 4C, 4C and 3B association schemes for MDEA, water and H2S, respectively. By using the obtained BIPs, 277 data points of the bubble pressure for H2O + MDEA + H2S system are predicted by PC-SAFT EoS with the AAD% of 25.5. To improve the accuracy of PC-SAFT EoS, the Born and MSA terms are added to PC-SAFT EoS. The BIPs between the ion-ion and molecules-ions are adjusted by the bubble pressure calculation algorithm using 277 experimental data points. Very good results with the AAD% of 18.6 are obtained by adjusting the binary parameters (MDEAH+−MDEA,MDEAH+−H2O,MDEAH+–H2S and MDEAH+−HS−) in H2O + MDEA + H2S ternary system. Finally, to investigate the predictive ability of the proposed ePC_SAFT-MB EoS, it is employed to model the selected 44 solubility data points of H2O + MDEA + H2S system without further adjustment for model parameters. The value of AADs% is obtained about 30.0 for the H2 S partial pressure, which shows the predictive ability of the proposed model.

Solubility of CO2 in 3-amino-1-propanol and in N-methyldiethanolamine aqueous solutions: Experimental investigation and correlation using the CPA equation of state

The solubility of CO2 in 1.3M and 2M aqueous N-methyldiethanolamine (MDEA) and 3-amino-1-propanol (MPA) solutions was experimentally measured at 298, 313, 323 and 333 K, using a pressure decay method. Since only limited experimental data exist in literature for MPA aqueous systems, the results of this study were compared with literature data mainly for 2M MDEA solutions, showing satisfactory agreement. The obtained new experimental data were used to parameterize the Cubic-plus-Association (CPA) equation of state using a pseudo chemical reaction approach, i.e. to account for chemical interactions as very strong specific intermolecular interactions, which is a crude approximation, but is necessary for applying equation of state models. It was found that the model satisfactorily describes the experimental data using six or four binary parameters for the CO2-MPA or CO2-MDEA interactions, respectively, which, however, are less than the number of adjustable parameters in similar literature models.

Absorption characteristics and kinetics of CO2 capture into N-methyldiethanolamine aqueous solution catalyzed by the immobilized carbonic anhydrase

Carbonic anhydrase (CA) is the most effective CO2 hydratase catalyst, but the poor storage stability and repeatability of CA limit its development. Therefore, CA was immobilized on the epoxy magnetic composite microspheres to enhance the CO2 absorption into N-methyldiethanolamine (MDEA) aqueous solution in this work. In the presence of immobilized CA, the CO2 absorption rate of MDEA solution (10 wt%) (0.63 mmol·min−1) was greatly improved by almost 40%, and their reaction equilibrium time was shortened from 150 min to 90 min compared with that into MDEA solution. The results indicated that the absorption of CO2 into MDEA solution had been significantly enhanced by using CA. After the 7th reuse recycle, the activity of the immobilized CA was still closed to its initial value at 313.15 K. Moreover, enzyme catalytic kinetics of immobilized CA was investigated using the p-nitrophenyl acetate (p-NPA) as substrate. The values of Michaelis–Menten constant (Km) and the maximum velocity (Vmax) of the immobilized CA were calculated to be 27.61 mmol/L and 20.14 × 10−3 mmol·min−1·mL−1, respectively. Besides, the kinetics of CO2 reaction into MDEA with or without CA were also compared. The results showed that CO2 absorption into CA/MDEA aqueous solution obeyed the pseudo first order regime and the second order kinetics rate constant (k2) was calculated to be 929 m3·kmol−1·s−1, which was twice higher than that of MDEA aqueous solution without immobilized CA (k2=414 m3·kmol−1·s−1) at 313.15 K.

Mass-Transfer Characteristics of CO2 Absorption into Aqueous Solutions of N-Methyldiethanolamine + Diethanolamine in a T-Junction Microchannel

The mass-transfer process of CO2 absorption into aqueous solution of N-methyldiethanolamine (MDEA) + diethanolamine (DEA) in a T-shaped microchannel was studied using a high-speed camera. The effec...

Experimental Study of Carbon Dioxide Solubility in Aqueous N-Methyldiethanolamine Solution with 1-Butylpyridinium Tetrafluoroborate Ionic Liquid

New experimental data for CO2 solubility in the aqueous solutions of N-methyldiethanolamine (MDEA) and 1-butylpyridinium tetrafluoroborate ([Bpy][BF4]) ionic liquid (IL) are reported. The experiments were conducted in a static high pressure equilibrium cell. Solubility measurement of CO2 was performed in various solution compositions of IL and MDEA in a wide temperature range of 298.15–343.15 K and pressures up to 4 MPa. The experimental results revealed that, by increasing the weight percent of IL, the absorption capacity of aqueous mixtures diminishes. It was also observed that the main capacity of CO2 loading in the absorbent solutions belonged to MDEA through chemical absorption, whereas its concentration was more effective than IL in gas solubility. The experimental results are correlated using a semiempirical model with good accuracy.

Enhancement of CO2 solubility in a mixture of 40 wt% aqueous N-Methyldiethanolamine solution and diethylenetriamine functionalized graphene oxide

Graphene oxide functionalized by diethylenetriamine (DETA) was prepared and characterized with SEM, XRD, BET, TGA and IR spectroscopy techniques to find out its morphology, crystalline building, porous structure, thermal stability and functional groups. The CO2 solubility in 40 wt% aqueous amine solution, 40 wt% aqueous amine solution +0.1 wt% GO, and 40 wt% aqueous amine solution +0.1 wt% DETA-GO is determined. The solubility measurements were performed at three temperature (303.15, 313.15 and 323.15 K) and CO2 partial pressures up to 2200 kPa. Addition of GO and DETA-GO to MDEA (N-Methyldiethanolamine) solution enhanced the CO2 adsorption capacity of the aqueous amine solution up to 7.5% and 12.5%, respectively. Increasing CO2 partial pressure and decreasing temperature enhanced the CO2 solubility.

Absorption performance of (CO2 + N2) gas mixtures in amino acid ionic liquids promoted N-methyldiethanolamine aqueous solutions

Amino acid ionic liquids (AAILs) including 1-butyl-3-methylimidazolium glycinate ([Bmim][Gly]), 1-butyl-3-methylimidazolium L-lysinate ([Bmim][Lys]) and tetramethylammonium glycinate ([N1111][Gly]) were used to enhance the absorption of CO2 in N-methyldiethanolamine (MDEA) aqueous solutions. The mole fractions of CO2 in N2+CO2 gas mixtures ranged from 0.2 to 1.0. The mass fractions of MDEA and AAILs respectively ranged from 0.300 to 0.400 and 0.050 to 0.100. The absorption capacity and absorption rate under series of conditions were presented and the influences of CO2 partial pressure and the types of AAILs on the absorption performance were demonstrated.

Thermophysical properties of concentrated aqueous solution of N -methyldiethanolamine (MDEA), piperazine (PZ), and ionic liquids hybrid solvent for CO 2 capture

In the present study, thermophysical properties such as density, refractive index, surface tension, and viscosity of the concentrated aqueous solution of N-methyldiethanolamine (MDEA), piperazine (PZ), and ionic liquids (ILs) 1-butyl-3-methylimidazolium trifluoromethanesulfonate [bmim][OTf], 1-butyl-3-methylimidazolium acetate [bmim][AC] were investigated. All the properties were measured at atmospheric pressure and temperature ranging from (298.15–343.15) K, with a regular interval of 5 K. The concentrations of N-methyldiethanolamine (MDEA) and piperazine (PZ) were kept constant at 30 and 3 wt%, respectively, while the concentration of ionic liquids [bmim][OTf], [bmim][AC] were varied between 5 and 20 wt%. All the properties under investigation demonstrated their significant dependence on temperature and ionic liquid concentration. Increasing temperature showed decreasing trend of density, viscosity, refractive index, and surface tension of the hybrid solvents. Except for surface tension, density, refractive index, and viscosity were increased by increasing the concentration of ionic liquid in the hybrid solvents. Surface tension data were decreased with an increase in the concentration of ionic liquids at a constant temperature. The thermophysical properties of concentrated aqueous solution of hybrid solvents were correlated using an empirical correlations approach with respect to temperature and concentration. A good agreement was found between the correlated and experimental data at all conditions.

Modeling of CO2 solubility in aqueous N-methyldiethanolamine solution using electrolyte modified HKM plus association equation of state

In this work, a new type of electrolyte cubic plus association equation of state as emHKM-CPA EoS has been developed and was used to modeling the CO2 solubility in aqueous alkanolamine such as N-methyldiethanolamine (MDEA) and diethanolamine (DEA) solutions. This EoS consists of the several terms as the cubic HKM part for dispersion contribution, electrolyte part and association term. The Mean Spherical Approximation (MSA) term together with Born term are used for electrostatic long-range interaction and charging processes, respectively, and for association the Wertheim equation was applied. Using the present EoS, the solubility of CO2 in aqueous MDEA solutions is modeled so that the 470 experimental solubility data were used at the different solution compositions, temperatures, pressures and acid gas loadings. At first, the pure components parameters were obtained through regression of the pure components vapor pressure and saturated liquid density experimental data. Consequently, the binary interaction parameters were calculated using the binary vapor-liquid equilibrium data. Finally, the ternary H2O-CO2-MDEA and H2O-CO2-DEA systems were modeled using a reactive bubble point pressure calculation method. Moreover, the present EoS is applied for LLE calculation of heptane-MEA system. The results showed that the calculated values were in good agreement with the experimental data. For the H2O-CO2-MDEA and H2O-CO2-DEA systems, the percentage of Absolute Average Deviation (AAD%) were 12.14 and 9.17, respectively, that shows emHKM- CPA is an efficient EoS which can be successfully applied to representation of the solubility of CO2 in aqueous alkanolamine solutions in wide ranges of temperature, pressure, acid gas loading, and amine concentration.

A new CO2 absorption data for aqueous solutions of N-methyldiethanolamine + Hexylamine

The aim of this work is to develop a new chemical solvent for CO2capture and compare its performance with a reference based solvent MDEA (MethylDiEthanolAmine). A mixture of MDEA and Hexylamine activator (HA) is designed to improve the performance of the process and allow a substantial gain in terms of energy regeneration and reducing the cost of capture. New CO2 absorption data is obtained using a Lewis cell gas-liquid interface at 298, 313 and 333 K with mass concentrations MDEA 37 wt%+ HA 3 wt%,MDEA 35 wt%+ HA 5 wt% and MDEA 33 wt%+ HA 7 wt%, to assess the CO2 absorption flux and the absorption capacity of the new solvent. Our results show that for the mixture of MDEA 37 wt%+ HA 3 wt%, the kinetics reaction is fast with reduced activation energy compared to that of MDEA 40 wt%.

Evaluation of density, viscosity, surface tension and CO2 solubility for single, binary and ternary aqueous solutions of MDEA, PZ and 12 common ILs by using artificial neural network (ANN) technique

In this study, density, viscosity, surface tension and CO2 solubility for single, binary and ternary aqueous solutions of N-methyldiethanolamine (MDEA), piperazine (PZ) and 12 common ionic liquids (ILs) were predicted by applying artificial neural network (ANN) technique. The input data included operating temperature (293.15–373.15K) and pressure (0.177–3938.400kPa) in addition to the weight fractions of aqueous solutions of MDEA, PZ and ILs which were respectively in the range of (0.0–1.0), (0.0–0.09) and (0.0–1.0) as well as the molecular weight of ILs (148.18–505.00g/mol) and their acentric factors (0.325–1.261). More than 2600 experimental data points for density, viscosity, surface tension and CO2 solubility were collected from literature. By using the Levenberg-Marquardt back-propagation and tan-sigmoid as learning algorithm and transfer function, respectively, four ANN models were examined to treat these data. It was found that the best ANN architectures for predicting these properties were respectively (7:3:0:1), (7:6:0:1), (7:4:0:1) and (7:10:0:1). The calculated properties were compared with the corresponding experimental data which indicated a negligible error.

Measuring solubility of hydrogen sulphide in aqueous blends of N-methyldiethanolamine and 2-((2 aminoethyl)amino)ethanol and correlating by the Deshmukh–Mather model

The solubility of hydrogen sulphide (H2S) in aqueous solution of N-methyldiethanolamine (MDEA) in the presence of different mole ratios of 2-((2-aminoethyl)amino)ethanol (AEEA) at low and medium pressures was obtained. The total concentrations of all the solutions have been fixed equal 3.36mol·L−1 (5.37 total moles of amines·kg−1 water). The mole ratio of [AEEA]/[MDEA] (mole ratio of AEEA per MDEA in fresh solutions) was set to 0.05, 0.10 and 0.125. The experimental total pressure varied from (7.3 to 1500) kPa and the temperatures were set to (313.2, 328.2, 343.2 and 358.2)K. The experimental values are presented as the total pressure against acid gas loading (mole H2S/total moles of amine). The results show that the AEEA concentration can improve absorption capacity of MDEA aqueous solution as the mole ratio [AEEA]/[MDEA] increases at constant total concentration. The Deshmukh–Mather model and Peng–Robinson equation of state were used for liquid and vapour phases, respectively to correlate the solubility of H2S in aqueous mixtures of AEEA and MDEA. The overall average absolute percent deviation (AAD%) in calculating the total pressure as a function of H2S loading obtained 8.15% for (AEEA–MDEA–H2S–H2O) quaternary system at the entire temperature and pressure ranges in this work.