Aqueous Methyldiethanolamine Research Articles

Modeling H2S solubility in aqueous MDEA, MEA and DEA solutions by the electrolyte SRK-CPA EOS

In this study, an electrolyte cubic plus association equation of state (e-CPA EOS) has been proposed to predict the vapor–liquid equilibrium of (H2S) in aqueous solutions of monoethanolamine (MEA), diethanolamine (DEA), and methyldiethanolamine (MDEA). This EOS is composed of repulsive forces, short-range interactions, short-range ionic interactions, association term, long-range ionic interactions, and Born term. The Soave– Redlich– Kwong EOS is used as a non-electrolyte part. A new iterative procedure based on the Jacobi method is introduced to obtain the compositions of all species in the liquid phase. The genetic algorithm (GA) is used to find the optimal values of binary interaction coefficients between molecules and ions. Compared with experimental data, the e-CPA EOS model successfully describes the vapor–liquid equilibrium of H2S in the aqueous solutions of MEA, DEA, and MDEA. The average absolute deviations for 313 data of MEA-H2S-H2O, 156 data of DEA-H2S-H2O, and 145 data of MDEA-H2S-H2O systems were obtained as 8.20 %, 8.04 %, and 9.41 %, respectively. In addition, for some similar cases, the capability of the e-CPA EOS was compared with the Clegg–Pitzer, N-Wilson-NRF, e-NRTL, and e-CTS models. The results indicated that the e-CPA EOS has less error than the four other models.

Measurements of density and viscosity of carbon dioxide-loaded and -unloaded nano-fluids: Experimental, genetic programming and physical interpretation approaches

In the present study, the density and viscosity of the CO2-loaded and –unloaded base solution and nano-fluid were experimentally measured and investigated from an intermolecular point of view. Nano-fluids are composed of nano-particles such as Al2O3 (0.1 wt.%), Silica-2-methylimidazole, zinc salt (Si-ZIF-8) (0.02 wt.%), and super activated carbon (SAC) (0.1 wt.%) dispersed in aqueous and hybrid Methyl diethanolamine context (MDEA, 40 wt.%) +Sulfolane (SFL), 30 wt.%) +H2O) Experimental measurements were carried out at the low-temperature ranges 303.15–315.15 K, atmospheric pressure, and three different CO2 loadings. The results show that nanomaterials do not have a significant effect on the density and viscosity of the unloaded suspension; however, the density and viscosity of loaded suspensions and base solvent become more by increasing CO2 concentration. In the case of CO2-loaded fluids, the comparison of the results in the presence and absence of nanoparticles shows that the density of the solution is not much different in the two cases, but the viscosity of CO2-loaded in Si-ZIF-8, SAC, and γ-Al2O3 base nano-fluids in comparison with base solvent shows an increase of 35 % in high CO2 loading, ∼0.3 mol CO2 per mol MDEA. Density and viscosity experimental data were modeled using the Genetic Programming approach. The highest values of absolute average relative deviation (AARD) and root mean square error (RMSE) parameters obtained for modeling data are 3.04 and 0.317, respectively, and the lowest value of regression coefficient (R2) is 0.995, which indicates the appropriate fitting of the results.

A comparative study of polyamine and piperazine as promoter for CO2 absorption performance in aqueous methyldiethanolamine blend system: 430 MW power plant data simulation and economic assessment

Fossil fuel power plants play a significant role in fulfilling global energy demands but are also responsible for high CO2 emissions. Amine-based post-combustion CO2 capture (PCC) is one of the technologies used in such power plants to reduce CO2 emissions. However, high energy consumption in amine-based PCC technology causes a reduction in the overall energy efficiency of power plants. The energy consumption significantly depends on the solvents used in the PCC process. Therefore, in this work, we performed CO2 absorption in the piperazine (PZ), triethylenetetramine (TETA), and N-methyldiethanolamine (MDEA) blend and tri-blend solvents. For the absorption performance and energy consumption calculation, a simulation is performed for the 430 MW power plant data in the DWSIM software. Initially, solvent screening was done, and four solvents are selected based on the optimum energy consumption of various solvents. Further, the solvents’ performance in terms of energy consumption is done based on the effect of different temperatures, CO2 composition in feed, and %CO2 recovery. Overall, the TETA+PZ MDEA tri-blend solvent showed optimum energy consumption for most of the conditions. Additionally, a techno-economy assessment was done considering annual capital cost and annual operating cost, and results revealed that the cost per ton of CO2 capture in 5 %TETA+ 5 %PZ+ 20 %MDEA solvent is 27.33 % lesser than industrial MEA solvent, and 1.56 % lower than 10 %PZ+ 20 %MDEA.

Modeling and Simulation of CO2 Capture Unit using Mixed Solvent of Aqueous Methyldiethanolamine and Piperazine for 6.4 MWe Power Plant

Carbon dioxide emissions are the largest greenhouse gases contributor, which is attributed to global warming. Therefore, the capture of CO2 is necessary, especially from large point sources. Post-combustion capture using chemical solvents is the most matured capture technology. In this paper, mixed solvents of methyldiethanolamine (MDEA) and piperazine (PZ) were studied to potentially address some issues related to the use of conventional monoethanolamine (MEA). Steady-state modeling and simulation of the post-combustion carbon capture using the mixed solvents for a typical 6.4 MWe power plant were done. The model developed was validated against experimented data with relative error between 1 – 4.73% for the absorber on CO2 capture efficiency and between 2.93 – 10.2% relative errors on CO2 regeneration efficiency. The model was scaled up to capture CO2 from the flue gas of a typical 6.4 MWe power plant. The scaled-up results showed packing height and diameter of absorber to be 5.5 m and 1.5 m; while that of the stripper was 5.08 m and 1.45 m respectively. Effect of flue gas temperature on the capture efficiency was studied, it was observed that as the temperature increased from 20 ºC, the capture efficiency increased, but at 70 ºC, the efficiency showed no significant increase which could be associated with the existence of a temperature bulge. Capture efficiency increases with an increase in PZ concentration due to increase in the rate of reaction with concentration. The absorption and regeneration results suggest that an aqueous MDEA/PZ blend could be a prospective absorbent for CO2 capture.

Solid base LDH-catalyzed ultrafast and efficient CO2 absorption into a tertiary amine solution

Due to its high capacity, low energy consumption, and low corrosiveness, chemical absorption using aqueous tertiary amine solutions is a potential approach for CO2 capture. The fundamental limitation of this technology is its low CO2 absorption kinetics (rate), which impedes its large-scale use. Here, five typical solid-base catalysts, MgAl-layered double hydroxide (LDH) and its corresponding layered double oxide (LDO), BaCO3, MgCO3, and CaCO3, were adopted to improve the rate of CO2 absorption in an aqueous methyldiethanolamine solution (MDEA). The results indicated that LDH and LDO promoted CO2 absorption, with LDH exhibiting significantly superior catalytic activity. In particular, compared to the non-catalytic absorption, using LDH considerably improved the CO2 absorption rate by 92.7%. The catalytic effects of LDH on CO2 absorption were demonstrated by 13C NMR and FT-IR techniques, and theoretical calculation. A possible catalytic CO2 absorption mechanism over LDH was suggested. Additionally, the stability of LDH was certified with 10 cyclic CO2 absorption–desorption experiments. The excellent catalytic CO2 absorption performance of LDH may be primarily owing to the chemical absorption improvement mechanism of basic sites. Therefore, the LDH-catalyzed CO2 absorption process is a promising option for increasing the CO2 absorption rate in tertiary amine solution. This work may open up a new approach to developing plentiful and affordable solid-base catalysts for CO2 capture technologies with faster absorption kinetics and lower energy requirement.

Energy efficient CO2 capture in dual functionalized ionic liquids and N-methyldiethanolamine solvent blend system at elevated pressures: Interaction mechanism and heat duties

In this study, three lab synthesized dual functionalized ionic liquids (DFILs) were utilized as promoters to improve the CO2 absorption performance of methyl diethanolamine (MDEA) absorbent under elevated pressures of 2–7 bar. Initially, 5 wt% DFILs containing polyamine cations (triethylenetetramine and diethylenetriamine) and cyclic amine anions (piperazine and imidazole) were blended with 20 wt% MDEA and their physical and chemical properties were examined. The pKa value at 303 K of the blend of [TETAH][Pz] + MDEA is found to be 9.83, which is nearly equal to the industrial 30 wt% monoethanolamine (MEA) solution. The CO2 absorption performance at different temperatures and pressures demonstrated that the blending of 5 wt% DFILs into aqueous MDEA significantly altered both the absorption rate and loading. The percentage loading showed a significant 22% increase in the [TETAH][Pz] promoted aqueous MDEA blend. This is attributed to the high amount of carbamate and bicarbonate formation in the DFILs blended aqueous MDEA as revealed by 13C NMR results. These results were possible due to the highly reactive piperazine anion being a crucial factor in the significant performance of the [TETAH][Pz] blend system. Further, when the regeneration heat duty of all these absorbents was calculated, it was found that MDEA and DFILs blended MDEA absorbents consumed 25.36% and 33.34–22.79% less energy than industrial MEA, respectively along with a low absorbent loss during regeneration thus, [TETAH][Pz] and [TETAH][Im] are potential promoters in an aqueous MDEA solvent system for pressurized capture of carbon dioxide.

Enhanced CO2 absorption and reduced regeneration energy consumption using modified magnetic NPs

This study aimed to investigate the ability of nanofluids in improving CO2 absorption and reducing regeneration energy demand in a bubble column reactor in the presence of functionalized-magnetic NPs. The first step was to synthesize Fe3O4 nanoparticles (NPs), which were then functionalized with Aspartic-acid and Lysine. Next, to study CO2 absorption and stripping performances, the NPs with different concentrations were dispersed in an aqueous methyl diethanol amine (MDEA) solution (10 wt%). The investigation of CO2 absorption performance, CO2 loading and pH of all nanofluids were reported at different times of absorption experiments. The obtained results indicated that Fe3O4@Aspartic (Fe3O4@Asp) and Fe3O4@Lysine (Fe3O4@Lys) NPs improved CO2 loading up to 15.3% and 21.4%, respectively, as compared to Fe3O4 NPs. In addition, the functionalized-magnetic NPs showed more positive effects on CO2 desorption compared to bare Fe3O4. To show regeneration efficiency, the outlet gas flow rate and its CO2 concentration were measured and the CO2 loading and pH were determined at the end of the desorption experiment. The results revealed that at 70 °C, the CO2 loading was reduced by 58.9% and 55.1% applying Fe3O4@Lys and Fe3O4@Asp, respectively. Therefore, more energy could be saved in desorption process using functionalized magnetic NPs.

Experimental investigation of carbon dioxide absorption by amine-based nanofluids containing two-dimensional hexagonal boron nitride nanostructures

In this research, the influence of the two-dimensional hexagonal boron nitride nanostructures (hBNNs) upon the process of carbon dioxide (CO2) absorption into the aqueous solution of methyl diethanolamine (MDEA) was investigated. The absorption tests were performed using the pressure drop technique in a stirred thermostatic reaction chamber. The hBNNs were synthesized through the sonication-assisted hydrolysis method and characterized by FTIR, XRD, FESEM, EDX, and TGA techniques. After synthesis and characterization, the nanostructures were dispersed in an aqueous MDEA solution at different concentrations via ultrasonication and without surfactants. The stability of the nanodispersions was measured by the zeta potential analysis. The effect of hBNNs loading, MDEA concentration in the base fluid, and amount of nanofluid on the absorption process was also studied. The results revealed that the addition of hBNNs into the base fluids up to a concentration of 0.025 wt% improves the initial CO2 absorption rate and the total amount of absorbed CO2, yet, by further increasing the concentration, the mentioned values are decreased. According to the absorption measurements, for the 5 wt% aqueous solution of MDEA containing 0.025 wt% hBNNs, the highest enhancement of the initial CO2 absorption rate and the total absorbed CO2 into the nanofluid were 5.1 and 3.98%, respectively. The results also indicated that higher MDEA concentrations weaken the enhancement effect of the nanofluids. Furthermore, it was observed that the effect of the nanofluids on the absorption process is independent of their amount. According to the experiments, hBNNs could be reused for at least five consecutive cycles, without a significant drop in the nanofluid efficiency. The results of this study indicated that the use of the two-dimensional hBNNs at very low concentrations improved the CO2 absorption process.

Utilization of an innovative sono-microreactor for CO2 stripping from aqueous methyldiethanolamine solution

In the present study, a novel designed ultrasound-equipped microchannel reactor has been used to improve the CO2 desorption process from aqueous N-methyldiethanolamine (MDEA) solutions. CO2 desorption rate for a microreactor without ultrasound irradiation was compared with an ultrasound-equipped one at various temperatures, flow rates, and ultrasound powers. The results revealed that ultrasound vibrations could facilitate CO2 desorption and cause a significant increase in the rate of that through generation of cavitation bubbles and turbulence. Evaluation of energy and mass transfer characteristics was performed; 37.8% energy saving and 144.2% increase in mass transfer coefficient was obtained using ultrasound at its maximum power compared to microreactor without ultrasound irradiation. Also, comparisons between the designed sono-microreactor and conventional methods for CO2 desorption were performed in terms of desorption energy consumption and mass transfer coefficient, indicating 40.9% energy saving compared to 30 wt% MEA benchmark process and 160 times increase in mass transfer coefficient. Due to its high performance in terms of energy saving and mass transfer enhancement compared to the conventional method, the newly designed sono-microreactor can be introduced as a highly efficient technique for solvent regeneration.

Diamine based hybrid-slurry system for carbon capture

Hybrid adsorption-absorption slurry systems are very attractive for CO2 capture, given their ability to simultaneously lower regeneration energy and increase absorption rate and uptake, because of enhanced mass and heat transfer mechanisms. In this work, novel hybrid slurries were formulated from the dispersion of 1 wt.% of solid adsorbents in a water-lean solvent of 30 wt.% of Tetramethyl-1,3-diaminopropane (TMPDA) + 10 wt.% Ethanol (EtOH) for CO2 capture. Different solid particles were suspended in the water-lean solvent such as activated carbon, ion-exchanged zeolite Y (Mg-Y), and polyethyleneimine doped silicas (PEI-SG and PEI-MCM-41). The CO2 uptake of the solid and fluid components of the slurries was confirmed by pH, density, and Fourier transform infrared analysis. The neat water lean solvent reduced the absorption energy by 16 % and slightly increased the CO2 uptake by 0.6 % compared to the aqueous TMPDA solvent. Additionally, the hybrid slurries exhibited further reductions in absorption energy of 10 – 30 % compared to the benchmark TMPDA-based solvents. The PEI-MCM-41-based slurry presented the highest CO2 uptake of 0.33 g CO2.g−1 and lowest regeneration energy of 2261.30 kJ.kg−1 among the studied systems. Additionally, the hybrid slurry exhibited a 21 % reduction in CO2 uptake compared to the benchmark 30 wt.% aqueous monoethanolamine (MEA) and similar capacity to aqueous methyl diethanolamine (MDEA), however, resulting in a far higher reduction in absorption enthalpy of 56 %, and 29 % compared to aqueous MEA and MDEA, respectively. The results obtained here encourage further development and optimization of hybrid slurry systems as potential efficient systems for CO2 capture.

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].

A simplified semi-empirical model for modeling of CO2 solubilities in aqueous MDEA and MEA solutions

A simplified semi-empirical model was developed for modeling of carbon dioxide (CO2) solubility in aqueous solutions of methyldiethanolamine (MDEA) and monoethanolamine (MEA) with a temperature range from 283.15 K to 393.15 K, and alkanolamine molarity (1–5) mol/L. This model accounts for chemical equilibria in the liquid phase and physical equilibria between the liquid and vapor phases, which can calculate the vapor liquid equilibria (VLE) of MDEA+H2O+CO2 system and MEA+H2O+CO2 system. This paper proposes a Simplified Kent-Eisenberg Model (SKEM) to describe the chemical equilibria in amine – acid system, which is built with the conception of ion pairs meets the like-ion repulsion assumption and the local electroneutrality assumption. In the physical equilibria, the Henley coefficient was refitted using a new correlation, which was built with the combinations of sines and cosines. Adjustable parameters of the SKEM model, representing chemical equilibrium constant including activity coefficients, were determined by data regression with 187 sets of data of MDEA+H2O+CO2 system and MEA+H2O+CO2 system. The SKEM model has a good predictive ability, the Absolute Average Relative Deviations (AARD) of predicted results of SKEM model in MDEA+H2O+CO2 system and MEA+H2O+CO2 systems are 13.66% and 8.33%, respectively.

Influence of interface‐related parameters on some heat stable salts in the corrosion studies of carbon steel for post‐combustion CO2 capture

AbstractThe effect of flow and temperature on the corrosion behavior of carbon steel in an aqueous methyldiethanolamine solution containing different heat stable salts, such as sodium sulfate, sodium sulfite and sodium thiosulfate, has been studied. The introduction of flow and increase in temperature generally caused an increase in the corrosion rate of carbon steel but the presence of the heat stable salts affected the corrosion behavior to different extents. Sulfate increased the corrosivity of the aqueous methyldiethanolamine solution, thus showed accelerated corrosion behavior in the presence of flow and with increase in temperature when compared with the solution without heat stable salts. The presence of sulfite reduced the corrosivity of the methyldiethanolamine solution due to its oxygen scavenging ability. Although flow and temperature stimulated an increase in the corrosion rate of carbon steel, the corrosion inhibiting effects of sulfite ions increased with the salt concentration. Also, the presence of sodium thiosulfate caused a reduction in carbon steel corrosion. Its inhibition ability is largely the result of the formation of FeS product layer resulting from its disproportionation reaction. This layer offered a slight resistance to the influence of flow and increase in temperature when compared with the system without heat stable salts.

The contribution of l-Arginine to the mass transfer performance of CO2 absorption by an aqueous solution of methyl diethanolamine in a microreactor

The current study investigates the effect of adding l-arginine as a potential promoter for the conventional methyl diethanolamine (MDEA) in the carbon dioxide (CO2) capture process in a T-junction microreactor. The overall gas-phase mass transfer coefficient (KGaV) and CO2 absorption efficiency (ef) were evaluated under distinct operating conditions, including total amine + amino acid concentration of 50 wt%, the liquid flow rate of 3–9 mL min−1, and gas flow rate of 120–300 mL min−1. The composition of different concentrations in the mixture were as MDEA (50%), MDEA + ARG (46 + 4%), MDEA + ARG (42 + 8%),MDEA + ARG (38 + 12%). The impact of amino acid concentration on the physical properties of the aqueous MDEA solution was also compared in four solutions. The results indicated that increasing the arginine concentration from 4 wt% to 12 wt% intensifies the ef values from 78.91 to 92.7%, while the solution density and viscosity grows slightly. Furthermore, the values of the KGaV in the CO2 absorption enhanced from 14.34 kmol/(m3 kPa h) in aqueous MDEA (50%) solution to 63 kmol/(m3 kPa h) in MDEA + ARG (38 + 12%). It confirmed that arginine could apply as a potential chemical activator in the mixture of MDEA-ARG to intensify the absorption of CO2 in the post-combustion CO2 capture processes.

Monitoring the effect of surface functionalization on the CO2 capture by graphene oxide/methyl diethanolamine nanofluids

Different processes exist to capture carbon dioxide (CO2) and reduce its undesirable effects on the atmosphere. Stable suspensions of graphene oxide (GO) nanosheets in aqueous methyl diethanolamine (MDEA) solutions have recently attracted great attention as a potential CO2 absorption medium. Moreover, experimental analyses confirmed that GO surface functionalization positively affects the CO2 absorption by MDEA-based nanofluids. To the best of our knowledge, there are no mathematical models to investigate the effect of surface functionalization on the CO2 capture ability of GO-amine nanofluids. Artificial intelligence (AI) techniques are reliable methodologies for understanding behavior of even the most complex systems. Therefore, different AI models are designed to reveal the effect of GO surface functionalization on the CO2 capture ability of MDEA-based nanofluids. Our AI models use operating temperature, pressure, functionalized group, and GO dosage in the amine solutions to predict CO2 solubility in GO/MDEA nanofluids. The results confirm that the cascade feedforward (CFF) neural network is the most accurate AI paradigm for estimating CO2 solubility in aqueous GO/MDEA nanofluids in a wide range of operation conditions (i.e., AARD = 1.78%, MSE = 0.007, RMSE = 0.08, and R2 = 0.9906). Simulation results justified that the surface functionalization of the GO nanosheets by the NH2 group provides the most promising results for CO2 capture by the GO/MDEA nanosuspensions.

Enhancement of kinetic rates of CO2 in aqueous solutions of piperazine and methyldiethanolamine with addition of sulfolane

AbstractMeasurements of kinetics rates of CO2 in aqueous solutions of methyldiethanolamine (MDEA), piperazine (PZ), and mixtures of (MDEA + PZ), (PZ + sulfolane) and (MDEA + sulfolane) were carried out using the stopped flow technique, and reported in terms of pseudo‐first‐order rate constants (k0). When possible, the second‐order reaction rate constants (k2) were regressed from the data. Experiments were performed over new concentration ranges of (10–60), (200–800), (200–800, 10–40), (10–40, 10–200), and (200–800, 10–200) mol/m3 for the above‐mentioned five systems, respectively, and at temperatures varying from (298.15–313.15 K). When sulfolane was added to the amine solution, pseudo‐first‐order rate constants in the mixed solvents were higher than in aqueous MDEA and PZ solutions at all temperatures. The kinetic rates were highest at 298.15 K and decreased at higher temperatures for aqueous (MDEA + sulfolane) solutions but increased with temperature for aqueous (PZ + sulfolane) systems. Reaction orders for both PZ and MDEA were practically one at all sulfolane concentrations and temperatures. The base catalysis mechanism was used to regress very well data for aqueous MDEA and (MDEA + sulfolane + water) and the termolecular mechanism was used for (PZ + sulfolane + water) system. Both the zwitterion and termolecular models were able to fit the experimental data for the aqueous PZ system well. Finally, the termolecular and a hybrid model based on the combination of the Zwitterion and base catalysis mechanisms were able to successfully correlate the experimental data for the mixed aqueous (MDEA + PZ) systems.

Solid–Liquid Equilibrium and Binodal Curves for Aqueous Solutions of NH3, NH4HCO3, MDEA, and K2CO3

Solid–liquid equilibrium (SLE) data were obtained at 0.1 MPa for binary, ternary, and quaternary aqueous solutions containing ammonia (NH3), ammonium bicarbonate (NH4HCO3), methyl diethanolamine (MDEA), and potassium carbonate (K2CO3) using a modified Beckmann apparatus. The reproducibility of the experimental method was verified by measuring the SLE of aqueous solutions containing NH3, K2CO3, or MDEA in a temperature range between 237 and 273 K. A total of 120 new data points were measured for MDEA–NH3 and NH4HCO3–H2O mixtures (250 to 305 K), and 23 new data points were obtained for MDEA–K2CO3–H2O solutions (250 to 270 K). These measurements allow for an accurate estimation of water activity in such mixtures and provide insights on the limits of solid formation. The results indicate that the addition of MDEA increases the solubility of NH4HCO3, whereas a liquid–liquid split was observed when K2CO3 was added to aqueous MDEA. This opens the possibility of using it as a phase demixing solvent for carbon capture. Despite the extensive literature regarding mixed salt–amine solutions, liquid demixing in such systems has not been reported before. For this reason, the binodal curve for the MDEA–K2CO3–H2O solution was measured at 293.15 K using the method of cloud point titration. These results assist the selection of operation parameters that avoid a liquid–liquid split in the process.

Are choline chloride-based deep eutectic solvents better than methyl diethanolamine solvents for natural gas Sweetening? theoretical insights from molecular dynamics simulations

Molecular dynamics simulations were performed to investigate the performance of three deep eutectic solvents (DESs) in the separation of acid gases from natural gas. To evaluate the efficiency of these DESs, their performance was compared with that of the conventional methyl diethanolamine (MDEA) system. For this purpose, the acidic DES (phenyl propionic acid and choline chloride; with 67 mol % Phpr), same acidic DES accompanied by boron-nitride nanotube (Nano-DES), and acidic DES with methyl diethanolamine (DES-MDEA) were considered. The solubility selectivity and diffusion selectivity were evaluated and compared to those of MDEA system. The Nano-DES system showed the best performance in terms of solubility selectivity of H2S over CH4, while the high solubility selectivity of CO2 over CH4 was obtained for pure DES systems. Likewise, the aqueous MDEA and the DES-MDEA systems exhibited the largest diffusivity selectivity of H2S over CH4 and CO2 over CH4, respectively. These results were rationalized and explained by analyzing the density profile and interaction energies. Besides, the radial and spatial distribution function, Gaussian normalized distribution of measured dipole moment of species, and the orientation of dipole moment species were investigated to explain the obtained results. Furthermore, dynamical properties such as mean square displacement and corrected diffusion coefficient of species indicated that CO2 molecules diffuse faster than H2S for studied systems except for aqueous MDEA. Likewise, the diffusion coefficient of H2S and CO2 in the considered systems follow the trends Nano-DES < DES-MDEA < DES < MDEA < aqueous MDEA, and DES < DES-MDEA < MDEA < Nano-DES < aqueous MDEA in the liquid phase, respectively.

Effect of Methane, CO2, and H2S on the Solubility of Methyl and Ethyl Mercaptans in a 25 wt % Methyldiethanolamine Aqueous Solution at 333 and 365 K

We have investigated the solubility of methanethiol and ethanethiol (methyl and ethyl mercaptans in an aqueous methyldiethanolamine solution (25 wt%) by using static-analytic method at 333 and 365K. The measurements were done for different pressure of methane in the absence of acid gas with individual acid gas present, and with mixture of acid gases present (CO2 and/with H2S). Additional measurement of Henry's law constant were realized by considering gas stripping method. Effect of total pressure (realized by addition of methane) and effect of acid gas loading for a constant total pressure around 7 MPa were studied. The increasing of pressure and acid gas loading increase the apparent Henry's law constant of the mercaptan, highlighting a drop out effect of the mercaptans.

A performance comparison study of five single and sixteen blended amine absorbents for CO2 capture using ceramic hollow fiber membrane contactors

• A new emerging topic in CO 2 gas separation and chemical engineering was presented. • CO 2 absorption using a hydrophobic modified ceramic hollow fiber membrane contactor. • CO 2 capture performances in twenty-one amine-based absorption systems were examined. • CO 2 capture performance order was MEA ≥ DEA ≥ PZ > AMP > MDEA. • MDEA blended DEA reaches a percentage of increase of CO 2 absorption flux over 500%. The present study has endeavored to establish the relations between the CO 2 absorption properties of five single amine-based absorbents including monoethanolamine (MEA), diethylamine (DEA), N -methyldiethanolamine (MDEA), 2-amino-2-methyl-1-propanol (AMP), and piperazine (PZ), and their sixteen binary mixtures in the blended amine-based absorbents for CO 2 chemical absorption using a hydrophobic modified ceramic hollow fiber membrane contactor (HFMC). Keeping all other variables constant, the CO 2 absorption properties of single and blended amine-based absorbents for CO 2 chemical absorption using hydrophobic modified ceramic HFMCs are highly dependent on their chemical nature and concentration. MEA and DEA have the highest CO 2 absorption flux among the single amine solutions. For the CO 2 absorption in the blended amine-based absorbents, the replacement of MDEA with 20 wt% DEA increased the CO 2 chemical absorption from 1 × 10 4 mol/m 2 s to about 7 × 10 4 mol/m 2 s. Aqueous MDEA blended DEA reaches a percentage of increase of CO 2 absorption flux over 500% in comparison with the corresponding aqueous solution of single MDEA.