Aqueous Monoethanolamine Research Articles

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.

Structural Features of Monoethanolamine Aqueous Solutions with Various Compositions: A Combined Experimental and Theoretical Study Using Vibrational Spectroscopy.

In this work, we studied aqueous solutions of monoethanolamine (MEA), which are widely used to remove CO2 from flue and oil gases. This study combined experimental and theoretical methods of vibrational spectroscopy, using high-temperature infrared spectroscopy, quantum-chemical calculations of theoretical vibrational spectra, and structural electronic and energy characteristics of model structures. MEA has a propensity to form associations between various compositions and structures with water molecules, as well as those composed solely of water molecules. The structural and energy characteristics of such associates were analyzed in terms of their ability to interact and retain carbon dioxide. The influence of elevated temperatures and concentration of aqueous MEA solution on change in the structure of associates has also been investigated. An analysis of theoretical and experimental vibrational spectra allowed us to examine the IR spectra of MEA solutions, and identify the bands responsible for the formation of associates that would sorb CO2 well, but would delay its desorption from the solution.

Evaluation of hybrid amines and alcohol solvent with ion-exchange resin catalysts for energy-efficient CO2 capture

Cation exchange resin catalysts are a novel approach to accomplish improvement in aqueous monoethanolamine (MEA) regeneration.

Transport properties of mixtures of acid gases with aqueous monoethanolamine solutions: A molecular dynamics study

We investigated the effect of temperature and monoethanolamine (MEA) concentration on the self-diffusivity of acid gases, CO2 , and H2S in aqueous MEA solutions. For this purpose, we computed densities of pure MEA and 30 wt% MEA/water solutions while scaling the LJ energy (ϵ) parameter and point charges of MEA. Results show that with a scaling factor of 0.80 applied to the point charges of MEA, computed densities agree well with the experimental ones from literature. This was tested by computing viscosities and the self-diffusivity of pure MEA and 30 wt% MEA/water solutions and comparing these with experiments. We showed that the scaling factor of 0.80 also works well for predicting transport properties of MEA/water solutions. Finally, we computed self-diffusivities of infinitely diluted CO2 and H2S for temperatures ranging from 293–353 K and MEA concentrations of 10–50 wt%. Our results show that the self-diffusivity of both acid gases depends significantly on the temperature and MEA concentration in the solution. The results of this study will contribute to the development of more efficient acid gas treatment processes.

Use of copper carbonate as corrosion inhibitor for carbon steel in post combustion carbon capture

The realisation of post-combustion CO2 capture (PCCC) at industrial scale remains limited; one challenge is the concerns around capital costs and another concern is corrosion of the system itself. Corrosion resistance and mitigation against the amine solvent monoethanolamine (MEA) was studied, using the inhibitor copper (II) carbonate basic (CC). Carbon steel (C1018) was tested in CO2 loaded, 5M aqueous MEA solution, alone and in the presence of CC, to assess the corrosivity of the solution. Immersion testing used mass loss, Fe and Cu ion concentration in solution via ICP-MS, imaging (SEM) and analytical techniques (XRD and EDX) to investigate the effect of corrosion. Generally, the use of CC improved C1018 corrosion resistance relative to C1018 alone. Even at low concentrations (0.9 mM), CC was effective in inhibiting corrosion against CO2 loaded MEA, as the observed corrosion rate was effectively zero and no dissolved Fe was detected in solution. There was no evidence of copper surface adsorption. To clarify the solution chemistry resulting in corrosion inhibition, the local chemical environment of Fe and Cu were probed by Cu and Fe K-edge X-ray Absorption Spectroscopy, respectively. The Cu K- edge HERFD-XANES spectra reveal that a Cu2+ amine complex forms, critical to understanding the structure which is promoting significant corrosion inhibition.

Membranes Based on PTMSP/PVTMS Blends for Membrane Contactor Applications.

In this work, perspective polymeric materials were developed for membrane contactor applications, e.g., for the dissolved oxygen removal from amine CO2 capture solvents. Several polymeric blends based on poly[1-trimethylsilyl-1-propyne] (PTMSP) and poly[vinyltrimethylsilane] (PVTMS) were studied. The gas and water vapor sorption and permeability coefficients for the PTMSP/PVTMS blend membranes at different PVTMS contents (0-100%) were obtained under temperatures of 30 and 60 °C for the first time. As the PVTMS content increases, the O2 and CO2 permeabilities decrease by 160 and 195 times at 30 °C, respectively. The fractional accessible volume of the polymer blends decreases accordingly. The transport of the CO2 capture solvent vapors through the PTMSP/PVTMS blend membranes were determined in thermo-pervaporation (TPV) mode using aqueous monoethanolamine (30%), N-methyldiethanolamine (40%), and 2-amino-2-methyl-1-propanol (30%) solutions as model amine solvents at 60 °C. The membranes demonstrated high pervaporation separation factors with respect to water, resulting in low amine losses. A joint analysis of the gas permeabilities and aqueous alkanolamine TPV data allowed us to conclude that the polymer blend composition of PTMSP/PVTMS 70/30 provides an optimal combination of a sufficiently high oxygen permeability and the pervaporation separation factor at a temperature of 60 °C.

CO2 absorption using benzylamine as absorbent and promoter in a hollow fiber membrane contactor: A numerical study

Benzylamine (BZA) is a novel amine that indicates a promising potential for CO2 absorption. In this work, a mathematical model has been presented to investigate the CO2 absorption using aqueous BZA compared to aqueous monoethanolamine (MEA), diethanolamine (DEA), and 4-diethylamino-2-butanol (DEAB) in a hollow fiber membrane contactor (HFMC). Several factors such as CO2 partial pressure, amine concentration, gas velocity, liquid velocity, temperature, wettability, and mass transfer resistance of phases have been studied. According to the results, increment in the amine concentration, CO2 partial pressure, liquid velocity, gas velocity, and temperature have enhanced the CO2 absorption flux. Also, adding BZA to aqueous MDEA and K2CO3 significantly increases the CO2 absorption flux in both solutions. Moreover, the mass transfer resistance of individual phases reveals that the liquid phase mass transfer resistance is the controlling phase in non-wetted mode, while with membrane wetting, contribution of membrane side mass transfer resistance increases and become the controlling phase. In general, BZA could be a prominent potential choice as absorbent and promoter for CO2 absorption in HFMCs.

Kinetics study and performance evaluation of a hybrid choline-glycine/polyethylene glycol/water absorbent for CO2 separation

Thermodynamic and kinetic properties of absorbents are beneficial in evaluating their CO2 separation performance. In this study, the kinetic properties of CO2 in a hybrid choline-glycine/polyethylene glycol/water absorbent, including the liquid-side mass-transfer coefficient, enhancement factor, and reaction rate constant, were systematically determined through experimental measurements and data processing. Furthermore, an index referred to as “absorbility” was proposed to combine the kinetic properties determined in this study with the thermodynamic properties obtained in our previous study to evaluate the CO2 separation performance. Additionally, the regeneration performance of the hybrid absorbent was also conducted. The results show that the performance of the hybrid absorbent (30 wt% [Cho][Gly] + 10 wt% PEG200 + 60 wt% H2O) is comparable to that of aqueous monoethanolamine, and is thus promising for CO2 separation, considering its low regeneration temperature and low environmental impact.

Impact of Solvent on the Thermal Stability of Amines.

Water-lean solvents have been proposed as a possible alternative to aqueous amine systems in postcombustion carbon capture. There is however little data available on how amine degradation is affected by different solvents. This study presents new insights on the effect of solvent on thermal degradation of alkanolamines from laboratory-scale degradation experiments. Replacing the water in aqueous monoethanolamine (MEA) solutions with organic diluents resulted in varying thermal degradation rates. Overall, all tested organic diluents (triethylene glycol, diethylene glycol, mono ethylene glycol, tetrahydrofurfuryl alcohol, N-formyl morpholine/water, and N-methyl-2-pyrrolidone) resulted in higher thermal degradation rates for loaded MEA. None of the proposed parameters, such as acid-base behavior, polarity, or relative permittivities, stood out as single contributing factors for the variation in degradation rates. The typical degradation compounds observed for an aqueous MEA solvent were also observed for MEA in various concentrations and with various organic diluents.

Experimental and Thermodynamic Investigation on CO2 Absorption in Aqueous MEA Solutions

The vapor-liquid equilibrium (VLE) of CO2 in a reactive solvent is essential for the proper simulation and design of CO2 absorption processes. This work presents a systematic investigation on CO2 absorption in various aqueous monoethanolamine (MEA) solutions. CO2 solubility in MEA was measured at 298, 313, 333, and 353 K with CO2 partial pressure ranging from 34.5 to 78.0 kPa. A modified Kent-Eisenberg model was developed based on the measured solubility data, showing good predictions over the liquid phase speciation for the CO2-H2O-MEA system. We presented a new analysis based on the first-order difference curve of distribution profiles of the species. Based on the main reactions that occurred, the CO2 absorption process was demonstrated to be divided into four regions with increasing CO2 loading from 0 to 1. Accordingly, kinetic study was proposed to be conducted in the first region, whereas measuring of mass transfer in the first three regions. The findings in this work extend the existing knowledge of CO2 absorption process in terms of speciation and can provide important guidance for further study of the process characteristics using aqueous amine absorbents.

Perstraction of Heat-Stable Salts from Aqueous Alkanolamine Solutions

Amine absorption processes designed to remove acid gases from gas streams generally face a major challenge of solvent degradation. This degradation leads to the formation of heat-stable salts (HSS), corrosive agents that irreversibly bind free alkanolamine. The present study proposes, for the first time, a method for HSS perstraction using a liquid–liquid membrane contactor that allows HSS to transfer through porous membranes from the solvent into a hydrophobic extractant represented by a methyltrioctylammonium solution in 1-octanol. The perstraction provides selective extraction of HSS anions without direct mixing of liquid phases or the formation of stable emulsions of the solvent and the extractant. For this purpose, a number of industrial and laboratory porous membrane samples fabricated from polyvinylidene fluoride, polypropylene, and polysulfone were investigated. Their chemical and morphological stability, surface properties, and transport properties were tested under prolonged (>600 h) contact with a model solvent (an aqueous monoethanolamine solution) and with the components of the selective extractant. The feasibility of HSS perstraction was demonstrated using the formic acid (as an HSS model) extraction from the model solvent. The most promising results were obtained for a system with a polyvinylidene fluoride membrane: up to 50% of formic acid was extracted over 18 h.

Nanostructured AlOOH – A promising catalyst to reduce energy consumption for amine-based CO2 capture

In order to alleviate the intensive energy demand of amine-based post-combustion carbon capture technology, metal oxyhydroxide AlOOH of nanoscale was synthesized through the hydrothermal method and applied to accelerate the CO2 desorption rate and reduce the regeneration heat duty of aqueous monoethanolamine (MEA) solution for the first time. Results showed that the use of AlOOH could accelerate the desorption rate by up to 560% and increase the desorption amount by 251%. By comparing the performance between AlOOH and Al2O3, it can be found that the presence of extra hydroxyl groups is 20.6% more efficient in catalyzing CO2 desorption. According to a simplified heat transfer model created in this work, AlOOH could reduce the heat duty by 17% with only 0.1 wt% loading, which exhibited the highest performance cost ratio among related literature. In addition, the cyclic stability of AlOOH was confirmed through various characterization methods, including XRD, FT-IR, SEM, and N2 adsorption–desorption. More importantly, a possible catalytic mechanism of AlOOH was discussed and proved where it could change reaction pathways in different CO2 loading regions. This work reveals a promising research direction towards cost-efficient and high-performance metal oxyhydroxide catalysts in the catalytic amine regeneration field to approach the net-zero carbon emission goal.

Capture of CO2 from Steam Reformer Flue Gases Using Monoethanolamine: Pilot Plant Validation and Process Design for Partial Capture

Carbon dioxide (CO2) capture from a slipstream of steam reformer flue gas (18–20 vol %wet CO2) using 30 wt % aqueous monoethanolamine was performed for ∼500 h in a mobile test unit (∼120 kg CO2/h). Specific reboiler duties (SRDs) of 3.6–3.8 MJ/kg CO2 were achieved at 90% capture. The pilot data validate the modeling of off-design partial capture, that is, operation at lower CO2 capture rates (at constant gas flow) than the absorption column was designed to achieve. This paper demonstrates that off-design partial capture enables significant energy savings (SRD, cooling) relative to on-design capture. The accrued savings depend on the column design (packing height, flooding approach) and the feed CO2 concentration. Finally, a concept for stepwise deployment of carbon capture and storage in industries with high-CO2 concentration sources (e.g., steel and cement manufacturing and refining) is introduced. Thanks to its inherent full-capture-ready design, the initial energy-efficient, off-design partial capture operation can be extended to full capture over time.

Exergy, advance exergy, and exergo-environmental based assessment of alkanol amine- and piperazine-based solvents for natural gas purification

Purification of Natural gas is vital for utilizing it as a source of energy harvesting for the world. Amine-based chemical absorption technique is the most utilized in the gas field for the purification of gas that ensures the purity of the sweet gas stream with the elimination of carbon dioxide. However, it is considered an energy-intensive process to deal with considerable energy loss and environmental damage to the ecosystem. Five cases have been developed in this study based on various blends comprising mono and tertiary amines in combination with piperazine with a focus on the use of Aqueous Monodiethanolamine (Aq. MDEA), Aqueous Monoethanolamine (Aq. MEA) and piperazine (Pz) for the CO2 sequestration from the sour natural gas extracted from the remote location located in the province of Baluchistan in Pakistan. The use of exergy, advanced exergy, and exergo environment for optimizing and selecting a suitable solvent combination that may result in an effective separation process has been proposed. Five cases have been developed based on various blends such as mono and tertiary amines combined with piperazine. From the results of all the studied scenarios, Case IV, based on the combination of Aqueous monoethanolamine and piperazine, provides reduced exergy destruction of 2551.7 KW. It was observed that the maximum removal of CO2 around 99.87 wt% is achieved in case IV. In addition, advance exergy analysis also highlights that case-IV has a venue of 25% exergy destruction avoidable, which would further enhance its performance. Nevertheless, still, case-IV has 75% exergy destruction unavoidable. The environmental factors show that Case-IV has a reduced exergy destruction factor of 0.96, a highly environmentally benign choice as a solvent with a high value of 1.03, and case-IV has the higher operational stability and higher exergy efficiency with an exergy stability value of 0.40. Therefore, monoethanolamine combined with piperazine to be an effective and efficient solvent blend that could be an energy-effective approach for sweetening the natural gas.

Studies on advanced configurations of post-combustion CO2 capture process applied to cement plant flue gases

This study used ProMax® 5.0 process simulator to develop three innovative configurations for cement plant flue gases specifically. A detailed evaluation of three innovative configurations was presented, and the advanced technical and economic benefits of the three innovative configurations were compared with the conventional configuration. The simulation consisted of three cases of flue gas compositions. The major case was simulated based on the published design parameters from an existing cement plant in Quebec, Canada. The other two cases of flue gas compositions were two assumptions for higher CO2 content of the cement plant flue gases, including 20 vol.% CO2 and 28.6 vol.% CO2. This research provided a comparison of the solvent regeneration energy using a single aqueous Monoethanolamine (MEA) solution and the solution activated with 1-(2-Aminoethyl)piperazine (AEP). The evaluations showed that the innovative configurations were able to reduce regeneration energy up to 22% and solvent demand up to 10%. The savings towards variable CO2 content of the flue gases were also discovered.

Nonaqueous (amine + glycol ether) solvents for energy-efficient CO2 capture: New insights into phase change behaviors and assessment of capture performance

Nonaqueous amine-based absorbents, particularly liquid biphasic solvents, have recently received increasing attention due to the potential for reducing the energy penalty of CO2 capture. In this work, a series of glycol ethers were used as cosolvents dissolving primary and secondary alkanolamines. Phase transition behavior, CO2 absorption and desorption characteristics have been investigated for the nonaqueous 5.0 M amine blends. Different phase behaviors upon CO2 absorption were discussed and well explained by the polarity change and the solubility parameter interaction distance (SPID) of components and the reaction products. Regeneration energy requirement was also experimentally estimated and compared with the reference aqueous monoethanolamine (MEA). The species in the CO2-loaded solution play a central role in regulating phase separation behaviour and CO2 capture performance. A defined SPID value was recommended to predict the monophasic and the biphasic states. Advanced systems of 2-(methylamino)ethanol (MAE) with diethylene glycol dimethyl ether (DEGDME) as liquid biphasic solvent and MAE with ethylene glycol monomethyl ether (EGME) as single phase solvent were proposed for energy-efficient CO2 capture. Among the systems investigated, MAE/EGME has the lowest regeneration energy consumption estimated at about 1.75 MJ kg−1 CO2 captured. The ionic carbonated products of alkanolamines can trigger the phase change behaviour due to their limited solubility in the more hydrophobic and weakly polar DEGDME, resulting in two opposite phases enriched in different components. Benefiting from the high enrichment (>95 %) of CO2 captured in the lower phase and the large cyclic capacity, MAE/DEGDME biphasic solvent can reduce the energy consumption by 50–59 % compared with aqueous MEA.

Corrosion Behavior of Stainless Steels in CO2 Absorption Process Using Aqueous Solution of Monoethanolamine (MEA)

The corrosion behavior of two stainless steels (316L and 304L) was evaluated using a CO2-loaded aqueous solution of 30 wt.% monoethanolamine (MEA) with a view to simulating corrosion related mechanisms in amine treatment procedures. Corrosion behavior was experimentally evaluated as a function of CO2 loading and solution temperature, using electrochemical techniques (polarization curves, cyclic polarization, and EIS measurement). The results reveal that the aqueous MEA solution containing CO2 creates a favorable environment for the corrosion of both stainless steels. The rate of corrosion is accelerated when the temperature of the loaded MEA solution rises, which was attributed to the thermal degradation of the loaded MEA, thus causing higher kinetics of the cathodic reactions at higher temperatures. More specifically, for the SS 304L the corrosion rate is almost doubled when the solution temperature is increased from 25 °C to 40 °C and is quadrupled when the solution temperature rises to 80 °C. For the SS 316L, the corrosion rate becomes almost threefold and sixfold upon increasing temperature of the load amine solution to 40 °C and 80 °C, respectively. The overall corrosion rate of SS 316L is lower with respect to the SS 304L for the same temperature and loading conditions. The essential dependency of corrosion rate on solution type (unloaded and loaded MEA solution) demonstrates that the corrosion process and reactions are controlled by a diffusion mechanism.

Effects of hydroxyethyl group on monoethanolamine (MEA) derivatives for biomethane from biogas upgrading

Upgrading of biogas to produce biomethane is an essential way to increase the calorific value of biogas by separating CH4 and CO2 to satisfy the global renewable energy demand. In this study, the efficiency of carbon dioxide (CO2) trapping in aqueous monoethanolamine (MEA), diglycolamine (DGA), diethanolamine (DEA), and triethanolamine (TEA) solution during biogas upgrading for biomethane was determined. Effects of hydroxyethyl groups on MEA derivatives were investigated in terms of biogas upgrading and regeneration, CO2 desorption heat, initial CO2 absorption rate and CO2/CH4 selectivity. The duration of upgraded biogas meeting certain European Union (EU) application standards for methane purity during upgrading was reduced by 70, 78 and 200 mins for DGA, DEA and TEA respectively compared to MEA due to the partial substitution of H-bonds by hydroxyethyl groups, and the absorption rate was also reduced, whereas TEA was not suitable for biogas upgrading as it was inefficient for biogas upgrading effect and absorption rate. The calculated results from the Gibbs-Helmholtz equation showed that MEA had the largest CO2 desorption heat (82.47 kJ/mol CO2) and the other MEA derivatives had lower desorption heat than MEA, indicating that MEA consumes more energy in the desorption process. As for the equilibrium partial pressure, all amine solutions absorbed less than 0.4% of the total volume of CH4 and had a high CO2/CH4 selectivity.

An experimental/computational study of steric hindrance effects on CO2 absorption in (non)aqueous amine solutions

AbstractThe reaction kinetics and molecular mechanisms of CO2 absorption using nonaqueous and aqueous monoethanolamine (MEA)/methyldiethanolamine (MDEA)/2‐amino‐2‐methy‐1‐propanol (AMP) solutions were analyzed by the stopped‐flow technique and ab initio molecular dynamics (AIMD) simulations. Pseudo first‐order rate constants (k0) of reactions between CO2 and amines were measured. A kinetic model was proposed to correlate the k0 to the amine concentration, and was proved to perform well for predicting the relationship between k0 and the amine concentration. The experimental results showed that AMP/MDEA only took part in the deprotonation of MEA‐zwitterion in nonaqueous MEA + AMP/MEA + MDEA solutions. In aqueous solutions, AMP can also react with CO2 through base‐catalyzed hydration mechanism beside the zwitterion mechanism. Molecular mechanisms of CO2 absorption were also explored by AIMD simulations coupled with metadynamics sampling. The predicted free‐energy barriers of key elementary reactions verified the kinetic model and demonstrated the different molecular mechanisms for the reaction between CO2 and AMP.

Formation and polymorph transformation trends of metal carbonate in inorganic CO2 conversion process using simulated brine: Study for post-treatment of industrial brine via CO2 conversion

To improve inorganic carbon capture utilization (CCU) technology, practical solution for global warming technology, we studied the formation and transformation trends of mineral carbonation using simulated brine. we converted CO2 into inorganic compounds, metal carbonate, using CO2 saturated aqueous monoethanolamine (MEA) solution. The produced metal carbonate varied according to the simulated brine's cation component, resulting from ion interactions in the system. It turns out that the common ion effect, which occurred due to the system's ion interactions involving changes of ionic atmosphere and salinity of the system, was the main reason for the various carbonation trends. Salting- out effect dominantly occurred in the single precipitation system whereas salting-in effect occurs in multi precipitation system (system CM and system CMN). However, salting-out effect also occurred in system CMN because of Na+. Moreover, we also found that Na+, which was overlooked in prior studies regarding polymorph transformation, also affects polymorph transformation. The interactions between the abovementioned effects involved the variation in the results. This variation interrupted the wide usage of the technology. However, through the study, we suggest ambient estimation of the final product with cation component. It would help future studies and demonstration of the inorganic CCU technology using brine.