Aqueous Solutions Of Methyldiethanolamine Research Articles

Evaluating the Effectiveness of Piperazine on Carbon Dioxide Loading in N-Methyl Diethanolamine Aqueous Solutions and Water/Oil Microemulsions

Evaluating the Effectiveness of Piperazine on Carbon Dioxide Loading in <i>N</i>-Methyl Diethanolamine Aqueous Solutions and Water/Oil Microemulsions

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.

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.

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.

Elucidation of Operating Parameters Influencing the Ultrasonic-Assisted Absorption of Bulk CO2 Using Unpromoted and Promoted Methyldiethanolamine

Various acid gas sweetening processes can be used to separate CO2 from natural gas. As one of the most matured and widely utilized gas sweetening processes, absorption has been continuously improved to meet the stringent separation requirement. Ultrasonic irradiation has recently been introduced as an alternative technique to intensify the absorption process. Nevertheless, further studies are still needed to mature this new technique, particularly using slow kinetic absorbents possessing high inherent CO2 absorption capacity. Moreover, performing experimental studies using blended solvents in the high-frequency ultrasonic-assisted absorption system has also introduced a new idea in this field. This experimental study presents the CO2 absorption into aqueous solutions of methyldiethanolamine (MDEA) and piperazine (PZ)-promoted MDEA in an ultrasonic-assisted batch reactor. The influences of various operating parameters on CO2 absorption performance were evaluated in both promoted and unpromoted conditions. The parameters of the experiments included ultrasonic power at a frequency of 1.7 MHz, absorbent concentration, temperature, and CO2 partial pressure. Based on the results, ultrasonic power was found to be the most critical factor influencing the CO2 absorption rate. Moreover, the potential of the high-frequency ultrasonic-assisted CO2 absorption reactor was further elucidated via comparison with the conventional stirring and silent conditions under identical operating conditions. The highest CO2 absorption rate was achieved at an ultrasonic power of 12.36 W, a temperature of 70 °C, a CO2 partial pressure of 10 bar, an absorbent concentration of 50 wt %, and a promoter concentration of 5 wt %. In addition, the CO2 absorption rate in the high-frequency ultrasonic-assisted reactor using the MDEA absorbent was 28 and 52 times higher compared to stirring and silent conditions, respectively. The CO2 absorption rate enhancement was approximately 17 and 54 times higher for the PZ-MDEA.

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.

Reduction of waste disposed to the environment through recycling of unused methyldiethanolamine

A 30% aqueous solution of waste methyldiethanolamine (MDEA) can be regenerated, reused in gas treatment, and its residue can be used as a secondary raw material in another area of production. (HOCH2CH2)2NСH3 is separated from water by a 30% aqueous vacuum-extraction method. MDEA and its destroyed part remain in the column. In laboratory conditions, it was shown that the degree of purification from destruction products by this method is from 60 to 78%. The analysis of the research results showed that the parameters of the main operational properties (density, viscosity, surface tension, foaming) of purified amine were significantly improved.

Experimental Study of the Influence of Different Load Changes in Inlet Gas and Solvent Flow Rate on CO2 Absorption in a Sieve Tray Column.

An experimental study was conducted in a sieve tray column. This study used a simulated flue gas consisting of 30% CO2 and 70%. A 10% mass fraction of methyl diethanolamine (MDEA) aqueous solution was used as a solvent. Three ramp-up tests were performed to investigate the effect of different load changes in inlet gas and solvent flow rate on CO2 absorption. The rate of change in gas flow rate was 0.1 Nm3/h/s, and the rate of change in MDEA aqueous solution was about 0.7 NL/h/s. It was found that different load changes in inlet gas and solvent flow rate significantly affect the CO2 volume fraction at the outlet during the transient state. The CO2 volume fraction reaches a peak value during the transient state. The effect of different load changes in inlet gas and solvent flow rate on the hydrodynamic properties of the sieve tray were also investigated. The authors studied the correlation between the performance of the absorber column for CO2 capture during the transient state and the hydrodynamic properties of the sieve tray. In addition, this paper presents an experimental investigation of the bubble-liquid interaction as a contributor to entropy generation on a sieve tray in the absorption column used for CO2 absorption during the transient state of different load changes.

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.

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.

Use of chicken feathers as potential adsorbent for the reclamation of industrial lean methyl diethanolamine solutions

ABSTRACT Sweetening units using methyl diethanolamine (MDEA) solvent are instrumental in removing hydrogen sulfide and carbon dioxide from natural gas. However, over time MDEA degrades and loses its scavenging efficiency due to the formation of heat-stable salts (HSS) that are hard to remove. Chicken feathers (CFs), a poultry waste by-product, are rich in functional groups that could help to remove HSS from alkanolamine solutions. CFs were characterized using XRD, SEM-EDX, TGA, DSC, and BET. FTIR spectroscopy analysis confirmed the presence of hydroxyl and amide groups that were responsible for the total organic acid (TOA) anions adsorption. The Freundlich model best fitted the equilibrium adsorption data with a maximum uptake capacity of 525 mg/g at 298 K. Kinetic analysis showed that the Pseudo-Second-Order model best fitted results with a rate constant of 0.0006 min−1. The equilibrium thermodynamic study showed that the biosorption process was spontaneous. CFs exhibited good recyclability and high TOA uptake capacity even after five cycles using absolute ethanol as the eluent, maintaining 88% of the adsorption ability. The results demonstrated that CFs could be employed as a low-cost alternative to commercial activated carbon absorbents that are currently used to clean industrial lean MDEA aqueous solutions from their HSS contaminants.

A Novel Methodology for Online Analysis of Amine Solution Degradation Caused by Fly Ash

Two research goals were set for this study. (1) The first goal was to develop a reliable and cost-effective online analytical technique to measure amine solvent concentration, loading, and to quantify the amine degradation process based on Gas Chromatography (GC). (2) The second goal was the investigation of amine degradation in the presence of fly ash, which includes: the identification of proper chemistry of degradation; and, the identification and quantification of the degradation products of the amines. For this study, aqueous monoethanolamine (MEA) and aqueous methyldiethanolamine (MDEA) have been selected. To accomplish the first goal, an online analytical technique to quantify the amine solvent chemistry based on Gas Chromatography (GC) was developed and set up in the lab. An automatic liquid sample injection system was attached to the GC to study the impact of the concentration of fly ash on the degradation process of two well-known amines (MEA and MDEA) by measuring the concentrations of amine, water and carbon dioxide (CO2). The flow system was equipped with filters to avoid the introduction of large particles into the GC column. A solvent back-flush system was used to allow for automated cleaning of the particulate filters. GC was then calibrated for the amine and water using various concentrations of aqueous amines (MEA and MDEA), and various CO2 loaded aqueous MDEA solutions and aqueous solutions of ammonium bicarbonate (NH4HCO3) were used to calibrate the GC for quantification of CO2 using a Total Organic Carbon / Total Inorganic Carbon (TOC/TIC) analyzer. To accomplish the second goal, two kinds of fly ash samples were collected from a coal burning power plant. Fly ash samples collected from the power plant were analyzed by SGS Canada Inc. ASTM methods were used to estimate the ash percentage, moisture content and elemental composition of the fly ash (silica and other metal oxides). A lab scale experimental setup was designed and developed to observe the influence of fly ash on amine-based solvents (MEA or MDEA) degradation.

Enhanced research of absorption by mass transfer promoters

Activators such as piperazine (PZ) are widely used to increase the CO2 absorption rate of aqueous methyldiethanolamine (MDEA) solutions by accelerating reaction. However, a big difference (1 to 2 orders of magnitude) in the enhancement of absorption rate with the addition of PZ was obtained in different studies. In this work, it was proved that mass transfer is the rate-limiting step in the above process and in most cases enhancing mass transfer is quite essential. Some low-polar solvents were screened as “mass transfer promoters (MTPs)” to enhance mass transfer by inducing interfacial turbulence, which markedly improved the CO2 absorption performance of MDEA solutions. The individual addition of PZ and MTPs to the MDEA solution, which correspond to the reaction enhancement and the mass transfer enhancement, increased the absorption rate by 131% and 33%–319%, respectively. The co-effects of enhancing both reaction and mass transfer (in the presence of activators and MTPs) can lead to 2 to 10-fold increase in the absorption rate. Furthermore, MTPs could increase the CO2 cyclic loading and desorption rate by 27% and 100%, respectively, indicating that the MDEA/MTPs had significant advantages for reducing the energy consumption in CO2 capture applications.

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.