Amine, 2-amino-2-methyl-1-propanol Research Articles

CO2 Capture and Release in Amine Solutions: To What Extent Can Molecular Simulations Help Understand the Trends?

Absorption in amine solutions is a well-established advanced technology for CO2 capture. However, the fundamental aspects of the chemical reactions occurring in solution still appear to be unclear. Our previous investigation of aqueous monoethanolamine (MEA) and 2-amino-2-methyl-1,3-propanediol (AMPD), based on ab initio molecular dynamics simulations aided with metadynamics, provided new insights into the reaction mechanisms leading to CO2 capture and release with carbamate formation and dissociation. In particular, the role of water-strongly underestimated in previous computational studies-was established as essential in determining the development of all relevant reactions. In this article, we apply the same simulation protocol to other relevant primary amines, namely, a sterically hindered amine (2-amino-2-methyl-1-propanol (AMP)) and an aromatic amine (benzylamine (BZA)). We also discuss the case of CO2 capture with the formation of bicarbonate. New information is thus obtained that extends our understanding. However, quantitative predictions obtained using molecular simulations suffer from several methodological problems, and comparison among different chemical species is especially demanding. We clarify these problems further with a discussion of previous attempts to explain the different behaviors of AMP and MEA using other types of models and computations.

Evaluation of a New Chemical Mechanism for 2-Amino-2-methyl-1-propanol in a Reactive Environment from CSIRO Smog Chamber Experiments.

Amines are considered as an emerging class of atmospheric pollutants that are of great importance to atmospheric chemistry and new particle formation. As a typical amine, 2-amino-2-methyl-1-propanol (AMP) is one of the proposed solvents for capturing CO2 from flue gas streams in amine-based post-combustion CO2 capture plants, and it is expected to result in AMP emission and secondary product formation in the atmosphere. However, the current knowledge of its atmospheric chemistry and kinetics is poorly understood, particularly in a reactive environment. In this work, we used the CSIRO smog chamber to study the photo-oxidation of AMP in the presence of volatile organic compound (VOC)-NOx surrogate mixtures over a range of initial amine concentrations. O3 formation was significantly inhibited when AMP was added to the surrogate VOC-NOx mixtures, implying that AMP could alter known atmospheric chemical reaction pathways and the prevailing reactivity. Simultaneously, a large amount of AMP-derived secondary aerosol was formed, with a considerably high aerosol mass yield (i.e., ratio of aerosol formed to reacted AMP) of 1.06 ± 0.20. Based on updated knowledge of its kinetics, oxidation pathways, and product yields, we have developed a new mechanism (designated as CSIAMP-19), integrated it into the Carbon Bond 6 (CB6) chemical mechanism, and evaluated it against available smog chamber data. Compared with the existing AMP mechanism (designated as CarterAMP-08), the modified CB6 with CSIAMP-19 mechanism improves prediction against AMP-VOC-NOx experiments across a range of initial AMP concentrations, within ±10% model error for gross ozone production. Our results contribute to scientific understanding of AMP photochemistry and to the development of the chemical mechanism of other amines. Once some potential limitations are considered, the updated AMP reaction scheme can be further embedded into the chemical transport model for regional modeling scenarios where AMP-related emissions are of concern.

Aqueous mixtures of AMP, HMDA-N,N′-dimethyl and TEG for CO2 separation: a study on equilibrium and reaction kinetics

The hindered amine 2-amino-2-methyl-1-propanol (AMP) is a capable CO2 separation solvent. HMDA-N,N′-Dimethyl (or HMDA-N,N′), which is the dimethyl derivative of 1,6-hexamethyl diamine, is a prospective activator of the absorption rate in AMP/H2O mixtures. If a less volatile co-solvent such as triethylene glycol (TEG) is used in AMP-based solutions, the regeneration energy constraint will be lowered. In this work, a formulated blend of AMP (2-3 M), HMDA-N,N′ (0.1–0.5 M), TEG (0.7–2 M) and water was suggested for improved CO2 capture from flue gas in thermal power stations. Kinetics of the CO2 reaction with the suggested blend was studied in a stirred cell at 35, 40, and 45 °C. The pathway was elucidated using the renowned zwitterion mechanism. Overall, it was envisaged that both AMP and HMDA-N,N′ react with CO2 in parallel. The values of the pseudo-first order rate constant were determined. It was found that HMDA-N,N′ reacts with CO2 according to a second-order reaction (rate constant k2,HMDA-N,N′ = 79,525 M−1 s−1 at 35 °C), whose energy of activation is 38 kJ mol−1. Lastly, the loading capacity of the suggested blend was measured in an ambient-pressure equilibrium setup. Its highest value was 1.4 mol CO2/mol amine, when equilibrium CO2 pressure was 4 kPa.

Precipitating non-aqueous amine systems for absorption of carbon dioxide using 2-amino-2-methyl-1-propanol

The aim of this study was to find a solvent to replace N-methyl-2-pyrrolidone (NMP) in CO2 absorption systems containing the amine 2-amino-2-methyl-1-propanol (AMP), in order to reduce the health risks associated with handling, as NMP is reproductively toxic. Seven organic solvents were investigated: dimethyl sulfoxide (DMSO), 3-(dimethylamino)propionitrile (3DMAPN), 1-pentanol (1 P), propylene carbonate (PC), 4-heptanone (4 H), 1-methylimidazole (1MIMI) and cyclohexanol (CH). Henry’s constant, the CO2 solubility and the differential heat of absorption were determined for the pure solvents, and in solvent mixtures containing 25 wt% AMP, at 25 °C and 40 °C.Three of the solvents were found to have promising absorption properties: DMSO, 3DMAPN and 1 P. In mixtures with AMP, precipitation was formed at both 25 and 40 °C, and the CO2 absorption capacity was similar to that in the AMP–NMP system, in terms of the CO2 loading for a given partial pressure of CO2. The results also indicated that the reaction of AMP and CO2 in these solvents can be described by the zwitterion reaction mechanism.

Influence of temperature and solvent concentration on the kinetics of the enzyme carbonic anhydrase in carbon capture technology

In this study the effect of carbonic anhydrase addition on the absorption of CO2 was investigated in a wetted wall column apparatus. Four different solvents: the primary amine monoethanolamine (MEA), the sterically hindered primary amine 2-amino-2-methyl-1-propanol (AMP), the tertiary amine N-methyl-diethanolamine (MDEA) and the carbonate salt solution K2CO3 were compared in concentrations from 5 to 50wt% in a temperature range of 298–328K with and without enzyme. Necessary mass transfer parameters such as liquid side mass transfer coefficient and solvent and enzyme reaction rates were determined and benchmarked to a 30wt% MEA solution. The study reveals that the addition of the enzyme carbonic anhydrase (CA) dramatically increases the liquid side mass transfer coefficient for MDEA, and K2CO3; AMP has a moderate increase whereas MEA was unchanged. The results confirm that just bicarbonate forming systems benefit from CA. The influence of temperature on the enzyme kinetics and mass transfer coefficients is different for different solvent types. A temperature increase resulted in lower liquid side mass transfer coefficient for MDEA and K2CO3 but in a higher coefficient for AMP. The overall first order enzyme reaction rate (s−1) was linearly dependent on enzyme concentration for MDEA and K2CO3 at 313K. Temperature and concentration did increase the enzymatic rate constant slightly in the concentration range of 5–15wt% K2CO3 and significantly between 15 and 20wt%. The enzymatic reaction rate constant for MDEA decreased with temperature, the solvent concentration had a negligible on it. The enzymatic reaction rate for AMP rose with temperature and was higher for lower solvent concentration.

Carbon dioxide capture characteristics from flue gas using aqueous 2-amino-2-methyl-1-propanol (AMP) and monoethanolamine (MEA) solutions in packed bed absorption and regeneration columns

Increasing concentration of CO2 in the atmosphere contributing potential negative impact to the environment has been the subject of worldwide attention over the past few decades. CO2, one of the main greenhouse gases (GHG) is getting emitted to the environment from different industries such as fossil fuelled power plants, cement industry, refinery and synthetic ammonia production units etc. Gas scrubbing using aqueous alkanolamine solutions is the most promising retrofit option for post combustion carbon dioxide capture in recent days. The present study investigates an effective means of eliminating CO2 from flue gas using two primary amines, namely conventional monoethanolamine (MEA) and a sterically hindered amine, 2-amino-2-methyl-1-propanol (AMP). The CO2 absorption characteristics were experimentally examined in a packed column under various process conditions viz. CO2 partial pressure, gas and liquid flow rates, solvent concentrations and operating temperature and pressure. While the regeneration of solvent was studied at the temperature range from 368 to 382K. The present work reports mainly a comparative study of absorption and regeneration behaviour of the two alkanolamines which necessarily include the specific rate of absorption, percentage of CO2 absorbed, CO2 loading during absorption and residual CO2 after solvent regeneration and regeneration efficiency. The specific rate of absorption of AMP and MEA are observed to be (2.11–4.03)×10−5kmol/m2s and (5.36–9.55)×10−5kmol/m2s, respectively. The maximum percentage of CO2 absorbed using MEA is 99.13% and AMP is 98.88%. In case of solvent loading capacity (moles of CO2 per mole of amine) AMP is much better than MEA; the value is 0.777 moles for AMP as compared to MEA value 0.478 moles. The regeneration efficiency of AMP ranging from 96.39 to 97.26% is superior over MEA which is in the range of (79.91–81.55) %. The entire experimental absorption rate data are plotted with the response surface methodology (RSM) fitted data which shows a good agreement with the experimental value for both the amine solvents.

CO2 Absorption and Sequestration as Various Polymorphs of CaCO3 Using Sterically Hindered Amine

One aspect of the attempt to restrain global warming is the reduction of the levels of atmospheric CO2 produced by fossil fuel power systems. This study attempted to develop a method that reduces CO2 emissions by investigating the absorption of CO2 into sterically hindered amine 2-amino-2-methyl-1-propanol (AMP), the acceleration of the absorption rate by using the enzyme carbonic anhydrase (CA), and the conversion of the absorption product to stable carbonates. CO2 absorbed by AMP is converted via a zwitterion mechanism to bicarbonate species; the presence of these anions was confirmed with (1)H and (13)C NMR spectral analysis. The catalytic efficiency (kcat/Km), CO2 absorption capacities, and enthalpy changes (ΔHabs) of aqueous AMP in the presence or absence of CA were found to be 2.61 × 10(6) or 1.35 × 10(2) M(-1) s(-1), 0.97 or 0.96 mol/mol, and -69 or -67 kJ/mol, respectively. The carbonation of AMP-absorbed CO2 was performed by using various Ca(2+) sources, viz., CaCl2 (CAC), Ca(OOCCH3)2 (CAA), and Ca(OOCCH2CH3)2 (CAP), to obtain various polymorphs of CaCO3. The yields of CaCO3 from the Ca(2+) sources were found in the order CAP > CAA > CAC as a result of the effects of the corresponding anions. CAC produces pure rhombohedral calcite, and CAA and CAP produce the unusual phase transformation of calcite to spherical vaterite crystals. Thus, AMP in combination with CAA and CAP can be used as a CO2 absorbent and buffering agent for the sequestration of CO2 in porous CaCO3.

Pilot plant experiments for two new amine solvents for post-combustion carbon dioxide capture

Pilot plant experiments for post-combustion capture (PCC) were carried out with two new amine based solvent systems: Solvent A and Solvent B. Solvent A is an aqueous solution of a secondary amine tested within an industrial partnership and Solvent B is an aqueous solution of a mixture of the sterically hindered amine 2-amino 2-methyl 1-propanol (AMP) and the primary diamine 1,2-ethanediamine (EDA) tested within the EU-project CESAR. Experiments were carried out at various liquid to gas flow ratios (L/G) with a constant CO2 partial pressure of 100mbar, a constant F-factor of 1.7Pa0.5 and a constant CO2 removal rate of 90%, which was achieved by an adjustment of the reboiler duty. For Solvent A and B, the optimum reboiler duty was found to be reduced by 16% and 9%, respectively, compared to the standard solvent MEA. Also the numbers for the optimum L/G ratio were lower than for MEA by 37% for Solvent A and 45% for Solvent B. The influence of kinetic effects was studied by lowering the gas flow rate at a constant L/G ratio. The results show that Solvent A has similar and Solvent B slightly slower overall mass transfer kinetics compared to MEA.

CO2 Solubility in a Mixture Absorption System of 2-Amino-2-methyl-1-propanol with Ethylene Glycol

A mixture system of sterically hindered amine 2-amino-2-methyl-1-propanol (AMP) with ethylene glycol (EG) was developed. The solubility of CO2 in mixture solutions of AMP–EG was measured at temperatures from 303.2 to 353.2 K and partial pressures of CO2 from 5 to 120 kPa. The concentration of AMP ranged from 0.4 to 1.0 mol/L. A model based on a zwitterion mechanism concerned with parameters independent of temperature and ion strength was derived, which could fit the experimental data very well. The calculated heat of absorption of CO2 in AMP–EG solution showed a decline compared to that in AMP–H2O solution. Comparing the solubilities of CO2 in different solvents with the same chemical absorber AMP, we found that the solvent has a significant influence on the solubility of CO2. Two possible aspects make contributions to the influence: deprotonation process and ion strength. The study of the influence of the solvent provides guidance for a reasonable selection and good design of the absorption process for CO2. Compared to AMP–DEG and AMP–TEG solutions, the loading of CO2 in AMP–EG solution is higher especially at lower partial pressure of CO2; the viscosity of AMP–EG solution is also lower. Compared to AMP–H2O solution, AMP–EG solution has higher circular loading of CO2 while the temperature changes especially at lower desorption temperature.

CO2 Solubility in a Mixture Absorption System of 2-Amino-2-methyl-1-propanol with Glycol

A mixture system of sterically hindered amine 2-amino-2-methyl-1-propanol (AMP) with glycol was developed as the working system to reduce energy consumption. The solubility of CO2 in the mixture solutions of AMP–diethylene glycol (DEG) and AMP–triethylene glycol (TEG) was determined by a fast measurement method. The results show that the physical absorption can be enhanced using TEG or DEG as a solvent. The heat of absorption of the CO2–AMP–glycol system ranges from 50 kJ/(mol CO2) to 62 kJ/(mol CO2) as the loading of CO2 (mol CO2/mol AMP) ranges from 0.2 to 0.8, which is much lower than that between monoethanolamine (MEA) and CO2. The absorption performance of the mixture system is sensitive both to temperature and pressure, which is different from the process with MEA as an absorbent. A reaction assumption of AMP with CO2 in DEG or TEG was suggested and a model for predicting the solubility of CO2 is developed accordingly. The prediction results show that the model can predict the absorption performance well. Comparing the MEA–TEG and AMP–TEG systems, we found that the AMP–TEG system would have much lower energy consumption in the CO2 absorption–regeneration process than the MEA–TEG absorption system.

Simulation of carbon dioxide recovery from flue gases in aqueous 2-amino-2-methyl-1-propanol solutions

The modeling and simulation of the absorption of dilute CO 2 into falling film of aqueous solutions of a sterically hindered amine, 2-amino-2-methyl-1-propanol (AMP), was carried out using COMSOL Multiphysics Version 3.3. The operating cases were divided in gas turbine cases (CO 2 3 mol%) and boiler cases (CO 2 8.5 mol%). The key operating parameters for the studied cases are CO 2 partial pressure, operating temperature and amine concentration in the aqueous solution. The simulation focused on: (1) CO 2 loading in aqueous AMP solution; (2) contact time to reach equilibrium; (3) pH of rich AMP aqueous solution; and (4) total required interfacial area/circulated AMP aqueous solution. The modeling was validated by comparison with experimental results for CO 2 loading available in the literature, with deviations below 4%. High operating pressure, low operating temperature, and low AMP aqueous concentration increase CO 2 loading. The compression need for gas turbine flue gas was found to be higher than for boiler flue gas. The pH of rich AMP aqueous solution at maximum CO 2 loading was 8. The needed contact time to reach equilibrium decreases with temperature increases. The results were utilized to estimate the lower bound to the size of structured packed columns to absorb CO 2 from flue gases.

Absorption of CO2 in a sterically hindered amine: modeling absorption in a mechanically agitated contactor

Abstract The absorption of dilute CO 2 into aqueous solutions of a sterically hindered amine, 2-amino-2-methyl-1-propanol (AMP), is modeled in the mechanically agitated contactor under the fast pseudo first-order reaction condition using the kinetic data for CO 2 –AMP presented elsewhere by this study group [A.K. Saha, S.S. Bandyopadhyay, A.K. Biswas, Kinetics of absorption of CO 2 into aqueous solutions of 2-amino-2-methyl-1-propanol, Chem. Eng. Sci. 50 (1995) 3587–3598.] Experimental results of absorption studies in the mechanically agitated contactor at 288 and 301.5 K over ranges of CO 2 partial pressure (5–15 kPa) and amine concentration (1–2 kmol m −3 ) are in excellent agreement with the results predicted from the numerical model, confirming the validity of the mathematical model proposed, and the kinetic data and the mechanism presented earlier by this study group for the CO 2 –AMP system [A.K. Saha, S.S. Bandyopadhyay, A.K. Biswas, Kinetics of absorption of CO 2 into aqueous solutions of 2-amino-2-methyl-1-propanol, Chem. Eng. Sci. 50 (1995) 3587–3598.] The maximum deviation between the predicted and experimental values of liquid-phase CO 2 loading with time was within 3%.

Influence of Process Parameters on Corrosion Behavior in a Sterically Hindered Amine−CO2 System

Corrosion behavior in a CO2 absorption process using a sterically hindered amine, 2-amino-2-methyl-1-propanol (AMP), was investigated by means of an electrochemical technique. The behavior was evaluated over ranges of three process parameters: 30−80 °C liquid temperature; 0.0−1.0 mol/mol of CO2 loading; 1.0−4.0 kmol/m3 AMP concentration. Experimental results show significant effects of the three process parameters on the corrosion behavior. An increase in each parameter generally aggravates system corrosiveness. Corrosiveness in the AMP system was also compared with that in the MEA system. It was found that the AMP system induces less corrosion rate than the MEA system at elevated temperature.

Studies of Corrosion and Corrosion Control in a CO2−2-Amino-2-methyl-1-propanol (AMP) Environment

Corrosion and corrosion inhibition in a sterically hindered amine, 2-amino-2-methyl-1-propanol (AMP), were investigated by static weight loss tests. The corrosion data were compared with those of monoethanolamine (MEA), a conventional alkanolamine, which was simultaneously tested under the same conditions. The results indicated that the AMP system was generally less corrosive to carbon steel than the MEA system, but corrosion control is still necessary. Sodium metavanadate (NaVO3) and sodium sulfite (Na2SO3) were proven to be effective corrosion inhibitors, with more than 90% protection efficiency.

Kinetics of the reaction of carbon dioxide with 2-amino-2-methyl-1-propanol solutions

Reaction rate constants for the reaction between CO 2 and the sterically hindered amine, 2-amino-2-methyl-1-propanol (AMP), were determined from measurements of the rate of absorption of CO 2 into both aqueous and nonaqueous (1-propanol) AMP solutions. A stirred-cell reactor having a horizontal liquid-gas interface was used for the absorption studies. The zwitterion mechanism was found to be suitable for modelling the absorption of CO 2 into the aqueous AMP solutions and into the 1-propanol-AMP solvent. The partial order in amine is greater than one for both cases. The kinetic parameters for aqueous AMP solutions were obtained for temperatures from 15 to 45°C and over the concentration range of 0.25–3.5 kmol m −3 of AMP.

Kinetics of absorption of CO 2 into aqueous solutions of 2-amino-2-methyl-1-propanol

The mechanism and kinetics of the reaction between CO 2 and aqueous solution of sterically hindered amine, 2-amino-2-methyl-1-propanol (AMP), were investigated at 294–318 K by gas absorption studies using a wetted wall column. The reaction was found to be first order with respect to both CO 2 and AMP. The values of the second order rate constant were found to be 439, 687, 1179 and 1650 m 3/(kmols) at 294, 301.5, 311.5 and 318 K, respectively, in the amine concentration range 0.5−2.0 kmol/m 3. These results agree closely with those of Alper (1990, Ind. Engng Chem. Res. 29, 1725–1728), who adopted a completely different methodology, the stopped flow technique, for investigating the kinetics of CO 2-AMP.

Solubility of acid gases in chemical and mixed solvents

A mixed solvent containing chemical and physical solvents can be used to remove acid gases from gas streams. The solubility data for mixtures of the acid gases, CO 2 and H 2S, in a mixed solvent at 40° and 100°C for partial pressures ranging from 19 to 3669 kPa and 55 to 4240 kPa respectively, have been obtained. The mixed solvent consists of an aqueous solution of a sterically hindered amine, 2-amino-2-methyl-1-propanol (AMP), and a physical solvent, sulfolane. The effect of the presence of one gas on the solubility of the other in the mixed solvent was studied. A mathematical model has been used to correlate the data for the individual gases in the mixed solvent. The model consists of chemical equilibria in the liquid phase, mass balance, electroneutrality, activity coefficient and vapour-liquid equilibrium equations for water. Parameters obtained for the individual gases in the solvent mixture have been used to predict the partial pressures of both CO 2 and H 2S in the gas mixtures. The predicted and measured values were in good agreement.

SOLUBILITY OF CO2 AND H2S IN A HINDERED AMINE SOLUTION

The solubility of H2S and CO2 in aqueous solutions of the sterically hindered amine, 2-amino-2-methyl-1-propanol (AMP), was determined at 40 and 100°C. Partial pressures of C)2 ranged from approximately 2 to 6000 kPa and of H2S from 2 to 2200 kPa. The solubility results were compared with previously reported acid gas solubilities in aqueous monoethanolamine (MEA) solutions.

CO 2 absorption in aqueous solutions of hindered amines

Sterically hindered amines constitute a new class of chemicals which have recently come into industrial use in a variety of gas-treating processes: chemical solvents in both aqueous and non-aqueous solutions, rate promotion additives for the hot carbonate process, and chemical solvents for the selective removal of hydrogen sulfide. The scant published data on the behavior of hindered amines do not allow one to estimate the actual values of the apparent kinetic constants or equilibrium constants, and even less to establish the chemical steps involved. In this paper, the results of an investigation of the behavior of one particular amine, 2-amino-2-methyl-1-propanol (AMP), as a chemical solvent for CO 2 in aqueous solutions are reported. The equilibrium behavior of a hindered monoamine like AMP in aqueous solutions is dominated by the values of two equilibrium constants: the protonation constant K p and the carbamate stability constant K c. The value of K p at infinite dilution has been determined experimentally, and is large enough to neglect formation of the carbonate ion. The value of K c has been found experimentally to be significantly less than 10 −1 1/gmol, as is expected for a hindered amine. A thermodynamic model has been developed and tested against experimental equilibrium data. Preliminary kinetic data seem to indicate that the reaction with CO 2 is first order with respect to both CO 2 and AMP. A first step in the elucidation of the chemical steps involved is presented.