Aqueous Solution Of 2-amino-2-methyl-1-propanol Research Articles

Solubility of CO2 in 2-Amino-2-methyl-1-propanol (AMP) and 3-(Methylamino)propylamine (MAPA): Experimental Investigation and Modeling with the Cubic-Plus-Association and the Modified Kent-Eisenberg Models

CO2 capture attracts significant research efforts in order to reduce the volume of greenhouse gases emitted from fossil fuels combustion. Among the studied processes, chemical absorption represents a mature approach and, in this direction, new solvents, alternatives to monoethanolamine (MEA), have been suggested. In this work, the solubility of CO2 in aqueous solutions of 2-amino-2-methyl-1-propanol (AMP) and 3-(methylamino)propylamine (MAPA), which were recently suggested as constituents of novel phase change solvent mixtures, is experimentally measured at 298, 313, 323, and 333 K and in a wide range of pressures, up to approximately 7 bar. As the available literature experimental data for MAPA aqueous solutions are very limited, the experimental results of this study were compared to respective literature data for AMP, and a very satisfactory agreement was observed. The new experimental data were correlated with the cubic-plus-association (CPA) and the modified Kent-Eisenberg models. It was observed that both models rather satisfactorily correlate the experimental data, with the Kent-Eisenberg model presenting more accurate correlations.

Best practices for the measurement of 2-amino-2-methyl-1-propanol, piperazine and their degradation products in amine plant emissions

We herein present the chemical-analytical setup used to measure atmospheric emissions of amines and amine degradation products from an amine-based post-combustion carbon capture plant. The emission measurements were carried out at the Technology Centre Mongstad (TCM) in Norway, in the frame of the ALIGN-CCUS campaign from September 2019 to January 2020, when the amine plant was operated with the CESAR 1 solvent. This advanced solvent is an aqueous solution of 2-amino-2-methyl-1-propanol (AMP) and piperazine (PZ). Four chemical-analytical techniques were deployed for characterizing emission of AMP, PZ and their degradation products: online Fourier Transform Infrared (FTIR) Spectroscopy, online Proton-Transfer-Reaction Time-of-Flight Mass Spectrometry (PTR-TOF-MS), online Proton-Transfer-Reaction Quadrupole Mass Spectrometry (PTR-QMS), as well as manual impinger sampling followed by offline Ion Chromatography Mass Spectrometry (IC-MS) analysis. AMP was detected by all four methods, with the results being in reasonably good agreement. PZ was detected by PTR-TOF-MS, PTR-QMS and IC-MS, but because of the low emission levels (single-digit ppb) the latter two methods suffered from a positive bias (due to an interfering compound) and a large measurement uncertainty, respectively. 17 amine degradation products were only detected by the PTR-ToF-MS analyzer. We present exemplary results from the emission measurements carried out during the ALIGN-CCUS 2019-2020 campaign and share some of the lessons learned from this exercise.

Desorption Rates of Carbon Dioxide with 2-Amino-2-Methyl-1-Propanol and Piperazine Blends

This work aimed to study the chemical desorption process of CO2 in an aqueous solution of 2-amino-2-methyl-1-propanol (AMP) and piperazine (PZ) carbonated blend. The desorption process was carried out on a wetted wall column with a 0.5 m long film promoter (stainless steel 28 mesh with a known surface area) and 2.2 cm diameter. The process was online monitored by infrared spectroscopy integrated with a PLS model, which allowed the quantification in the liquid phase of free AMP and PZ, PZ mono- and dicarbamate, bicarbonate and total CO2 absorbed in all its chemical forms. The model had a drawback predicting PZ at low concentrations. The desorption was measured at atmospheric pressure (0.93 atm) and at temperatures of 50, 60 and 70 °C and blends of 30/0, 25/5, 20/10 and 0/15 %wt AMP/%wt PZ respectively. A total of 16 experiments were carried out.

Ab Initio Study of CO2 Capture Mechanisms in Aqueous 2-Amino-2-methyl-1-propanol: Electronic and Steric Effects of Methyl Substituents on the Stability of Carbamate

Ab initio quantum chemical calculations, combined with the SMD solvation model, have been conducted to reveal CO2 absorption mechanisms and the origin of the reduced stability of carbamate in aqueous solution of 2-amino-2-methyl-1-propanol (AMP). The calculated Gibbs free energy change for all the elementary steps in the conversion of carbamate to bicarbonate reveals that the reduced thermodynamic stability of AMP carbamate is largely ascribable to the shift of the equilibrium from the carbamate to the zwitterion intermediate, from which CO2 can be released and successively converted to bicarbonate. This feature of AMP is an attribute of the electronic effects of the substitution by methyl groups specifically at the α-carbon. Furthermore, the steric effects of the methyl groups are investigated from a dynamical point of view that suggests a new scenario in which the methyl groups promote the release of CO2 from the zwitterion intermediate.

Application of aqueous blends of AMP and piperazine to the low CO2 partial pressure capturing: New experimental and theoretical analysis

In this study, a new equilibrium solubility data for carbon dioxide in aqueous solutions of 2-amino-2-methyl-1-propanol (AMP) and piperazine (PZ) were provided. The two famous Deshmukh-Mather and Kent Eisenberg thermodynamic models were utilized to predict the CO2 absorption. CO2 loading data in aqueous AMP + PZ were assessed over the different ranges of temperatures (293, 303, 313 and 323 K), CO2 partial pressures (18.13, 27.19 and 72.52 kPa) and solvent concentrations ((0.1, 0.2, 0.3 M PZ) + (1.5, 2, 3, 4 M AMP)) in local atmospheric pressure (90.66 kPa) on samples of flue gases from thermal and central power plants of Esfahan Steel Company. For high partial pressure of CO2 in feed gas stream, the addition of PZ promotes the absorption rate. However, at low CO2 partial pressure, PZ addition results in less CO2 loading. The Deshmukh-Mather model could provide an accurate prediction of the experimental data at high partial pressure of CO2 whereas the modified Kent-Eisenberg model could capture the inverse effects of the PZ at low partial pressure and provides a relatively good approximation of experimental data at low partial pressure. The Average Absolute Deviation percentage (AAD%) used to adjust the parameters of the models. The AAD was calculated 15.02% and 19.49% for the Deshmukh-Mather and Kent-Eisenberg models, respectively.

Dynamic modeling and validation of amine-based CO2 capture plant

It is widely known that, fossil power plants are required to be operated in dynamic scenario due to the timely variation of the grid demand. Flexible operation of post combustion CO2 capture imposes process disturbances and further investigation of dynamic behavior is required. For this purpose, a dynamic mathematical model of CO2 capture process in aqueous solution of 2-amino-2-methyl-1-propanol (AMP) has been developed. The mathematical model of proposed includes mass and heat transfer models, reaction kinetics, vapor–liquid equilibrium, hydrodynamic aspects etc., in order to study the coupled effect of temperature and concentration on the absorption rate. For model validation the pilot plant simulation results were compared to experimental data from literature. Temperature and composition profiles within the columns are predicted successfully by the model, illustrating its predictive capabilities. Dynamic simulations were performed to analyze the capability of the model to predict the effect of the disturbances from the up-stream power plant and the operating conditions of the plant itself, on the plant operation.

Pilot-scale evaluation of AMP/PZ to capture CO2 from flue gas of an Australian brown coal–fired power station

Monoethanolamine (MEA) is a well-established absorption liquid used in post-combustion capture (PCC) technology that has a high rate of reaction with CO2. However, an absorption liquid with improved properties, such as less degradation, less corrosion and a lower energy requirement for solvent regeneration, would greatly benefit the PCC process. An alternative to MEA is an aqueous solution of 2-amino-2-methyl-1-propanol (AMP), promoted with piperazine (PZ). This absorption liquid is expected to improve CO2 recovery and reduce reboiler heat duty for solvent regeneration in PCC plants.This paper evaluates the pilot-scale performance of an aqueous mixture of 25wt% AMP and 5wt% PZ (AMP/PZ) with a total amine concentration of 30wt% compared with the baseline performance of aqueous MEA (30wt%). We evaluated the reboiler heat required for solvent regeneration and CO2 recovery for AMP/PZ and MEA as both a function of CO2-lean loading at a similar liquid to gas (L/G) ratio, and as a function of L/G ratio at a similar CO2-lean loading.Our results show that AMP/PZ is a promising alternative to MEA. At a similar L/G ratio, both MEA and AMP/PZ required lower reboiler heat duty when CO2-lean loading was reduced. At higher CO2-lean loadings, neither absorption liquid showed any changes in reboiler heat duty as a function of L/G ratio. One exception occurred for AMP/PZ at lower CO2-lean loadings (0.03 and 0.08mol CO2/mol amine), when reboiler heat duty dropped as the L/G ratio rose. In most experiments with AMP/PZ, the condenser heat and sensible heat were the major contributors to the reboiler heat duty at lower CO2-lean loadings (<0.1mol CO2/mol amine). For MEA, the condenser heat had the highest portion in the reboiler heat duty at a CO2-lean loading of <0.18mol CO2/mol amine. Increasing condenser heat was associated with an increase of heat for water evaporation to generate steam for CO2 stripping. The reboiler heat duty to capture ∼80% and ∼85% CO2 was similar for both absorption liquids; yet, to capture this proportion of CO2, AMP/PZ required a higher L/G ratio than MEA.

Density Functional Theory Study on Carbon Dioxide Absorption into Aqueous Solutions of 2-Amino-2-methyl-1-propanol Using a Continuum Solvation Model

We used density functional theory (DFT) calculations with the latest continuum solvation model (SMD/IEF-PCM) to determine the mechanism of CO(2) absorption into aqueous solutions of 2-amino-2-methyl-1-propanol (AMP). Possible absorption process reactions were investigated by transition-state optimization and intrinsic reaction coordinate (IRC) calculations in the aqueous solution at the SMD/IEF-PCM/B3LYP/6-31G(d) and SMD/IEF-PCM/B3LYP/6-311++G(d,p) levels of theory to determine the absorption pathways. We show that the carbamate anion forms by a two-step reaction via a zwitterion intermediate, and this occurs faster than the formation of the bicarbonate anion. However, we also predict that the carbamate readily decomposes by a reverse reaction rather than by hydrolysis. As a result, the final product is dominated by the thermodynamically stable bicarbonate anion that forms from AMP, H(2)O, and CO(2) in a single-step termolecular reaction.

Absorption of carbon dioxide in piperazine activated concentrated aqueous 2-amino-2-methyl-1-propanol solvent

In this work new experimental data on the rate of absorption of CO 2 into piperazine (PZ) activated concentrated aqueous solutions of 2-amino-2-methyl-1-propanol (AMP) over the temperature range 303–323 K are presented. The absorption experiments have been carried out in a wetted wall contactor over CO 2 partial pressure range of 5–15 kPa. PZ is used as a rate activator with a concentration ranging from 2 to 8 wt% keeping the total amine concentration in the solution at 40 wt%. The physical properties such as density and viscosity of concentrated aqueous AMP+PZ, as well as physical solubility of CO 2 in concentrated aqueous AMP+PZ, are also measured. New experimental data on vapor liquid equilibrium (VLE) of CO 2 in these concentrated aqueous solutions of AMP+PZ in the temperature range of 303–323 K have also been presented. The VLE measurements are carried out in an equilibrium cell in CO 2 pressure range of 0.1–140 kPa. A thermodynamic model based on electrolyte non-random two-liquid (eNRTL) theory is used to represent the VLE of CO 2 in aqueous AMP+PZ. Liquid phase speciations are estimated considering the nonideality of concentrated solutions of the amines and the calculated activity coefficients by eNRTL model. The CO 2 absorption in the aqueous amine solutions is described by a combined mass transfer-reaction kinetics model developed according to Higbie's penetration theory. The model predictions have been found to be in good agreement with the experimental results of the rates of absorptions of CO 2 into aqueous AMP+PZ.

Study on carbamate stability in the Amp/CO2/H2O system from 13C-NMR spectroscopy

Qualitative and quantitative 13C NMR studies were performed on 30 wt % aqueous solution of 2-amino-2-methyl-1-propanol (AMP) with different amount of CO2 at 25 °C. The results suggested that the main species in this system are: AMP/AMPH+, AMPCO2− and HCO3−/CO32−. The carbamate was observed at low loading and the carbamate stability constant was calculated based only on the experimental species concentration from NMR analysis. Based on the liquid phase speciation from NMR, the carbamate stability constant on mol fraction basis was found to be about 0.47 at 25 °C.

Electrolyte UNIQUAC−NRF Model to Study the Solubility of Acid Gases in Alkanolamines

Thermodynamic modeling of solubility of acid gases in aqueous alkanolamine solutions is essential in design of the absorbers for sweetening of natural gas. A thermodynamic consistent model was developed for calculation of the vapor−liquid equilibria in acid gases (H2S and CO2)−alkanolamine−water system. This model accounts for both chemical and phase equilibria in liquid and vapor phases. For nonideality of species in the liquid phase, the UNIQUAC-NRF equation with ion-pair approach was applied. For long-range interaction, the Pitzer−Debye−Huckel term was used. The model was applied for correlation of the solubility of acid gases in binary and ternary aqueous solutions of monoethanolamine (MEA) and methyldiethanolamine (MDEA). Also, prediction of the solubility of acid gases in binary and ternary aqueous solution of 2-amino-2-methyl-1-propanol (AMP) was investigated. A general correlation function in terms of temperature was used for each parameter so that the model can be applied to predict the solubilit...

Enthalpy of solution of CO 2 in aqueous solutions of 2-amino-2-methyl-1-propanol

The enthalpies of solution of CO 2 in aqueous solution of 2-amino-2-methyl-1-propanol (AMP) 15 wt% and 30 wt% were measured at 322.5 K and pressures range from (0.2 to 5) MPa using a flow calorimetric technique. The gas solubilities were simultaneously determined from the calorimetric data. The solubilities were compared to available literature values obtained by direct measurements. The experimental enthalpies of solution were compared to the values derived from the literature vapor liquid equilibrium data. This work provides calorimetric data that will be used later for the development of a thermodynamic model to predict both solubilities and enthalpies of solution of acid gases in aqueous amine solutions.

Modeling of CO2 absorber using an AMP solution

AbstractAn explicit model for carbon dioxide (CO2) solubility in an aqueous solution of 2‐amino‐2‐methyl‐1‐propanol (AMP) has been proposed and an expression for the heat of absorption of CO2 has been developed as a function of loading and temperature. A rate‐based steady‐state model for CO2 absorption into an AMP solution has been proposed, using both the proposed expression for the CO2 solubility and the expression for the heat of absorption along with an expression for the enhancement factor and physicochemical data from the literature. The proposed model has successfully been applied to absorption of CO2 into an AMP solution in a packed tower and validated against pilot‐plant data from the literature. © 2006 American Institute of Chemical Engineers AIChE J, 2006

Thermal effects of CO2 absorption in aqueous solutions of 2‐amino‐2‐methyl‐1‐propanol

AbstractIn this work, the process of carbon dioxide absorption is analyzed at high partial pressures, in aqueous solutions of 2‐amino‐2‐methyl‐1‐propanol (AMP), with respect to the thermal effects involved. The experiments were carried out in a stirred tank reactor with a plane and known interfacial area. The variables considered were the AMP concentration and the temperature, within the ranges 0.1–3.0 kmol/m3 and 288–313 K, respectively. From the results, we deduce that the absorption process of pure carbon dioxide into aqueous solutions of AMP takes place in the instantaneous nonisothermal regime at low concentrations, whereas at high concentrations the regime may be fast. In the experiments at low amine concentrations, we propose an equation, which not only relates the experimental results to the initial amine concentration but at the same time enables the evaluation of the rise in temperature in the gas–liquid interface. From the results at high concentrations, we determined a reaction order of one with respect to the amine and an expression for the kinetic constant valid throughout the entire range of temperatures and concentrations assayed: k = 4.8 × 1012exp(−8186.9/T). © 2005 American Institute of Chemical Engineers AIChE J, 2005

Selective absorption of H2S from gas streams containing H2S and CO2 into aqueous solutions of N-methyldiethanolamine and 2-amino-2-methyl-1-propanol

Selective absorption of H2S from N2 streams containing H2S and CO2 into aqueous solutions of 2-amino-2-methyl-1-propanol (AMP) as well as N-methyldiethanolamine (MDEA) was investigated in a 2.81×10−2 m o.d. stainless steel wetted-wall column at atmospheric pressure and constant feed gas ratio. In the range of gas flow rates studied (90–180×10−6 m3/s), the effect of gas-phase resistance on the absorption of H2S was significant. The rates of absorption of H2S and the selectivity factor decreased with the contact time for both alkanolamine solutions. With increasing amine concentration in the range 2.0–3.0 kmol/m3, the rates of absorption of both CO2 and H2S increased, but relatively more for CO2, resulting in a consequent decrease in the selectivity factor. In the temperature range 293–313 K, the rates of absorption of CO2 increased marginally with the increase in temperature while the rates of absorption of H2S and the selectivity factor decreased. The maximum selectivity observed in this work was 17.57 and 23.02 for AMP and MDEA, respectively. The acid gas mass transfer has been modelled using equilibrium-mass-transfer-kinetics-based combined model for CO2 and gas-phase transport equation-based approximate model for H2S considering negligible interaction between CO2 and H2S in the liquid phase. The experimental and model results have been found to be in good agreement.