Impact of speciation on CO2 capture performance using blended absorbent containing ammonia,triethanolamine and 2-amino-2-methyl-1-propanol

In our previous study, a high CO₂ absorption rate was achieved using a blended absorbent containing AMP, NH₃, and TEA. The species of the blended absorbent was determined in this study using ¹³C nuclear magnetic resonance (NMR) spectroscopy and a modified Kent-Eisenberg model. The carbamate formation constant was also regressed using the model. Bicarbonate and carbonate ions decrease the absorption efficiency and have a positive effect on CO₂ stripping. Carbamate has a negative effect on regeneration; a regeneration temperature of 373 K minimized the energy needed. In conclusion, the prediction equation and NMR analysis provide an easy way of determining carbonate group species and carbamate species concentrations, and this method will be helpful in optimizing CO₂ capture with blended absorbents.     

Equilibrium model for CO2 absorption in an aqueous solution of 2-amino-2-methyl-1-propanol

A semi-empirical gas-liquid equilibrium model for the absorption of CO₂ in aqueous 3M AMP (2-amino-2-methyl-1-propanol) is presented. It applies to high CO₂ loadings (y > 0.5) in the temperature range between 20 and 50 °C, and is based on experimental solubility and pH determinations. For a given amine concentration, it yields the equilibrium partial pressure of CO₂ as a function of only two variables: the CO₂ loading and temperature. The model correlates the expressions for the chemical equilibria involved as follows: p = m y × 10^x, where p is the equilibrium partial pressure, x = logK - pH, m is the amine molarity, y the CO₂ loading, and K is a parameter involving Henry's law constant, H, and the first dissociation constant, K₁, of carbonic acid. pH is found to depend on both temperature and CO₂ loading while logK depends only on the CO₂ loadIng. Correlations for pH and logK are presented. The model fits own data for 3M AMP very well as well as the equilibrium data found in recent literature.     

Simultaneous absorption of carbon dioxide and hydrogen sulfide into aqueous blends of 2-amino-2-methyl-1-propanol and diethanolamine

This work presents an experimental and theoretical investigation of the simultaneous absorption of CO₂ and H₂S into aqueous blends of 2-amino-2-methyl-1-propanol (AMP) and diethanolamine (DEA). The effect of contact time, temperature and amine concentration on the rate of absorption and the selectivity were studied by absorption experiments in a wetted wall column at atmospheric pressure and constant feed gas ratio. The diffusion-reaction processes for CO₂ and H₂S mass transfer in blended amines are modeled according to Higbie's penetration theory with the assumption that all reactions are reversible. The blended amine solvent (AMP+DEA+H₂O) has been found to be an efficient mixed solvent for simultaneous absorption of CO₂ and H₂S. By varying the relative amounts of AMP and DEA the blended amine solvent can be used as an H₂S-selective solvent or an efficient solvent for total removal of CO₂ and H₂S from the gas streams. Predicted results, based on the kinetics-equilibrium-mass transfer coupled model developed in this work, are found to be in good agreement with the experimental results of rates of absorption of CO₂ and H₂S into (AMP+DEA+H₂O) of this work.     

Absorption of carbon dioxide into aqueous blends of 2-amino-2-methyl-1-propanol and diethanolamine

This work presents an experimental and theoretical investigation of CO₂ absorption into aqueous blends of 2-amino-2-methyl-1-propanol (AMP) and diethanolamine (DEA). The CO₂ absorption into the amine blends is described by a combined mass transfer-reaction kinetics-equilibrium model, developed according to Higbie's penetration theory. The model predictions have been found to be in good agreement with the experimental rates of absorption of CO₂ into (AMP+DEA+H₂O). The good agreement between the model predicted rates and enhancement factors and the experimental results indicate that the combined mass transfer-reaction kinetics-equilibrium model with the appropriate use of model parameters can effectively represent CO₂ mass transfer for the aqueous amine blends AMP/DEA.     

Absorption of carbon dioxide into aqueous blends of 2-amino-2-methyl-1-propanol and monoethanolamine

This work presents an investigation of CO₂ absorption into aqueous blends of 2-amino-2-methyl-1-propanol (AMP) and monoethanolamine (MEA). The acid gas mass transfer has been modeled using equilibrium-mass transfer-kinetics-based combined model to describe CO₂ absorption into the amine blends according to Higbie's penetration theory. The effect of contact time and relative amine concentration on the rate of absorption and enhancement factor were studied by absorption experiment in a wetted wall column at atmospheric pressure. The model was used to estimate the rate coefficient of the reaction between CO₂ and monoethanolamine at 313 K from experimentally measured absorption rates. A rigorous parametric sensitivity test has been done to identify the key systems’ parameters and quantify their effects on the mass transfer using the mathematical model developed in this work. The model predictions have been found to be in good agreement with the experimental rates of absorption of CO₂ into (AMP+MEA+H₂O).     

Characteristics of absorption and regeneration of carbon dioxide in aqueous 2-amino-2-methyl-1-propanol/ammonia solutions

In this study, the removal efficiency, absorption amount, and loading value of CO₂ into aqueous blended 2-amino-2-methyl-1-propanol (AMP)/ammonia (NH₃) solutions were measured by using the absorption and regeneration continual process. The effect of adding NH₃ to enhance absorption characteristics of AMP was investigated. The performance was evaluated under various operating conditions. As a result, the method of blending AMP and NH₃ was not adequate because of a problem with scale formation. Consequently, NH₃ of 1, 3, 5, and 7 wt% was added to 30 wt% AMP. Of these additions, 5 wt% NH₃ was the optimum concentration because the CO₂ removal efficiency and absorption amount were almost 100% and 2.17 kg CO₂/kg absorbent, respectively. Also, the scale problem was almost absent. As the regenerator temperature varied from 80–110 °C, the loading of rich amine was almost constant, but the loading of lean amine was decreased as the regenerator temperature increased. Thus, the optimum regenerator temperature was 110 °C in this experiment.     

Separation of CO2 by 2-amino-2-methyl-1-propanol aqueous solution in microporous hydrophobie hollow fiber contained liquid membrane

The absorption of CO₂ from a mixture of CO₂/N₂ gas was carried out using a flat-stirred vessel and the polytetrafluoroethylene hollow fiber contained aqueous 2-amino-2-methyl-1-propanol (AMP) solution. The reaction of CO₂ with AMP was confirmed to be a second order reversible reaction with fast-reaction region. The mass transfer resistance in the membrane side obtained from the comparison of the measured absorption rates of CO₂ in a hollow fiber contained liquid membrane with a flat-stirred vessel corresponded to about 90% of overall-mass-transfer resistance. The mass transfer coefficient of hollow fiber phase could be evaluated, which was independent of CO₂ loading.     

CO2 capture into aqueous solutions of piperazine activated 2-amino-2-methyl-1-propanol

In this work, experimental data and a simplified vapor–liquid equilibrium (VLE) model for the absorption of CO₂ into aqueous solutions of piperazine (PZ) activated 2-amino-2-methyl-1-propanol (AMP) are reported. The purpose of the work was to find the AMP/PZ system with the highest concentration and cyclic capacity, which could be used in the industry without forming solid precipitations at operational temperatures. The effect of the AMP/PZ ratio and the total concentration level of amine was studied. The highest possible ratio of AMP/PZ, which does not form solid precipitates during the absorption of CO₂ at 40 °C (40 wt% amine), was identified. Considering the maximum loading found in the screening tests for AMP/PZ (3+1.5 M) and for 30 wt% MEA systems, the AMP/PZ system has about 128% higher specific cyclic capacity if operating between 40 and 80 °C, and almost twice the CO₂ partial pressure at 120 °C compared to MEA.     

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 CO₂ 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 CO₂ 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 CO₂ in concentrated aqueous AMP+PZ, are also measured. New experimental data on vapor liquid equilibrium (VLE) of CO₂ 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 CO₂ 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 CO₂ 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 CO₂ 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 CO₂ into aqueous AMP+PZ.     

Absorption of carbon dioxide into aqueous solutions of piperazine activated 2-amino-2-methyl-1-propanol

In this work, new experimental data on the rate of absorption of CO₂ into piperazine (PZ) activated aqueous solutions of 2-amino-2-methyl-1-propanol (AMP) are reported. The absorption experiments using a wetted wall contactor have been carried out over the temperature range of 298-313 K and CO₂ partial pressure range of 2-14 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 30 wt%. The CO₂ absorption into the aqueous amine solutions is described by a combined mass transfer-reaction kinetics-equilibrium model, developed according to Higbie's penetration theory. Parametric sensitivity analysis is done to determine the effects of possible errors in the model parameters on the accuracy of the calculated CO₂ absorption rates from the model. The model predictions have been found to be in good agreement with the experimental results of rates of absorption of CO₂ into aqueous (PZ+AMP). The good agreement between the model predicted rates and enhancement factors and the experimental results indicates that the combined mass transfer-reaction kinetics-equilibrium model with the appropriate use of model parameters can effectively represent CO₂ mass transfer in PZ activated aqueous AMP solutions.     

Liquid heat capacity of aqueous sulfolane + 2-amino-2-methyl-1-propanol solutions

Heat capacities of aqueous solutions of sulfolane with 2-amino-2-methyl-1-propanol (AMP) were measured over the temperature range from 303.15 to 353.15 K with a differential scanning calorimeter. Twelve solutions of sulfolane + AMP + water that cover the mole fractions of water from 0.6 to 0.8 were studied. The liquid heat capacities of sulfolane alone and of binary mixtures such as sulfolane + water and sulfolane + AMP were also studied. The heat capacities of sulfolane and sulfolane + water were found to be in good agreement with those values reported in the literature. A Redlich-Kister type equation was applied to represent the composition dependence of the heat capacities of binary and ternary systems. For 132 data points of sulfolane + AMP + water, the fitted results of heat capacity calculations (overall average absolute percentage deviation (AAD%)) were 0.3 and 7.7% for the molar heat capacity and the excess molar heat capacity, respectively. The heat capacities of aqueous mixtures of sulfolane with AMP presented in this study can be used to estimate the head load of absorbents in acid gas capture process when using sulfolane + AMP + water as the absorbent.     

Absorption of carbon dioxide by the absorbent composed of piperazine and 2-amino-2-methyl-1-propanol in PVDF membrane contactor

This paper tests the performance of microporous polyvinylidinefluoride (PVDF) hollow fiber in a gas absorption membrane process (GAM) using the aqueous solutions of piperazine (PZ) and 2-amino-2-methyl-1-propanol (AMP). Experiments were conducted at various gas flow rates, liquid flow rates and absorbent concentrations. Experimental results showed that wetting ratio was about 0.036% when used with the aqueous alkanolamine solutions, while that was 0.39% with aqueous piperazine solutions. The CO₂ absorption rates increased with increasing both liquid and gas flow rates at N_Re < 20. The increase of the PZ concentration showed an increase of absorption rate of CO₂. The CO₂ absorption rate was much enhanced by the addition of PZ promoter. The resistance of membrane was predominated as using a low reactivity absorbent and can be neglected as using absorbent of AMP aqueous solution. The resistance of gas-film diffusion was dominated as using the mixed absorbents of AMP and PZ. An increase of PZ concentration, the resistance of liquid-film diffusion decreased but resistance of gas-film increased. Overall, GAM systems were shown to be an effective technology for absorbing CO₂ from simulated flue gas streams, but the viscosity and solvent-membrane relationship were critical factors that can significantly affect system performance.     

Simultaneous absorption of carbon dioxide,sulfur dioxide and nitrogen dioxide into aqueous 2-amino-2-methy-1-propanol

The absorption mechanism of three acidic gases in alkali solution, such as the system of carbon dioxide, sulfur dioxide, and nitrogen dioxide in 2-amino-2-methyl-1-propanol (AMP), was used to predict the simultaneous absorption rates using the film theory. Diffusivity, Henry constant and mass transfer coefficient of each gas were used to obtain the theoretical enhancement factor of each component. The theoretical molar fluxe of each gas was obtained by an approximate solution of mass balances with reaction regions of the first order reaction of CO₂ and instantaneous reactions of SO₂ and NO₂ in CO₂-SO₂-NO₂-AMP system. From the comparison between the theoretical total fluxes of these gases and the measured ones, the solubility and the reaction rate between each gas and AMP influenced its molar flux.     

Encapsulation of 2-amino-2-methyl-1-propanol with tetraethyl orthosilicate for CO2 capture

Carbon capture is widely recognised as an essential strategy to meet global goals for climate protection. Although various CO₂ capture technologies including absorption, adsorption and membrane exist, they are not yet mature for post-combustion power plants mainly due to high energy penalty. Hence researchers are concentrating on developing non-aqueous solvents like ionic liquids, CO₂-binding organic liquids, nanoparticle hybrid materials and microencapsulated sorbents to minimize the energy consumption for carbon capture. This research aims to develop a novel and efficient approach by encapsulating sorbents to capture CO₂ in a cold environment. The conventional emulsion technique was selected for the microcapsule formulation by using 2-amino-2-methyl-1-propanol (AMP) as the core sorbent and silicon dioxide as the shell. This paper reports the findings on the formulated microcapsules including key formulation parameters, microstructure, size distribution and thermal cycling stability. Furthermore, the effects of microcapsule quality and absorption temperature on the CO₂ loading capacity of the microcapsules were investigated using a self-developed pressure decay method. The preliminary results have shown that the AMP microcapsules are promising to replace conventional sorbents.     

Absorption of carbon dioxide into aqueous solution of 2-amino-2-methy-1-propanol and 1, 8-diamino-p-menthane

Carbon dioxide was absorbed into an aqueous solution containing two reactants of 2-amino-2-methyl-1-propanol (AMP) and 1,8-diamino-p-menthane (DAM) in a stirred semi-batch tank with a planar gas-liquid interface within a range of 0?C3.0 kmol/m³ of AMP, 0?C0.2 kmol/m³ of DAM, and 298.15?C323.15 K at 15% of CO₂ and 101.3 kPa. Diffusivity, Henry constant and mass transfer coefficient of CO₂ in the mixed solution of AMP and DAM were used to calculate the theoretical enhancement factor of CO₂, which was obtained by an approximated solution of mass balances with the instantaneous and fast regime in CO₂-AMP-DAM system. The method of the classification of the chemical regime in the heterogeneous system was used to determine the enhancement factor by adding DAM under the limited concentration of AMP.     

A comparative study on the carbon dioxide capture power between 30 wt% 2-amino-2-methyl-1-propanol and 30 wt% methyldiethanol amine aqueous solutions

A comparative study has been performed to compare the 30 wt% of 2-amino-2-methyl-1-propanol (AMP) aqueous solution and 30 wt% of methyldiethanol amine (MDEA) aqueous solution to capture carbon dioxide contained in the flue gas stream. The equilibrium constants for each electrolyte reactions have been used to estimate the carbon dioxide absorption process. Henry’s constants for each binary pairs between solute gases and solvent have been used to estimate solubility of the gas components.     

Comprehensive reaction kinetics model of CO2 absorption into 1-dimethylamino-2-propanol solution

In the present work, the kinetics of the reactive absorption of CO₂ in 1-dimethylamino-2-propanol (1DMA2P) solution were experimentally measured using a laminar jet absorber over a temperature range of 298–313 K, 1DMA2P concentration range of 0.5–2.0 mol/L, and CO₂ loading range of 0–0.06 mol CO₂/mol amine. The measured kinetics data were then used to develop a comprehensive numerical kinetics model using a FEM-based COMSOL software. The reaction rate model of the CO₂ absorption into 1DMA2P solution were then validated by comparing model rates with the experimental rates. An excellent agreement of model data with experimental data was achieved with an absolute average deviation (AAD) of 6.5%. In addition, vapor–liquid equilibrium plots of all ions in the 1DMA2P-H₂O-CO₂ system were also developed. Further, this work has provided an effective criterion for evaluating CO₂ absorption, that can be used for both the conventional amines and alternative amines for the purpose of providing guidelines or information on how to effectively screen solvents.     

R-2-氨基-3-甲基-1,1-二苯基-1-丁醇的合成

R-2-氨基-3-甲基-1,1-二苯基-1-丁醇是一种合成手性催化剂的重要中间体。从原料R-缬氨酸经甲酯化,苄氧羰基保护制得R-2-苄羰基氨基-3-甲基-丁酸甲酯,然后与苯基溴化镁反应制得（R）-2-苄氧羰基氨基-3-甲基-1,1-二苯基-1-丁醇。接着在5%Pd/C催化加氢下脱除苄氧羰基得到目标化合物,总收率58%。此制备方法涉及的中间体及目标化合物易于纯化,总收率高且重现性好。     

Hollow fiber supported liquid membrane process for the separation of NH3 from aqueous media containing NH3 and CO2

A hollow fiber supported liquid membrane (SLM) process was investigated experimentally and theoretically for the separation of NH₃ from aqueous solutions containing NH₃ and CO₂. DTPA and D2EHPA were used as carriers and n-decanol was used as a diluent in this process. The membrane stripping experiments, as well as the extractive equilibrium experiments, indicate that DTPA is a better carrier than D2EHPA in relation to the increase in the NH₃ stripping rate. The influence of operating conditions, such as flow rate, the ratio of NH₃ to CO₂, and carrier concentration, on the membrane stripping rate were examined. The experimental data demonstrate that the NH₃ stripping rate by an SLM process is not significantly influenced by the amount of CO₂ present, as is that by the supported gas membrane. To predict the stripping of NH₃ from solutions containing NH₃ and CO₂, a mathematical model incorporating chemical equilibria and Nernst–Planck diffusion was developed to describe the mass transport. The experimental data suggested that the SLM process can effectively strip NH₃ from aqueous solutions containing NH₃ and CO₂.     

CO2 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 CO₂ 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 CO₂ is first order with respect to both CO₂ and AMP. A first step in the elucidation of the chemical steps involved is presented.