Stirred Cell Reactor Research Articles

Insight into CO2 capture by aqueous solutions of N,N‐diethylethanolamine promoted with potassium salts of amino acids

AbstractN,N‐Diethylethanolamine (DEEA) is a potential high‐capacity CO2‐capturing solvent. The CO2 reactivity of DEEA can be improved by the addition of rate promoters. Both equilibrium CO2 solubility and desorption rate are also influenced by promoters. In this work, the effect of promotion of DEEA with three amino acid salts, potassium arginate (PA), potassium prolinate (PP), and potassium glycinate (PG), was investigated. In a stirred cell reactor, CO2 reactivity of the promoted solutions was studied at 303 K. Rate promotion with PA was most effective; this was then followed by PP and PG. The value of the liquid‐side mass transfer coefficient (0.005 cm/s) for CO2 absorption in water inside the stirred cell was found. Equilibrium CO2 solubility in the promoted mixtures was measured. Empirical equations that predicted solubility data (accuracy 99%) were proposed. Desorption trials were performed at 363 K. PA, PP, and PG lowered sensible energy constraint by 59%, 32%, and 30%. PA was most‐suited for faster desorption of aqueous solutions of DEEA. Overall, potassium salts of arginine, proline, and glycine were promising candidates for improving the performance of the tertiary amine DEEA. Finally, catalytic desorption of loaded solutions of DEEA was studied and it was found that alumina was a promising catalyst for faster desorption.

An insight on reaction kinetics of amino-acid-functionalized ionic liquid monoethanolamine glycinate for CO2 capture

ABSTRACT Recently, the application of functionalized ionic liquids in carbon dioxide (CO2) capture has received significant attention. In this research, the absorption kinetics of CO2 into the aqueous amino-acid-functionalized monoethanolamine glycinate ionic liquid in a stirred cell reactor was investigated. Amino acids are less volatile and have good resistance against oxidative degradation. Experiments were accomplished over a temperature range of 298–308 K and solution concentrations ranging from 0.5 to 2.5 M in the pseudo-first-order regime. The dimensionless Hatta number and infinite enhancement factor were calculated to check the fast pseudo-first-order reaction assumption. The reaction rate constant has been evaluated by recording the system pressure reduction rate over time. Increasing the IL concentration and temperature results in a significant increase in the reaction rate. The obtained kinetic constants have the same order of magnitude as those existing for primary amines.

Kinetics of CO2 absorption in N-Methyldiethanolamine solution promoted by potassium sarcosine

Potassium sarcosine (KSar) shows promise as an effective co-promoter of N-methyldiethanolamine (MDEA), a tertiary amine known for its high CO2 absorption capacity but relatively slow kinetics. This study investigated the CO2 absorption kinetics in a KSar + MDEA + H2O solution using the pressure-decay technique in a stirred cell reactor. The experiments were performed at temperatures ranging from 303.15 K to 333.15 K, with varying concentrations of KSar (ranging from 3% to 15% by weight), while keeping the MDEA concentration constant at 20% by weight. Furthermore, the study involved assessing the physicochemical and mass transfer properties and comparing them to those of a solution containing MDEA (30 wt%) + H2O solution. Properties like density, viscosity, Henry's constant (HN2O), and the physical mass-transfer coefficient of the liquid phase (kl) were measured and applied to analyze CO2 absorption kinetics. The overall reaction rate constant (kOV) was assessed using both termolecular and zwitterion mechanisms within a pseudo-first-order reaction regime. Additionally, kOV was estimated via correlated Arrhenius power law expression of the individual rate contributions of CO2−MDEA, CO2–H2O, and CO2−KSar. The calculated kOV values were found to closely match the experimental data, with absolute average relative deviations (AARD) of 4.53% and 3.03% for the termolecular and zwitterion models, respectively. The experimental results clearly showed that the rate of CO2 absorption, represented by kOV, can be significantly enhanced by adding a small amount of KSar into the MDEA + H2O solution.

Kinetics of carbon dioxide absorption in aqueous blend of 1-(2-aminoethyl) piperazine using a stirred cell reactor.

Carbon capture utilization and storage (CCUS), the technology for decarbonizing carbon dioxide (CO2) from greenhouse gas emitters such as steel, cement, oil, gas, petrochemicals, chemicals, and fertilizers, has a critical role to play in the world to achieve industrial net zero targets by 2050. CO2 can be separated from industrial exhaust gases/flue gases using amine-based solvents utilizing the post-combustion CO2 Capture process. One most crucial solvent characterization for this application is the kinetics of CO2 absorption. This work identifies aqueous 1-(2-aminoethyl) piperazine (AEPZ) as a potential candidate for CO2 capture solvent. The kinetics of absorption of CO2 in aqueous AEPZ is studied using stirred cell reactor. The experiments are performed at temperatures ranging from 303 to 333K with weight fractions of AEPZ in an aqueous solution ranging from 0.1 to 0.4. One of the critical parameters of the kinetic study is Henry's constant which is determined experimentally using another stirred cell reactor at a similar temperature and pressure range. The experimental data shows that the overall rate constant is Kov = 2.52987 × 10-4mol/m2s-kPa for 0.1 wt fr. of AEPZ at 313K with an initial CO2 partial pressure of 10kPa. The temperature dependency relation of the second-order reaction rate constant, [Formula: see text] is found to be [Formula: see text] using the Arrhenius equation. The activation energy of 0.3 wt fr. AEPZ is found to be 42.42kJ/mol. In addition, the density and viscosity of the aqueous solvent are determined at a wide range of temperatures. The diffusivity of CO2 and physical solubility used in the model development has also been determined. The kinetic parameters obtained from this study are helpful in the process design of CO2 capture in a regenerative process with a blended solvent with AEPZ.

On the CO2 absorption kinetics, loading capacity, and catalytic desorption of aqueous solutions of N‐methyl‐D‐glucamine

AbstractCO2 separation with harmful chemicals will damage the environment. It is essential to explore greener solvents that are producible from renewable resources such as biomass. The suitability of N‐methyl‐D‐glucamine (MG), also known as meglumine, for capturing CO2, was explored in this work. This nontoxic amino sugar, which is derived from sorbitol, represents a renewable bio‐solvent. It was found that MG is especially reactive with CO2. Trials were performed in a stirred cell reactor with a flat gas–liquid interface between 303 and 313 K. The values of the pseudo‐first‐order reaction rate constant, reaction orders, and activation energy were found. The loading capacity (α) of 0.5 M MG solution was measured at T = 308 K. For a typical value of α = 0.524 mol CO2/mol MG, the corresponding equilibrium partial pressure of CO2 was 22 kPa. Finally, it was found that the catalyst Al2O3 aided in the desorption of CO2‐loaded MG solutions. Desorption efficiency using Al2O3 was higher (74%) than that achieved without this catalyst (45%). It is thus clear that MG represents a potential solvent for improved CO2 separation from gases.

Glucosamine for CO2 Capture: Absorption Kinetics, Promoted Absorption Rate, and Comparison with Other Amino Sugars

Amino sugars─sugars wherein the amine group substitutes the hydroxyl group─are renewable and ecofriendly CO2 separation solvents. In this work, the kinetics of CO2 absorption in the amino sugar glucosamine (GA) was studied. Absorption rates in aqueous GA solutions (0.1–1 M) were measured in a stirred cell reactor in the 303–313 K range. At T = 308 K, the value of the reaction rate constant for GA (0.1 M) was 27 M–1 s–1. The two-step zwitterion mechanism was employed for describing the reaction pathway. Some useful characteristics of GA solutions, such as density and viscosity, were measured. Using the modified Stokes law and the N2O analogy method, the diffusivity and solubility of CO2 in solutions were determined. The liquid-side mass-transfer coefficient was found to be 0.005 cm/s at 308 K. Three amine promoters were chosen to improve the reactivity of GA, viz., monoethanolamine (MEA), 2-amino-2-methyl-1-propanol (AMP), and piperazine (PZ). Mixtures of GA/PZ (2.5/0.5 M) were the most reactive. The reactivity of two further amino sugars, N-acetyl-d-glucosamine (NAG) and N-methyl-d-glucamine (NMG), was also studied, and a comparison with GA was provided. NMG was the most reactive with CO2, whereas GA was the least reactive. This work will draw attention to this new category of CO2-capturing solvents.

Kinetics study of CO2 absorption into methyldiethanolamine, potassium lysinate, and their blends in aqueous solution

AbstractIn this work, the kinetics for the reaction of CO2 with three chemical solvents were studied experimentally and theoretically. The CO2 absorption flux into the potassium lysinate (K‐Lys), methyldiethanolamine (MDEA), and their blends was measured over the CO2 partial pressure range of 50–500 kPa, and at temperatures 298.15, 303.15, and 313.15 K using a stirred cell reactor. The effect of the addition of K‐Lys on the absorption flux of CO2 into MDEA solution at low and high pressure was investigated. The reaction kinetics of CO2 absorption in CO2‐loaded MDEA, K‐Lys, and MDEA + K‐Lys solutions were also examined and absorption flux of CO2 as a function of CO2 loading was determined. The values of CO2 diffusivity, viscosity, the liquid mass transfer coefficient, the overall reaction rate constant, and the physical solubility of CO2 into MDEA + K‐Lys solution were reported. Furthermore, a standard kinetics model was developed to describe the CO2 absorption behavior in the solution at low and high pressures, for both unloaded and CO2‐loaded systems.

CO2 absorption/desorption rates in aqueous DEEA/MDEA and sulfolane-contained hybrid solutions: effects of physical properties and reaction rate.

The rates of CO2 absorption into fresh and regenerated aqueous solutions of N,N-diethylethanolamine (DEEA), N-methyldiethanolamine (MDEA), and their mixture with sulfolane are investigated in a batch stirred cell reactor. The data are obtained in the temperature range of 293.15-313.15K, pressures up to 800kPa, and different concentrations of alkanolamines and sulfolane. The diffusion coefficients and Henry's law constants for all the solutions are obtained. The absorption rate of DEEA solutions increased by increasing component concentrations and pressure, but the effects of temperature on the absorption rates of hybrid and aqueous DEEA solutions are different. Comparison of absorption rates in aqueous and hybrid solutions under the same conditions can determine the role of sulfolane as the physical solvent. It has been found that sulfolane acts as an effective absorption activator in the hybrid DEEA solutions. However, in the MDEA solutions, in all experimental conditions except for high pressure ([Formula: see text] 400kPa) and certain MDEA concentration (20 wt%), sulfolane has a negative effect on the absorption rate. The absorption rates of regenerated aqueous DEEA solutions are in the range of 50.5-87.7% of fresh ones, while these values for the hybrid DEEA solution are in the range of 75-90.5%. These values for the aqueous and hybrid MDEA solutions are almost equal. Based on the values of Hatta number and enhancement factor, the CO2 absorption regime in the DEEA solutions is determined as the fast second-order reaction. The absorption rate can be interpreted considering the tradeoff between kinetics and thermodynamics of CO2 absorption in the aqueous and hybrid DEEA/MDEA solutions. The desorption rates in hybrid DEEA/MDEA solutions are higher than those in aqueous solutions.

Effect of physical properties of synthesized protic ionic liquid on carbon dioxide absorption rate.

The concentration of carbon dioxide gas has accelerated over the last two decades which cause drastic changes in the climatic conditions. In industries, carbon capture plants use a volatile organic solvent which causes many environmental threats. So, a low-cost green absorbent has been formulated with nontoxicity and high selectivity properties for absorbing carbon dioxide gas. This paper contains the synthesis process along with the structure confirmation using 1H NMR, 13C NMR, FT-IR, and mass spectroscopy. Density, viscosity, and diffusivity are measured at different ranges with standard instruments. The kinetic studies were also conducted in a standard predefined-interface stirred cell reactor. The kinetic parameters were calculated at different parameters like agitation speeds, absorption temperature, initial concentrations of ionic liquid, and partial pressure of carbon dioxide. The reaction regime of carbon dioxide absorption is found to be in fast reaction kinetics with pseudo-first-order. The reaction rate and the activation energy of CO2 absorption are experimentally determined in the range of 299 to 333K with different initial concentrations of ionic liquid (0.1-1.1 kmol/m3). The second-order rate constant and activation energy of carbon dioxide absorption in the synthesized ionic liquid is found to be 9.48 × 103m3mol-1s-1 and 16.61kJmol-1 respectively. On increasing the viscosity of the reacting solvent, the diffusivity of CO2 gas molecules decreases, and thus the rate of absorption decreases. This solvent has shown great potential to absorb CO2 at a large scale.

Ozonation of phenol and substituted phenols: Dependency of the reaction rate constant on the molecular structure

AbstractOzonation is a prospective method for the treatment of phenol‐contaminated wastewaters. In the present work, the reaction of ozone with 10 different substituted phenols was studied at acidic pH in two model gas–liquid contactors to investigate the dependency of the ozonation rate constant on the molecular structure of the phenolic compound. While three phenols were attached to electron‐donating functional groups, seven were characterized by the presence of electron‐accepting groups in their structure. In a stirred cell reactor (with flat‐cell interface) and mechanically agitated contactor, reaction kinetics for these two types of phenols were studied in the fast pseudo‐first order and chemical reaction controlled regime, correspondingly at T = 30°C. The effect of the electron‐donating or electron‐accepting functional group attached to the phenolic ring on the reactivity was studied and the linear dependence of the relative oxidation rate constant (with respect to phenol) on the Hammett substituent constant was proven in a Hammett plot. The values of susceptibility factor for the Hammett plots of phenols with electron‐donating and electron‐accepting substituents were −7.89 and −1.25, respectively. This work is useful to establish the ozonation pathway and predict the reaction rate constant from the molecular structure of the phenolic compound.

Investigation of Biocatalytic Absorption and Ultrasound-Assisted Desorption Performance of CO2 Capture

The CO2 absorption-desorption performance of non-aqueous solutions comprising a sterically hindered amine system (2-amino-2-ethyl-1,3-propanediol (AEPD): 1-hexanol) was investigated in a gas-liquid stirred cell reactor under sequential absorption-desorption cycles. The absorption capacity and initial absorption rate were calculated for different concentrations of AEPD: 1-hexanol at 303 K and 2 bar absolute pressure. Increasing the amount of AEPD increased the CO2 absorption capacity. The biocatalytic effect of a constant amount of carbonic anhydrase (CA) on the CO2 absorption performance was also investigated, and the CA enzyme was found to increase the total amount of absorbed CO2. The CO2 loading of AEPD: 1-hexanol and CA activated AEPD: 1-hexanol were 0.88 and 0.97 mol CO2/mol AEPD, respectively. CO2 desorption experiments were performed in different sequences of the same experimental set-up at 363 K and 1.1 bar absolute N2 pressure. The effect of ultrasonic irradiation on the desorption performance of 0.1 g/L CA catalyzed AEPD: 1-hexanol system was also investigated. It was observed that ultrasonic assistance shortened the desorption time and enhanced the desorption rate. Furthermore, the effectiveness of regeneration, the reusability, and performance loss of AEPD: 1-hexanol, in the presence and absence of CA, were analyzed by Fourier transform infrared spectrometry.

Kinetics of Carbon Dioxide Removal Using N-Acetylglucosamine.

Glucosamine, the amino sugar made from glucose, is a safe and natural reagent for post-combustion carbon dioxide capture. Its most plentiful derivative, N-acetylglucosamine (or NAG), was studied in this work with respect to its reaction kinetics in aqueous solutions. A stirred cell reactor with a flat gas–liquid interface was used, and it was found that CO2 reacts with NAG via a pathway similar to that with alkanolamines. In the 20–100 mM range of NAG concentration, the second-order rate constant at T = 308 K was 125 kmol m–3 s–1. For the 303–313 K range, the activation energy was 42 kJ mol–1. In a study on vapor–liquid equilibrium, it was found that the loading capacity of NAG (100 mM) at 303 K was 0.6 mol CO2/mol NAG, while the equilibrium partial pressure of CO2 was 0.8 kPa. Three rate promoters were tested, and piperazine showed better efficacy than monoethanolamine and 2-amino-2-methyl-1-propanol in aqueous NAG solutions. This work is expected to stimulate further interest in this new, green CO2 capturing solvent.

Kinetics of chemical absorption of carbon dioxide into aqueous calcium acetate solution

AbstractIncreasing energy demand in the world leads to more electricity generation mainly at fossil fuel power plants. Greenhouse gases are thus produced and mostly emitted to the atmosphere directly, resulting in global warming and climate change. Carbon dioxide is believed to be a main pollutant among greenhouse gases responsible from global warming. Conventional systems using mostly amine solutions to capture carbon dioxide at the source have some disadvantages, and alternatives are constantly being searched. In this work, a benign system of aqueous calcium acetate solution was investigated for this purpose. Calcium acetate is easy to produce, relatively cheap, environmentally friendly, nonhazardous, and noncorrosive. These properties make it a great alternative for use in capturing carbon dioxide. This absorption process is accompanied by chemical reaction. Therefore, the reaction kinetics needs to be investigated before its use in absorbers. A stirred cell reactor was used in the experiments using aqueous calcium acetate solution of different concentrations (2‐20% w/w) and different carbon dioxide concentrations in gas mixtures (4.5‐100% v/v dry carbon dioxide) at temperatures ranging from 286 to 352 K. The Gibbs free energy change for the overall reaction between carbon dioxide and aqueous calcium acetate solution was found to be –2.75 kJ/mol that shows the reaction is exergonic and occurs spontaneously. It was also found out that the reaction is pseudo–first order with respect to carbon dioxide which was also proven by calculating the Hatta number. Activation energy and Arrhenius (frequency) constant were also determined experimentally.

Kinetics study of CO2 absorption in potassium carbonate solution promoted by diethylenetriamine

In this work, characterization and kinetics of CO2 absorption in potassium carbonate (K2CO3) solution promoted by diethylenetriamine (DETA) were investigated. Kinetics measurements were performed using a stirred cell reactor in the temperature range of 303.15–323.15 K and total concentration up to 2.5 kmol m−3. The density, viscosity, physical solubility, CO2 diffusivity and absorption rate of CO2 in the solution were determined. The reaction kinetics between CO2 and K2CO3 + DETA solution were examined. Pseudo-first order kinetic constants were also predicted by zwitterion mechanism. It was revealed that the addition of small amounts of DETA to K2CO3 results in a significant enhancement in CO2 absorption rate. The reaction order and activation energy were found to be 1.6 and 35.6 kJ mol−1, respectively. In terms of reaction rate constant, DETA showed a better performance compared to the other promoters such as MEA, EAE, proline, arginine, taurine, histidine and alanine.

The Effects of Mass Transfer on the Determination of Gas–Liquid Reaction Kinetics in a Stirred Cell Reactor: In the Case of CO2 Absorption by Aqueous Alkanolamine Solution

In order to be able to understand and compensate for the mass transfer effects on the reaction kinetics that typically occur in these studies, the influences of diffusion and gas phase resistance o...

Kinetics of CO2 Absorption in Novel Tertiary N-Methyl-4-Piperidinol Solvent

In the present work, the reaction kinetics of CO2 absorption into aqueous solutions of novel N-methyl-4-piperidinol (MPDL) was experimentally determined in a stirred cell reactor over a MPDL concentration range of 0.5-2.0 M and a temperature range of 303-333 K. Based on the pseudo-first order assumption, a drop of pressure technique was used to extract the reaction rate constant, in terms of overall reaction rate constant (kov) and second-order reaction rate constant (k2,MPDL), from the experimental absorption data. Additionally, the physical properties and mass transfer data (i.e., density, viscosity, Henry’s constant, and liquid phase mass transfer coefficient) of aqueous MPDL solutions were experimentally measured and comprehensively discussed. In the present work, the experimental k2,MPDL is firstly introduced and can be expressed as: k2,MPDL=1.66×107Exp-3903.6T. The results also show that the CO2 absorption kinetics of MPDL can be ranked as: MEA > DEA > AMP > MPDL > MDEA. Even though novel MPDL has faster kinetics than conventional MDEA, it possesses too slow absorption kinetics to be used as a single solvent. Thus, it should be promoted with a very reactive amine to improve the overall CO2 absorption performance.

Kinetics of Carbon Dioxide Absorption into Water-Lean Potassium Prolinate/Ethylene Glycol Solutions

Kinetics of the reaction of carbon dioxide (CO2) with potassium prolinate (ProK) in water-lean ethylene glycol was measured using a stirred cell reactor at temperatures from 283.2 to 313.2 K with ProK concentrations ranging from 0.5 to 2.0 M. Physicochemical properties including Henry’s constant of N2O and CO2 were measured or estimated for the investigated solutions. A proposed correlation was used to calculate the liquid-side physical mass transfer coefficient. The observed reaction rate constants (kobs) were obtained from the measured absorption flux against CO2 partial pressure under the pseudo-first-order regime conditions. Results show that the overall pseudo-first-order rate constant kov increases remarkably as the increasing ProK concentration and temperature. The reaction order with respect to ProK is found to vary between 1.76 and 1.91 over the temperature range, which is quite different from that observed in aqueous ProK systems. The kinetic results were also nonlinearly regressed to fit the mo...

Kinetics of Ozonation of Phenol and Substituted Phenols

In the treatment of wastewaters contaminated with phenol and substituted phenols, an intermediate chemical step of partial oxidation is often employed to facilitate the ensuing biodegradation process. Ozonation is a candidate technique for partial oxidation of phenolics. In this study, the kinetics of ozonation reactions of 20 substituted phenols is investigated using the renowned theory of mass transfer with chemical reaction. The stirred (Lewis) cell with a flat interface is used as a model contactor. It is found that the second-order rate constants for the reactions with the chosen phenolic compounds are in the 104–107 M–1 s–1 range. In particular, the rate constant for ozonation of phenol is 5.06 × 106 M–1 s–1. The liquid-side mass-transfer coefficient is estimated by using the chemical method, and its value (kL = 0.052 cm s–1) is in line with those typical of stirred-cell reactors. This work is useful for the design, operation, and scale-up of ozonation reactors used in wastewater treatment.

Characterization of the superior CO2-capturing absorbent blend AMP/PZ/EGMEE/Water

Together, 2-amino-2-methyl-1-propanol (AMP), piperazine (PZ), ethylene glycol monoethyl ether (EGMEE or 2-ethoxyethanol) and water form a capable, non-traditional CO2-separation solvent. Detailed characterization and scrutiny of the CO2 absorption capacity and reactivity of this solvent is hitherto missing. In this work, we investigated equilibrium and reaction kinetic features of the AMP/PZ/EGMEE/H2O blend for the first time. We worked at different molarities of AMP (2–3 M), PZ (0.2-0.6 M) and EGMEE (0.8–2.5 M) to look at their specific roles in the absorption process. In a stirred cell reactor, we measured CO2 absorption rates in the 30–45 °C range and reported the fast pseudo-first order rate constant. The prevalent reaction pathway was elucidated using zwitterion mechanism. Additional useful information was also extracted from the kinetic data of pure CO2 absorption. For example, it was found that PZ reacts with CO2 according to a second-order reaction (rate constant k2,PZ = 5.6 × 104 M−1 s−1 at T = 35 °C) with activation energy value of 43 kJ mol−1. In an ambient-pressure vapor-liquid-equilibrium (VLE) apparatus, we reported the dependence of equilibrium CO2 pressure on absorption capacity of the chosen blend at T = 30 °C; loading capacity was markedly higher than that in AMP/H2O and AMP/PZ/H2O mixtures. This progress in knowledge will stimulate further interest into this promising solvent.

Kinetic Study of Carbon Dioxide Reaction with Binding Organic Liquids

Binding organic liquids are strong base of amidine have been used for CO2 capture. Up to now, there is no known datum on the reaction kinetics of CO2 with 1.5-Diazabicyclo [4.3.0] non-5-ene (DBN). In this paper, Kinetics of reaction between CO2 and DBN/MDEA in 1-Pentanol was performed utilizing the stirred cell reactor with DBN concentration (2 – 2.9 M) and at room temperature. The reaction path was qualified using zwitterion and the termolecular mechanism. From the kinetic datum with DBN concentrations (2 - 2.9 M), it was found that the capturing process happened in a fast reaction system with a second-order reaction kinetics of DBN/MDEA and first order with CO2. In addition, CO2 absorption was achieved using gas-liquid contact system. CO2 absorption rate was (2×10−5−2.8 × 10−5kmol⁄m2.sec) at DBN concentration (2 – 2.9 M). Finally, it is known that DBN/MDEA/1-Pentanol/CO2 system is easily switchable and can be used both CO2 capture and for other applications that require rapid change of medium from nonionic to ionic liquid.