Kinetics of carbon dioxide chemical absorption into cyclic amines solutions

Chemical reaction kinetics between carbon dioxide with two cyclic amines (pyrrolidine and piperidine) have been studied using a stirred tank reactor with a planar interfacial area. The operational variables considered in this work have been the amine concentration in the liquid phase and the reaction temperature. Specific absorption rates have been determined under different experimental conditions. Results indicate that the absorption process occurs in a pseudo first reaction regime exhibited first‐order kinetic with respect carbon dioxide and a second order for both cyclic amines. The reaction‐rate constant was determined under the different experimental conditions, and it was correlated depending on the temperature by means of an Arrhenius type equation. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Kinetics of the absorption of carbon dioxide into aqueous ammonia solutions

Experiments were performed in a customized double stirred tank reactor to study the kinetics of CO₂ absorption into NH₃ solutions at concentrations ranging from 0.42 to 7.67 kmol·m^?3 and temperatures between 273.15 and 293.15 K. The results show that the reactive absorption was first order with respect to CO₂ but fractional order (1.6–1.8) with respect to ammonia. Experimental data can be satisfactorily interpreted by a termolecular mechanism using and . © 2016 American Institute of Chemical Engineers AIChE J, 62: 3673–3684, 2016     

Absorption of carbon dioxide into aqueous methyldiethanolamine

Gas absorption rates in a laminar liquid jet were measured for carbon dioxide in methyl- diethanolamine (MDEA) solutions. It was found that for the short contact times (<0.012s) of these absorption experiments there is only a small effect of any reaction between carbon dioxide and MDEA. Solubilities and molecular diffusivities for carbon dioxide in aqueous MDEA are estimated from measurements with nitrous oxide. The absorption rate data are described well using the solubilities and diffusivities measured in this work. Solubilities were measured over the temperature range 15 to 35°C and for MDEA concentrations up to 40%. Diffusion coefficients and viscosities were measured over the same temperature range and MDEA concentrations up to 20%.     

Kinetics and modeling of carbon dioxide absorption into aqueous solutions of piperazine

In this work, the kinetics of the reaction between CO₂ and aqueous piperazine (PZ) have been estimated over the temperature range of 298-313 K from the absorption data obtained in a wetted wall contactor. The absorption data are obtained for the PZ concentrations of 0.2- and for CO₂ partial pressures up to 5 kPa. A coupled mass transfer-kinetics-equilibrium mathematical model based on Higbie's penetration theory has been developed with the assumption that all reactions are reversible. The model is used to estimate the rate constants from the experimental data for absorption of CO₂ in aqueous PZ. The estimated rate constants of this study are in good agreement with those reported in the literature.     

Absorption of chlorine into aqueous sodium carbonate solutions and desorption of carbon dioxide

The absorption of pure chlorine into aqueous sodium carbonate solutions accompanied by the desorption of carbon dioxide was studied both theoretically and experimentally. The absorption rates of chlorine and the desorption rates of carbon dioxide were measured at 25°C using a baffled agitated vessel operated batchwise. The experimental results were analyzed with the chemical absorption theory based on the Lévěque model. The measured absorption and desorption rates were in good agreement with the theoretical predictions.     

Kinetics of carbon dioxide reaction with diethylaminoethanol in aqueous solutions

Differential rates of CO₂ adsorption into 0.90, 0.47 and 0.24 M aqueous solutions of 2-(diethylamino)ethanol (DEAE) were measured at 323 K over a wide range of carbonation ratios. A rigorous thermodynamic model was used to define species activities which were coupled with Danckwerts' gas-liquid reaction model to deduce the kinetics. The reaction of CO₂ with this highly basic tertiary amine occurs by two pathways: (1) a minor path via the CO₂ reaction with hydroxide ion and (2) a predominant reaction pathway that can be characterized by its first order dependency on the free amine concentration. The second reaction was proposed to involve an internal salt-like intermediate,.     

Absorption of carbon dioxide into non-aqueous solutions ofN-methyldiethanolamine

The chemical absorption rate of carbon dioxide was measured in non-aqueous solvents, which dissolved N-methyldiethanoamine (MDEA), such as methanol, ethanol, n-propanol, n-butanol, ethylene glycol, propylene glycol, and propylene carbonate, and water at 298 K and 101.3 kPa using a semi-batch stirred tank with a plane gas-liquid interface. The overall reaction rate constant obtained from the measured rate of absorption of carbon dioxide under the condition of fast pseudo-first-order reaction regime was used to get the apparent reaction rate constant, which yields the second-order reaction rate constant and the reaction order of the overall reaction. There was approximately linear dependence of the logarithm of the rate constant for the overall second-order reaction on the solubility parameter of the solvent. In non-aqueous solutions of (MDEA), dissolved carbon dioxide is expected to react with solvated (MDEA) to produce an ion pair.     

Absorption of carbon dioxide into aqueous colloidal silica solution with diisopropanolamine

Carbon dioxide was absorbed into the aqueous nanometer-sized colloidal silica solution of 0–31 wt% and diisopropanolamine of 0–2 kmol/m³ in a flat-stirred vessel with the impeller of various sizes and speeds at 25 °C and 0.101 MPa to measure the absorption rate of CO₂. The volumetric liquid-side mass transfer coefficient (k_La) of CO₂ was used to obtain the empirical correlation formula containing the rheological behavior of the aqueous colloidal silica solution. Reduction of the measured k_La was explained by the viscoelastic properties of the aqueous colloidal silica solution. The theoretical value of the absorption rate of CO₂ was estimated from the model based on the film theory accompanied by chemical reaction and compared with the measured value.     

Kinetics of absorption of carbon dioxide in aqueous piperazine solutions

In the present work the absorption of carbon dioxide into aqueous piperazine (PZ) solutions has been studied in a stirred cell, at low to moderate temperatures, piperazine concentrations ranging from 0.6 to , and carbon dioxide pressures up to 500 mbar, respectively. The obtained experimental results were interpreted using the DeCoursey equation [DeCoursey, W., 1974. Absorption with chemical reaction: development of a new relation for the Danckwerts model. Chemical Engineering Science 29, 1867-1872] to extract the kinetics of the main reaction, 2PZ+CO₂→PZCOO^-+PZH⁺, which was assumed to be first order in both CO₂ and PZ. The second-order kinetic rate constant was found to be at a temperature of , with an activation temperature of . Also, the absorption rate of CO₂ into partially protonated piperazine solutions was experimentally investigated to identify the kinetics of the reaction . The results were interpreted using the Hogendoorn approach [Hogendoorn, J., Vas Bhat, R., Kuipers, J., Van Swaaij, W., Versteeg, G., 1997. Approximation for the enhancement factor applicable to reversible reactions of finite rate in chemically loaded solutions. Chemical Engineering Science 52, 4547-4559], which uses the explicit DeCoursey equation with an infinite enhancement factor which is corrected for reversibility. Also, this reaction was assumed to be first order in both reactants and the second-order rate constant for this reaction was found to be at 298.15 K.     

Absorption of co2 into aqueous tertiary amine/mea solutions

Absorption rates for CO₂ into aqueous solutions of TEA, MDEA and blends of MEA with MDEA and TEA were measured in a stirred cell by a method similar to that used by Laddha and Danckwerts (1981). Second order rate constants for CO₂-TEA and CO₂-MDEA were obtained from the single amine data for temperatures in the range of 25-60°C. A modified pseudo first order model based on the film theory is used to predict the rate of absorption of CO₂ into mixed amine solutions. This model accounts for the variation of amine concentration in the film and assumes a shuttle mechanism for rate enhancement. Bulk liquid concentrations of the various species present are obtained from a simplified thermodynamic model. The model predicts absorption rates that are in agreement with experimental measurements.     

Kinetics of carbon dioxide absorption in aqueous solutions of diisopropanolamine

A bubble column absorber was used to investigate kinetics of the reaction between carbon dioxide and aqueous solutions of diisopropanolamine (DIPA), by means of gas absorption experiments. These were conducted in the temperature range of 20 to 40°C, with DIPA concentrations from 5 to 500 mol/m³, and CO₂ partial pressures between 5 and 101 kPa. A model based on the Danckwerts' surface reneval theory was used to analyze the experimental results and to determine the rate constant. The obtained data support the assumption of a second-order overall reaction, with the rate constants being well correlated by the Arrhenius equation:      

Absorption of carbon dioxide into aqueous PAA solution containing diethanolamine

Carbon dioxide was absorbed into aqueous polyacrylamide (PAA) solution containing diethanolamine (DEA) of 0–2 kmol/m³ in a flat-stirred vessel with the impeller of 0.034 m and agitation speed of 50 rpm at 25 °C and 0.101 MPa to measure the absorption rate of CO₂. The volumetric liquid-side mass transfer coefficient (k_La) was obtained from the dimensionless empirical correlation formula presenting the rheological behavior of aqueous PAA solution. PAA with elastic property of non-Newtonian liquid made the rate of chemical absorption of CO₂ accelerate compared with Newtonian liquid based on the same viscosity of the solution. The estimated value of the absorption rate of CO₂ was obtained from the model based on the film theory accompanied by chemical reaction and compared with the measured value.     

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.     

Kinetics of absorption of carbon dioxide into aqueous solutions of 2-amino-2-hydroxymethyl-1,3-propanediol

In this work the kinetics of the reaction between CO₂ and a sterically hindered alkanolamine, 2-amino-2-hydroxymethyl-1,3-propanediol (AHPD) were determined at temperatures of 303.15, 313.15 and 323.15 K in a wetted wall column contactor. The AHPD concentration in the aqueous solutions was varied in the range 0.5-2.4 kmol m⁻³. The ratio of the diffusivity and Henry's law constant for CO₂ in solutions was estimated by applying the N₂O analogy and the Higbie penetration theory, using the physical absorption data of CO₂ and N₂O in water and of N₂O in amine solutions. Based on the pseudo-first-order for the absorption of CO₂, the overall pseudo-first-order rate constants were determined from the kinetics measurements. By considering the zwitterion mechanism for the reaction of CO₂ with AHPD, the zwitterion deprotonation and second-order rate constants were calculated. The second-order rate constant, k₂, was found to be 285, 524, and 1067 m³ kmol⁻¹ s⁻¹ at 303.15, 313.15, and 323.15 K, respectively.     

Kinetics of carbon dioxide absorption into catalysed potassium carbonate solutions

Carbon dioxide was absorbed in potassium carbonate-bicarbonate buffer solutions. Some of these solutions contained arsenious ion as catalyst. The experiments were performed in a wetted wall absorber, in conditions of stagnant gas phase and at constant temperature, with the aim of elucidating the influence of the carboante ion concentration on the catalytic process. A kinetic equation was obtained, that was critically compared with the experimental data published previously by various investigators.     

Enhancement of carbon dioxide absorption into aqueous methyldiethanolamine using immobilised activators

Blends of ‘activating’ primary or secondary amines (diethanolamine, DEA) with tertiary amines, (methyldiethanolamine, MDEA) are commonly used for the removal of CO₂ from gas mixtures. To avoid undesirable side-effects from these activators, such as increased corrosion or higher energy requirements for regeneration, we propose using immobilised primary or secondary amine groups on solid supports. In this manner the activating additives can be localised to those parts of the absorption column where the high absorption rates achieved are truly beneficial and excluded elsewhere.The studies presented were carried out to provide an initial evaluation of the feasibility of this novel concept. Preliminary experiments carried out in a discontinuously operated stirred tank reactor reveal similar enhancement of the CO₂ absorption into ‘activated’ MDEA solution, when the soluble DEA additive is replaced by a suspended solid adsorbent, containing the equivalent quantity of immobilised amine groups. Further experiments examined the CO₂ absorption in a three phase fluidised bed column. They demonstrated that the immobilised activator can be employed in a continuously operated process too.All experimental results support the basic feasibility of using immobilised primary amines in place of homogeneous additives to enhance CO₂ absorption in tertiary amine solutions.     

Kinetics of carbon dioxide absorption into aqueous amine amino acid salt: 3-(methylamino)propylamine/sarcosine solution

A string of discs contactor apparatus was used to measure the CO₂ absorption kinetics into an unloaded aqueous amine amino acid salt, 3-(methylamino)propylamine/sarcosine, SARMAPA solution. The solution was prepared by mixing equinormal proportions of sarcosine, SAR and 3-(methylamino)propylamine, MAPA. Experiments were carried out for the concentration range 1.0–5.0 kmol m⁻³ and for temperatures 25–62 °C. The termolecular mechanism was applied to interpret the experimental data after correcting for non-idealities from the ionic strength using an ionic correction factor. A model correlation without the ionic strength correction was found not to give a good fit to the experimental data. The reaction rate constant for aqueous SARMAPA was determined and found to be comparable to values for amines. It increases significantly with temperature and concentration. The reaction rate constant for water is higher in the SARMAPA system than in amine systems indicating that water contributes significantly to the overall absorption rate and more than in amine systems. The reaction order with respect to the amino acid salt, SARMAPA, concentration varies from 1.06 to 1.43 with an average value of 1.21. A simplified approach applied to the complex speciation chemistry of the amine amino acid salt, AAAS, system gave a good representation of the experimentally observed kinetic rate constant.