Kinetics of the reaction of carbon dioxide with aqueous sodium and potassium carbonate solutions

Kinetics for CO₂ absorption into 5–30 wt-% sodium carbonate solutions and 5–50 wt-% potassium carbonate solutions up to 70 °C were studied in a string of discs apparatus under conditions, in which the reaction of CO₂ could be assumed pseudo-first-order. The experimental data were evaluated based on the use of activities in the reaction rate expressions. The second order kinetic constant for the CO₂ reaction CO₂+OH^??HCO₃^? at infinite dilution is discussed and an expression for it is obtained up to 70 °C.The difference between the activity and concentration based kinetic constants were found to be small at low concentrations, where the apparent Henry’s law constant is close to that at infinite dilution in water. However, at high concentrations (high apparent Henry’s law constants), the difference was bigger. Using the activity based approach, the second order kinetic constant was calculated, compared to the second order kinetic constant in infinite dilution and found to be independent of both carbonate concentration and the cation present in the solution.     

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%.     

Chemical absorption and desorption of carbon dioxide from hot carbonate solutions

Absorption and desorption rate data for the system CO₂-hot carbonate solutions are presented. The data are interpreted on the basis of a film-theory model developed following the procedure recently presented by Astarita and Savage [1]. The agreement is very satisfactory. Values of the kinetic constant of the rate-determining step, previously known only up to a temperature of 40°C, have been obtained up to 110°C.     

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 laminar falling films of aqueous kaolin slurries containing sodium hydroxide

To confirm the theory for gas absorption accompanied by an instantaneous irreversible reaction in laminar falling films of power-law liquids which was presented in a previous paper, experiments were carried out on the absorption of pure carbon dioxide into aqueous kaolin slurries containing sodium hydroxide by using a long wetted-wall column. The experimental data were in fairly good agreement with the theoretical predictions, the average deviation being 3.0%. The discussion on the effect of the power-law index of the liquid upon the reaction factor suggested an approximate method of estimating the reaction factors for power-law liquids.     

Gas absorption with consecutive chemical reaction: Absorption of carbon dioxide into aqueous amine solutions

Experiments were carried out over a wide range of contact time for the absorption of carbon dioxide into aqueous amine solutions. It was suggested from the experimental results with a laminar liquid-jet, a wetted wall column and a quiescent liquid absorber that the present absorption processes should be analyzed by a gas absorption with the consecutive reaction of the form of A + 2B →k_I R and A + R →k_II Products. The values of rate constants for the second-order first reaction step (k₁) for the diethanolamine and triethanolamine were estimated as 1340 and 16.8 1/mol-sec, respectively. The value of rate constant for the second reaction step was found to be constant irrespective of the liquid reactant.     

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.     

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.     

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 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     

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.     

Organic and carbon xerogels derived from sodium carbonate controlled polymerisation of aqueous phenol-formaldehyde solutions

Porous carbons were synthesized from aqueous sodium carbonate catalysed solutions of the low cost precursors phenol and formaldehyde, applying ambient pressure drying without prior solvent exchange. Many of the samples are found to crack during drying, however, the resulting porous carbons show porosities up to 80%, specific surface areas up to 746 m²/g, and micropore volumes up to 0.29 cm³/g; the mesopore volume and external surface area of the derived carbons, however, is small indicating the dominance of macropores. An unusual gelation kinetic, i.e., the formation of precipitating flakes instead of the classical sol–gel-transition is observed; this is likely due to nuclei growth from a metastable state in the phase diagram and makes it challenging to reproduce samples with well defined properties. Nevertheless mechanically stable macroporous monoliths, that survive the ambient pressure drying without prior solvent exchange can be synthesized; the system presented, however, seems not to be suitable as base system for highly mesoporous carbon samples (aerogels, cryogels, xerogels) or large scale production of porous carbon materials.     

Absorption and desorption of carbon dioxide in several water types

This study investigated the effect of water type on the rate of CO₂ transfer from/to an aqueous phase with varying degree of water salinity. The absorption and desorption experiments were conducted on reverse osmosis product, brackish well, and brackish water reverse osmosis reject waters as well as seawater in a mechanically agitated tank. Results show that the direction of mass transfer has a major impact on the value of the volumetric mass transfer coefficient, k_La, with the absorption experiments always rendering higher values. Furthermore, k_La values always decreased with salinity in both absorption and desorption experiments until a certain critical salinity value was reached, beyond which mass transfer increased again. However, k_La values were found to decrease continuously with an increase in the water alkalinity in absorption experiments, while no clear conclusion could be drawn for the alkalinity effect in the case of desorption experiments. These observations suggest that the effect of alkalinity should be further investigated to elucidate its impact along with the salinity on the volumetric mass transfer rate.     

活性炭/水浆料中CO2吸收过程的增强

针对分散相微粒增强难溶气体的吸收过程,提出了一个一维非稳态非均相传质的二区模型,并进行了理论求解。根据表面更新理论,得到了增强因子的数学表达式。利用恒温反应釜,对活性炭/水浆料中发生的CO2吸收过程进行了实验研究,测定了不同颗粒浓度及转速下的增强因子。实验结果与模型预测值吻合良好,表明本文模型具有很高的预测精度。     

Absorption of oxygen by aqueous sodium sulphite solutions

New data have been reported on the absorption of oxygen by aqueous sodium sulphite solutions with cobalt sulphate as catalyst at 30°C. It is observed that the absorption rate increases up to a critical sulphite concentration beyond which the absorption rate becomes constant and this critical concentration varies with the catalyst concentration. The order of reaction with respect to sulphite and oxygen in the constant absorption rate regime was found to be zero and two respectively. The absorption rate is affected by the total ionic strength (sulphite and sulphate) in addition to the effect of pH and catalyst concentraion. The reported data were also analysed to ascertain the effect of temperature and a relationship has been proposed for prediction of the second order reaction rate constant.     

Equilibrium between carbon dioxide and aqueous monoethanolamine solutions

The partial pressure of carbon dioxide has been measured over aqueous monoethanolamine solutions (1.0, 2.5, 3.75 and 5.0 N) at temperatures of 25, 40, 60, 80, 100 and 120°C. Partial pressures of CO₂ ranged between 0.2 and 6616 kPa.^b The results extend previously published data to higher partial pressures. Comparisons have been made with two methods of prediction based upon a thermodynamic model.     

Absorption of chlorine in aqueous solutions of sodium hydroxide: Desorption of hypochlorous acid followed by its dissociation to chlorine monoxide

The absorption of chlorine in aqueous solutions of sodium hydroxide with concurrent desorption of hypochlorous acid (followed by its dissociation to chlorine monoxide) was studied at 55 and 75°C in a model stirred contactor with a flat gas-liquid interface. Theoretical and experimental aspects of this unique case of desorption (followed by dissociation) have been considered.A reasonably good agreement between the theoretical predictions and experimental observations has been found.