Hyperthermophilic Carbamate Kinase Stability and Anabolic In Vitro Activity at Alkaline pH.

The solubility of carbon dioxide in aqueous alkanolamine solutions was investigated in the high gas loading region based on experimental measurements and thermodynamic modeling. An experimental phase equilibrium study was performed to evaluate the absorption of carbon dioxide in aqueous solutions of five representative alkanolamines, including monoethanolamine, diethanolamine, N-methyldiethanolamine, 2-amino-2-methyl-1-propanol and piperazine. The carbon dioxide loadings of these solutions were determined for a wide range of pressures (62.5 kPa to 4150 kPa), temperatures (303.15 K to 343.15 K) and alkanolamine concentrations (2 M to 4 M). The results were found to be largely consistent with those previously reported in the literature. Furthermore, a hybrid Kent–Eisenberg model was developed for the correlation of the experimental data points. This new model incorporated an equation of state/excess Gibbs energy model for determining the solubility of carbon dioxide in the high-pressure–high gas loading region. This approach also used a single correction parameter, which was a function of the alkanolamine concentration. The results of this model were in excellent agreement with our experimental results. Most notably, this model was consistent with other reported values from the literature.

As part of an ongoing project dealing with the measurement and correlation of phase equilibria in aqueous solutions containing a weak base like ammonia and acid gases like carbon dioxide, sulfur dioxide and hydrogen cyanide, the solubility of carbon dioxide was measured in aqueous solutions containing the single salts sodium sulfate and ammonium sulfate as well as in a solution containing both salts. The temperature ranged from 313.15 K to 433.15 K and pressures up to 10 MPa. Pitzer's semiempirical model is used to correlate the new data. From the results for the solubility of carbon dioxide in the single salt aqueous solutions, interaction parameters were determined. With these parameters the solubility of carbon dioxide in an aqueous mixture containing both salts is predicted quantitatively.

Rate constants, ΔH‡ and ΔS‡ have been measured by the conductimetric stopped-flow technique for the reaction of carbon dioxide in aqueous solution with the primary amines 2-methoxyethylamine, 2-aminoethanol, 3-aminopropan-1-ol, 2-aminopropan-2-ol, DL-aminopropan-2-ol and the secondary amines 1,1′-iminodipropan-2-ol, 2-amino-2-(hydroxymethyl) propane-1,3-diol, 2,2′-iminodiethanol, 2,2,6,6-tetramethylpiperidin-4-ol, and morpholine. The observed first-order rate constants fit the equation kobs=kAM[R2NH]2+kW[R2NH][H2O]. The much-quoted Danckwerts mechanism is shown to be unlikely.

In this study, the solubility of carbon dioxide (CO2) in the aqueous solution of piperazine (PZ) activated N-methyldiethanolamine (MDEA) was investigated. In the aqueous solution the concentrations of the N-methyldiethanolamine (MDEA) and piperazine (PZ) were kept constant at 30 wt. % and 3 wt. %, respectively. The solubility experiments were carried out between the temperatures ranges of 303.15 to 333.15 K. The pressure range was selected as 2-50 bar for solubility of carbon dioxide in the aqueous solution. The solubility of the CO2 is reported in terms of CO2 loading capacity of the solvent. The loading capacity of the solvent is the ratio between the numbers of moles of CO2 absorbed to the numbers of moles of solvent used. The experimental data showed that the CO2 loading increased with increase in CO2 partial pressure, while it decreased with increase in system's temperature. It was also observed from the experimental data that the higher pressure favors the absorption process while the increased temperature hinders the absorption process of CO2 capture. The loading capacity of the investigated solvent was compared with the loading capacity of the solvents reported in the literature. The investigated solvent showed better solubility in terms of loading capacity.

Equilibrium solubility of carbon dioxide in aqueous solutions of (diethylenetriamine + piperazine)

High pressure solubility of carbon dioxide (CO 2) in aqueous piperazine solutions

The solubility of carbon dioxide in aqueous N-methyldiethanolamine solutions

Diffusivities of carbon dioxide in aqueous mixed electrolyte solutions

Reliable data for the solubility of carbon dioxide in aqueous solutions of monoethanolamine are required for the design and evaluation of postcombustion carbon capture processes. As published experimental data for the solubility of carbon dioxide in aqueous solutions of monoethanolamine show considerable scatter, the solubility of carbon dioxide in aqueous solutions containing (15 and 30) mass percent of monoethanolamine; that is, (2.9 and 7.0) mol·(kg H2O)−1 respectively, was measured at molar ratios of carbon dioxide to monoethanolamine in the liquid solution from 0.1 to 1.3 at (313, 353 and 393) K. An apparatus based on headspace gas chromatography (on the synthetic gas solubility method) was used for the experiments at low (high) gas loadings, that is, at partial pressures of carbon dioxide from (1 to 80) kPa (from (0.4 to 8.6) MPa). The new experimental results are compared to literature data and used to parametrize a physicochemical thermodynamic model based on the extended Pitzer equation for the G...

Measurement of the Absorption Rates of Carbon Dioxide in Aqueous Solutions of Piperazine and Sulfolane Using the Stopped-flow Technique

The solubility of carbon dioxide in aqueous solutions containing 2-amino-2-methyl-1-propanol (AMP) was measured in the temperature range from 313 to 353 K at total pressures up to 2.7 MPa using an analytical method. A model taking into account chemical reactions in the liquid phase as well as physical interactions is used to correlate the new data. To test the predictive capability of the model, the solubility of carbon dioxide in an aqueous solution containing AMP and N-methyldiethanolamine (MDEA) was measured at 313 K. Experimental results are reported and compared to literature data and calculations.

Nowadays, environmental concern on climate change and global warming is the main issue because of the higher content of carbon dioxide discharge from power plant to the atmosphere. Chemical absorption with amine solution is a proven technology to remove carbon dioxide. The commercially used amine solution are monoethanolamine (MEA) and methyl diethanolamine (MDEA). However, it still has disadvantages such as low cyclic capacity and high energy requirement. Therefore, new solvents for carbon dioxide capture have been developed to enhance the amine performance. Consequently, the objective of this study is to measure the solubility of carbon dioxide in an aqueous solution of 2-(Diethylamino)ethanol (DEAE) used as a new solvent. It is measured at 30-80 degrees Celsius and carbon dioxide partial pressures ranging from 5 to 100 kPa. The concentration of aqueous DEAE solution are 3, 4 and 5 M. The solubility data of carbon dioxide in aqueous solution of DEAE are compared with that of aqueous solution of MEA and MDEA at the same conditions. The results show that the DEAE has higher cyclic capacity than that of commercial absorbents at the post combustion power plant flue gas stream conditions. This means DEAE can use less energy for regeneration and lead to high energy saving for carbon capture process.

Solubility of carbon dioxide in aqueous solutions of amino acid salts

The solubility of carbon dioxide in aqueous solutions containing acetic acid and in aqueous solutions containing sodium hydroxide was measured in the temperature range from 313 to 433 K and total pressures up to 10 MPa. The molalities of acetic acid or sodium hydroxide in the liquid phase were about 4 and 1 mol/kg, respectively. Experimental results are reported and compared to correlations and predictions.

The Direct Determination of Carbon Dioxide in Aqueous Solutions by a Simple Distillation Method Amir Hussain Abstract A direct method for the determination of CO2 in aqueous solutions using a simple distillation was undertaken. The amount of CO2 was calculated from the monomeric pressure obtained. The results show that the determination is successful and the closed system was checked to make sure that there were no leaks as this would affect the results. The samples tested were carbonated soft drinks. This is a novel method for the direct determination of CO2. Full Text: PDF DOI: 10.15640/jcb.v6n2a1