Polarographic Effect of Carbon Dioxide in Solutions of Ethyl Alcohol

Hydration of carbon dioxide in water solution is the rate limiting step for the CO2 mineralization process, a process which is at the base of many carbon capture and utilization (CCU) technologies aiming to convert carbon dioxide to added-value products and mitigate climate change. Here, we present a combined experimental and computational study to clarify the effectiveness and molecular mechanism by which nickel nanoparticles, NiNPs, may enhance CO2 hydration in aqueous solutions. Contrary to previous literature, our kinetic experiments recording changes of pHs, conductivity, and dissolved carbon dioxide in solution reveal a minimal effect of the NiNPs in catalyzing CO2 hydration. Our atomistic simulations indicate that the Ni metal surface can coordinate only a limited number of water molecules, leaving uncoordinated metal sites for the binding of carbon dioxide or other cations in solution. This deactivates the catalyst and limits the continuous re-formation of a hydroxyl-decorated surface, which was a key chemical step in the previously suggested Ni-catalyzed hydration mechanism of carbon dioxide in aqueous solutions. At our experimental conditions, which expand the investigation of NiNP applicability toward a wider range of scenarios for CCU, NiNPs show a limited catalytic effect on the rate of CO2 hydration. Our study also highlights the importance of the solvation regime: while Ni surfaces may accelerate carbon dioxide hydration in water restricted environments, it may not be the case in fully hydrated conditions.

The solvation of carbon dioxide in solution represents a key step for the capture and fixation CO2 in nature, which may be further influenced by the formation of (bi)carbonate species and/or the formation of CO2 clusters in solution. The latter processes are strongly dependent on the exact environment of the liquid state (e.g., pH value, solvated ions, etc.) and may interfere with the experimental determination of structural, dynamical, and thermodynamic properties. In this work a hybrid quantum mechanical/molecular mechanical (QM/MM) simulation approach at correlated ab initio level of theory resolution-of-identity second-order Møller-Plesset Perturbation Theory (RI-MP2) has been applied in the framework of thermodynamic integration (TI) to study structure, dynamics, and the hydration free energy of a single carbon dioxide molecule in aqueous solution. A detailed analysis of the individual QM/MM potential energy contributions demonstrate that the overall potential remains highly consistent over the entire sampling phase and that no artificial contributions are influencing the determination of the hydration free energy. The latter value of 0.01 ± 0.92 kcal/mol was found in very good agreement with the values of 0.06 and 0.24 kcal/mol obtained via quasi-chemical theory and experimental measurements, respectively. In order to obtain detailed information about the C- and O C-water interaction, conically restricted regions with respect to the main axis of the CO2 molecule have been employed in structural analysis. The presented data not only provide detailed information about the hydration properties of CO2 but act as a critical validation of the simulation technique, which will be beneficial in the study of nonaqueous solvents such as pure and aqueous NH3 solutions, which have been suggested as potential candidates to capture CO2 from anthropogenic sources.

The chemical absorption of carbon dioxide by a laminar jet of ethylenediamine has been studied at 25.5°C under pseudo‐first‐order kinetic conditions. The reaction was found to be second‐order with a rate constant of 1.0 x 105 1/g. mole sec. Equilibrium calculations at 18°C indicate that the partial pressure of carbon dioxide is very low, even over highly carbonated ethylenediamine solutions. The effects of amine concentration and carbonation ratio on the physical solubility and diffusivity of carbon dioxide in solution were inferred from corresponding results for nitrous oxide

CHAPTER 26 - SOME BIOLOGICAL ANALYTICAL METHODS

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.

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...

1. Sprout growth is inhibited at 10°C by a concentration of 15 per cent of carbon dioxide in the storage atmosphere, decreased by lower concentrations, and stimulated by still lower concentrations. The optimum concentration for growth need not necessarily be the same in all cases; but appears to be about 2–4 per cent, which would give a concentration in the cell sap of some 0.04–0.05 ml carbon dioxide per ml sap. 2. In agreement with reports by other workers, sprout growth was found to be stimulated by reducing the concentration of oxygen in the storage atmosphere to 5 per cent, which would give a concentration of oxygen in the cell sap of about 0.006 ml oxygen per ml sap. 3. A reduced oxygen tension causes augmented growth either by means of an increase in the number of sprouts or in the number of cells in individual sprouts. A raised carbon dioxide tension causes an increase in the number of cells in the sprouts and also marked cell elongation. 4. Over the range 10–25 C the effect of temperature upon respiration and upon the solubility of gases — and hence upon the concentrations in the cell sap of dissolved oxygen and, more particularly, carbon dioxide —could be an important factor contributing to the effect of temperature upon sprout growth. In some cases the increased sprout growth after some time at a higher temperature may be no more than would be expected as a result of the increased carbon dioxide in solution. 5. Discussion of the results in the light of other work suggests several mechanisms through which changes in the carbon dioxide or oxygen concentrations may influence sprout growth. Such suggestions must be very tentative pending more detailed investigation of the systems involved.

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.

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.

The present article reports the development of a novel electrochemical carbon dioxide minisenso based on hemoglobin which is incorporated into self‐assembled bilayer lipid membranes (s‐BLMs) on a metal support. The presence of carbon dioxide in solution was found to modulate the ion conductivity of BLMs containing hemoglobin, when using a lipid composition containing egg phosphatidylcholine (egg PC) and dipalmitoylphosphatidic acid (DPPA). The use of stabilized metal‐supported BLMs has allowed the electrochemical investigation of the reversibility of the response to carbon dioxide and of hemoglobin binding to lipid membranes. The effects of hemoglobin concentration, composition of BLMs in DPPA and pH on the sensitivity of the response were examined. The sensor provides the advantages of fast response times (on the order of ca. 10 s) to alterations of carbon dioxide concentration, low detection limits (ca. 0.4 × 10−6 M) and capability of analysing small sample volumes. Semisynthetic platelet‐activating factor (PAF; 1‐O‐alkyl‐2‐acetyl‐sn‐glyceryl‐3‐phosphorylcholine, AGEPC) was found to improve the response characteristics of the carbon dioxide sensor (i.e., decrease of the detection limit to nM range and increase of the dynamic range of carbon dioxide determination). The biosensor was routinely mechanically stable and functional for over 48 h. During this time it showed reproducible sensitivity and response to a given concentration of carbon dioxide in solution.

Emission from the tris(1,10-phenanthroline)ruthenium(II) complex (Ru(phen)32+) bearing a (dimesityl)boryldurylethynyl (DBDE) charge transfer unit at the 4-position of one of the three phen ligands ([Ru(phen)2(4-DBDE-phen)] = 4BRu2+) was quenched by carbon dioxide in solution with the rate constant of ∼106 M−1 s−1.

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

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

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

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.