Investigation of new potential amine activa-tors for carbon dioxide absorption in carbonate solutions

The relative efficiencies of water, sodium carbonate solutions (0.025 to 0.4 M), and triethanolamine solutions (0.05 to 1.0 M) for the removal of carbon dioxide from air containing up to 12% of the gas, at 40–50°F., was determined using 12 in. diameter towers packed to a depth of 40 in. with 1‐in. Raschig rings. Coefficients of absorption for sodium carbonate and triethanolamine solutions were 30–60% less than comparable coefficients for water. Desorption coefficients for sodium carbonate and triethanolamine solutions were larger than absorption coefficients under comparable conditions but somewhat less than desorption coefficients for water, except for dilute conditions. Desorption coefficients for dilute solutions (less than 0.15 M) were up to three times as large as those for water. These results indicate that the use of sodium carbonate or triethanolamine solutions instead of water (as frequently used at present) would permit the use of smaller desorption equipment in applications such as scrubber systems for the removal of carbon dioxide from controlled atmosphere storage rooms for fruits and vegetables.Solubility data for carbon dioxide in sodium carbonate and triethanolamine solutions at temperatures and carbon dioxide partial pressures of interest in this study were also determined.

Preliminary screening experiments of carbon dioxide (CO2) absorption into aqueous 35 wt % equivalent potassium carbonate (K2CO3) solution with different additives were performed in a wetted-wall column at 322 K. Arginine was found as an effective promoter to enhance the absorption rate in aqueous K2CO3 solution. The effect of arginine concentration and CO2 loading on the absorption rate into carbonate solutions is discussed. The vapor–liquid equilibrium of 35 wt % equivalent K2CO3 with 0–5 wt % arginine was obtained in the temperature range from 323 to 343 K using inert-gas stripping method. Desorption curves of the unpromoted and arginine-promoted carbonate solutions are also discussed.

Electrochemical and spectroscopic studies of neptunium, plutonium, americium, californium, and terbium in concentrated aqueous carbonate and carbonate-hydroxide solutions have been carried out. Changes in the absorption spectra of Np(VII), Np(V), Pu(VI), Pu(V), Am(VI), and Am(V) in concentrated Na/sub 2/CO/sub 3/ solution and in the formal potentials of the Np(VI)/Np(V) and Pu(VI)/Pu(V) couples as a function of pH were observed. Heptavalent neptunium in concentrated Na/sub 2/CO/sub 3/ solution could only be producted at pH values close to or greater than 14. Plutonium(VII) in 2 M Na/sub 2/CO/sub 3/ solution could only be produced at hydroxide ion concentrations in excess of about 2.5 M. The complexation of Np(VII) and Pu(VII) in Na/sub 2/CO/sub 3/-NaOH solution seems to be mainly by hydroxide ions. Neptunium(IV) and plutonium(IV) are insoluble in Na/sub 2/CO/sub 3/ solution above ca. pH 11-12. Neptunium(III) in carbonate solution is rapidly oxidized by water to Np(IV). Plutonium(III) is insoluble in Na/sub 2/CO/sub 3/ solution. In K/sub 2/CO/sub 3/ solution Pu(III) is stable to oxidation by water but is very sensitive to air oxidation. The redox properties of Cf(III) in Na/sub 2/CO/sub 3/ and K/sub 2/CO/sub 3/ solutions at pH values from 8 to 14 were investigated. The oxidation of terbium(III) in K/sub 2/CO/sub 3/-KOH solution was studied. Spectroscopic and electrochemical studies of cerium, samarium, europium, ytterbium, uranium, neptunium, plutonium, and americium in molten dimethyl sulfone (DMSO/sub 2/) at 400 K were performed. Differences in the DMSO/sub 2/ solution absorption spectra of trivalent Sm, Eu, and Yb and divalent Eu compared with those in aqueous solution were observed. Complexation effects on the spectra of Ce(III), Ce(IV), U(VI), Np(VI), Pu(VI), and Am(VI) are more noticeable in poorly coordinating DMSO/sub 2/ than they are in water. 123 references, 54 figures, 11 tables.

Kinetic study of carbon dioxide absorption with aqueous potassium carbonate promoted by arginine

Effect of iron(II) and manganese(II) on oxidation and co-precipitation of cobalt(II) in ammonia/ammonium carbonate solutions during aeration - An update and insight to cobalt losses in the Caron process for laterite ores

Chemical absorption and desorption of carbon dioxide from hot carbonate solutions

Absorption of carbon dioxide into carbonate solution (Na2CO3) with PAM (non-Newtonian fluid) has been performed in a countercurrent packed column (0.075m i.d. ×1.25 m height) packed with glass Raschig rings (1×1cm) to a depth of 1m. The influence of liquid flow rate, gas flow rate, liquid temperature, and polyacrylamind (PAM) concentration on the absorption rate, overall mass transfer coefficient and the reaction kinetics regime are studied at constant carbonate concentration and atmospheric pressure. The results show that the absorption rate and overall mass transfer coefficient increases with increasing liquid flow rate and temperature. The mass transfer coefficient decreases with increasing gas flow rate while the absorption rate of carbon dioxide is virtually independent of gas flow rate. This indicates that carbon dioxide absorption is liquid film controlled. Increasing PAM concentration results of reduction of absorption rate and overall mass transfer coefficient. The reaction kinetics between carbon dioxide and carbonate solution with PAM was obtained as a pseudo first order reaction (Hatta number, Ha >>1).

Absorption with chemical reaction: evaluation of rate promoters effect on CO2 absorption in hot potassium carbonate solutions

Absorption of carbon dioxide by carbonate solutions in a disc column

A study of both a wetted‐disc and a wetted‐wall column has indicated that the latter is the more suitable for obtaining mass‐transfer data in spite of the tendency to ripple formation.A study has been made of the absorption of hydrogen sulphide and carbon dioxide from a gas mixture with a CO2 H2S ratio of 30: 1 in solutions of sodium and potassium carbonates.Selectivity for the absorption of hydrogen sulphide has been found to decrease with increase in wetting rate and with increase in temperature. It increases with increase in gas rate and increases slightly with increase in concentration of sodium carbonate in the solution above about 1·1–1·3‐N. The concentration of hydrogen sulphide in the gas has no effect on the selectivity provided it is more than 1·3% but below this concentration, the selectivity decreases as the concentration decreases.The gas film conditions are more important than those in the liquid film for hydrogen sulphide concentrations in the gas of about 1%. The absorption of carbon dioxide is independent of gas film conditions and is controlled by the rate of a slow reaction in the liquid film.The practical absorption conditions required to secure maximum removal of hydrogen sulphide and minimum removal of carbon dioxide are listed.

Anthropogenic emissions of greenhouse gases into the atmosphere is inducing global warming, ocean acidification, polar ice melting, rise in sea level, droughts and hurricanes, thus threatening human health and the global economy. Therefore, there is a need to develop cost-effective technologies for CO2 capture. For instance, solution absorption is promising due to a large processing capacity, high flexibility and reliability, and rich experience in engineering applications. Nonetheless, actual commercial solutions, solvents and processes for CO2 capture suffer from slow reaction kinetics, low absorption capacity, high-energy consumption, susceptibility to corrosion, toxicity, low stability and high costs. Therefore, current research focuses on developing more economical, effective, green and sustainable technologies. Here we review 2015–2020 findings on CO2 capture using liquid absorption methods. Methods are based on various solutions, solvents and processes such as carbonate solution, ammonia solution, amine-based solution, ionic liquid, amino acid salt, phase changing absorbent, microcapsulated and membrane absorption, nanofluids and phenoxide salt solution. We discuss absorption performance, absorption mechanism, enhancement pathways and challenges. Amine- and NH3-based absorbents are widely used, yet they are limited by high regeneration energy, corrosiveness and degradation, reagent loss and secondary pollution caused by NH3 escape. Phase changing absorbents are getting more attention due to their lower cost and lower energy penalty. The incorporation of membrane and microencapsulation technologies to absorbing solvents could enhance CO2 absorption performance by reducing corrosion and increasing selectivity. Adding nanoparticles to solvents could improve CO2 absorption performance and reduce energy requirement. Besides, solvent blends and promoter-improved solvents performed better than single and non-promoted solvents because they combine the benefits of individual solvents and promoters.

Amines act as homogeneous catalysts for the carbon dioxide hydrolysis reaction, so that they are very effective rate promoters for carbon dioxide absorption in carbonate solutions. Experimental data show that the rate-promotion effect is a very conspicuous one, to the point where the catalysed reaction can be regarded as essentially instantaneous in comparison with diffusion phenomena. Possible mechanisms of this effect are discussed.The rate-enhancement effect is in addition to the effect that amines have on the capacity of carbonate solutions. The relationship between the rate and capacity effects is discussed.

The kinetics for the reactions of carbon dioxide with 2‐amine‐2‐methyl‐1‐propanol (AMP) and carbon dioxide (CO2) in both aqueous and nonaqueous solutions were measured using a microfluidic method at a temperature range of 298–318 K. The mixtures of AMP‐water and AMP‐ethylene glycol were applied for the working systems. Gas‐liquid bubbly microflows were formed through a microsieve device and used to determine the reaction characteristics by online observation of the volume change of microbubbles at the initial flow stage. In this condition, a mathematical model according to zwitterion mechanism has been developed to predict the reaction kinetics. The predicted kinetics of CO2 absorption in the AMP aqueous solution verified the reliability of the method by comparing with literatures’ results. Furthermore, the reaction rate parameters for the reaction of CO2 with AMP in both solutions were determined. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4358–4366, 2015

PUBLICATION RIGHTS RESERVED This paper is to be presented at the 36th Annual Fall Meeting of the Society of Petroleum Engineers of AIME in Dallas October 8–11, 1961, and is considered the property of the Society of Petroleum Engineers. Permission to publish is hereby restricted to an abstract of not more than 300 words, with no illustrations, unless the paper is specifically released to the press by the Editor of JOURNAL OF PETROLEUM TECHNOLOGY or the Executive Secretary. Such abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in JOURNAL OF PETROLEUM TECHNOLOGY or SOCIETY OF PETROLEUM ENGINEERS JOURNAL is granted on request, providing proper credit is given that publication and the original presentation of the paper. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and considered for publication in one of the two SPE magazines with the paper. Abstract The activity of hot potassium carbonate solutions has been found to be a function of contaminants, having a deleterious effect, and catalysts, which activate the solution. A small amount of "Catacarb" catalyst cancels the effect of contamination and larger amounts give a much more active solution than pure potassium carbonate. In commercial plant tests in existing carbonate plants, the Catacarb Process resulted in increased capacity, reduced steam usage, and less residual CO2. In new plant construction, less equipment and utility requirements of the Catacarb process permit savings in capital investment and operating costs. Introduction The hot potassium carbonate process, developed by the Bureau of Mines, has been applied extensively in recent years to CO2 removal in the purification of hydrogen and natural gas. Most of tee hot carbonate units are in ammonia plants, but use of the process for treating natural gas, including sour gas, is increasing. The equipment involves the familiar absorber and regenerator. The usual process cycles have been previously described. As compared with amine scrubbing the main advantages of hot carbonate are the elimination of heat exchange equipment and the lower steam and cooling water requirements. The disadvantage of a hot carbonate system is the inability to secure a satisfactory degree of clean up in the scrubbed gas except with very large towers, a more complicated process cycle or even a second absorber operated at high pressure. This paper deals with "Catacarb", the catalytic process for CO2 removal. In the Catacarb Process a catalyst is used to activate a carbonate solution in the absorption and desorption of carbon dioxide, thus overcoming the above disadvantage of carbonate scrubbing. THEORY AND DEFINITIONS The absorption of an acid gas in any alkaline solution is classed as chemi-sorption, that is, absorption accompanied by chemical reaction. The rate of chemical reaction determines the size of the towers required by the process. Unlike caustic, a carbonate solution has very few hydroxyl ions to react directly with CO2. Therefore, it is believed that CO2 must first become hydrated, or react with water to form carbonic acid, which in turn reacts with a carbonate ion to form two bicarbonate ions. CO2 + H2O = H2CO3 (1) H2CO3 + CO3 = 2 HCO-3 (2) Confirmation of the reaction with water is the finding, both in commercial plant operations and laboratory experiments, that dilute solutions which have a higher concentration of free water, are more active than concentrated carbonate solutions. The term "free water" takes into account the well known fact that potassium ions are highly hydrated, although the exact ratio of combined water to potassium is uncertain and probably varies with concentration. As in any practical chemical process, we are concerned with equilibrium and with kinetics. Equilibrium for the potassium carbonate-bicarbonate-CO2-water system has been reported. We now focus our attention on heretofore neglected kinetics or solution activity, which is the relative rate of approach to equilibrium.

Kinetics of carbon dioxide absorption in solutions of methyldiethanolamine