Solubilltles of N20, C2H4, and C2H2 and dlffuslvlty of N20 In various aqueous solutions of amines (MEA, DEA, TEA, MIPA, DIPA, and EDA) were measured at 25 OC and I atm of pressure. For these present systems, solubllity and dlffuslvlty data could not be correlated by suitable correlations. The best ways to estimate solubility and dlffusivily of C02 in aqueous solutions of amines may be log (a/a,)co, = log (~/Q,)N,o and (D/D,)co, = ( D/Dw)N,O, respectively, using the Corresponding data for N20.Aqueous solutions of amines are widely used in gas-liquid contact operations for the removal of acidic gases. The solubility and the diffusivity of the acidic gas in these solutions are fundamental physicochemical properties necessitated in the design of gas-liquid contactors. These properties, however, cannot be conventionally measured because of the presence of chemical reaction and, hence, must be estimated by the corresponding data for nonreacting gases. For the time being, no correlation has been developed on the solubility and the diffusivity of gases in amine solutions. I t is rather essential to systematically accumulate data on solubility and diffusivity.The previous paper (2) reported that the solubility of CO, in aqueous amine (monoethanolamine, diethanolamine, triethanolamine, or ethylenediamine) solution may be reliably estimated from the corresponding values of N20 by log (~/ c u , )~, = log ( O I / C U~)~,~. Such a correlation is considered to be applicable to estimate the diffusivity of CO,.In view of these facts, the solubility of N20, C2H4, or C2H, in aqueous solutions of amines was measured by a volumetric method and the diffusivity of N20 by means of a laminar liquid-jet apparatus. Experimental SectionAqueous solutions of amines (monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), mono(isopropy1 alcoho1)amine (MIPA), di(isopropy1 alcoho1)amine (DIPA), and ethylenediamine (EDA)) were prepared from distilled water and reagent grade amines of guranteed purity. The solution was degassed by refluxing it for a sufficient length of time before being used in the solubility experiment. The composition of the solution was determined by volumetric titration.For gases, N,O, C, H, , and C, H2 were supplied from commercial cylinders with minimum purities 99.8, 99.6, and 99.9 %, respectively, and confirmed by analyzing by gas chromatography.The gas solubilities were measured by a volumetric technique. Systems studied were N20-MIPA and -DIPA, C2H4-MIPA and -DIPA, and C2H2-MEA, -DEA, -TEA, -MIPA, -DIPA, and -EDA. The apparatus and operating method were essentially the same as those employed in our previous study (2). Briefiy, the principle of the apparatus used is that a measured volume of solute gas is brought in contact with a measured quantity of gas-free liquid, equilibrium is established by agitation, and the remaining volume of gas (undissolved) is measured. The change in the gas volume gives the amount dissolved in the liquid. Further details of

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The kinetics of the reaction of carbon dioxide with mono-and diethanolamine in such nonaqueous solvents as methanol, ethanol, and %propano1 and in water were studied using a stirred tank absorber with a plane gas-liquid interface at 303 K. The reaction was found to be of first order with respect to carbon dioxide for every solvent. The order of reaction with respect to ethanolamine was found to be unity only for an aqueous solution of monoethanolamine and for the other solutions, ranged from 1.4 to 2, depending on the solvent species. The reaction order was increased in the order of water, methanol, ethanol, and Zpropanol. The variation of the reaction order with the solvent species could be explained in terms of a reaction scheme via a zwitterion. Almost linear dependence of the logarithm of the reaction rate constant on the solubility parameter of the solvent was derived. SCOPEGas purification by chemical absorption is of great industrial importance. Alkanolamine solutions are frequently used for the removal of acid gases (Wall, 1975). Although many studies have been done toward the mechanisms and kinetics of the reaction between carbon dioxide and various amines (Blauwhoff et al., 1983), the reaction media are limited to aqueous solutions. In practice, nonaqueous systems comprising methanol solution of alkanolamine have been commercially employed for absorption of carbon dioxide, hydrogen sulfide, carbonyl sulfide, etc., because of their high solubility and capacity, their low corrosiveness, and their low energy consumption during regeneration of used liquor (Bratzler and Doerges, 1974). Nonaqueous systems, which are essentially used in a closed loop, should be considered more for acid gas removal.The reaction between carbon dioxide and monoethanolamine in aqueous solutions has already been found to be of first order with respect to both species, while for the carbon dioxidediethanolamine system in aqueous solutions, the order of reaction with respect to diethanolamine has not been determined to be of first or second order. Danckwerts (1979) and Laddha and Danckwerts (1981) proposed a new reaction mechanism comprising formation of a zwitterion followed by the removal of proton by a base (diethanolamine) to explain such contradiction of the reaction order. It would be expected that the order of reaction with respect to ethanolamine ranges from first to second order in nonaqueous solvents. The variation of the reaction order with a physicochemical property of the solvent and the resultant reaction rate constants seem to be of practical interest.In the present work, the kinetics of the reaction of carbon dioxide with mono-and diethanolamine in such nonaqueous solvents as methanol, ethanol, and Z-propanol were investigated using a stirred tank absorber with a plane gas-liquid interface. The absorption rate data under the fast reaction regime were analyzed in terms of the reaction mechanism proposed by Danckwerts (1979). An attempt was made to correlate the derived reaction rate constants in different nonaqueous s...

The absorption of dilute NO into aqueous mixed solutions of Fe"-edta and Na, SO, was carried out by use of a semibatch bubble column at 308 K and 0.10 MPa total pressure. Chemical reactions accompanyin this chemical absor tion were investigated through quantitative determination of gasand liquid-phase species. Fe' was oxidized

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The absorption rates of (1) NO in aqueous solutions of Fe"-EDTA, (2) NO in aqueous solutions or slurries of MgS03 with added Fe'-EDTA, and (3) NO in the presence of S02 in aqueous slurries of MgS03 with added Fen-EDTA were measured using a stirred vessel with a plane gas-liquid interface at 25 °C and 1 atm. The forward rate constant of the complexing reaction, NO + Fe"-EDTA <=± Fen(EDTA)(NO), at various pH's was derived from the enhancement factor for absorption of NO in aqueous solutions of Fen-EDTA. The reduction of NO coordinated to Fen-EDTA with S032~i s found to be very slow as compared with the above complexing reaction. Coexisting S02 can promote the absorption rate of NO by aqueous slurries of MgS03 with Fen-EDTA. It is believed that coexisting S02 plays a part of releasing S032" from the complex Fe"(EDTA)(S032~)(N0) and that the presence of S02 in the gas phase effectively improves the pH of the solution at the interface toward favorable values for the reaction of NO with Fen-EDTA.

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