Diffusivity Of N2O Research Articles

Novel models for correlation of Solubility constant and diffusivity of N2O in aqueous 1-dimethylamino-2-propanol

The solubility constant of N2O in aqueous 1-dimethylamino-2-propanol (1DMA2P) solution in the concentration range of 0–3.0 mol/L was measured over the temperature range of 298–333 K, and the data used to fit existing models: Redlich-Kister, semi-empirical, and polynomial. A new model has also been developed to predict the solubility constant. Also, N2O diffusivity in aqueous 1DMA2P solution was measured over the concentration range of 0.5–2.0 mol/L and temperature range of 298–313 K. All models used fitted the solubility constant of N2O solubility in 1DMA2P solution data with absolute average deviations (ADDs) for the Redlich-Kister, semi-empirical, polynomial models and a new model of 12.2%, 8.1%, 0.2% and 2.2%, respectively. The data for N2O diffusivity in aqueous 1DMA2P solution were represented by the modified Stokes-Einstein and semi-empirical models (AADs of 2.3% and 13.6%, respectively). A new mechanism-based model was equally developed to better correlate experimental results and understand the process of diffusivity.

Characterization and kinetics of CO2 absorption in potassium carbonate solution promoted by 2-methylpiperazine

In this work, the absorption performance of potassium carbonate (K2CO3) promoted by 2-methylpiperazine (2-MPZ) was examined for CO2 capture by using a stirred cell reactor at temperatures between 303 and 323 K. The density, viscosity and loading capacity of K2CO3 + 2MPZ solutions were experimentally measured. Moreover, Hatta number, enhancement factor, Henry’s constant and diffusivity of CO2 and N2O in K2CO3 + 2MPZ solution was also determined to check the fast pseudo-first-order reaction regime. Furthermore, kinetics of the reaction of CO2 with K2CO3 + 2MPZ solution was studied and described in detail using zwitterion mechanism. The CO2 absorption rate along with the reaction rate constant (k2) for the CO2 + K2CO3 + 2MPZ system were obtained and the results were compared with other systems. It was concluded that the CO2 absorption rate is first order with respect to both 2MPZ and CO2, the activation energy and k2 were found to be 62.45 kJ/mol and8.92×1014exp(−7511.8T), respectively. The results revealed that the K2CO3 + 2MPZ solution could be an attractive solvent for post-combustion CO2 capture due to its excellent characteristics such as the higher CO2 absorption rate and capacity compared to MEA.

Measurement and Correlation of the Physicochemical Properties of Novel Aqueous Bis(3-aminopropyl)amine and Its Blend with N-Methyldiethanolamine for CO2 Capture

Physicochemical properties such as density and viscosity of aqueous novel bis(3-aminopropyl)amine (APA) and an aqueous novel blend of N-methyldiethanolamine (MDEA) and APA solutions as well as solubility and diffusivity of N2O into these binary and ternary solutions were measured from temperature T = 298 to 323 K at atmospheric pressure. In this study, experiments cover the molality range for APA = 0–1.291 mol·kg–1 and MDEA = 2.915–4.416 mol·kg–1. The diffusivity and solubility experiments were conducted with a wetted wall column absorber and Corning glass equilibrium cell, respectively. The experimental binary and ternary density data as well as binary viscosity data were correlated by Redlich–Kister equation whereas ternary viscosity data were correlated by the Grunberg and Nissan model. On the other hand, solubility and diffusivity were correlated with different models. All of the correlations based on the different model performed are capable of adequately predicting experimental physicochemical data.

Influence of biofilm thickness on nitrous oxide (N2O) emissions from denitrifying fluidized bed bioreactors (DFBBRs)

Nitrous oxide (N2O) is a significant anthropogenic greenhouse gas emitted from biological nutrient removal (BNR) processes. This study tries to get a deeper insight into N2O emissions from denitrifying fluidized bed bioreactors (DFBBRs) and its relationship to the biofilm thickness, diffusivity, and reaction rates. The DFBBR was operated at two different organic and nitrogen loading rates of 5.9–7kgCOD/(m3d) and 1.2–2kgN/(m3d), respectively. Results showed that the N2O conversion rate from the DFBBR at a biofilm thickness of 680μm was 0.53% of the total influent nitrogen loading while at the limited COD and a biofilm thickness of 230μm, the N2O conversion rate increased by 196–1.57% of the influent nitrogen loading concomitant with a sevenfold increase in liquid nitrite concentration. Comparing the N2O emissions at different biofilm thickness showed that the N2O emission decreased exponentially with biofilm thickness due to the retention of slow growth denitrifiers and the limited diffusivity of N2O.

Determining the Diffusivity of Nitrous Oxide in Soil using In Situ Tracers

Diffusion is a key process for understanding the movement of nitrous oxide (N2O), carbon dioxide (CO2), methane (CH4), oxygen (O2), and other biogeochemically important gases in soil. Soil gas diffusivity is highly variable, which makes the application of generic predictive models based on soil macrofeatures uncertain. In situ methods provide greater certainty but intensive sampling usually makes such determinations expensive. We compared single and inter-port diffusivity determinations using a sparse sampling alternative. We used 28 in situ profile probes with ports at five depths for pulse sulfur hexafluoride (SF6) and N2O tracer injections at single ports followed by two or three measurements in five adjacent ports at an agricultural site in southwest Michigan, USA. We repeated this procedure for three dates in the summer and two in the fall. In general, the sparse method provided accurate measurements of soil diffusivity. Estimated diffusivities of SF6 and N2O had poorer agreement in the summer (r2 = 0.49) than in the fall (r2 = 0.96), likely due to less uniform soil moisture in summer. The low N2O to SF6 diffusivity ratio (0.67 compared with 1.82 in free air) suggests that water solubility of N2O plays a significant role in retarding its movement in the soil. Movement of the relatively insoluble SF6 is not obscured by dissolution in water making SF6 a superior tracer compared with N2O. Median diffusivities in ports where the gas was injected were only moderately correlated (r2 = 0.45) with diffusivities at the same depth measured by the inter-port method, likely due to an increase in the variability of diffusivity with distance from the injection port. Results show it is possible to estimate N2O diffusivity with sparse measurements; accuracy can likely be further improved with knowledge of soil moisture and texture in the immediate vicinity of the injection and sampling ports, as uncertainty in water modeling is reduced.

Isotopomer analysis of production, consumption and soil-to-atmosphere emission processes of N2O at the beginning of paddy field irrigation

In irrigated rice paddies, episodic release of nitrous oxide (N2O) from the soil to the atmosphere has been observed during the first flood irrigation, but the biogeochemical mechanisms underlying these emissions remain unclear. To elucidate both microbial pathways of N2O production, consumption and emission processes of N2O from soil surfaces, we analyzed isotopomer ratios (bulk nitrogen and oxygen isotope ratios, δ15Nbulk and δ18O, and intramolecular 15N site preference, SP) of surface-emitted N2O and N2O in soil gas from paddy fields in Japan at the beginning of irrigation. Results indicate that surface-emitted N2O is produced at shallow depths above the rising groundwater table, and that it is emitted by diffusive transport through air-filled soil pores. Immediately after soil surfaces are submerged, N2O accumulates in the soil because of the low diffusivity and high solubility of N2O in water. Isotopomer analysis revealed that high N2O emissions during the flooding process resulted mainly from N2O production by bacterial denitrification (nitrate reduction). Moreover, as soil submergence progressed, declining soil NO3− concentration promoted the use of N2O as an electron acceptor. Thereby, most of the N2O was reduced to N2. N2O emissions were increased by nitrogen fertilizer application before irrigation. The applied nitrogen fertilizer might enhance N2O production.

Measurements and Correlations of Diffusivities of Nitrous Oxide and Carbon Dioxide in Monoethanolamine + Water by Laminar Liquid Jet

The molecular diffusivities of nitrous oxide (N2O) with aqueous monoethanolamine (MEA) solutions up to 12 M were studied over a temperature range from 298.15 to 333.15 K under atmospheric pressure using a laminar liquid jet absorber. The diffusivities of CO2 in aqueous MEA solutions were calculated by the “N2O analogy” method. A simple and effective thermal control technique was used to control the temperatures of gas and liquid in the laminar liquid jet absorber. The rates of absorption were determined by measuring the flow of gas needed to replace the gas absorbed. The results showed that the diffusivities of both N2O and CO2 into aqueous MEA solution decrease with the increase of the concentration of MEA, and increase with an increase of the temperature of the solution. The relationship between the diffusivity and the viscosity of the solution roughly agrees with the modified Stokes–Einstein equation, but an exponent mathematical model was employed to simulate the diffusivity data and shows a better ag...

Density, viscosity, physical solubility and diffusivity of CO2 in aqueous MDEA + [bmim][BF4] solutions from 303 to 333 K

In this study, the physical solubility and diffusivity of N2O in aqueous MDEA+[bmim][BF4] solutions were measured over a range of temperatures of 303–333K and [bmim][BF4] concentrations of 0–2.0molL−1 at atmospheric pressure. The total MDEA concentration in the solutions was kept constant at 4molL−1. The “N2O analogy” was then used to estimate the physical solubility and diffusivity of CO2 in aqueous MDEA+[bmim][BF4] solutions. The density and viscosity of aqueous MDEA+[bmim][BF4] solutions were also measured over the same range of temperatures and concentrations of the ionic liquid. These data were used to develop correlations for the prediction of CO2 diffusivity in these systems.

The physical solubilities and diffusivities of N2O and CO2 in aqueous ammonia solutions on the additions of AMP, glycerol and ethylene glycol

Carbon dioxide (CO2) is a major greenhouse gas, the emissions of which should be reduced. There are various technologies for the effective separation of CO2. Of these, chemical absorption methods are generally accepted as the most effective. The monoethanolamine (MEA) process is an effective way to remove CO2, but is an expensive option for the separation of CO2 from massive gas-discharging plants. Therefore, ammonia solution, which is less expensive and more effective than MEA, was used for the removal of CO2. In this study, the physical solubility of N2O in (ammonia+water), (ammonia+2-amino-2-methyl-1-propanol+water), (ammonia+glycerol+water) and (ammonia+ ethylene glycol+water) was measured at 293, 303, 313, 323 K. Additive concentrations of 1, 3, and 5 wt% AMP, glycerol and ethylene glycol were added for each 9 wt% ammonia solution. A solubility apparatus was used to investigate the solubility of N2O in ammonia solutions. The diffusivity was measured with a wetted wall column absorber. The “N2O analogy” is used to estimate the solubility and diffusivity of CO2 in the aqueous ammonia solutions. OriginPro 7.5 was used to correlate the solubility and diffusivity of N2O in ammonia solutions. The parameters of the correlation were determined from the measured solubility and diffusivity.

Physicochemical Properties of Aqueous Solutions of 2-(1-Piperazinyl)-ethylamine

The density and viscosity of aqueous solutions of 2-(1-piperazinyl)-ethylamine (PZEA) as well as the Henry’s law constants and diffusivity of N2O in these solutions were measured at temperatures in the range (298 to 323) K at atmospheric pressure of 0.1 MPa. The mass fractions of PZEA used were (0.0108 to 0.158). The “N2O analogy” was used to estimate the Henry’s law constants and diffusivity of CO2 in aqueous PZEA solutions. The experimental density, viscosity, Henry’s law constants, and diffusivity data are correlated as a function of temperature and concentration of amine.

Physicochemical Properties of Aqueous Solutions of 2-Amino-2-hydroxymethyl-1,3-propanediol

The density and viscosity of aqueous solutions of 2-amino-2-hydroxymethyl-1,3-propanediol (AHPD) as well as the Henry’s law constants and diffusivity of N2O in these solutions were measured over the temperature range from (298 to 323) K at atmospheric pressure. The mass fractions of AHPD used were (2.17 to 21.7) %. The “N2O analogy” was used to estimate the Henry’s law constants and diffusivity of CO2 in aqueous AHPD solutions. The experimental density, viscosity, Henry’s law constants, and diffusivity data are correlated as a function of temperature and concentration of amine and compared with the available data in the literature.

Physical Solubility and Diffusivity of N2O and CO2 in Aqueous Solutions of Piperazine and (N-Methyldiethanolamine + Piperazine)

In this work, the physical solubility and diffusivity of N2O in aqueous solutions of piperazine (PZ) and an aqueous blend of N-methyldiethanolamine (MDEA) and piperazine have been measured over a range of temperatures and at atmospheric pressure. For the binary mixtures, the mass percents of PZ used are (1.74 to 12) %. For the ternary mixtures, the total amine strength in the solution has been kept at 30 mass %. The “N2O analogy” is then used to estimate the physical solubility and diffusivity of CO2 in aqueous PZ and PZ-blended aqueous MDEA solutions. The experimental physical solubility and diffusivity data have been correlated as a function of temperature and concentration of amine and compared with the available data in the literature.

Kinetics of CO2 Absorption in Aqueous Sodium Glycinate Solutions

The physical solubility and diffusivity of N2O and CO2 in aqueous sodium glycinate (SG) solutions of various concentrations (1.0−3.5 kmol/m3) and temperatures (303.15−323.15 K) were reported. The kinetics of the reaction between CO2 and SG has been studied using absorption data measured by a wetted-wall column apparatus at various temperatures and concentrations. The second-order rate constant of CO2 with SG was determined to be k2(m3 kmol-1 s-1) = 1.95 × 1013 exp(−7670/T), where T is the absolute temperature (given in Kelvin). The activation energy for the reaction of CO2 with SG was calculated to be 63.8 kJ/mol.

Physical Solubility and Diffusivity of N2O and CO2 in Aqueous Sodium Glycinate Solutions

Physical solubility and diffusivity of N2O and CO2 in pure water and of N2O in aqueous sodium glycinate solutions of mass fraction (0.1 to 0.5) were measured at T = (303.15 to 323.15) K. Since it was not possible to measure these properties for CO2 due to the chemical reaction between CO2 and the amine group of sodium glycinate, these were estimated using the well-known N2O analogy. While the physical solubility increases with a decrease in temperature and with a decrease in mass fraction, diffusivity decreases with a decrease in temperature as well as an increase in mass fraction except for concentrated solution (mass fraction 0.4 and 0.5) where it increases with a decrease in temperature.

Physical Solubility and Diffusivity of N2O and CO2 into Aqueous Solutions of (2-Amino-2-methyl-1-propanol + Diethanolamine) and (N-Methyldiethanolamine + Diethanolamine)

In this work the physical solubility of N2O in (diethanolamine + water), (2-amino-2-methyl-1-propanol + water), (N-methyldiethanolamine + water), (N-methyldiethanolamine + diethanolamine + water), and (2-amino-2-methyl-1-propanol + diethanolamine + water) as well as the diffusivity of N2O in (N-methyldiethanolamine + diethanolamine + water) and (2-amino-2-methyl-1-propanol + diethanolamine + water) have been measured at (293, 298, 303, 308, and 313) K. For the binary mixtures the amine concentration ranges studied are (2.0, 2.5, and 3.0) kmol·m-3. For the ternary mixtures the total amine strength in the solution was kept at 30 mass %, in view of the recent interest in using concentrated amine solutions in gas treating. A solubility apparatus was used to measure the solubility of N2O in amine solutions. The diffusivity was measured with a wetted wall column absorber. The uncertainty of the measurement is estimated to be ±2%. A semiempirical model of the excess Henry's constant proposed by Wang et al. (Chem...

Changes in Composition of Nitrogen‐15‐Labeled Gases during Storage in Septum‐Capped Vials

We tested the reliability of 12‐mL Exetainers (Labco Ltd., High Wycombe, UK) fitted with bromobutyl rubber septa for the storage of a gas sample containing15N‐labeled N2O and N2The gas mixture was analyzed monthly over a 1‐yr storage period by continuous‐flow isotope‐ratio mass spectrometry (IRMS). After a year the N2O concentration had decreased by 30% but the change in15N enrichment of N2O was not detectable. Accurate determination of the N2O concentration was possible up to 1 yr if a calibration gas was stored and analyzed along with the test mixture. This technique has wide applicability because diffusive loss of N2O as a fraction of starting concentration was predicted by Fick's Law to be almost independent of concentration above 3 μL L−1The rate of decrease in the enrichment of N2as measured by the ratio differences for 29/28 and 30/28 was slow. Decreases were not significantly different from time zero values after storage for 8 wk. After 1 yr of storage the losses of29N2and30N2significantly lowered the calculated value for the fraction of the N2from the labeled pool (d) by about 2% of the initial value, but had no effect on the calculated value for the enrichment of the labeled pool (15XN). The diffusivity of N2O, calculated from loss rate and concentration gradient between Exetainer and atmosphere using Fick's Law, was 40 times higher than that of29N2or30N2Nitrous oxide may have been lost from the Exetainer because of adsorption by the septum as well as diffusion through the septum.

Kinetics of Absorption of Carbon Dioxide into Aqueous Solutions of Monoethanolamine + Triethanolamine

Kinetics of the absorption of CO2 into monoethanolamine (MEA) + triethanolamine (TEA) + water were investigated at 30, 35, and 40 °C using a laboratory wetted wall column. Ten systems of which 0.5 and 1.0 kmol m-3 TEA mixed with various MEA concentrations (0.1, 0.2, 0.3, 0.4, and 0.5 kmol m-3) were studied. Densities and viscosities of 10 blended-amine systems and solubilities and diffusivities of N2O in the solutions were measured. The N2O analogy was applied to estimate the solubilities and diffusivities of CO2 in amine systems. On the basis of the fast pseudo-first-order rate for CO2 absorption, the overall pseudo-first-order reaction rate constants were determined from kinetic measurements. The addition of small amounts of MEA to TEA results in a significant enhancement of CO2 absorption rates. A hybrid reaction rate model, a zwitterion mechanism for MEA and a first-order reaction for TEA, was used to model the kinetic data. The model is satisfactory to represent CO2 absorption rates in TEA + MEA aqueous systems.

Density, Viscosity, Solubility, and Diffusivity of N2O in Aqueous Amino Acid Salt Solutions

Solubility and diffusivity of N2O in aqueous solutions of potassium taurate are reported over a wide range of concentration and temperature. Also, the solubility of N2O in aqueous potassium glycinate solution is reported at 295 K. The ion specific constants, based on the model of Schumpe,5,6 are reported for taurate and glycinate anions. A modified Stokes−Einstein relationship is proposed for the diffusivity of N2O in aqueous potassium taurate solution in the temperature range 293−308 K.

Physical Solubility and Diffusivity of CO2 in Aqueous Diethanolamine Solutions

The physical solubility and diffusivity of CO2 in aqueous DEA solutions were measured directly in this work via the “protonation method”. The concentration of DEA in the aqueous solutions was 10, 20, and 30 mass %. The measurements were done in the temperature range (25−60) °C at atmospheric pressure. Correlations for the solubility and diffusivity as a function of temperature were developed. The results were compared with the values calculated on the basis of the N2O analogy. New correlations for the solubilities and diffusivities of CO2 and N2O in water were also developed.

Diffusivity of Nitrous Oxide in Aqueous Alkanolamine Solutions

The diffusivities of nitrous oxide (N2O) in aqueous alkanolamine solutions have been measured at (30, 35, and 40) °C. The systems studied are aqueous monoethanolamine, diethanolamine, diisopropanolamine, triethanolamine, and 2-amino-2-methyl-1-propanol solutions. The concentration of amine for monoethanolamine ranges from (1 to 5) kmol·m-3 and for other amines from (0.5 to 2.5) kmol·m-3. The viscosities of diisopropanolamine and triethanolamine and the densities and viscosities of aqueous diisopropanolamine and triethanolamine solutions were also measured at (30, 35, and 40) °C. A simple correlation was used to correlate the diffusivity of N2O in amine solutions. The parameters of the correlation were determined from the measured diffusivity data and the available data in the open literature. The correlation has been shown to represent reasonably the diffusivity of N2O in six aqueous amine solutions: MEA, DEA, DIPA, MDEA, TEA, and AMP. The correlations are, in general, satisfactory for estimating the dif...