Density and Surface Tension Measurements of Partially Carbonated

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Density and Surface Tension Measurements of Partially Carbonated Aqueous Monoethanolamine Solutions Sanoja A. Jayarathna,† Chameera K. Jayarathna,‡ Deshaka A. Kottage,† Sithara Dayarathna,† Dag A. Eimer,†,‡ and Morten C. Melaaen*,†,‡ †

Telemark University College, Porsgrunn, Norway Tel-Tek, Porsgrunn, Norway

‡

ABSTRACT: Densities and surface tensions of carbon dioxide (CO2) loaded (partially carbonated), aqueous monoethanolamine (MEA) solutions with amine mass ratio of 0.8 are measured within a temperature range from (313.15 to 343.15) K. The series of aqueous MEA solutions cover a range of CO2 loading from (0 to 0.5). All of the density data points are compared with the predictions of the model from Weiland et al., and data regression is performed to fit the parameters of the model. Predictions from the fitted model are compared with the data reported in this work. The model of Connors and Wright is selected to expand for the H2O−MEA−CO2 tertiary system. Surface tension data from this work are used to fit the parameters of the Connors and Wright model, and the model predictions are compared with the same set of data.

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INTRODUCTION Chemical absorption is an efficient method for CO2 capture, especially from the gas streams with low CO2 concentrations.1−3 Aqueous alkanolamine solutions are widely used in the absorption−desorption process for the removal of CO2 from the gas streams. Industrially important alkanolamines for the absorption of CO2 are monoethanolamine (MEA), diethanolamine (DEA), and methyldiethanolamine (MDEA). High-concentration amine solutions are interesting since amine circulation can be reduced and energy can be saved. Physical properties like density, surface tension, viscosity, and solubility of CO2 in such solutions are with great importance for further analysis of the use for CO2 capture as well as for the equipment design and related analysis via modeling and simulation. Density and surface tension measurements of single alkanolamine solutions, mixed amine solutions, and activated amine solutions have been presented in literature.4−13 Published measurements of partially carbonated high concentration MEA solutions are scarce though. This work presents a set of measurements covering high concentration (mass ratio of MEA, r = Mamine/Mamine+water = 0.8) aqueous MEA solutions, with the range of CO2 loading, n(CO2)/n(MEA), α = (0 to 0.5), in the range of temperature, T = (313.15 to 343.15) K. A widely used correlation exists for the prediction of the densities of the aqueous amine solutions either single or mixed and CO2 loaded or unloaded.5,11 The predictions from the correlation are not able to be in good agreement with the measurements made during this work. An estimation of the parameters of the correlation is performed as a part of this work to obtain a good representation of the density of the high concentration partially carbonated MEA solutions. © 2013 American Chemical Society

Surface tension measurements of partially carbonated MEA solutions expand the research frontier further as these measurements cover a composition and temperature range that has not been reported earlier. Surface tension data from this work are given as a custom fit equation as well as a fit to a literature model.14,15

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EXPERIMENTAL SECTION This section provides an insight to the procedures of sample preparation, sample analysis, and measurement performance. A description of MEA and CO2 are given in Table 1. Table 1. Chemical Sample Descriptions

a

chemical abbreviation

source

initial mole

analysis method

CO2 MEA

AGA Merck

0.9999 0.995

GCa

Gas−liquid chromatography.

Preparation of the Aqueous Solutions. Aqueous solutions of MEA were prepared using degassed, deionized water and MEA. Water deionization and degassing were done using a Milli-Q integral water purification system and a rotary evaporator, respectively. Amines are used as received. Water and amines are measured using an analytical balance with an accuracy of ± 1·10−7 kg and mixed with the appropriate proportion to achieve the required mass ratio, r = 0.8. The loaded amine samples were prepared using an equilibrium cell. The equilibrium cell was built similar to the Received: August 23, 2012 Accepted: December 20, 2012 Published: January 4, 2013 343

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apparatus explained by Ma’mum et al.16 by replacing the temperature control system with a more sophisticated one with an accuracy of ± 0.1 K. The liquid samples taken for vapor− liquid equilibrium experiments were used for the physical property measurements at the corresponding temperatures. Analysis of the Aqueous Solutions. All of the CO2 loaded aqueous amine solutions were analyzed using a titration method to check the loading value and the amine mass ratio. The mass ratio analysis was done via titration of the preprepared samples with a 1 mol·dm−3 HCl solution to find the equilibrium point. The samples used for titration were prepared by mixing a sample of 2 g from each prepared amine solution with deionized water until each sample became 100 cm3 in total. The amount of HCl used in the titration was used to calculate the amount of amine presented in each sample and subsequently the mass ratio of the corresponding aqueous amine solution. The sample preparation for the loading analysis was performed by mixing about (0.5 to 1.0) g of the loaded amine solution with 50 cm3 each from 0.3 mol·dm−3 BaCl2 and 0.1 mol·dm−3 NaOH. Those samples were boiled for 5 min to let the CO2 in the samples to react with BaCl2 and precipitate as BaCO3, then cooled down in a water bath and filtered to collect the precipitate. Each collected precipitate was added into 100 cm3 deionized water and then titrated with 0.1 mol·dm−3 HCl solution until the mixture reached the equilibrium point. The mixture was then heated to remove all of the dissolved CO2 and back-titrated with 0.1 mol·dm−3 NaOH solution to calculate the amount of excess HCl. Finally, the moles of HCl reacted with BaCO3 precipitate was used to find the amount of CO2 in the corresponding partially carbonated aqueous amine sample and subsequently the CO2 loading value of the solution. Density Measurements. Densities of the partially carbonated aqueous MEA solutions were measured using an Anton Paar densimeter; model DMA 4500. The DMA 4500 was calibrated using degassed water and air occasionally, but a density check was performed more frequently to check the validity of the previous calibration. The operation of DMA 4500 is limited to atmospheric pressure and 363.15 K of temperature. The measuring procedure of the densimeter is based on an oscillatory U-tube method, and the accuracy of the measurements is very much dependent on the calibration of the equipment. A separate sample has been used to take each measurement at each temperature and composition. Surface Tension Measurements. Surface tension values of the partially carbonated aqueous MEA solutions were measured using a Ramé-Hart advanced goniometer; model 500 with DROPimage Advanced v2.4 software. The goniometer was calibrated using the calibration tool provided with the instrument occasionally, but surface tension measurements of water were performed more frequently to check the previous calibration. The measured surface tension values for water were compared with literature data to make sure that the error is within ± 0.0004 N·m−1, which is about ± (0.5 to 0.6) %. This error is considered as the instrument accuracy for uncertainty calculations of the surface tension measurements reported in this work. The measuring procedure of the goniometer is based on a calculation of the droplet/bubble geometry size, which is obtained by digitizing the image from the camera, and the accuracy of the measurements is very much dependent on the calibration of the equipment. The traditional pendant drop

method was not adopted due to possible concentration changes and issues related to temperature monitoring and control as explained by Han et al.11 The same measurement procedure as explained by Han et al.11 is adopted and the CO2 loading of the used samples were analyzed via titration to observe losses of CO2 from the samples. Each surface tension value reported is an average of the measurements for at least 10 different bubbles with about 10 measurements per bubble, with a maximum deviation less than ± 0.002 N·m−1 from the average value. A separate sample has been used to take each measurement at each temperature and composition. A set of surface tension measurements are taken for pure H2O and MEA, and those are compared with the data from literature as an attempt of demonstrating the measurement accuracy. Data from this work show a good agreement with the literature data, and the comparison is given in Table 2. Table 2. Surface Tension, σ, of Pure H2O and MEAa,b 293.15 K this work Han et al.11 Vázquez et al.13

0.07256

this work Han et al.11 Vázquez et al.13

0.04848

303.15 K

313.15 K

σwc/N·m−1 0.07090 0.06981 0.07130 0.06960 0.07121 0.06952 σac/N·m−1 0.04764 0.04688 0.04810 0.04670 0.04814 0.04643

323.15 K 0.06772 0.06800 0.06792

0.04560 0.04481

Standard uncertainties u are u(T) = ± 0.5 K; instrument accuracy = ± 0.0004 N·m−1. bThe combined expanded uncertainties Uc are Uc(σw) = ± 0.0004 N·m−1 and Uc(σa) = ± 0.0004 N·m−1 (level of confidence = 0.95, where k = 2). cσw = surface tension of H2O; σa = surface tension of MEA. a

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RESULTS AND DISCUSSION Results obtained from this work are two-fold: 1. Density measurements of partially carbonated aqueous MEA solutions from T = (313.15 to 343.15) K for r = 0.8 and α in the range from (0.0 to 0.51). 2. Surface tension measurements of partially carbonated aqueous MEA solutions from T = (313.15 to 343.15) K for r = 0.8 and α in the range from (0.0 to 0.5). Density measurements and surface tension measurements of the MEA solutions with r = 0.8 are given in Tables 3 and 4, respectively. Both the density and the surface tension of the partially carbonated aqueous MEA solutions show an increase with increasing CO2 loading and a decrease with increasing temperature. Density Model. A model to predict the density of partially carbonated amine solutions (for MEA, DEA, and MDEA) has been published by Weiland et al.5 This model predicts the density as a ratio of the average molar weight to the mean molar volume of the solution. The Weiland’s model has been fitted for partially carbonated MEA by Han et al.11 for data up to r = 0.6. Predictions from the Weiland model with the originally fitted parameters and with the parameters fitted by Han et al.11 were found to be unsatisfactory for partially carbonated MEA solutions in the range of r, T, and α used in this work. The reason for this observation is that the data they have used to fit the parameters are not in the range of r, T, and α used in this work. The average absolute deviation (AAD) of the predictions from the 344

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Table 3. Densities, ρ, of Partially Carbonated Aqueous MEA Solutions from T = (313.15 to 343.15) K and CO2 Loading, n(CO2)/n(MEA), α from (0.00 to 0.51) at the MEA Mass Ratio r = 0.8a,b,c ρ/kg·m−3

α n(CO2)/n(MEA)

xMEA

xCO2

313.15 K

323.15 K

333.15 K

343.15 K

0.07 0.21 0.22 0.28 0.29 0.30 0.31 0.35 0.37 0.38 0.40 0.42 0.43 0.44 0.45 0.46 0.47 0.48 0.49 0.50 0.51

0.5214 0.4860 0.4836 0.4700 0.4678 0.4656 0.4634 0.4550 0.4509 0.4489 0.4449 0.4410 0.4390 0.4371 0.4352 0.4333 0.4314 0.4296 0.4278 0.4259 0.4241

0.0365 0.1021 0.1064 0.1316 0.1357 0.1397 0.1437 0.1593 0.1668 0.1706 0.1780 0.1852 0.1888 0.1923 0.1958 0.1993 0.2028 0.2062 0.2096 0.2130 0.2163

1053.4 1115.0, 1114.8, 1117.6

1039.1 1102.6, 1101.4 1104.5

1031.8 1096.7, 1095.5 1098.8

1148.6 1154.0 1154.0, 1152.0 1158.2 1173.3 1181.5 1189.9, 1188.7 1197.2 1209.0

1046.3 1108.5, 1108.7 1111.1 1142.9 1148.2 1148.2, 1146.5 1150.9 1167.8 1176.0 1184.5, 1183.0 1191.8 1203.7

1135.8, 1139.7 1140.2 1143.6 1161.8 1168.8, 1179.3 1177.3 1185.5 1198.2 1205.2

1130.4 1135.0, 1134.5 1138.5 1156.6 1163.6 1174.0, 1171.5 1179.9 1192.3 1198.8

1216.4

1210.8 1207.8

1198.8

1220.8 1223.4 1232.5 1232.1

1213.8 1217.1 1226.1 1226.6 1232.3

1220.9 1223.9

1215.1

1240.9

Multiple data points are available at some α and T, due to multiple samples measured with different r values (r values are still close to 0.8). b Standard uncertainties u are u(α) = ± 0.005, u(T) = ± 0.03 K; instrument accuracy = ± 0.05 kg·m−3. cThe combined expanded uncertainty Uc is Uc(ρ) = ± 6.34 kg·m−3 (level of confidence = 0.95, where k = 2). a

Table 4. Surface Tension, σ, of Partially Carbonated Aqueous MEA Solutions from T = (313.15 to 343.15) K and CO2 Loading, n(CO2)/n(MEA), α from (0.00 to 0.50) at the MEA Mass Ratio r = 0.8a,b σ/N·m−1

α n(CO2)/n(MEA)

xMEA

xCO2

313.15 K

323.15 K

333.15 K

343.15 K

0.00 0.07 0.22 0.30 0.38 0.50

0.5412 0.5214 0.4836 0.4656 0.4489 0.4259

0.0000 0.0365 0.1064 0.1397 0.1706 0.2130

0.0515 0.0530 0.0571 0.0594 0.0617 0.0664

0.0504 0.0517 0.0561 0.0589 0.0605 0.0647

0.0493 0.0506 0.0546 0.0570 0.0597 0.0639

0.0481 0.0497 0.0541 0.0562 0.0584 0.0628

Standard uncertainties u are u(α) = ± 0.02, u(T) = ± 0.5 K; instrument accuracy = ± 0.0004 N·m−1. bThe combined expanded uncertainty Uc is Uc(σ) = ± 0.0018 N·m−1 (level of confidence = 0.95, where k = 2). a

n

Weiland model with the parameters from Weiland et al.5 and Han et al.11 from the measurements reported in this work are given in Table 5. Parameters of the Weiland’s model are fitted against the measurements from this work with the expectation of expanding the usability of the model for CO2 loaded aqueous MEA solutions with high mass ratios, up to r = 0.8. The structure of the model is given below by eqs 1 and 2.

ρ=

313.15 K

323.15 K

333.15 K

343.15 K

36.2 41.7 1.73

33.6 51.5 1.76

28.9 59.0 2.34

24.7 65.9 1.79

(1)

∑ (Vj·xj) + xj = 2·xj = 3·V * + xj = 1·xj = 3·V ** j=1

(2)

Here eq 1 comes from the basic definitions of the density of a solution. The symbols ρ, x, M, and Vs are the density, mole fraction, molar weight, and mean molar volume of the solution. The symbol Vj represents the molar volume of pure components and the species CO2, H2O, and amine are represented by j = 1, 2, and 3, respectively. Note that the molar volume of CO2 is used to represent the dissolved CO2, and it is different from the component’s pure component value.5 The molar volumes associated with the interactions between the amine and CO2, and the amine and H2O are given by V**

AAD/kg·m−3 source

Vs 3

Vs =

Table 5. AAD of the Density Predictions for CO2 Loaded Aqueous MEA Solutions for T = (313.15 to 343.15) K at the MEA Mass Ratio r = 0.8

Weiland et al.5 Han et al.11 this work

∑ j = 1 (xj·Mj)

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and V*. The V** is found as a function of mole fraction of amine and given by eq 3, V ** = e + f ·xj = 3

deviation of the predictions from the experimental data is within acceptable error. Surface Tension Model. Surface tension data presented in this work are correlated as a function of the CO2 loading value; α, which has the format of eq 5 (a quadratic polynomial function).

(3)

where, e and f are constants, and x3 is the mole fraction of MEA. The VCO2, V**, and V* values are estimated with the data from this work using linear data regression (with the method of least-squares), and the fitted parameters are given in Table 6.

σmix = a ·α 2 + b·α + c

Here σmix is the surface tension of the solution/N·m . The values of the parameters a, b, and c at each temperature and the AAD between the predictions and the data reported in this work are given in Table 8. Predictions of the fitted correlation

Table 6. Parameters of the Weiland’s Density Model5 Fitted for Partially Carbonated Aqueous MEA Solutions for T = (313.15 to 343.15) K at the MEA Mass Ratio r = 0.8 313 323 333 343

K K K K

VCO2

V*

e

f

2.8209(−5) 9.7923 (−5) 2.0678(−4) 1.0381(−4)

−3.8698(−6) −4.3185(−6) −5.2325(−6) −4.6838(−6)

−8.4511(−5) −4.0154(−4) −9.0243(−4) −4.3861(−4)

9.1119(−5) 4.5112(−4) 1.0000(−3) 5.0114(−4)

Table 8. Parameters and Prediction Accuracy of the Surface Tension Correlation (eq 5) for CO2 Loaded Aqueous MEA Solutions with r = 0.8 313 323 333 343

Molar volumes of H2O and MEA are predicted using the correlations that has been developed via fitting the density data presented in Han et al.11 The fitted density correlations for MEA and H2O are in the form of eq 4, ρj = a ·T 3 + b ·T 2 + c·T + d

(5) −1

K K K K

a

b

c

AAD/N·m−1

1.763(−2) 7.085(−3) 1.709(−2) 1.043(−2)

2.072(−2) 2.544(−2) 2.093(−2) 2.400(−2)

5.153(−2) 5.018(−2) 4.918(−2) 4.805(−2)

1.157(−4) 2.258(−4) 0.700(−4) 1.310(−4)

and the experimental data are given in Figure 2. Deviation between the predictions and the experimental data is small and negligible for engineering calculations.

(4)

−3

where, ρj is the density/kg·m of species j and T is the temperature/K. The fitted parameters are given in Table 7. Table 7. Parameters of the Density Correlation (eq 4) for Pure H2O and MEA MEA H2O

a

b

c

d

0 4.007(−6)

−5.327(−4) −6.875(−3)

−4.566(−1) 2.740(−4)

1.195(3) 6.852(2)

Figure 2. Surface tension data and the predictions of the fitted correlation for MEA with r = 0.8 and CO2 loading, n(CO2)/n(MEA), α = (0 to 0.5). ■, □, ●, and ○, experimental data at T = 313.15 K, 323.15 K, 333.15 K, and 343.15 K, respectively; , -·-, ···, and ---, predictions of the correlation at T = 313.15 K, 323.15 K, 333.15 K, and 343.15 K, respectively.

The predictions from the newly fitted model for MEA at r = 0.8 are given in Figure 1 along with the data from this work. The average absolute deviations (AAD) between the predictions and our data in kg·m−3 are given in Table 5. The

In applications like modeling and simulation, it is always interesting to present data with relation to existing model describing the physical properties, rather than a polynomial function fitted to a specific set of data. To achieve such a general presentation of the surface tension data for partially carbonated MEA solutions, an extension of an existing model is considered. Followed by the good predictability expressed for aqueous MEA and the ease of extension, the model presented by Connors and Wright14,15 is selected to be fitted in this work, after comparing with several models presented in literature.17,18 The surface tension model is given by eq 6.

σmix Figure 1. Density of MEA with r = 0.8 and CO2 loading, n(CO2)/ n(MEA), α = (0.07 to 0.51). (a) T = 313.15 K, (b) T = 323.15 K, (c) T = 333.15 K, and (d) T = 343.15 K. , model prediction; *, experimental data.

⎛ ⎞ ⎜ ⎟ bixi ⎟· = σ2 + ∑ ⎜1 + aj ⎛ ⎞⎟ i = 1,3 ⎜ ⎜ ⎟ ⎜ (1 − ai) · 1 + ∑j = 1,3 (1 − a ) ·xj ⎟ ⎝ ⎠⎠ j ⎝ (xi·(σi − σ2))

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(6)

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Here, σ1, σ2, and σ3 represent the surface tension of CO2, H2O and MEA, respectively, and a1, a3, b1, and b3 are fitting parameters of the model. Surface tension of pure H2O and MEA are computed using a correlation presented by Asprion15 for predicting the pure component surface tensions. The accuracy of the predictions from the correlation for pure component surface tension is checked against the data from this work and literature, and the AAD values are given in Table 9. Surface tension of pure CO2 was considered as a fitting parameter as CO2 does not exist as a liquid above its critical point temperature.

Figure 3. Surface tension data and the predictions of the Connors and Wright model14,15 fitted for MEA with r = 0.8 and CO2 loading, n(CO2)/n(MEA), α = (0 to 0.5). ■, □, ●, and ○, experimental data at T = 313.15 K, 323.15 K, 333.15 K, and 343.15 K, respectively; , -·-, ···, and ---, model predictions at T = 313.15 K, 323.15 K, 333.15 K, and 343.15 K, respectively.

Table 9. Prediction Accuracy of the Surface Tension Correlation from Asprion15 for Pure Components AAD/N·m−1 MEA H2O

Vázquez et al.13

Han et al.11

this work

5.7(−5) 3.68(−4)

5.98(−4) 2.83(−4)

7.34(−4) 5.96(−4)

Uncertainty of Surface Tension Measurements. The accuracy for the temperature measurements related to the thermocouple and the thermometer used for temperature monitoring, U(T), is taken as ± 0.5 K. The maximum gradient of surface tension against temperature, ∂σ/∂T, is found as 1.85·10−4 N·m−1·K−1. The corresponding uncertainty in σ, (∂σ/ ∂T)·ΔT, is ± 9.25·10−5 N·m−1. The uncertainty U(α) and the gradient ∂σ/∂α are found as ± 0.02 and 0.0393 N·m−1. The resulting uncertainty in the measurements, (∂σ/∂α)·Δα, is ± 7.86·10−4 N·m−1. Instrument accuracy for the advanced goniometer, Ramé-Hart model 500, is taken as ± 0.0004 N·m−1, which is the tolerance limit for the water check measurements. The overall uncertainty of σ, U(σ), was calculated by combining the partial uncertainties reported in this section with a root sum of square method and found to be ± 0.0009 N·m−1. The combined expanded uncertainty of the surface tension measurements, Uc(σ), was found as ± 0.0018 N·m−1 (level of confidence = 0.95). The combined expanded uncertainty of the CO2 loaded aqueous MEA solutions are about five times higher than that of the unloaded aqueous MEA solution reported by Han et al.11 This can be justified by relating with the difficulties in the experimental determination of the surface tension when CO2 is involved. The tendency to release CO2 from the MEA solution during the experiments (when the samples are heated up to the required temperature) is considered as the main cause for the comparatively large uncertainties of the measurements. Further, the higher value assigned as the instrument accuracy compared to the value used by Han et al.11 also has a considerable contribution.

Parameters of the model proposed by Connors and Wright,14 fitted using the data reported in this work, are given with the AAD between the predictions and the measurements in Table 10. Model predictions show higher AADs compared to that of the fitted correlation (eq 5) for the data from this work, but the general presentation can be useful for engineering calculations depending on the focus. Model predictions together with the experimental data from this work are presented in Figure 3.

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EXPERIMENTAL UNCERTAINTIES The uncertainty of the density and surface tension measurements of CO2 loaded aqueous MEA solutions arises as a combination of the uncertainties of temperature measurements, CO2 loading, and the measuring instrument itself. All of the uncertainty values related to the measurements reported in this work are given under the corresponding data tables. Uncertainty of Density Measurements. The accuracy for the temperature readings, U(T), is given for the DMA 4500 as ± 0.03 K. The maximum gradient of density against temperature, ∂ρ/∂T, is found as 1.24 kg·m−3·K−1. The corresponding uncertainty in ρ, (∂ρ/∂T)·ΔT, is then calculated as ± 0.0372 kg·m−3. The uncertainty of the properties of the samples is taken as the maximum error related to α of the prepared samples. The uncertainty U(α) and the gradient ∂ρ/ ∂α are found as ± 0.005 and 635 kg·m−3. Resulting uncertainty in the measurements, (∂ρ/∂α)·Δα, is ± 3.17 kg·m−3. The instrument accuracy for DMA 4500 is given as ± 0.05 kg·m−3. The overall uncertainty of ρ, U(ρ), was calculated by combining the partial uncertainties reported in this section with a root sum of square method and found to be ± 3.17 kg·m−3, and the combined expanded uncertainty of the density measurements, Uc(ρ) was found as ± 6.34 kg·m−3 (level of confidence = 0.95).

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CONCLUSIONS Densities and surface tensions of the CO2 loaded aqueous MEA solutions with mass ratio; r = 0.8 and CO2 loading; α = (0 to 0.5) at temperature; T = (313.15 to 343.15) K have been measured. An increase in the density and surface tension with increasing CO2 loading and a decrease in the density and

Table 10. Fitted Parameters of the Connors and Wright Model14,15 and the Prediction Accuracy of the Fitted Model

313 323 333 343

K K K K

a1

a3

b1

b3

σ(CO2)

AAD/N·m−1

−4.616 6.767 2.046(1) 6.347(−1)

−7.941 7.513 1.193(1) 1.216

−3.285 3.82 1.932(1) 8.584(−2)

1.03 −1.627 −2.47 −5.695(−1)

1.312(−1) 1.334(−1) 1.265(−1) 1.144(−1)

3.52(−4) 3.54(−4) 3.64(−4) 5.20(−4)

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surface tension with increasing temperature was observed. The model presented by Weiland et al.5 was used to correlate the density data. The average absolute deviations between the predictions and measurements in kg·m−3 are 1.73, 1.76, 2.34, and 1.79 for T = (313.15 to 343.15) K, respectively. Surface tension data were correlated by a quadratic polynomial function, which has shown a predictability of 0.0001, 0.0002, 0.0001, and 0.0001 of AAD/N·m−1 with the present data at each temperature. The model presented by Connors and Wright14 was fitted to predict the surface tension of MEA solutions with r = 0.8 and absorbed CO2. The AAD between the predictions and measurements in N·m−1 are 0.0004, 0.0004, 0.0004, and 0.0005 at T = (313.15 to 343.15) K, respectively. The fitted models for estimating the density and surface tension values of partially carbonated aqueous MEA solutions show a satisfactory representation with errors that would be negligible for engineering applications.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Phone: +47 3557 5286. Fax: +47 3557 5001. Funding

The authors would like to thank the Norwegian Research Council and Statoil for financial support. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The assistance from Anita Elverøy, Van Khanh Tong, and Achini Weerasooriya are gratefully acknowledged. REFERENCES

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dx.doi.org/10.1021/je300920t | J. Chem. Eng. Data 2013, 58, 343−348