Experimental and an electrolyte non-random two-liquid model to predict the vapor–liquid equilibrium of CO 2 in aqueous solutions of diethylenetriamine

Abstract

The absorption and desorption data of CO₂ in aqueous solutions with a mass fraction of 10% and 20% of diethylenetriamine are measured at 313.15, 343.15, 373.15, and 393.15 K. The electrolyte non-random two-liquid theory is developed using Aspen V9.0 to correlate and predict the vapor–liquid equilibrium of CO₂ in aqueous diethylenetriamine solutions. The model predicted the heat capacity and saturated vapor pressure data of diethylenetriamine, the mixed heat of a diethylenetriamine–H₂O binary system, and the vapor–liquid equilibrium data of a diethylenetriamine–H₂O–CO₂ ternary system. The physical parameters and the interaction parameters of the model system are calculated. The model predicted CO₂ solubility showing a 10% average absolute deviation from experimental data. The calculated values of the model are basically consistent with the experimental values.

Introduction

With the development of economies and society, the demand for fossil fuels is increasing rapidly, which makes the emission of CO₂ and global warming increasingly serious. A recent study by Rosenfeld ¹ shows that global warming problem is more serious than previously estimated. As a greenhouse gas, carbon dioxide is a major factor contributing to the growth of global warming.^2,3 China’s coal-based energy structure demands that any potential approach toward large-scale and effective CO₂ emission reduction is CO₂ capture and storage. ⁴ As for CO₂ capture, the solvent absorption method is mainly adopted in industry to realize large-scale CO₂ treatment, which has advantages of fast absorption, a simple process, and large processing capacity, but also has disadvantages of high consumption and significant corrosion of equipment. ⁵ In order to develop CO₂ capture and storage technology with low energy consumption and low cost, it is necessary to model, expand simulations, and utilize thermodynamic properties such as phase equilibrium and chemical equilibrium, and optimize CO₂ capture processes. There are three kinds of commonly used thermodynamic models for evaluating the thermodynamic properties of acidic gas absorption processes: the first is the KE model with simple and non-strict form. ⁶ This model has poor universality, but the fitting effect is a good in the specific load range. It cannot be extended to the absorption process of a mixed gas, and it cannot be used to predict the reaction heat of each component. The second category is the more rigorous activity coefficient model and equation of state. For the activity coefficient model, more variables are required and the model is more complex. As the most widely used model in this class, Deshmukh and Mather ⁷ model has been successfully used to calculate the phase equilibrium of the monoethanolamine–H₂O–CO₂ (MEA–H₂O–CO₂) system. The third category encompasses more complex and more rigorous models, including non-random dual fluid electrolyte (e-NRTL) and extended UNIQUAC models, which have been widely used in aqueous amine systems, ⁸ while extended UNIQUAC models are rarely used. In the CO₂ capture based on amines, the reaction between CO₂ and the aqueous solution of amine will form numerous ions. Due to interactions between ions, the non-ideal nature of the electrolyte system is relatively strong. How to accurately describe the non-ideal nature of the solution is the key to simulate the electrolyte solution system. The e-NRTL model proposed by Mock et al. ⁹ can correct the non-ideal nature of the multi-component electrolyte system and can be used to simulate the capture process of CO₂. Therefore, this paper selects the e-NRTL model for the relevant thermodynamic simulation.

Diethylenetriamine (DETA) is a polyamine containing three amine functionalities (two primary and one secondary amine), which is expected to have high CO₂ loading capacity.^10,11 Compared to typical alkanolamines, DETA has a high capacity for binding CO₂, a high absorption rate and a high boiling point.^12,13 Therefore, aqueous solutions of DETA can be potential solvents for CO₂ capture. Due to the advantages mentioned above, a series of studies have been carried out on DETA recently, including mixing of DETA with PZ, ¹⁴ impregnating of plaza-activated carbon, alumina^15,16 and polymethyl methacrylate polymeric materials, ¹⁷ anhydrous solvent ionic liquid based on DETA.^18,19

In this work, new experimental CO₂ solubility data in aqueous DETA solutions (mass fraction of 10% and 20% of DETA) are generated over a wide pressure range (up to 480 kPa) and temperature (313.15–393.15 K) to extend the limited experimental data found in the literature. The detailed process is described in the literature.^20,21

Results and discussion

Chemical equilibrium

The chemical reaction of DETA is complex because DETA is a tertiary amine consisting of primary and secondary amino groups in its structure. So a wide range of chemical reactions is possible with a large number of species formed. The following possible parallel reversible chemical reactions in liquid phase for the (DETA–H₂O–CO₂) system are presented below. The constant-volume method, combined with gas chromatography analysis was used to measure the equilibrium solubility at different concentrations. The schematic diagram of the CO₂ absorption measurement device is presented in Figure 1.

Figure 1.

Schematic diagram of the constant temperature CO₂ absorption solubility measurement device.

Dissociation of water

$$2H_{2}O\stackrel{kw}{\leftrightarrow }{H}_3{O}^{+}+O{H}^{-}$$

(1)

Formation of bicarbonate

$$2H_{2}O+C{O}_2\stackrel{k_{C{O}_2}}{\leftrightarrow }{H}_3{O}^{+}+HC{O}_3^{-}$$

(2)

Formation of carbonate

$$HC{O}_3^{-}+H_{2}O\stackrel{k_5}{\leftrightarrow }{H}_3{O}^{+}+C{O}_3^{2-}$$

(3)

Amine deprotonation

$$DETA{H}^{+}+H_{2}O\stackrel{k_{DETA{H}^{+}}}{\leftrightarrow }{H}_3{O}^{+}+DETA$$

(4)

$$DETA{H}_2^{2+}+H_{2}O\stackrel{k_{DETA{H}_2^{2+}}}{\leftrightarrow }{H}_3{O}^{+}+DETA{H}^{+}$$

(5)

$$DETA{H}_3^{3+}+H_{2}O\stackrel{k_{DETA{H}_3^{3+}}}{\leftrightarrow }{H}_3{O}^{+}+DETA{H}_2^{2+}$$

(6)

Dissociation of carbamate

$$DETACO{O}^{-}+H_{2}O\stackrel{k_{DETACO{O}^{-}}}{\leftrightarrow }HC{O}_3^{-}+DETA$$

(7)

$$DETA{(COO)}_2^{2-}+H_{2}O\stackrel{k_{DETA{(COO)}_2^{-}}}{\leftrightarrow }HC{O}_3^{-}+DETACO{O}^{-}$$

(8)

Due to the complex species of the system, there are many isomers. The main reaction equations are outlined. The chemical equilibrium constants of equations (1)–(8) are a function of temperature, which can be expressed by the following formula

$$\ln K=A+\frac{B}{T}+C\ln T+D*T$$

(9)

where K is the reaction equilibrium constant; T is the reaction temperature; A, B, C, and D are the parameters of each reaction equilibrium constant, the values of which are taken from the literature^22,23 and are listed in Table 1.

Table 1.

The parameters of the equilibrium constants of the reactions in the DETA–H₂O–CO₂ system.

Equation No.	A	B	C	D	T/ C
1	132.899	−13,445.900	−22.477	0.000	0–225 24
2	231.465	−12,092.100	−36.782	0.000	0–50 24
3	216.049	−12,431.700	−35.482	0.000	25–120 24
4	−4.813	−5510	0.000	0.000	20–60 25
5	−3.0355	−5710.9	0.000	0.000	20–60 25
6	0.0699	−3509.4	0.000	0.000	20–60 25
7	−31.0591	8689.9	0.000	0.000	40–120 25
8	−32.825	8360.2	0.000	0.000	40–121 25

Phase equilibrium

The vapor–liquid equilibrium is defined by the equality of the fugacity at a given temperature and pressure. In the process of thermodynamic calculations, different reference states correspond to different phase equilibrium relations, so the appropriate reference state must be selected for our case study. In the model, CO₂ was set as the Henry component, so the reference states of the ions and CO₂ in the solution were in a state of infinite dilution, and the reference states of water and DETA were pure liquid. Therefore, DETA and H₂O have the following phase equilibrium relationship

$$y_i{\phi }_{i}P=x_i{\gamma }_i{P}_i^0$$

(10)

The phase equilibrium relationship between CO₂ and ions is as follows

$$y_i{\phi }_{i}P=x_i{\gamma }_i^{*}{H}_i$$

(11)

where $y_i$ and $x_i$ are the molar composition of the gas phase and the liquid phase, respectively, ${\phi }_i$ is the fugacity coefficient for the gas phase, ${\gamma }_i$ and ${\gamma }_i^{*}$ are the activity coefficients of the species i when the reference states are pure and a state of infinite dilution, $P_i^0$ and $H_i$ are the saturated vapor pressure and Henry coefficient of the pure component i. The e-NRTL model is used to calculate the activity coefficient of each component in the liquid phase and the gas phase fugacity coefficient is obtained from the Redlich–Kwong state equation. The specific equations are as follows

$$P=\frac{RT}{V_m-b}-\frac{a}{T^{0.5}{V}_m(V_m+b)}$$

(12)

$$\ln H_i=A_i+\frac{B_i}{T}+C_i\ln T+D_i\ast T$$

(13)

The model results

DETA systems

By fitting the data of the liquid heat capacity ²⁶ and saturated vapor pressure for DETA, ²⁷ the coefficients of the Antoine equation and specific heat capacity equations (14) and (15) were obtained. The results are shown in Tables 2 and 3. The experimental values and the calculated values from the model for the specific heat capacity are shown in Figure 2. The average relative deviation of DETA is 0.41%. Figure 3 compares the experimental values of the saturated vapor pressure with the model fitting values, and the average relative deviation of saturated vapor pressure is 1.3%. It can be seen from the figures that the experimental values are in good agreement with the model fitting values, and the parameters obtained can accurately describe the properties of the pure absorbent

Table 2.

Values of the specific heat capacity equation parameter (kJ/kmol/K).

	C1	C2	C3	C4	C5	C6	C7	C8	C9	C10	C11
DETA	−2039.19	20.016	−0.058193	5.63E−05	0	0	1.26E−08	1000	0	0	0

DETA: diethylenetriamine.

Table 3.

Values of the Antoine equation parameter (atm).

	C1	C2	C3	C4	C5	C6	C7	C8	C9
DETA	58.72324	−9047.33	−9.94509381	−3.65E−03	−6.1241	7.82E−18	6	234.15	676

DETA: diethylenetriamine.

Figure 2.

Comparison of the e-NRTL model predictions with experimental data for the specific heat capacity of DETA from 300 to 400 K.

Figure 3.

Comparison of the e-NRTL model predictions with experimental data for the saturated vapor pressure of DETA from 350 to 550 K.

$$\begin{array}{l}\ln p_i=C_1+\frac{C_2}{T+C_3}+C_{4}T+C_5\ln (T)+C_6{T}^{C_7}\\ \mathrm{for}{C}_8\le T\le C_9\end{array}$$

(14)

$$\begin{array}{l}{C}_p^{ig}=C_1+C_{2}T+C_3{T}^2+C_4{T}^3+C_5{T}^4+C_6{T}^5\\ \mathrm{for}{C}_8\le T\le C_9\\ C_p^{ig}=C_9+C_{10}{T}^{C_{11}}\mathrm{for}T\le C_7\end{array}$$

(15)

Binary systems: DETA–H₂O

The binary interaction coefficients of the e-NRTL model were obtained by fitting the mixed heat data of the DETA–H₂O system. ²⁰ Figure 4 compares the experimental values and the model calculation values of the mixed heat data of the DETA–H₂O system. The average relative deviation of the mixed heat data of {DETA–H₂O} is about 5%. It can be seen from the figure that the thermodynamic model can accurately predict the vapor–liquid equilibrium and mixed heat data of the system.

Figure 4.

Excess molar enthalpy for the binary mixtures {DETA (2) + H₂O (1)}.

Ternary systems: DETA–H₂O–CO₂

As the system of polyamines is relatively complex compared with that of monoamines, the thermodynamic reactions between substances in the system should be clarified before setting up the thermodynamic model. Hartono ²⁸ determined the species distribution of the DETA–H₂O–CO₂ system by nuclear magnetic resonance (NMR) spectrometry, and found that there were 24 species in the system. The main species are DETACOO⁻, $DETA{(COO)}_2^{2-}A$ , $HC{O}_3^{-}$ and $C{O}_3^{2-}$ . No clear evidence was found of any tricarbamate species and free CO₂ in the system.

For the amine + H₂O + CO₂ system, there is not only the interaction between the amine and the CO₂ and H₂O molecules, but also the interaction between ion pairs and molecules. The values of the action parameters can be obtained by fitting the solubility data of CO₂ in amine aqueous solutions of different concentrations at different temperatures by applying the short-range term of e-NRTL. DETA has two symmetric primary amines (p) and a tertiary amine (s), so the species in aqueous solution is complex and there are many isomers. For the DETA + H₂O + CO₂ system, regression parameters are required as follows: a binary interaction parameter of H₂O–DETA, an interaction parameter between the molecule {H₂O, DETA, CO₂} and the ion pair {DETAH⁺(s), DETAH⁺(p), $DETA{H}_2^{2+}$ (pp), $DETA{H}_2^{2+}$ (sp), $DETA{H}_3^{3+}$ , $HC{O}_3^{-}$ , DETACOO⁻(s), DETACOO⁻(p), $DETA{(COO)}_2^{2-}$ (pp), and $DETA{(COO)}_2^{2-}$ (pp)}. The parameters obtained are shown in Tables S1 and S2 of the supporting information.

Figures 5 and 6 describe the CO₂ solubility in DETA solutions with mass fractions of 10% and 20%, respectively, and compare the calculated results with the experimental values. The measured temperatures of solubility were 313.15, 343.15, 373.15, and 393.15 K, respectively, and the CO₂ loading ranged from 0.0 to 1.9. The deviation of experimental data and fitting data is shown in the Table 4. As DETA is a ternamine, the species of the system is relatively complex. In the model calculation, some isomers were approximated, and the calculation error at low temperature was slightly larger. Under the conditions of low pressure, the partial pressure of CO₂ in the gas phase is relatively low, the amount of CO₂ in the vapor phase is relatively small, and the average relative deviation will be large. At low temperature, the error in the fitting results is relatively large. The reason may be that at low temperature, the solution has a strong CO₂ absorption capacity and a low gas pressure, resulting in a large measurement error, which will affect the final simulation results.

Figure 5.

Solubility of CO₂ in a DETA solution with a mass fraction of 10%.

Figure 6.

Solubility of CO₂ in a DETA solution with a mass fraction of 20%.

Table 4.

The average relative deviations.

	313.15 K	343.15 K	373.15 K	393.15 K
10 mass% DETA	0.0960	0.0718	0.0766	0.0808
20 mass% DETA	0.0956	0.0982	0.0974	0.1065

Conclusion

In this work, new experimental CO₂ solubility in aqueous DETA solutions (mass fraction of 10% and 20% of DETA) have been measured over a wide range of pressure (up to 480 kPa) and temperature (313.15–393.15 K) to extend the limited experimental database. A thermodynamic model based on e-NRTL was established and used to correlate VLE data to predict CO₂ partial pressure for the DETA–CO₂–H₂O system. The model predicted results are in good agreement with experimental VLE data with an average relative deviation of 10%. The parameters of the thermodynamic model can be used to simulate and optimize CO₂ absorption process.

Experimental section

Materials

The molecular formula, CAS number, purity, and source are reported in Table 5. The aqueous solutions are prepared using ultrapure water, which was prepared using a Center 120 FV-S ultrapure water generator. All reagents were used as supplied without any further purification.

Table 5.

Specifications and sources of the chemicals used in this work.

Chemical	CAS number	Molecularformula	Purity a	Supplier
Diethylenetriamine	111-40-0	C4H13N3	0.99 (mass fraction)	J&K Scientific
Carbon dioxide	124-38-9	CO2	0.99999 (mole fraction)	Beijing Millennium Capital Gas Co. Ltd
Nitrogen	7727-37-9	N2	0.99999 (mole fraction)	Beijing Millennium Capital Gas Co. Ltd

a

Used without any further purification.

Apparatus and procedure

The constant-volume method, combined with gas chromatography analysis was used to measure the solubility at different concentrations. The schematic diagram of the CO₂ absorption measurement device is presented in Figure 1. A detailed description of the vapor–liquid equilibrium apparatus can be found in the literature. ²⁹ It is comprised of two stainless steel tanks for the buffer and reaction. Both tanks are equipped with temperature probes and pressure transducers. The principle of this method is to absorb a known volume of gas known volume of polyamine solution. The amount of CO₂ gas introduced into the reaction tank $n_{{\mathrm{CO}}_2}^{\mathrm{all}}$ , was determined by the change in the buffer tank, before and after injection. After equilibrium was achieved at a constant temperature, the amount of CO₂ gas absorbed in the solution $n_{{\mathrm{CO}}_2}^{\mathrm{l}}$ was equal to $n_{{\mathrm{CO}}_2}^{\mathrm{all}}$ subtracted by the amount of CO₂ in the vapor phase $n_{{\mathrm{CO}}_2}^{\mathrm{g}}$ . The CO₂ solubility, ${\alpha }_{{\mathrm{co}}_2}$ , in the liquid phase is defined as $n_{{\mathrm{CO}}_2}^{\mathrm{l}}$ divided by the number of mole of amine. In accordance with the Peng–Robinson (PR) equation, the precise amount of CO₂ in the gas phase was determined using the volume, pressure, and temperature. ²⁴ The accuracy of the volume, pressure, and temperature is ± 0.1 mL, ± 0.1 K, and ± 0.5%, respectively. According to the above description, the experimental error of CO₂ solubility can be calculated, and is about ± 8%.

At low partial pressure (<10 kPa), the pressure transducer error may have a greater impact on the results. Therefore, the CO₂ partial pressure was obtained using gas chromatography (Agilent 7890). The apparatus was verified by determining the solution of CO₂ in 30 mass% MEA solution at T = 313.15 and 393.15 K. The results are compared with reported data.^25,30,31 Our results are in agreement with reported data, and details are given in our previous work. ³² The solubility of DETA aqueous solutions with mass fractions of 10% and 20% at 313.15, 343.15, 373.15, and 393.15 K are measured using the above-mentioned CO₂ absorption device. The values are shown in Table 6.

Table 6.

CO₂ solubility ( ${\alpha }_{{\mathrm{co}}_2}$ ) in 10 wt% and 20 wt% amine aqueous solution at different temperatures: ${\alpha }_{{\mathrm{co}}_2}$ (mol CO₂/mol amine), $p_{{\mathrm{CO}}_2}$ (kPa). ^a

DETA 10%
313.15 K		343.15 K		373.15 K		393.15 K
${\alpha }_{{\mathrm{co}}_2}$	$p_{{\mathrm{CO}}_2}$	${\alpha }_{{\mathrm{co}}_2}$	$p_{{\mathrm{CO}}_2}$	${\alpha }_{{\mathrm{co}}_2}$	$p_{{\mathrm{CO}}_2}$	${\alpha }_{{\mathrm{co}}_2}$	$p_{{\mathrm{CO}}_2}$
0.8744 ± 0.0699	0.098 ± 0.0010	0.6642 ± 0.0531	0.3558 ± 0.0036	0.3168 ± 0.0253	0.92 ± 0.0092	0.2547 ± 0.0203	3.1 ± 0.0310
1.0231 ± 0.0818	0.3 ± 0.0030	0.8045 ± 0.0643	0.776 ± 0.0078	0.6157 ± 0.0493	4.48 ± 0.0448	0.459 ± 0.0367	8.75 ± 0.0875
1.2212 ± 0.0977	1.48 ± 0.0148	0.9516 ± 0.0761	1.81 ± 0.0181	0.9128 ± 0.0730	19.11 ± 0.1911	0.6538 ± 0.0523	21.52 ± 0.2152
1.3019 ± 0.1042	2.98 ± 0.0298	1.0429 ± 0.0834	3.45 ± 0.0345	1.1326 ± 0.0906	61.96 ± 0.6196	0.8318 ± 0.0665	47.21 ± 0.4721
1.409 ± 0.1127	9.67 ± 0.0967	1.1521 ± 0.0922	7.87 ± 0.0787	1.2891 ± 0.1031	139.12 ± 1.3912	0.9567 ± 0.0765	87.6 ± 0.8760
1.4906 ± 0.1192	23.58 ± 0.2358	1.2586 ± 0.1007	18.23 ± 0.1823	1.3936 ± 0.1115	241.76 ± 2.4176	1.0426 ± 0.0834	135.56 ± 1.3556
1.5593 ± 0.1247	46.88 ± 0.4688	1.3448 ± 0.1076	42.96 ± 0.4296	1.4434 ± 0.1155	308.76 ± 3.0876	1.1156 ± 0.0892	198.13 ± 1.9813
1.6254 ± 0.1300	85.48 ± 0.8548	1.4307 ± 0.1145	81.76 ± 0.8176	1.4923 ± 0.1194	380.1 ± 3.8010
1.6827 ± 0.1346	131.48 ± 1.3148	1.5017 ± 0.1201	138.26 ± 1.3826	1.5274 ± 0.1222	444.91 ± 4.4491
1.7298 ± 0.1384	193.28 ± 1.9328	1.5511 ± 0.1241	193.21 ± 1.9321	1.5468 ± 0.1237	483.8 ± 4.8380
1.7826 ± 0.1426	278.08 ± 2.7808	1.5932 ± 0.1275	255.96 ± 2.5596
1.8255 ± 0.1460	357.68 ± 3.5768	1.6339 ± 0.1307	321.56 ± 3.2156
		1.6751 ± 0.1340	406.46 ± 4.0646
DETA 20%
313.15 K		343.15 K		373.15 K		393.15 K
${\alpha }_{{\mathrm{co}}_2}$	$p_{{\mathrm{CO}}_2}$	${\alpha }_{{\mathrm{co}}_2}$	$p_{{\mathrm{CO}}_2}$	${\alpha }_{{\mathrm{co}}_2}$	$p_{{\mathrm{CO}}_2}$	${\alpha }_{{\mathrm{co}}_2}$	$p_{{\mathrm{CO}}_2}$
1.2515 ± 0.1001	1.84 ± 0.0184	0.8444 ± 0.0676	1.24 ± 0.0124	0.4706 ± 0.0376	0.94 ± 0.0094	0.3099 ± 0.0248	3.2 ± 0.032
1.3669 ± 0.1094	7.09 ± 0.0709	0.9527 ± 0.0762	2.51 ± 0.0251	0.6583 ± 0.0527	3.11 ± 0.0311	0.4359 ± 0.0348	6.0 ± 0.06
1.4075 ± 0.1126	13.06 ± 0.1306	1.0508 ± 0.0841	5.39 ± 0.0539	0.855 ± 0.0684	12.54 ± 0.1254	0.5719 ± 0.0458	11.04 ± 0.1104
1.4538 ± 0.1163	23.67 ± 0.2367	1.1472 ± 0.0918	10.24 ± 0.1024	1.0494 ± 0.0839	37.39 ± 0.3739	0.7442 ± 0.0595	27.65 ± 0.2765
1.4984 ± 0.1199	43.2 ± 0.432	1.2078 ± 0.0966	18.31 ± 0.1831	1.2114 ± 0.0969	112.01 ± 1.1201	0.8366 ± 0.0669	41.3 ± 0.413
1.538 ± 0.1230	68.5 ± 0.685	1.2549 ± 0.1004	34.27 ± 0.3427	1.2815 ± 0.1025	182.56 ± 1.8256	0.9298 ± 0.0744	63.29 ± 0.6329
1.574 ± 0.1259	102.9 ± 1.029	1.2957 ± 0.1037	52.49 ± 0.5249	1.3373 ± 0.1069	268.17 ± 2.6817	1.0254 ± 0.0820	100.83 ± 1.0083
1.6061 ± 0.1285	144.3 ± 1.443	1.3366 ± 0.1069	77.58 ± 0.7758	1.3677 ± 0.1094	337.8 ± 3.378	1.1193 ± 0.0895	163.14 ± 1.6314
1.6328 ± 0.1306	188.1 ± 1.881	1.3735 ± 0.1099	109.69 ± 1.0969	1.3916 ± 0.1113	398.96 ± 3.9896	1.1762 ± 0.0941	222 ± 2.22
1.6561 ± 0.1325	235 ± 2.35	1.408 ± 0.1126	156.19 ± 1.5619	1.4059 ± 0.1125	435.79 ± 4.3579	1.2044 ± 0.0964	259.11 ± 2.5911
1.6801 ± 0.1344	287.1 ± 2.871	1.4369 ± 0.1149	204.19 ± 2.0419			1.2358 ± 0.0988	304.2 ± 3.042
1.6993±0.1359	336.1 ± 3.361	1.4617 ± 0.1169	258.89 ± 2.5889			1.2647 ± 0.1012	355.38 ± 3.5538
1.7231 ± 0.1378	403.1 ± 4.031	1.4854 ± 0.1188	316.89 ± 3.1689
		1.506 ± 0.1205	377.99 ± 3.7799

a

Standard uncertainties u(c) = ±0.01 mol/L, u(T) = ±0.1 K, u_r (p) = ±0.5%, u_r( ${\alpha }_{{\mathrm{co}}_2}$ ) = ±8%

Supplemental Material

supporting_information – Supplemental material for Experimental and an electrolyte non-random two-liquid model to predict the vapor–liquid equilibrium of CO2 in aqueous solutions of diethylenetriamine

Supplemental material, supporting_information for Experimental and an electrolyte non-random two-liquid model to predict the vapor–liquid equilibrium of CO2 in aqueous solutions of diethylenetriamine by Ruilei Zhang, Yandong Tang, Weifeng Shan, Haijun Liu, Haijun Li and Jian Chen in Journal of Chemical Research