Solubility for dilute sulfur dioxide, viscosities, excess properties, and viscous flow thermodynamics of binary system N,N-dimethylformamide + diethylene glycol
Introduction
Sulfur dioxide (SO2) is a significant atmospheric pollutant, and therefore it is severe in environmental protection. Its main source is flue gas from the burning of fuels with high sulfur content from 0.03 mg m−3 in the air up to several g m−3 in a typical flue gas [1]. Thus, it is necessary to remove SO2 from gaseous streams before emitted. Many technologies for removing SO2 have been proposed, such as limestone scrubbing, which have some inherent disadvantages, including high capital and operating costs, a larger water requirement, poor quality of byproduct, and secondary pollution [2], [3]. Recently, more and more organic solvents were used in gas sweetening absorption processes [4], [5]. Among numerous organic solvents, the mixtures of amine with alcohols showed favorable absorption and desorption properties for acid gases in industrial processes [6], [7], [8], [9]. Room-temperature ionic liquids (RT-ILs) [10], [11], [12], [13] attracted more interest due to their advantages, such as good solubility and high selectivity to SO2. However, the high expense and viscosity of ionic liquids limited their use in industry application. Wei and his co-workers had paid attention to the alcohol system to remove SO2 for several years [14], [15], [16], [17], [18]. The previous work [6], [15], [19] showed that diethylene glycol (DEG) was a promising solvent to the application of flue gas desulfurization (FGD) because of its strong absorption and desorption capacities to SO2, good selectivity, low vapor pressure, low melting point, low toxicity, and high chemical stability. Roizard et al. [20], [21] reported SO2 solubility in some organic solvents and found that N,N-dimethylformamide (DMF) had a strong absorption and desorption capacities for SO2. However, its relatively high vapor pressure results in significant vaporization and solvent loss [22]. Mehta [23] reported that the carbonyl group of DMF could interact with the hydroxyl group of ethylene glycol (EG), which indicated that the mixture of DMF + DEG may result in moderate viscosity and vapor pressure. The properties of such as densities, viscosities, and gas–liquid equilibrium (GLE) data for SO2 in the mixture of DMF + DEG were significant for the potential application of this system in desulfurization.
In this work, we explored GLE data for dilute SO2 in various binary mixtures of DMF + DEG at T = 308.15 K and p = 122.66 kPa, which had not been reported so far in the previous literatures. Then, Henry's law constants (HLC) were obtained by calculating the linear slope of GLE data curves. Moreover, densities and viscosities for the binary mixtures of DMF + DEG were measured over the whole concentration range at T = (298.15, 303.15, 308.15, 313.15, and 318.15) K under atmospheric pressure. Meanwhile, excess molar volume (VmE), viscosity deviation (Δν), enthalpy of activation for viscous flow (ΔH*), entropy of activation for viscous flow (ΔS*), and Gibbs free energy of activation for viscous flow (ΔG*) were calculated. The results of this work can be used to provide a potential industrial application in flue gas desulfurization processes.
Section snippets
Materials
The analytical grade DMF and DEG were obtained from Beijing Reagent Company (Beijing, China). DEG (≥99.4%) was purified from DEG (A.R, ≥98.0%, made in China) dehydrated by Na2SO4 and distilled. The purity of the final DEG, as found by gas chromatograph (GC), was better than 99.4%. Meanwhile, DMF (99.2%) was purified from DMF (A.R, ≥98.0%, made in China) dried over molecular sieves (type 4A) and degassed by ultrasound just before the experiment. The purity of the final DMF, as found by gas
GLE data
A series of GLE experiments for DMF (1) + DEG (2) + SO2 (3) + N2 (4) were performed at T = 308.15 K and p = 122.66 kPa. These GLE data are listed in Table 3, and the GLE curves are plotted in Fig. 2.
In Table 3, x1 is molar fraction of DMF in the actual operation, is the volume fraction of SO2 in the gas phase as are the partial pressure and total pressure of GLE system, respectively, and denotes the molarity concentration of SO2 in the
Conclusion
In this work, the isothermal GLE data of dilute SO2 in pure DMF and pure DEG was measured at T = (298.15, 303.15, 308.15, 313.15, and 318.15) K and p = 122.66 kPa. The absorption of dilute SO2 in DMF + DEG obeys Henry's law at lower pressure. Based on these isothermal GLE data, the thermal parameters of the dissolving process of SO2 in pure DMF and pure DEG were obtained, which indicates that the process of SO2 dissolving in pure DMF and pure DEG was enthalpy driving, exothermic and reversible at the
Acknowledgments
This work was supported by foundation of the “western light” visiting scholar plan, the National Natural Science Foundation of China (21166017), the Research Fund for the Doctoral Program of Higher Education of China (20111514120002), the Natural Science Foundation of Inner Mongolia Autonomous Region (2011BS0601), Program for New Century Excellent Talents in University (NCET-12-1017), Inner Mongolia Autonomous Region's Educational Commission (NJZZ11068), Program for Young Talents of Science and
References (48)
- et al.
J. Chem. Thermodyn.
(1996) - et al.
Energy Procedia
(2009) - et al.
J. Chem. Thermodyn.
(2013) - et al.
Fluid Phase Equilib.
(2010) - et al.
Fluid Phase Equilib.
(2012) - et al.
Fluid Phase Equilib.
(2013) - et al.
J. Chem. Thermodyn.
(2011) - et al.
J. Chem. Thermodyn.
(2007) - et al.
J. Chem. Thermodyn.
(2013) - et al.
J. Chem. Thermodyn.
(2002)