Excess/deviation properties of binary mixtures of 2,5-dimethylfuran with furfuryl alcohol, methyl isobutyl ketone, 1-butanol and 2-butanol at temperature range of (293.15–323.15) K

. Experimental values of density and speed of sound for binary liquid mixtures of 2,5-dimethylfuran (2,5-DMF) with furfuryl alcohol (FA), methyl isobutyl ketone (MIBK), 1-butanol and 2-butanol and over the entire composition range of 2,5-DMF and at the temperature range of 293.15 – 323.15 K at 10 K intervals and at pressure p = 0.1MPa were reported. Experimental data were used to assess the thermodynamics properties of studied mixtures. These properties were used to interpret the molecular interactions among component of liquids. The values of excess/deviation functions have been ﬁ tted to Redlich (cid:1) Kister type polynomial equation. From the obtained results, a discussion was carried out in terms of nature of intermolecular interactions and structure factors in the binary mixtures.


Introduction
Nowadays, fossil energies such as petroleum, natural gas and coal dominate approximately more than 80% of primary energy consumption estimated by sources [1]. This excessive reliance on fossil fuels in the world has serious reservations about their depletion and green house emission. Now, with increasing the demand for environmental concerns about global warming, the development of eco-friendly and renewable energy sources have been a most important topic in the last few years [2,3]. The energy-efficient processes for the sustainable production of fuels derived from biomass such as biodiesel fuel (BDF), bio-ethanol and liquid alkanes have also attracted attention over the year [4]. 5-hydroxymethylfurfural (HMF), obtained by dehydration of monosaccharides, is considered to be most promising important intermediate for the synthesis of a wide variety of chemicals and alternative fuels based on bio-refinery [5]. To upgrade furanic compounds toward bio-fuels, hydrogenation is the most versatile reaction. Among several furan-based biofuel candidates, which include 2,5-dimethylfuran (2,5-DMF), 2-methylfuran (2-MF), 5-ethoxymethylfurfural (EMF) and ethyl levulinate (EL), 2,5-dimethylfuran is known as one of the potential transportation fuels because of its high energy density (30 kJ · cm À3 ) togther octane number (RON = 119), these values are similar to the gasoline which also have high energy density (34ckJ · cm À3 ) together octane number (RON = 96). Moreover, DMF is nearly immiscible with water and thus easier to blend with gasoline than ethanol.
To explore the application of DMF as a fuel or as a gasoline additive, it is necessary to characterize its thermophysical properties including density, sound velocity, refractive indices, viscosity, surface tension and vaporliquid equilibrium as a pure fluid as well as mixed with hydrocarbons or other gasoline additives. In the face of their importance, experimental and theoretical investigations concerning key properties are scarce and limited to narrow experimental conditions.
For the case of binary systems {2,5-dimethylfuran (2,5-DMF) + FA or MIBK or 1-butanol, or 2-butanol}, neither excess molar volumes (V E m ), nor isentropic compressibility (ks) data have been previously reported. Consequently, and as continuation of our systematic studies on thermodynamic and thermophysical properties of binary mixtures containing solvents derived from biomass, the present work is undertaken to measure new experimental data of densities, sound velocity, refractive indices of pure DMF and of the binary systems {2,5-dimethylfuran (2,5-DMF) + FA or MIBK or 1-butanol, or 2-butanol} over the entire composition range at (293. 15, 303.15, 313.15 and 323.15) K and at pressure p = 0.1 MPa. Reliable density and speed of sound data for the measured systems are needed for optimized design of several industrial processes such as separation, storage, mixing processes, and transport. These data also used to develop accurate empirical equations, models and simulation programs. The results from these studies can provide valuable information about fluid at different temperature conditions including room temperatures to higher temperatures at 50°C.
2 Experimental details 2.1 Chemicals 2,5-dimethylfuran (2,5-DMF), FA and 2-butanol were purchased from Sigma Aldrich, while 1-butanol was from Biochem and MIBK was from Fluka. The purity of these chemicals were declared to be more than 0.99 on mass fraction basis. The source and the purity of the utilized chemicals are shown in Table 1. As well the purity was checked by comparing the measured densities, speed of sound and refractive index, which are in good accord with literature values  and are presented in Table 2. All chemicals were kept in bottles to avoid contamination and evaporation during mixing.

Apparatus and procedure
The binary mixtures were prepared by mass measurement using an OHAUS analytical mass balance with a precision of ±0.0001 g. The uncertainty in the mole fraction was ±0.0005. Density and speed of sound for pure components and their binary mixtures were measured using a digital vibrating-tube densimeter and sound velocity analyzer (Anton Paar DSA 5000M) with uncertainty of ±0.02 K in temperature. The speed of sound was measured using a propagation time technique with frequency of 3 MHz. The estimated uncertainty in density and speed of sound were ±0.003 g·cm À3 and ±1.2 m·s À1 , respectively. The refractive indices of the pure liquids used in the present work were measured using an Abbe digital refractometer (Model Abbemat 300, Anton Paar), with uncertainty of ±0.02 K in temperature. The measured values of the refractive indices using the method and apparatus were estimated to be ±0.005 of their true values.

Density
The values of density r were measured at (293.15, 303.15, 313.15 and 323.15) K, and at pressure p = 0.1 MPa for the binary systems {2,5-dimethylfuran (2,5-DMF) + FA or MIBK or 1-butanol, or 2-butanol} and are given in Table 3. The plots of density versus concentration at investigated temperatures are given in Figure S1 (a)-(d). From Figure S1 (a)-(d), it can be seen that the r value decreases with an increase in temperature, and increases with an increase in concentration for all investigated binary systems, except for the system containing FA whereas a decreasing value of r with an increase in concentration was observed.

Speed of sound
The measurement of speed of sound, u, has been successfully employed in understanding the nature of molecular interactions in pure liquids and their liquid mixtures [66][67][68]. Speed of sound measurements are highly sensitive to molecular interactions and can be used to provide qualitative information about the physical nature and strength of molecular interaction in liquid mixtures [66][67][68]. In this regards, the speed of sound data, were also measured in the same conditions for all binary systems and are also given in Table 3. The plots of speed of sound versus concentration, at investigated temperatures, are given in Figure S2 (a)-(d). From Figure S2 (a)-(d), it can be seen that the u value also decreases with an increase in temperature, and in general, decreases with an increase in concentration for all binary systems excluding the {2,5-dimethylfuran + MIBK) system, whereas an increasing value of u with an increase in concentration was observed. Figure S2 (a)-(d), representing the variation of u as a mole fraction of 2,5dimethylfuran for the systems containing FA or MIBK or 1butanol, or 2-butanol, shows that at a given temperature, the curve of u as a function of x 1 has a maximum of x 1 = 0.6773 for MIBK whereas a minimum of x 1 = 0.9004 for FA, x 1 = 0.7944 for 1-butanol and x 1 = 0.6860 for 2-butanol. The minimum of x 1 observed for the systems whereas u value decreases with an increase in concentration while maximum of x 1 observed for the systems whereas an increasing value of u with increasing concentration was observed.   [22] 1257 [33] 0.8098 [23] 1256.8 [34] 0.80965 [32] 1257.66 [35] 0.8095 [33] 0.809530 [34] [14] 1240.37 [37] 1.3969 [14] 0.8070 [15] 1240. 25 [42] 1195 [42] 0.7980 [34] 1194 [34] 3

.3 Excess molar volumes
The excess molar volumes,V E m , were calculated from the density data of the mixture and the pure components using Equation (1): where x 1 and x 2 are mole fractions; M 1 and M 2 denote molar masses; r 1 and r 2 are the densities; where 1 refers to 2,5dimethylfuran and 2 refers to FA or 1-butanol or 2-butanol or MIBK, and r is the density of the mixtures. Table S1 represents the results of excess molar volume, V E m , for the studied system and is also plotted in Figure S1       systems (2,5-dimethylfuran + MIBK, or FA). The positive V E m values can be explained by (i) mutual loss of dipolar association due to addition of the 1-butanol or 2-butanol and contributions due to difference in size and shape of the components in the mixtures, and (ii) dipole-dipole and dipole-induced dipole interaction between unlike molecules. The first factor contributes to expansion in volume and second factor contributes to decrease in volume, which will cause contraction in volume. The experimental results in this work suggested that the factors responsible for expansion Standard uncertainties u are u(T) = ±0.02 K, u(p) = ±0.04 MPa and the combined expanded uncertainty Uc in mole fraction, density and sound velocity were Uc(x) = ±0.0005, Uc(r) = ±0.003 g · cm À3 and Uc(u) = ±1.2 m · s À1 , respectively, (0.95 level of confidence). in volume are dominant over the entire composition range in the mixtures (2,5-DMF + the 1-butanol or 2-butanol) systems whereas an inversion in sign for (2,5-DMF + MIBK or FA) systems suggested that factors responsible for decrease in volume are dominant over the composition range. As can been seen the results in Table S1, the V E m values at x 1 = 0.5938 for 2-butanol>1-buta-nol>MIBK>FA indicating that the interaction between 2,5-DMF with FA or MIBK or 1-butanol or 2-butanol as in order FA>MIBK>1-butanol>2-butanol. This observation based on fact that lower the V E m values have stronger interaction and vice versa. From Figure 1

Isentropic compressibility, and deviation in isentropic compressibility
The Newton-Laplace equation was used to calculate the isentropic compressibility, k s , The deviations in isentropic compressibility, Dk s , were calculated using the equation given below: where k s , i and x i are the isentropic compressibility and mole fractions of the pure component i, respectively. The results of isentropic compressibility, k s , for studied systems at 293.15, 303.15, 313.15 and 323.15 K are given in Table 3 and are also plotted in Figure S3 (a)-(d). The isentropic compressibility, k s , value increases with an increase in Table 4. Coefficients A i , and standard deviations, obtained for the binary systems studied in this work at different temperatures and at pressure p = 0.1 MPa for the Redlich-Kister equation. temperature at a fixed composition for all binary systems due to an increase in thermal agitation, making the solution more compressible [69]. The k s value increases with an increase in temperature and increases with an increase in the concentration of 2,5-DMF at a fixed temperature for the system of 2,5-DMF with FA, 1-butanol and 2-butanol except for the 1-butanol, 2-butanol systems whereas start decreasing from x 1 = 0.5099, x 1 = 0.1972 upwards respectively, while for the MIBK solution of 2,5-DMF, decreases with concentration. It is well known that the addition of 2,5-DMF molecules to self-associated hydrogen bonded FA,1-butanol and 2butanol will induce breaking of clusters of these molecules thereby releasing so many dipoles, which interact with dipoles of 2,5-DMF. This causes an increase in free space, decrease in speed of sound and positive deviation in isentropic compressibility [70]. The calculated Dk s values for studied system at (293.15, 303.15, 313.15 and 323.15) K are also given in Table S1 and are graphically presented in (Figure 2 [71].
The positive values of Dk s may be due to rupture of hydrogen bonded associates of 1-butanol or 2-butanol dominated over hydrogen bonding between unlike molecules.

Correlation of derived properties
Experimental excess/deviation properties of the {2,5dimethylfuran (DMF)+FA or 1-butanol or 2-butanol, or MIBK} were correlated by Redlich-Kister Equation (4): where X is excess molar volumes, V E m and deviation in isentropic compressibility, Dk s . The values of the fitting parameters A i have been evaluated using a least-square method. These results are summarized in Table 4, together with the corresponding standard deviations, s, which was determined using Equation (5): where N is the number of experimental points and k is the number of coefficients used in the Redlich-Kister equation. The values of V E m and Dk s as well as the plots of the Redlich-Kister model are displayed in Figures 1 (a)-(d) and 2 (a)-(d), respectively. The standard deviations, between the experimental data and those calculated using Redlich-Kister equation are also given in Table 4, show very small values at the investigated temperatures for all the systems.

Conclusion
In this work, density and speed of sound of {2,5dimethylfuran (DMF) + FA or 1-butanol or 2-butanol, or MIBK} systems were measured over the temperature range of 293.15-323.15 K and at atmospheric pressure. The experimental values were used to calculate the excess functions, which were then correlated using a Redlich-Kister-type polynomial equation. The excess molar volumes were negative for {2,5-dimethylfuran (DMF) +F) or MIBK} systems and positive for {2,5-dimethylfuran (DMF)+1-butanol or 2-butanol} systems; deviations in isentropic were negative for (2,5-DMF+MIBK) binary system, and both positive and negative for the system (2,5-DMF+FA). The positive values of Dk s are also observed for (2,5-DMF+1-butanol or 2-butanol) systems.

Supplementary Material
Supplementary figures and table.