Densities, Viscosities, and Speeds of Sound of n-Tetradecane and n-Alkylcyclohexane Binary Mixtures within the Temperature Range (288.15–333.15) K

Abstract

This work reports on the densities, viscosities, and speeds of sound of 2-component mixtures of n-tetradecane and n-alkylcyclohexanes (methyl-, ethyl-, propyl-, butyl-, pentyl, hexyl-, heptyl-, octyl-, decyl-, and dodecylcyclohexane) at select temperatures between 288.15 and 333.15 K and pressure of 0.1 MPa. Decreases in mixture densities, viscosities, and speeds of sound were found with increases in temperature and in the component with the lower property value, except for the speeds of sound of n-butylcyclohexane mixtures in which the equimolar mixture had a speed of sound lower than the individual component values. Lengthening the alkyl chain on the n-alkylcyclohexanes (1) decreased the mixture excess molar volumes (V m E), (2) decreased the excess speeds of sound (c E’s) and viscosity deviations (Δη) until minimums were reached after which the c E’s and Δη’s increased, and (3) increased the excess isentropic compressibilities (K s E’s) until a maximum was reached after which it decreased. For all alkylcyclohexanes tested, except methylcyclohexane, V m E’s and K s E’s had the same sign, suggesting that the changes in the volume occupied by the molecules influence the mixture compressibility. In contrast, methylcyclohexane had the largest positive V m E but a negative K s E, which indicates that the expanded volume was not more compressible. Most of V m E’s, c E’s, and Δη’s of n-tetradecane mixtures fell between those reported for n-tridecane and n-hexadecane. n-Tetradecane could be used in fuel surrogates where larger density, viscosity, and speeds of sound are needed to emulate the real fuel.

n-Pentadecane and n-Alkylcyclohexane Mixtures: Viscosity Deviations and Excess Molar Volumes, Speeds of Sound, and Isentropic Compressibilities at 0.1 MPa

“…Figure A,B also shows that increasing the alkyl chain length on the n -alkylcyclohexane tends to increase the α E ’s. For equimolar mixtures shown in Figure B, the trend in the data for n -pentadecane is consistent with trends for n -tetradecane and n -tridecane mixed with the same n -alkylcyclohexanes. , There is very little difference in the α E ’s for these three alkanes in mixtures with higher molecular weight n -alkylcyclohexanes.…”

“…The V m E ’s appear to decline linearly with temperature for methyl-, ethyl-, n- propyl-, n- decyl-, and n- dodecyl-cyclohexanes mixtures with coefficients of determination ( R 2 ) for the linear fits generally above 0.98 (Table S5). Linear relationships between V m E and temperature have been reported for ionic liquids and select n -alkylcyclohexanes with n -tridecane and n -tetradecane. , Linear fits for the other n -alkylcyclohexane mixtures compounds had R 2 < 0.98 (Table S5), and second-order fits were better able to capture the trends in the data (Figure ). These results suggest that the packing arrangements of the shorter chain n -alkylcyclohexanes are more affected by temperature than are the longer chain n -alkylcyclohexanes.…”

“…Excess molar thermal expansion coefficients, α E , for (A) n -alkylcyclohexane and n -pentadecane for all mole fractions x 1 tested and for (B) equimolar mixtures of n -alkylcyclohexane and n -pentadecane compared with previously reported values for n -tridecane and n -tetradecane. , The α E ’s are based on temperatures 288.15, 293.15, and 298.15 K.…”

“…The deviations of the measured values from literature values are plotted in figures in the Supporting Information (Figures S1–S3). The properties of the remaining compounds have been published previously ,,, and can be found with the reported mixture properties.…”

“…In general, researchers have found that equimolar mixtures of a linear alkane with an n -alkylcyclohexane have V m E ’s that increase with an increase in the linear alkane’s molar mass and a decrease in n -alkylcyclohexane’s molar mass. − ,,, The maximum V m E for a mixture did not always occur at a mole fraction of 0.5, but the values at 0.5 were close to the maximum value. The c E ’s of n -alkylcyclohexanes mixed with equimolar amounts of a longer chain alkane ( n -tridecane, n -dodecane, n -tetradecane, or n -hexadecane) have a pattern of the c E ’s decreasing in value until a minimum value and then increasing again as the alkyl chain length was increased. − ,, The pattern for Κ E ’s for these systems was the opposite of that of c E ’s with a maximum Κ E value at the same n -alkylcyclohexane that showed the minimum c E . − , For equimolar mixtures of small n -alkylcyclohexanes ( n -pentylcyclohexane and smaller) and larger linear alkanes ( n -hexadecane, n -tetradecane, n -tridecane, and n -dodecane), Δη’s have been found to decrease as the alkane size decreased or the n -alkylcyclohexane size increased. − ,, For these same larger linear alkanes, a minimum in Δη was found when mixed with larger n -alkylcyclohexanes, but the n -alkylcyclohexane that produced the minimum depended on the linear alkane (e.g., n -hexylcyclohexane with n -dodecane and n -decylcyclohexane with n -hexadecane). − ,, …”