Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

ABSTRACT

In this experimental, the densities of monoethanolamine (MEA) + alcohol binary mixtures were measured at temperatures from (293.15 to 333.15) K at 0.1 MPa. The studied alcohols include straight-chain ones, ethanol, n-propanol and n-butanol, and branched-chain ones, isopropanol, isobutanol and tertbutanol. From the experimental density values, we calculated the molar volume (Vm), the thermal expansion coefficient (alphap) and excess molar volume (VmE). The VmE values for the six binary systems are all negative ranging from (-1.020 to -0.064) cm3*mol-1. For straight-chain alcohol mixtures, the VmE values follow the increasing order of ethanol less than n-propanol less than n-butanol. And for the branched-chain alcohol mixtures, the VmE values follow the increasing sequence of tertbutanol less than isobutanol less than n-butanol. All these result from the intermolecular interactions and structural characteristics. For smaller ethanol molecule and MEA, the molar volume is quite similar to each other. However, VmE value for ethanol + MEA system is the most negative. Therefore, the formation of hydrogen bonds plays a leading role for excess molar volume in small molecule alcohol systems. On the other hand, for larger butanol molecule + MEA systems, steric effect leads to a decrease in excess molar volume with the increase in butanol molar volume. Furthermore, the VmE values were correlated with Redlich-Kister polynomial equation with the largest deviation of 0.048.