Volumetric properties of monoethanolamine and alcohol binary mixtures at different temperatures and 0.1 MPa

Highlights: • The densities for amine + alcohol six binary solutions were measured. • The $V_{\text{m}}^{\text{E}}$ values are negative with x_MEA from 0 to 1. • For straight chain alcohol mixtures, $V_{\text{m}}^{\text{E}}$ values follow: ethanol < n-propanol < n-butanol. • For branched chain alcohol mixtures, $V_{\text{m}}^{\text{E}}$ values follow: tertbutanol < isobutanol < n-butanol. • $V_{\text{m}}^{\text{E}}$ values were correlated with Redlich-Kister polynomial equation. -- 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 (V_m), the thermal expansion coefficient (α_p) and excess molar volume ($V_{\text{m}}^{\text{E}}$). The $V_{\text{m}}^{\text{E}}$ 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 $V_{\text{m}}^{\text{E}}$ values follow the increasing order of ethanol < n-propanol < n-butanol. And for the branched-chain alcohol mixtures, the $V_{\text{m}}^{\text{E}}$ values follow the increasing sequence of tertbutanol < isobutanol < 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, $V_{\text{m}}^{\text{E}}$ 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 $V_{\text{m}}^{\text{E}}$ values were correlated with Redlich-Kister polynomial equation with the largest deviation of 0.048.