Deep eutectic solvents (DES) are a type of ionic solvents composed of two components and that have a melting
point lower than either of the individual components. DES's can be prepared combining a hydrogen bond donor
(HBD) and a hydrogen bond acceptor (HBA). In this study, benzyl tri-methyl ammonium chloride (BTMAC) is
used as the hydrogen bond acceptor, and p-toluene sulfonic acid (PTSA), citric acid (CA), and oxalic acid (OX)
are used as the HBD. The physical properties of DES 1 (BTMAC-PTSA), DES 2 (BTMAC-CA), and DES 3 (BTMACOX)
were investigated at their respective eutectic points. The refractive index, conductivity, density, viscosity,
and pH values were measured for the three DES between 293.15 and 333.15 K. As expected, the density, refractive
index, and viscosity decreased and the ionic conductivity increased with increasing temperature, whereas,
the pH values remained constant. The catalytic activities of the DES were tested in the esterification reaction between
acetic acid and butanol. The results showed the superiority of DES 1 (BTMAC: PTSA) which gave the
highest conversion of acetic acid and a further parametric study including the effects of catalyst loading, mole
ratio, alcohol type, and reusability were conducted using DES 1. The obtained results showed a high applicability
of DES for catalytic applications.