Measurement and correlation of isobaric molar heat capacities of deep eutectic solvents consisting of choline chloride and triethylene glycol

• C p of choline chloride and triethylene glycol were measured. • C p varies linearly with temperature, pressure and molar fraction of triethylene glycol. • Correlation of choline chloride and triethylene glycol were proposed for calculating C p accurately. Deep eutectic solvents are environmentally friendly substitutes to room temperature ionic liquids in broad engineering applications like biofuel purification, polymer synthesis, gas capture, and organic extraction. In this work, the isobaric molar heat capacities of deep eutectic solvents consisting of choline chloride and triethylene glycol (in molar ratio of 1: 3, 1: 4, and 1: 5) are investigated by flow method in the temperature from 334.91 K to 364.98 K and pressure from 0.19 MPa to 25.21 MPa. The relative expended uncertainty of measurement system is calculated to be 1.4 % within 95 % degree of confidence. Experimental results show that the isobaric molar heat capacity increases linearly with higher temperature and lower pressure. With choline chloride added in triethylene glycol, the heat capacity decreases linearly with the decreasing of triethylene glycol molar fraction. Finally, the correlation of these binary mixtures is established based on the experimental data with the maximum absolute relative deviation and average absolute relative deviation of 1.01 % and 0.31 %, respectively.