Isobaric Molar Heat Capacities of Binary Mixtures of Diethyl Carbonate and Methyl Caprate at High Pressures

Biodiesel is a very promising renewable fuel, and adding diethyl carbonate (DEC) can improve the combustion process of biodiesel. In this work, the isobaric molar heat capacities (Cp) of DEC, methyl caprate, and their binary mixtures were measured at temperatures from 314.75 to 344.75 K and at pressures up to 25.2 MPa over the molar fraction of DEC from 0.1 to 0.9 with a flow calorimeter. The relative expanded uncertainty of the experimental system was lower than 0.01. Experimental results show that the Cp values of DEC, methyl caprate, and their binary mixtures increase approximately linearly with increasing temperature and decreasing pressure. Meanwhile, the Cp values of the binary mixtures were observed to decrease with the increase of DEC content, indicating that the addition of DEC can indeed improve the combustion process of methyl caprate. Besides, the excess isobaric molar heat capacities (CpE) of the binary mixtures were calculated; it was found that they are so small compared with the Cp and that the binary mixtures can be considered as ideal solutions. At last, a correlation for the Cp of the binary mixtures was proposed with the maximum absolute relative deviation of 0.81% and an average absolute relative deviation of 0.23%, respectively.