Molar Heat Capacity (Cp) of Aqueous Cyclic Amine Solutions from (298.15 to 353.15) K

Abstract

Molar heat capacities at 11 different temperatures in the range (298.15 to 353.15) K are reported for aqueous 1,4-dimethyl piperazine (1,4-DMPZ), 1-(2-hydroxyethyl) piperazine (1,2-HEPZ), 1-methyl piperazine (1-MPZ), 3-morpholinopropyl amine (3-MOPA), and 4-(2-hydroxyethyl) morpholine (4,2-HEMO) solutions. Molar heat capacities of MDEA and MEA were also measured and compared with published data resulting in a 1 % experimental uncertainty. Molar excess heat capacities were correlated as a function of mole fraction and temperature employing the Redlich–Kister relation. Excess partial molar quantities were calculated and reported. Group additivity analysis was performed using the molar heat capacities for all the above cyclic amines, and data were fitted with less than 0.5 AAD%. Among the five amines studied, 3-MOPA had the highest values of molar heat capacity and 1-MPZ had the lowest. The values of molar heat capacity of amines were dominated by −CH2 and −OH group contributions. The contributions of −CH2, −N, −OH, −O, and −NH2 groups increased with increasing temperature, and the contributions of −NH and −CH3 groups decreased with increasing temperature for these cyclic amines.