Heat Capacity of Alkanolamine Aqueous Solutions

Heat capacities of monoethanolamine, diglycolamine, diethanolamine, di-2-propanolamine, triethanolamine, N -methyldiethanolamine, 2-amino-2-methyl-l-propanol, and 2-piperidineethanol aqueous solutions were measured from 30 to 80 °C with a differential scanning calorimeter (DSC). The mole fractions of alkanolamines studied are 0.2, 0.4, 0.6, and 0.8. Heat capacities of N -methyldiethanolamine aqueous solutions have been measured to verify the validity of C p measurements for alkanolamine aqueous solutions. The estimated uncertainty of the measured heat capacities is ±3%, including the effect of up to 5% impurities in a substance. An excess molar heat capacity expression using the Redlich−Kister equation for the composition dependence is used to represent the measured C p of alkanolamine aqueous solutions. For a total of 374 data points, the calculation results for eight alkanolamine solutions give the overall average absolute deviations of 11.9% and 0.29% for the excess molar heat capacity and the heat capacity, respectively. The heat capacities presented in this study are, in general, of sufficient accuracy for most engineering-design calculations.