Heat capacity of alkanolamine aqueous solutions

Heat capacities of monoethanolamine, diglycolamine, diethanolamine, di-2-propanolamine, triethanolamine, N-methyldiethanolamine, 2-amino-2-methyl-1-propanol, and 2-piperidineethanol aqueous solutions were measured from 30 to 80 degrees C with a differential scanning calorimeter (DSC). The mole fractions of alkanolamines studied are 0.2, 0.4, 0.6, and 0.8. Neat 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.