Measurement for the critical temperatures, pressures, and thermal diffusivities of monoethanolamine, diethanolamine, and 2-amino-2-methyl-1-propanol

The critical pressures, critical temperatures, and thermal diffusivities have been measured for monoethanolamine (MEA), diethanolamine (DEA), and 2-amino-2-methyl-1-propanol (AMP). These compounds are the components of mixtures used for the capture of various greenhouse gases, mainly CO₂. The pulse-heating method applicable to highly thermally unstable compounds has been used to measure the critical properties. The combined relative expanded uncertainties at 0.95 level of confidence are 0.015 for the critical temperatures and from 0.036 to 0.047 for the critical pressures. The acentric factors of the alkanolamines under study have been calculated. The critical properties of the alkanolamines measured in this work have been compared with the literature data as well as with the values estimated by the group contribution methods of Wilson and Jasperson, Nannoolal et al., and Hukkerikar et al. All the group-contribution methods underestimate both the critical temperatures and pressures of the alkanolamines with one exception: the critical pressure of DEA estimated by the method of Nannoolal et al. is higher than the experimental value. In addition, such a comparison has been made with the critical properties of alkanolamines obtained using three versions of the SAFT equation of state (PρT-SAFT-HR, PC-SAFT, and SAFT-HR). These models of the SAFT EoS overestimate the critical temperature of the MEA and AMP and the critical pressure of the MEA but underestimate the critical pressure of the AMP.

The thermal diffusivities of MEA, DEA and AMP have been measured by the laser flash method using a LFA 457 MicroFlash system (Netzsch, Germany) at atmospheric pressure; the temperature range covered has been from 303.15 to 373.15 K. Linear polynomials have been used to describe the dependences of the thermal diffusivity on temperature. The thermal conductivities of the alkanolamines have been calculated from the experimental data on thermal diffusivity and the literature data on density and heat capacity. The combined relative expanded uncertainties are 0.05 and 0.06 for thermal diffusivity and thermal conductivity, respectively. The equations for calculating the thermal conductivities of MEA, DEA, and AMP have been obtained using the experimental data obtained in this work and taken from the literature. The comparison of the experimental values of thermal conductivity and those calculated by the method of Govender et al. has been performed. The technique of Govender and co-workers significantly overestimates the thermal conductivity of the alkanolamines.