Heat of absorption data for solvents containing 10 wt % diisopropylamine

Figure 4 shows the integral heat of absorption obtained for solutions containing mixtures of different diluents and 10 wt % diisopropylamine only at 40 °C. Data for the heat of absorption at both 40 and 80 °C can be found in the Supporting Information together with its uncertainties.”


“Figure 4. Integral heat of absorption data for solvents containing 10 wt % diisopropylamine.”

“The heat of absorption in aqueous diisopropylamine is surprisingly high, perhaps due to unaccounted phase-transition phenomena, e.g., a biphasic solvent endothermically becoming single phase upon loading, or maybe sublimation of products over cold spots inside the equipment as also experienced at 80 °C. For ethylene glycol + diisopropylamine, the heat of absorption is that typical of secondary and/or hindered amines such as aqueous DEA or aqueous AMP, (48) ΔH ≈ 65–70 kJ·mol CO2–1 for loadings below α = 1 mol CO2·mol amine–1 at both 40 and 80 °C (ΔH does seem to decrease slightly from 40 to 80 °C, but given the uncertainties of the experiment, this reduction is most certainly negligible). More interestingly, the heat of absorption in NMP–diisopropylamine is about 20 kJ·mol CO2–1 at 40 °C and 13 kJ·mol CO2–1 at 80 °C. These results are congruent with physical absorption heat (38) and are further indication of the severe abatement of chemical reaction caused using N-methyl-2-pyrrolidone as a solvent.”

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