Research Articles (Chemistry and Polymer Science)

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Direct determination of enthalpies of sorption using pressure-gradient differential scanning calorimetry: CO2 sorption by Cu-HKUST
(Wiley, 2020-06-01) Feldmann, Wesley K.; White, Kerry-Anne; Bezuidenhout, Charl X.; Smith, Vincent J.; Esterhuysen, Catharine; Barbour, Leonard J.
Enthalpy of sorption (ΔH) is an important parameter for the design of separation processes using adsorptive materials. A pressure-ramped calorimetric method is described and tested for the direct determination of ΔH values. Combining a heatflow thermogram with a single sorption isotherm enables the determination of ΔH as a function of loading. The method is validated by studying CO2 sorption by the well-studied metal–organic framework Cu-HKUST over a temperature range of 288–318 K. The measured ΔH values compare well with previously reported data determined by using isosteric and calorimetric methods. The pressure-gradient differential scanning calorimetry (PGDSC) method produces reliable high-resolution results by direct measurement of the enthalpy changes during the sorption processes. Additionally, PGDSC is less labor-intensive and time-consuming than the isosteric method and offers detailed insight into how ΔH changes over a given loading range.