Temperature Extrapolation of Henry’s Law Constants and the Isosteric Heat of Adsorption

Computational screening of adsorbent materials often uses the Henry’s law constant (K H) (at a particular temperature) as a first discriminator metric due to its relative ease of calculation. The isosteric heat of adsorption in the limit of zero pressure (q st ∞) is often calculated along with the Henry’s law constant, and both properties are informative metrics of adsorbent material performance at low-pressure conditions. In this article, we introduce a method for extrapolating K H as a function of temperature, using series-expansion coefficients that are easily computed at the same time as K H itself; the extrapolation function also yields q st ∞. The extrapolation is highly accurate over a wide range of temperatures when the basis temperature is sufficiently high, for a wide range of adsorbent materials and adsorbate gases. Various results suggest that the extrapolation is accurate when the extrapolation range in inverse-temperature space is limited to |β – β0 | < 0.5 mol/kJ. Application of the extrapolation to a large set of materials is shown to be successful provided that K H is not extremely large and/or the extrapolation coefficients converge satisfactorily. The extrapolation is also able to predict q st ∞ for a system that shows an unusually large temperature dependence. The work provides a robust method for predicting K H and q st ∞ over a wide range of industrially relevant temperatures with minimal effort beyond that necessary to compute those properties at a single temperature, which facilitates the addition of practical operating (or processing) conditions to computational screening exercises.