Measurements of water vapour sorption isotherms for RD silica gel, AQSOA-Z01, AQSOA-Z02, AQSOA-Z05 and CECA zeolite 3A

• Isotherms of 5 desiccants are measured over wide temperature and pressure ranges.
• Data is compared with the literature and fit to theoretical and numerical functions.
• The isosteric heat of adsorption is calculated as a function of uptake.
• The sorption hysteresis is investigated for 3 desiccants with Type IV isotherms.

The water vapour adsorption isotherms of RD silica gel, AQSOA-Z01, AQSOA-Z02, AQSOA-Z05 and CECA zeolite 3A are measured for temperatures between 20 °C and 160 °C and vapour partial pressures between 1 and 500 mbar. The measurements were fit to a theoretical isotherm function and for some materials the RMS deviation was less than 5%. Since others had a poorer theoretical fit, all data was also fit to spline functions for use in numerical simulations. The variation of isosteric heats of adsorption as a function of uptake, calculated using a least squares fitting approach, are compared over a range of uptake values for each adsorbent. The heats of adsorption were between 1 and 1.6 times the heat of vaporisation for uptake values above 10% of the maximum uptake for each adsorbent. The AQSOA adsorbents display Type IV isotherm shapes and the silica gel and 3A zeolite display Type I shapes. The sorption hysteresis is investigated for the AQSOA adsorbents at a selected temperature. These adsorbents displayed a small degree of hysteresis with an H1 type behaviour.

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