Gas phase dehydration using hydrogels

Hydrogels are cross-linked networks of water soluble polymers that have the potential to be used in the dehydration of wet gas. In this work, the uptake of hydrogels and molecular sieves were assessed in controlled humidity environments including in the presence of steam (100% relative humidity) and under pressurized conditions (6 MPa). The recyclability of the hydrogels and molecular sieves at 115 °C was also studied. At 98% humidity, the hydrogel was able to absorb twice its own mass while molecular sieves were only able to adsorb 0.3% of their mass. In the presence of steam (100% relative humidity), hydrogels absorb a maximum of approximately 23 times the absorbent's own mass while the molecular sieves merely adsorb an average of 0.4 times the adsorbent's mass under the identical experimental condition. Under pressurized conditions, hydrogels were able to absorb a maximum of approximately 6 times the absorbent's initial mass and an approximate of 0.25 times the adsorbent's initial mass. In terms of the recyclability, regeneration time and temperature the hydrogels show improved performance compared to molecular sieves. The superior uptake is due to the fundamentally different mechanism of dehydration of the hydrogel which results from swelling of the particles. This creates issues in terms of swelling and blocking of a dehydration column so methods to overcome this were explored by supporting the hydrogel. Owing to the outstanding water uptake performance, fast and complete regeneration, and readily available commercial supply, the hydrogel is considered as a viable and economical alternative to the commonly applied molecular sieve for gas phase dehydration.