Multi-stimuli Responsive Smart Hydrogels for Energy-Efficient CO2 capture

Aqueous amine scrubbing at its various forms is currently the best available technology and has been demonstrated at various scales. However, despite the intensive developments at various scales over recent years, its large energy penalty, equivalent up to 20% of a typical power plant output, still remains a major performance barrier. Clearly, new cost-effective and energy-efficient capture concepts leading to substantial reductions in energy penalty need to be explored.

Prompted by recent research in areas of thermo-responsive hydrogels which has led to successful applications in advanced target separations, this proposal aims to develop a new concept of CO2 scrubbing with photo-thermo dual-responsive smart hydrogels, which is expected to be substantially more energy-efficient than amine scrubbing. In this new capture concept, functionalised smart hydrogels, which are mechno-chemically responsive to both heat and sunlight radiation, are used as the absorbent for CO2 capture. The rapid response of the hydrogels to heat and/or light combined with the induced pH swing can facilitate rapid sorbent regeneration/CO2 recovery under much milder conditions. It is anticipated that the temperature swing range for sorbent regeneration can be narrowed to as low as 20-30 degree C, from ca. 70-90 degree C for amine scrubbing. More importantly, the photo-thermo dual-responsive hydrogels-based CO2 capture could potentially make it possible to make use of low grade heat and/or sunlight or solar radiation to drive the CO2 capture system. The major objectives include:

(i) To develop photo-thermal dual responsive hydrogels with high reversible CO2 absorption capacities and favourable volume phase transition behaviours;

(ii) To characterise the physicochemical properties and the CO2 absorption/desorption characteristics of different dual-responsive hydrogels under various temperature swing and light radiation conditions to identify the best-performing smart hydrogels for CO2 capture.

(iii) Once the optimal hydrogels have been identified, scale-up production of the hydrogels will be carried out to perform cyclic CO2 scrubbing tests with the smart hydrogels, using the purpose-designed lab-scale film and column absorbers under different thermal swing conditions with and without light radiation at variable intensities. The test results will be used to assess the feasibility of this new CO2 scrubbing concept to facilitate further development and scale-up of the technology.