Synthesis of Novel Regenerable 13X Zeolite-Polyimide Adsorbent Foams

A new generic synthesis method is presented for the production of a polyimide (PI)/adsorbent (80 wt% 13X zeolite) regenerable foam filter. The method uses a dual parallel reaction foaming process comprising CO ₂ generation (blowing) and polymerisation reactions. The paper describes the development of the foam structure and its characterisation in the context of removing CO ₂ from air. Polyvinylpyrrolidone (PVP) of different molecular weights (10k, 40k and 58k) was used as a pore former to allow more adsorption sites to be exposed to CO ₂. In dynamic adsorption breakthrough experiments at 101.325 kPa and 293 K, 10k PVP foams demonstrated an equilibrium loading of 0.039 g g ⁻¹ for CO ₂ (at 40,000 ppmv in air), showing the best equilibrium time and adsorption capacity. The foams and equivalent commercial 13X beads were able to achieve loadings of 0.094 g g ⁻¹ and 0.097 g g ⁻¹ (at 40 mbar), respectively, when tested using pure CO ₂ in an Intelligent Gravimetric Analyser. At pressures beyond 100 mbar, a weighted average isotherm shows only a 1.3 wt% reduction in adsorption capacity due to the polymer binder. The foams showed superior CO ₂/N ₂ selectivity compared to other adsorbents in literature. The thermal analysis of pure PI and 13X powder showed that the foams can be regenerated at 300 °C. Computational Fluid Dynamics simulation was successfully implemented in order to understand the CO ₂ adsorption behaviour on the new foam filter. Such modelling proved to be invaluable in understanding adsorptive behaviour through the complex foam structures as this is difficult to achieve experimentally.