Synthesis of novel regenerable 13X zeolite-polyimide adsorbent foams

Abstract

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 CO2 generation (blowing) and polymerisation reactions. The paper describes the development of the foam structure and its characterisation in the context of removing CO2 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 CO2. 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 CO2 (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 CO2 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 CO2/N2 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 CO2 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.