Development of CO2 adsorbing chitosan aerogels for application in submarines

Kurzfassung

The traditional way of CO2 removal from enclosed spaces via dilution is considered as an outdated technology due to negative economic and environmental impact. Developments in nanostructured chitosan aerogel filters for selective CO2 adsorption open up new perspectives for climate control strategies. Considering the requirements of industrial partners in terms of productivity and throughput the JetCutter technology was used right from the beginning of development. Chitosan bead generation was performed at throughput rates of 50+ kg/h. Spherical gel beads were produced in different sizes between 300 and 2500 µm. After regeneration of the chitosan gel beads chemical functionalization was performed by grafting different polyethyleneimine sources (PEI) onto the nanostructured gel backbone. Established drying with super critical CO2 was used to produce materials of pronounced mesoporosity. Functionalized chitosan aerogel beads were characterized according to aerogel standards including porosity, BET surface area, pore size distribution and thermal conductivity of a mixed bed. In addition to that dynamic breakthrough measurements were performed with gas atmospheres of varying concentrations of CO2 in nitrogen. Optical image analysis gave monodisperse particle size distribution, see Fig.1. Scanning electron microscopy revealed homogeneous and expanded three dimensional interconnected fibrillary nanostructures, see Fig.2. Pore size distributions were between 2 and 200 nm ensuring good permeability of the filter material. Specific surface areas were around 240 m2/g matching typical values for chitosan aerogels. Packing densities were calculated to be above 65 %. Fourier transform infrared spectrometry performed on different intermediate stages during the functionalization proofed successful linkage between chitosan and PEI. Dynamic breakthrough measurements revealed adsorption capacities up to 0.6 mmol/g at 5 % CO2 in nitrogen, ambient pressure and 25°C. CO2 adsorption was measured to be reversible at temperatures below 120°C under steady nitrogen gas flow. According to these results functionalized chitosan aerogel beads are affordable future materials for efficient climate control in ECS for submarines.