Synthesis and functionalization of cauliflower-like mesoporous siliceous foam materials from oil shale waste for post-combustion carbon capture

In this work, meso-structured siliceous form materials (SFM) were synthesized from oil shale ash via a green and time-saving microemulsion templating method and modified with polyethleneimine (PEI) for post-combustion carbon capture. The effects of preparation conditions, such as P123/TMB ratio, aging temperature and pH values, on sample morphology and pore structure were studied to understand the characteristics of inorganic silica precursors. Results show that the SFMs possess 3-dimensional porous framework with a large surface area of 901.3 m3/g and a pore volume of 2.0 cm3/g. The CO2 adsorption behaviour of PEI-impregnated SFMs were investigated in terms of CO2 adsorption capacity and temperature swing adsorption (TSA) cycling stability under a simulated flue gas condition (75 °C and 15% CO2/N2). The results show that pore-expanded SFMs with 50 wt% PEI loading exhibited higher CO2 uptake (109 mg/g-adsorbent) compared to non-pore-expended materials (50 mg/g-adsorbent) and no appreciable reduction in CO2 uptake was observed in the first 10 cycles. However, the DRIFTS spectra of CO2-evacuated adsorbents revealed the presence of alkylammonium carbamates residuals and formations of urea species. This could explain the reduction in CO2 adsorption capacity after 10 cycles.