The effects of pore shape and geometry on the storage of CO2 in mesoporous media

Abstract

The confinement of fluids and phase transition is of great interest for gas storage and separation in nanoporous materials. CO₂ adsorption at moderate temperatures is particularly critical for advancing carbon capture and storage. To this end, we investigate the CO₂ isotherm in Mobil Composition of Matter No. 48 (MCM-48), Mobil Composition of Matter No. 41 (MCM-41), and Santa Barbara Amorphous-16 (SBA-16) using a novel patented gravimetric apparatus. Comprehensive characterization of materials was performed using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscope (SEM), and environmental transmission electron microscopy (ETEM). Specifically, ETEM provided the details about the connectivity and the geometry of mesopores. The results reveal that the relationship between CO₂ adsorption capacity and surface area, as MCM-41, with the largest surface area and pore volume, exhibits a correspondingly the highest CO₂ uptake at bulk pressure and capillary pressure. In addition, it is also observed that smaller pores exhibit low chemical potential, indicating strong fluid-wall interaction and molecular-molecular interaction. The hysteresis was only observed in SBA-16 at −20 °C. Contrary to the traditional assumed pore-blocking effect in inkbottle structures, our findings suggested that pore geometry facilitated evaporation instead of blockage. This research highlights the temperature, pore shape and geometry effect on the storage capacity and adsorption mechanisms. Meanwhile, it compensates for the data gap od CO₂ isotherms in mesoporous material and further contribute to the development of efficient CO₂ capture and storage.