Solid Sorbents as a Retrofit Technology for CO₂ Removal from Natural Gas Under High Pressure and Temperature...

The capture of CO₂ under high pressure and temperature is challenging and is required in a number for industrial applications including natural gas processing. In this work, we examine the use of benchmark hybrid ultraporous materials HUMs for their potential use in CO₂ adsorption processes under high-pressure conditions, with three varying temperatures (283, 298 and 318 K). NbOFFOVE-1-Ni and SIFSIX-3-Ni were the selected HUMs given their established superior CO₂ capacity under low pressure (0-1 bar). Both are microporous with highly ordered crystalline structures as compared to the mesoporous hexagonal silica (Santa Barbara Anhydrous-15 (SBA-15)). SBA-15 was previously tested for both low and high-pressure applications and can serve as a benchmark in this study. Sorbent characterization using XRD, SEM, FTIR and N₂ adsorption were conducted to assure the purity and structure of the sorbents. TGA analysis were conducted to establish the thermal stability of the sorbents under various temperatures. High-pressure CO₂ adsorption was conducted from 0-35 bar using magnetic suspension balance (Rubotherm). Although the SBA-15 had the highest surface (527 m³/g) are of the three adsorbents, the CO₂ adsorption capacity (0.42 mmol/g) was an order of magnitude less than the studies HUMs with SIFSIX-3-Ni having 2.6 mmol/g, NbOFFIVE-1-Ni achieving 2.5 mmol/g at 298 K. Multistage adsorption isotherms were obtained at different pressures. In addition, results indicate that electrostatics in HUMs are most effective at improving isosteric heat of adsorption Q_st and CO₂ uptake. Higher temperatures had negative effect on adsorption capacity for the HUMs and SBA-15 at pressures between 7-9 bar. In SAB-15 the effect of temperature is reversed in what is known as a cross over phenomena.