Carbon Dioxide Capture in Homogeneous and Heterogeneous Surfaces of Porous Silica Glass

Abstract

Experimental and simulation studies for carbon dioxide (CO2) adsorption on porous silica glass were performed to reveal how surface heterogeneity can affect the adsorption mechanism of CO2. In performing the simulation, the structure of porous silica glass was modeled as a slit pore consisting of parallel walls of connected SiO4 units. The adsorption isotherms of CO2 at 283 K were generated for a series of pore widths using a Monte Carlo ensemble. The defective surfaces created by random removal of surface atoms and the surfaces containing hydroxyl functional groups were chosen to represent the surface heterogeneity for the simulation tasks. The isotherms derived for the defective surfaces showed a rapid adsorption at low pressures because of the stronger interaction between the rough nonuniform surfaces and CO2 molecules. For the role of surface functional groups, the adsorption isotherms dramatically increased with an increasing number of functional groups. The amount of CO2 adsorbed for randomly placed functional groups was greater than that for the presence of functional groups at the pore edges. The proper control of surface heterogeneity by manipulating both the amounts of hydroxyl surface groups and surface defects should help enhance the efficient capture of CO2 in porous silica glass.

Interfacial stabilizing and reinforcing effects of silsesquioxane-based hybrid Janus molecules in extrusion supercritical CO2 foaming of polypropylene

“…As mentioned, owing to the better affinity of silica and silanol structures with CO 2 than PP and the good affinity of the nonpolar isobutyl groups with PP [30][31][32][33] it is expected that HOS could diffuse from the melt to PP-CO 2 interface during the foaming process, giving rise to the unique HOS arrangement illustrated in Fig. 1c.…”

“…1a and 1b. Since the organic groups in HOS are compatible with PP, while the inorganic part consisting of silanol and siloxane have better affinity with CO 2 than PP [30][31][32][33], we hypothesised that HOS may diffuse from the polymer melt to the PP melt-CO 2 interface during foaming to lower interfacial tension and stabilise the cells during their growth stage. This would lead to reduced diffusive gas loss, hence improving ER.…”