Template Removal from SBA-15 by Ionic Liquid for Amine Grafting: Applications to CO₂ Capture and Natural Gas Desulfurization

Abstract

A new ionic liquid treatment method has been developed for removing the organic template from mesoporous silica SBA-15. Compared with conventional template removal by air calcination, the novel ionic liquid treatment method efficiently removed the organic template at a low temperature and preserved the surface silanol groups. The significantly increased silanol density led to higher amine loadings on amine grafted SBA-15. Consequently, the ionic liquid treated sample showed 63% more CO 2 capacity at conditions relevant to CO 2 capture from flue gas. Moreover, the ionic liquid treated sample exhibited significantly higher capacities for H 2 S capture from natural gas as well as CO 2 adsorption capacities for direct air capture which were nearly 3 times higher than the conventionally treated sample. The adsorbent stability, the isosteric heats of adsorption, and the effect of moisture were also investigated for the ionic liquid treated sample. The mechanism of template removal by ionic liquid is discussed, and the feasibility of recovery/reuse of the ionic liquid and the template is shown.

SBA-15 Functionalized with Amines in the Presence of Water: Applications to CO2 Capture and Natural Gas Desulfurization

“…Thermal analysis was conducted on all dry and wet grafted adsorbents to determine the amine loadings. Weight loss before 150 °C is due to the removal of atmospheric CO 2 and adsorbed water; as such, it was omitted. ,− The decomposition of the grafted amine occurs above 150 °C and leveled off around 600 °C. As shown in Figure , the amine loadings of dry grafted conventional and pore expanded SBA-15 were 26 and 28%, respectively.…”

“…The thermogravimetric data was used to calculate the diffusion time constant. The diffusion time constant ( D/R 2 , where D is the pore diffusivity and R is the radius of the particle) is used to express the uptake rates. ,,, The calculated D / R 2 values are outlined in Table . As listed in Table , the uptake rates for wet grafted SBA-15-PE are significantly higher than those of wet grafted SBA-15.…”

“…In contrast, chemically grafted adsorbents are tightly tethered to the support and are less susceptible to these issues. Chemically grafted adsorbents, however, do not achieve the high capture capacity of wet impregnated adsorbents due to lower amine loadings brought on by limited availability of surface silanol groups. − In order to increase the amines loaded during the chemical grafting process, water is added during the grafting process. We hypothesize that water addition hydrates the adsorbent surface (increasing the hydroxyl groups) and also leads to the polymerization of the aminosilanes via siloxane bridges of free aminosilanes to other grafted aminosilanes as proposed by Feng et al and Harlick et al , …”

Impacts of nano-scale pore structure and organic amine assembly in porous silica on the kinetics of CO2 adsorptive separation

“…Compared to those of 2N-CSD sorbent, the worse sorption performance of 2N-SBA15 is consistent with its disordered amine assembly. Sorption capacities of 2N-CSD, 50PEI-MSN, and other sorbents reported in published papers are summarized in Table 4 [3,[41][42][43][44][45][46][47][48]. Compared to sorbents with their sorption capacity reported at 30 °C, 2N-CSD sorbent shows superior sorption capacity.…”

“…Sorption capacity of 2N-CSD and 50PEI-MSN in comparison with other sorbents reported in the Refs [3,[41][42][43][44][45][46][47][48]. …”