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

Abstract

Nano structure including pore structure and amine assembly is critical for improving sorption and desorption kinetics for adsorptive CO 2 separation. The present work delineates (1) the influence of the nano-scale pore structure of amine-functionalized solid sorbents, and (2) effect of changing the assembly of amine molecules on surface of nano-porous SiO 2 on the rates of adsorption and desorption of CO 2 . 50PEI-MSN sorbent with inverted cone-shaped pores was prepared by using mesoporous silica nanospheres (MSN) with inverted cone-shaped pores for the loading of polyethyleneimine (PEI). Co-structure-directing (CSD) method was used to synthesize the sorbent with arranged amine assembly at nano-scale (2N-CSD). By comparison with 50PEI-SBA15 as a benchmark sorbent, both sorbents have improved sorption and desorption kinetics. There are significant effects of nano pore structure and amine assembly on the sorption and desorption kinetics. The inverted cone-shaped pores in MSN allow loading polymeric amines in their narrower ends and leaving larger pore mouths open for the transport of CO 2 ; 50PEI-MSN shows a maximum sorption rate of 81.4 mg•g −1 •min −1 with average sorption rate of 25.4 mg•g −1 •min −1 at 80 °C which are 34% and 59% higher than the corresponding values for 50PEI-SBA15; a maximum desorption rate of 38.4 mg•g −1 •min −1 with average desorption rate of 11.8 mg•g −1 •min −1 ramping from 30 to 95 °C which are 37% and 156% higher than the corresponding values for 50PEI-SBA15. The arranged monolayer-like amine assembly on surface of nanoporous SiO 2 likely provides high amine sorption sites through improved accessibility of amine, and 2N-CSD shows a maximum sorption rate of 60.5 mg•g −1 •min −1 , with average sorption rate of 12.8 mg•g −1 •min −1 at 30 °C which are 108% and 205% higher than the corresponding values for 50PEI-SBA15; a lower maximum desorption rate of 9.7 mg•g −1 •min −1 and average desorption rate of 9.8 mg•g −1 •min −1 ramping from 30 to 95 °C which is 250% higher than the corresponding value for 50PEI-SBA15. The present work demonstrates the importance of tailoring nano-scale pore structure and amine assembly for significantly improving sorption and desorption kinetics of adsorptive CO 2 separation.

Developing High-Capacity Solid “Molecular Basket” Sorbents for Selective CO2 Capture and Separation

“…Consequently, the 3-D MBSs exhibited a significantly higher CO 2 sorption capacity and a faster sorption rate compared with those of 1-D MBSs (Figure A). Additionally, the temperature dependence on 3-D MBS is much less than that of 1-D MBS, which can also be attributed to the 3-D pore structure facilitating CO 2 diffusion and promoting PEI dispersion (Figure B; the definition and details of the number of PEI coverage layers can found in ref ).…”

“…(C) Normalized sorption capacity of 2N-CSD, PEI-50/MSN, and PEI-50/SBA-15 at 30 °C (insets: TEM and SEM images of PEI-50/MSN). (D) Schematic illustration of CO 2 sorption over 2N-CSD, PEI-50/MSN, and PEI-50/SBA-15 sorbents [reproduced with permission from ref , copyright 2021 Springer].…”

“…Since then, amine-based solid sorbents have received increasing attention worldwide. The related research and publications increased considerably, as they demonstrate many advantages including high CO 2 capacity and selectivity, fast kinetics, good stability, and tolerance to water with no or less corrosion of the equipment. ,− They can also be applied to other applications such as biogas upgrading − and hydrogen purification. − This Account summarizes our efforts in developing MBSs for CO 2 capture and separation from various gas streams, from fundamental work including qualitative and quantitative characterization and sorption mechanism clarification − ,,,− to applications including CO 2 capture from real flue gases and bench-scale pilot testing. ,− …”

Improvement in CO2 Capture of Polyamine with Micro-Interfacial System

“…Silica (SiO 2 )-based materials have garnered significant attention for their capability to improve CO 2 capture. − Their high surface area, nanopore sizes, , and chemical stability render them ideal for CO 2 absorption. , Goeppert et al conducted a study on CO 2 adsorption using polyethylenimine (PEI M w 25000) deposited on fumed SiO 2 . The study found that the sample with 50 wt % PEI had a higher adsorption capacity of 1.71 mmol/g.…”

Polyethyleneimine-Modified Amorphous Silica for the Selective Adsorption of CO2/N2 at High Temperatures

“…Polyethyleneimine (PEI) has high CO 2 absorption capacity, which is used as a modifier to modify silica for improving CO 2 adsorption performance and selectivity. ,− The most commonly used method for constructing amine-silica adsorbents is the solvent impregnation method, in which amine can be uniformly dispersed on the silica. However, the silica with high amine loading is easy to agglomerate, and the use of organic solvents for dispersion also increases the production cost.…”