Single-Walled Zeolitic Nanotubes: Advantaged Supports for Poly(ethylenimine) in CO₂ Separation from Simulated Air and Flue Gas

Abstract

Previous research has demonstrated that amine polymers rich in primary and secondary amines supported on mesoporous substrates are effective, selective sorbent materials for removal of CO 2 from simulated flue gas and air. Common substrates used include mesoporous alumina and silica (such as SBA-15 and MCM-41). Conventional microporous materials are generally less effective, since the pores are too small to support low volatility amines. Here, we deploy our newly discovered zeolite nanotubes, a first-of-their-kind quasi-1D hierarchical zeolite, as a substrate for poly(ethylenimine) (PEI) for CO 2 capture from dilute feeds. PEI is impregnated into the zeolite at specific organic loadings. Thermogravimetric analysis and porosity measurements are obtained to determine organic loading, pore filling, and surface area of the supported PEI prior to CO 2 capture studies. MCM-41 with comparable pore size and surface area is also impregnated with PEI to provide a benchmark material that allows for insight into the role of the zeolite nanotube intrawall micropores on CO 2 uptake rates and capacities. Over a range of PEI loadings, from 20 to 70 w/w%, the zeolite allows for increased CO 2 capture capacity over the mesoporous silica by ∼25%. Additionally, uptake kinetics for nanotube-supported PEI are roughly 4 times faster than that of a comparable PEI impregnated in SBA-15. It is anticipated that this new zeolite will offer numerous opportunities for engineering additional advantaged reaction and separation processes.

Amine Sorbents for Sustainable Direct Air Capture: Long-Term Stability and Extended Aging Study

“…This reduction is quantitatively evident in the decrease in the BET surface area and pore volume, detailed in Table . With an increase in amine loadings, a greater decline in surface area and pore volume was observed, attributed to the filling of pores, a characteristic behavior observed in the functionalization of supports, consistent with findings from prior studies. ,,, …”

Ambient and sub-ambient temperature direct air CO2 capture (DAC) by novel supported in situ polymerized amines

“…26 Each class has its own set of pros and cons. Class I sorbents are the easiest to prepare and offer higher amine loadings, 2,27,28 but they suffer from stability issues due to amine leaching. 29 Class II sorbents are more stable due to chemical tethering but have lower CO 2 uptake and involve a more complex synthesis process.…”

Minimal Kinetic Model of Direct Air Capture of CO2 by Supported Amine Sorbents in Dry and Humid Conditions

“…The effect of water on CO 2 adsorption has been recently reviewed by Sayari and co-workers, 10 while Jones and co-workers have investigated many different types of porous supports loaded with poly(ethylenimine) (PEI). 34,35 Molecular simulations at both the molecular mechanical and quantum mechanical levels have been employed to understand the DAC of CO 2 and its interaction and reaction with amines as well. 36−39 A few recent kinetic modeling efforts have examined carbon capture under the DAC conditions.…”

“…Most of the experimental and modeling work on amines focused on much higher CO 2 partial pressures. ,− Enhanced CO 2 adsorption in the presence of H 2 O has been widely observed in amine adsorbents. ,− Moreover, other chemisorption systems using superbase-derived ionic liquids have been developed. , Although researchers have turned their attention to DAC conditions, ,, how sorbent properties and H 2 O affect CO 2 adsorption at DAC conditions is not well understood from a modeling perspective. − On the experimental side, Sayari, Jones, and many others have extensively examined amine-functionalized mesoporous silica for DAC. The effect of water on CO 2 adsorption has been recently reviewed by Sayari and co-workers, while Jones and co-workers have investigated many different types of porous supports loaded with poly­(ethylenimine) (PEI). , Molecular simulations at both the molecular mechanical and quantum mechanical levels have been employed to understand the DAC of CO 2 and its interaction and reaction with amines as well. − …”