Facile fabrication of silica aerogel supported amine adsorbent pellets for Low-concentration CO2 removal from confined spaces

Abstract

Amine-based adsorbents show promise for removing low-concentration CO2 from environmental control and life support systems (ECLSSs), while the powder adsorbents are facing the challenges of reaction non-uniformity, pressure drop and material elutriation. To solve the problems, amine-based adsorbent pellets are fabricated by the extrusion–spheronization (ES), agar-assisted moulding (AM) and graphite-casting (GC) methods. The adsorbent pellets are further modified with pore-forming template for improved CO2 adsorption performance. The influences of granulation and pore-forming template modification on the structure-performance relationships of the adsorbent pellets are investigated. Granulation exerts adverse effect on the pore structure of tetraethylenepentamine supported on silica gel (TEPA-SG) adsorbent, which is not conducive to the bulk diffusion of CO2, and the CO2 adsorption capacity and kinetics thus have been impaired. The TEPA-SG-ES adsorbent pellets prepared by the extrusion–spheronization method show a relatively higher CO2 capture capacity of 1.01 mmol CO2/g due to better textural parameters and uniform dispersion of amine species. Thanks to the extrusion process, the adsorbent pellets also exhibit good mechanical properties with a high compressive strength of 10.90 MPa and low abrasion index of 0.36%. Both the textural properties and CO2 uptakes of the pellets can be restored upon template modification, and the promoting effect depends on the different templates employed due to their distinct pyrolysis rates and pathways. Mechanical properties will be adversely affected by the doped pore-forming template. The TEPA-SG-ES-UA pellets prepared with urea modification exhibit a great CO2 capture capacity of 1.48 mmol CO2/g and good mechanical properties with a high compressive strength of 4.90 MPa and a low abrasion index of 0.87%, and it could be a nice adsorbent candidate for removing low-concentration CO2 from ECLSSs.