Spectroscopic Investigation into Oxidative Degradation of Silica‐Supported Amine Sorbents for CO₂ Capture

Abstract

Oxidative degradation characteristics of silica-supported amine sorbents with varying amounts of tetraethylenepentamine (TEPA) and polyethylene glycol (PEG; P200 or P600 represents PEG with molecular weights of 200 or 600) have been studied by IR and NMR spectroscopy. Thermal treatment of the sorbents and liquid TEPA at 100 °C for 12 h changed their color from white to yellow. The CO2 capture capacity of the TEPA/SiO2 sorbents (i.e., SiO2-supported TEPA with a TEPA/SiO2 ratio of 25:75) decreased by more than 60 %. IR and NMR spectroscopy studies showed that the yellow color of the degraded sorbents resulted from the formation of imide species. The imide species, consisting of NH associated with two C—O functional groups, were produced from the oxidation of methylene groups in TEPA. Imide species on the degraded sorbent are not capable of binding CO2 due to its weak basicity. The addition of P200 and P600 to the supported amine sorbents improved both their CO2 capture capacities and oxidative degradation resistance. IR spectroscopy results also showed that TEPA was immobilized on the SiO2 surface through hydrogen bonding between amine groups and the silanol groups of SiO2. The OH groups of PEG interact with NH2/NH of TEPA through hydrogen bonding. Hydrogen bonds disperse TEPA on SiO2 and block O2 from accessing TEPA for oxidation. Oxidative degradation resistance and CO2 capture capacity of the supported amine sorbents can be optimized through adjusting the ratio of hydroxyl to amine groups in the TEPA/PEG mixture.

Comparative Study of Molecular Basket Sorbents Consisting of Polyallylamine and Polyethylenimine Functionalized SBA‐15 for CO2 Capture from Flue Gas

“…[57] It is clear evidences howingt hat the oxidative degradation of PEI-I(50)/SBA-15 occurredd uring the heat treatment process.I nc ontrast, over the PAA(50)/SBA-15 sorbent after 260 ho fh eat treatment, although the same new IR band at 1659 cm À1 was also observed, the intensity was much lower compared with the PEI-I(50)/SBA-15 sample after 260 ho fh eat treatment (Figure 10 B). [45,[66][67][68][69][70][71] The oxidative degradation of the amine polymer was also supported by the color change in the sorbenta fter 260 ho fh eat treatment.…”

Applicability of linear polyethylenimine supported on nano-silica for the adsorption of CO2from various sources including dry air

“…58 who studied the oxidative degradation of silica supported pentaethylenehexamine (PEHA), the methylene groups in immediate proximity to the amino groups can undergo oxidation in the presence of oxygen to form mostly amide and imide groups (Scheme 2). Sayari et al…”

Experimental and Theoretical Investigation of SO2 Adsorption over the 1,3-Phenylenediamine/SiO2 System

“…The presence of the sulfate anion at the amine site may behave as an oxidizing agent, leading to the oxidation and formation of the −NO 2 and CO species. 77 The oxidation of the amine sites were also accompanied by an increase in IR intensity at 1682 cm −1 , corresponding to the formation of a CO group, suggesting the oxidation of the aromatic ring produced a quinone type species. The carbon oxidation also corresponded to a decrease in the IR intensity for the ν(C−H) vibration at 3042 cm −1 .…”