Valorization Strategies in CO2 Capture: A New Life for Exhausted Silica-Polyethylenimine

Abstract

The search for alternative ways to give a second life to materials paved the way for detailed investigation into three silica-polyethylenimine (Si-PEI) materials for the purpose of CO₂ adsorption in carbon capture and storage. A solvent extraction procedure was investigated to recover degraded PEIs and silica, and concomitantly, pyrolysis was evaluated to obtain valuable chemicals such as alkylated pyrazines. An array of thermal (TGA, Py-GC-MS), mechanical (rheology), and spectroscopical (ATR-FTIR, ¹H-¹³C-NMR) methods were applied to PEIs extracted with methanol to determine the relevant physico-chemical features of these polymers when subjected to degradation after use in CO₂ capture. Proxies of degradation associated with the plausible formation of urea/carbamate moieties were revealed by Py-GC-MS, NMR, and ATR-FTIR. The yield of alkylpyrazines estimated by Py-GC-MS highlighted the potential of exhausted PEIs as possibly valuable materials in other applications.

Keywords: carbon capture; pyrolysis; silica-PEI adsorbent; solvent extraction.

Figure 4

ATR-FTIR plotting of the PQ4, SP0, SP2 and SP3 materials using VMS-DRAW [47].

Figure 1

Scheme of the outline of the present investigation.

Figure 2

From left to right: PQ4; SP0; SP2; and SP3 samples.

Figure 3

TGA thermograms of SP0 (A, black), SP2 (B, red), and SP3 (C, blue) in a nitrogen atmosphere.

Figure 5

TGA thermograms of (A) P0 (—), P2 (—), and P3 (—) in nitrogen atmosphere and (B) S0 (—), S2 (—), and S3 (—).

Figure 6

Viscosity curves of the lyophilized extracted PEI: P0 (black squares), P2 (red circles) and P3 (blue triangles).

Figure 7

¹³C NMR spectrum (zoom between 35 and 62 ppm) of samples P0 (black), P2 (red), and P3 (blue). The peak numbers indicate the carbon attribution given in the inset.

Figure 8

MS-pyrograms from Py-GC-MS at 600 °C of (from bottom to top) SP0 (green), SP3 (light blue), S3 (purple), P (red). The magnified pyrogram of P3 is also shown (red dotted line) with the mass spectra of GC peaks #1, #2, and #3, indicative of degradation. IS stands for internal standard.