Hybrid Ionic Liquid–Silica Xerogels Applied in CO2 Capture

Abstract

The imidazolium-based ionic liquids (ILs) are solvents known for selectively solubilizing CO2 from a gas CH4/CO2 mixture, hence we have produced new hybrid adsorbents by immobilizing two ILs on xerogel silica to obtain a solid–gas system that benefits the ILs’ properties and can be industrially applied in CO2 capture. In this work, the ILs (MeO)3Sipmim.Cl and (MeO)3Sipmim.Tf2N were used at different loadings via the sol–gel process employing a based 1-methyl-3-(3-trimethoxysylilpropyl) imidazolium IL associated to the anion Cl− or Tf2N− as a reactant in the synthesis of silica xerogel. The CO2 adsorption measurements were conducted through pressure and temperature gravimetric analysis (PTGA) using a microbalance. SEM microscopies images have shown that there is an IL limit concentration that can be immobilized (ca. 20%) and that the xerogel particles have a spherical shape with an average size of 20 µm. The adsorbent with 20% IL (MeO)3Sipmim.Cl, SILCLX20, shows greater capacity to absorb CO2, reaching a value of 0.35 g CO2 / g adsorbent at 0.1 MPa (298 K). Surprisingly, the result for xerogel with IL (MeO)3Sipmim.Tf2N shows poor performance, with only 0.05 g CO2 / g absorbed, even having a hydrophobic character which would benefit their interaction with CO2. However, this hydrophobicity could interfere negatively in the xerogel synthesis process. The immobilization of ionic liquids in silica xerogel is an advantageous technique that reduces costs in the use of ILs as they can be used in smaller quantities and can be recycled after CO2 desorption.

Porous Aromatic Melamine Schiff Bases as Highly Efficient Media for Carbon Dioxide Storage

“…Porous nanocarbons with a small surface area (439 m 2 /g) provided a low CO2 uptake (1.94 mmol/g [30]. Ionic liquids in a silica matrix led to materials having a very small surface area (1-9 m 2 /g) and relatively poor sorption capacity towards CO2 as 0.35 g of CO2 per g of adsorbent [27]. As seen in Figures 10-13, Schiff bases 1-4 do not have an apparent adsorption-desorption hysteresis, which indicates the reversible adsorption of CO 2 within the Schiff base pores at the temperature and pressure used (323 K and 40 bars).…”

“…Porous nanocarbons with a small surface area (439 m 2 /g) provided a low CO 2 uptake (1.94 mmol/g [30]. Ionic liquids in a silica matrix led to materials having a very small surface area (1-9 m 2 /g) and relatively poor sorption capacity towards CO 2 as 0.35 g of CO 2 per g of adsorbent [27].…”

“…The adsorption capacity of calcium oxide is limited but sufficiently high to facilitate its use as an effective medium for CO 2 capture. Several other materials such as ionic liquids in a solid matrix [27], zeolites [28], silica [29], and those containing activated carbons [30][31][32] have been evaluated as CO 2 sorbents. Some of these materials possess unique thermal properties, high chemical stability, high surface area, tunable chemical structures, recyclability, and reusability.…”

Synthesis and use of carvedilol metal complexes as carbon dioxide storage media

“…On the other hand, porous nanocarbons that have small surface area (439 m 2 /g) leads to a lower CO 2 adsorption (1.94 mmol/g) [17]. Silica matrix contacting ionic liquids have a very small surface area (up to 9 m 2 /g) and poor CO 2 adsorption capacity (0.35 g of CO 2 per g of adsorbent) [15].…”

“…Materials with high adsorption capacity such as ionic liquids, zeolites, silica, and activated carbons have been used to capture CO 2 [14][15][16][17][18]. However, limited progress has been achieved since ionic liquids are expensive to recycle and zeolites are highly hydrophilic and not suitable for flue gases [19].…”