Structural and Thermochemical Chemisorption of CO₂ on Li_4+x(Si_1–xAl_x)O₄ and Li_4–x(Si_1–xV_x)O₄ Solid Solutions

Abstract

Different Li(4)SiO(4) solid solutions containing aluminum (Li(4+x)(Si(1-x)Al(x))O(4)) or vanadium (Li(4-x)(Si(1-x)V(x))O(4)) were prepared by solid state reactions. Samples were characterized by X-ray diffraction and solid state nuclear magnetic resonance. Then, samples were tested as CO(2) captors. Characterization results show that both, aluminum and vanadium ions, occupy silicon sites into the Li(4)SiO(4) lattice. Thus, the dissolution of aluminum is compensated by Li(1+) interstitials, while the dissolution of vanadium leads to lithium vacancies formation. Finally, the CO(2) capture evaluation shows that the aluminum presence into the Li(4)SiO(4) structure highly improves the CO(2) chemisorption, and on the contrary, vanadium addition inhibits it. The differences observed between the CO(2) chemisorption processes are mainly correlated to the different lithium secondary phases produced in each case and their corresponding diffusion properties.

CO2 chemisorption and evidence of the CO oxidation–chemisorption mechanisms on sodium cobaltate

“…The DH à change may be related to different factors, such as the CO 2 chemisorptiondesorption equilibrium, intercrystalline diffusion processes and cobalt reduction. In addition, these k and DH à values are not substantially different from those reported for other sodium ceramics [18,20,47,48]. For example, the reported k values for Na 2 ZrO 3 are between 1 Â 10 À3 and 2 Â 10 À2 s À1 at the optimum CO 2 capture temperatures (i.e., 600-700°C) with a DH à value of 33 kJ/mol [18,20], and Na 2 TiO 3 exhibited a k values of 1.7-2.5 Â 10 À4 s À1 and a DH à value of 140.9 kJ/mol under the best capture conditions (i.e., 600 and 650°C) [49].…”

“…Equation (1) represents the different kind of vacancies. Therefore, these vacancies might improve the sodium diffusion through the structure during CO 2 chemisorption and CO oxidation-chemisorption, as it has been reported for other alkaline ceramics (Na 2 (Zr-Al)O 3 , Li 2+x CuO 2+x/2 and Li 4 (Si-Al)O 4 , among others [10,[20][21]24,48]). …”

“…In these cases, the alkaline element can diffuse easily, improving the CO 2 chemisorption process [18][19][20][21]24]. In addition, it has been probed that the formation of different structural defects on the alkaline ceramics modified the diffusion processes [10,24,48]. Therefore, the crystalline structure of this material might improve the sodium diffusion in the CO 2 chemisorption process.…”

High temperature capture of CO2on Li4SiO4-based sorbents from biomass ashes

“…Nowadays, high‐temperature absorbent materials such as hydrotalcites (HTLs) , calcium oxides , and lithium ceramics , attracted increasing attention. Among these materials, the lithium ceramics were considered as promising CO 2 captors, especially, lithium orthosilicate (Li 4 SiO 4 ) received further attention . For example, during the first few minutes, Li 4 SiO 4 can absorb four or more times more CO 2 than other lithium ceramics, such as lithium metazirconate (Li 2 ZrO 3 ) .…”

Catalytic Constructive Deoxygenation of Lignin-Derived phenols: New C–C Bond Formation Processes from Imidazole-Sulfonates and Ether Cleavage Reactions

“…Among the alkaline and/or alkaline-earth oxides, various lithium, sodium, potassium, calcium and magnesium ceramics have been proposed for CO 2 capture through adsorption and chemisorption processes [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. These materials can be classified into two large groups: dense and porous ceramics.…”