Ultra-low-cost synthesis of amine modified MCM-41 for CO2 capture

AQUINO, GUILLERMO D.; BENEDICTTO, GERMÁN P.; MORENO, MARIO S.; PEREYRA, ANDREA M.; BASALDELLA, ELENA I.

Buenos Aires

Congreso; 11th World Congress of Chemical Engineering; 2023

Asociación Argentina de Ingenieros Químicos

The increase in CO2 concentration in the atmosphere contributes to global warming, which is currently one of the major environmental problems. An alternative to mitigate CO2 emissions are the combined use of carbon capture and storage (CCS) technologies, which is becoming increasingly relevant to science. Efforts are focused on achieving more efficient use of already available adsorbents, seeking to improve adsorption capacity and reduce its synthesis costs. Among them MCM-41 mesoporous silica presents high specific surface area and functionalization potential to be used as adsorbent.In this context, the objective of this work was to synthesize MCM-41 silicas using inexpensive sources of silicon and surfactant and to compare their performance in CO2 adsorption with those obtained using traditional raw materials.The low-cost MCM-41 were obtained by hydrothermal synthesis using an industrial sodium silicate and less expensive industrial hexadecyltrimethylammonium chloride. A traditional tetraethylorthosilicate-based Sol-Gel synthesis was employed to obtain a reference sample of MCM-41.SEM images presented a marked difference in the morphology and particle size of the solids obtained using different raw materials. The MCM-41 synthesized using TEOS produced spherical particles with a mean diameter of 0.7 μm. In the case of the silicas obtained from the industrial reactants, they presented an irregular morphology with an average diameter of 50 μm. SAXS analysis showed that low-cost silicas have a higher ordering degree, evidenced by the higher definition of the reflections. TEM images displayed textural properties and long-range ordering consistent with the results obtained by SAXS. The N2 adsorption/desorption results exhibited specific surface values above 1100 m2/g for solids obtained by both routes. However, the sample synthesized from sodium silicate presented a significantly higher pore volume.Both MCM-41 were functionalized with 3-aminopropyltrimethoxysilane by the grafting method [1].The carbon dioxide adsorption capacity of the support and the amino-modified MCM-41 was analyzed using a Quantachrome Autosorb iQ sortometer. While the not modified silicas present a low sorption capacity, the functionalized materials notably increase the CO2 sorption. The chemisorbed gas increased from 70-90 μmol/g for the support to above 750 μmol/g for the amino-MCM-41. The best performance was achieved by the low-cost MCM-41, with a chemisorption capacity about 800 μmol/g.The results indicated that hydrothermal synthesis using an industrial reactant promoted the obtention of MCM-41 with superior textural features and greater pore ordering than those obtained through the TEOS-based sol-gel process. This fact combined with the amine-funcionalization contributed to increasing CO2 adsorption. Besides, the proposed synthesis allowed to decrease in the manufacturing cost by 80%.