Captura de CO2 usando líquidos iônicos dicatiônicos imobilizados em sílica com propriedades magnéticas e não magnéticas

Abstract

The gases responsible for the greenhouse effect have become a major environmental problem, especially anthropogenic emissions, with the burning of fossil fuels such as coal, oil and gas. CO2 has become a gas with a strong environmental impact, due to the large emissions generated since the beginning of the industrial era. A series of technologies for capturing and storing CO2 to mitigate this gas have been developed and applied. Currently, post-combustion using aqueous amines solutions is benchmark technology. However, this solvent presents a series of problems such as the high demand for water, corrosivity in equipment, chemical degradation and high energy consumption for regeneration, generating a high cost. Ionic liquids (IL) immobilized on solid mesoporous supports have emerged as an interesting alternative to solve such problems, since ILs have negligible vapor pressure, are not corrosive, present high thermal stability, lower energy requirement for regeneration and selectivity for CO2, while mesoporous silica supports are inert, have catalytic and adsorptive applicability, with well-defined pores, high specific surface area and thermal stability. Supporting ILs in solid support can overcome the IL disadvantages as high viscosity and mass transfer limitation. Dicationic ionic liquids (DILs) have demonstrated a greater selectivity capacity for CO2 capture than conventional liquids, being a possibility to enhance the functionality of the materials. As well as magnetic ionic liquids, which are a new generation that has demonstrated the possibility of an increase in the selectivity of gas capture from the influence of an external magnetic field. In this work, three based-imidazole cation DILs connect by polyethylene glycol, immobilized on a commercial silica mesoporous support (SBA-15) were obtained. Selectivity up to ~3.8 times greater than the pure support for CO2/N2 mixtures, increasing from 3.22 (±0.45) to 12.27 (±0.72) for SBA@DIL_FeCl4 was obtained. The ability to capture CO2 at low pressures and temperatures (1 bar and 25°C) was similar for both the pure SBA- 15 [58.61 (±0.93) mg CO2/g] and SBA@DIL_FeCl4 [57.31 (±0.02) mg CO2/g]. The improvement in selectivity and the constancy in CO2 sorption capacity indicates the DIL as a good option for CO2 capture.