Evaluación de la captura de gases Hidrofluorocarbonados R-32, R-125, R-134a en liquidos Ionicos Fluorados mediante metodos computacionales.

Abstract

Hydrofluorocarbon gases (HFCs) are mainly emitted by air conditioners, and other anthropogenic activities¹. They contribute to the greenhouse effect (F-GHG), due to their high Global Warming Potential (GWP). The design of alternatives requires the recycling of low to moderate GWP compounds from current refrigerant mixtures representing a challenge for the refrigeration industry. However, there is no developed and standardized technology available to recover them, and once the life cycle of the refrigeration equipment is over, most of the gases are incinerated². The environmental impact of fluorinated gases (F-gases) requires the development of green technologies to mitigate them. Fluorinated ionic liquids (LIFs) emerged as an alternative absorbent due to their unique and exceptional properties³. The gases HFCs, difluoromethane (R-32), pentafluoroethane (R-125) and 1,1,1,2-tetrafluoroethane (R-134a) have been captured with fluorinated ionic liquids (FILs) [C₂C₁Im][NTf₂], [C₂C₁Py][NTf₂], [C₂C₁Im][BETI], [C₂C₁Py][BETI], based on the imidazolium and pyridine cation⁵ ⁶.

In this work, an optimization of the geometries is carried out by Density Funtional Theory (DFT) at the level of theory B3LYP/6-311++G*(d, p) of Gaussian 09 and Gaussian view. for HFCs gases (R-32, R-125 and R-134a) with fluorinated ionic liquids (FILs) reported in literature such as [C₂C₁Im] [NTf₂], [C₂C₁Py] [NTf₂], [C₂C₁Im] [BETI] y [C₂C₁Py] [BETI]. In addition, FILs [P₂₂₂₂][BETI] and [P₂₂₂₂][NTf₂] are proposed as potential solvents for the capture of HFCs. Therefore, the geometric optimization of the cation, anion, cation-anion gas HFCs and the LIFs-gas complex is carried out by means of a mechano-quantum analysis that allows to evaluate the interactions of the H bonds of each HFCs gas with the LIFs based on the imidazolium, pyridine and phosphonium cations. Finally, the binding energies of these molecular systems are calculated and compared, concluding that the best ionic liquids that could capture the hydrofluorocarbon gases R-32, R-125 and R-134a depending on their bond energies are [C₂C₁Im][NTf₂], [C₂C₁Py][BETI], and [C₂C₁Py][BETI], respectively, calculated using the BSSE by DFT at the theory level B3LYP/6-311++G*(d, p) gaussian 09. By vibratory analysis of the complexes [C₂C₁Im][NTf₂], [C₂C₁Py][NTf₂], [P₂₂₂₂][NTf₂], [C₂C₁Im][BETI], [C₂C₁Py][BETI], [P₂₂₂₂][BETI] with the hydrofluorocarbon gases R-32, R-125 and R-134a, the simulated spectra of the capture of the gases by the FILs are obtained.