ORALS

The increase in carbon dioxide (CO₂) emissions from burning fossil fuels is the largest contributor to global warming of anthropic origin. Nevertheless, CO₂ is a nontoxic, nonflammable, and renewable feedstock. CO₂ utilization for the production of cyclic carbonates has gained great notoriety in the last decades because it is an environmentally benign alternative to reduce CO₂ emissions. Cyclic carbonates can be used as intermediates in the synthesis of fine chemicals, as monomers in polymerization reactions and as aprotic polar solvents. Cyclic carbonate is produced by cycloaddition of CO₂ with epoxides in the presence of catalysts due to CO₂ thermodynamical stability. Currently, the exploration of efficient catalysts for CO₂ coupling reactions is still necessary to promote an efficient reaction [1]. Ionic liquids (ILs) are salts composed of organic cations and organic or inorganic anions with melting point lower than 100°C [2]. These compounds have been proposed as homogeneous catalysts. The high price of ILs, however, and the difficulty to separate ILs from reaction media represent a barrier to implement them in the industry [3]. One solution for overcoming this disadvantage is silica xerogel functionalization with ILs [4]. In this study, a series of silica xerogels functionalized with imidazolium-based ILs ([BMIM][Cl], [BMIM][NTf2], [MBMIM][NTf2], [EMIM][NTf2], [EMIM][MSO₃] and [EMIM] [CF₃SO₃]) were synthesized by sol gel method and characterized by BET, RAMAN, TGA, FESEM and TEM. The catalytic performance of these compounds for CO₂ chemical transformation into cyclic carbonates by cycloaddition of CO₂ with epoxides was investigated. All cycloaddition reactions were performed at 40 bars and 110°C during six hours in a 120 cm³ titanium reactor equipped with magnetic stirring and temperature controller. The highest yield was obtained with [BMIM][Cl] (82.6%) and [EMIM][MSO3] (91.6%), both showing 99% selectivity. These results highlight the potential of these compounds as new catalysts.

References:
[1] L. Liu, S. M. Wang, Z. B. Han, M. Ding, D. Q. Yuan and H. L. Jiang, Inorganic Chemistry, 2016, 55, 3558-3565.
[2] R. M. Cuéllar-Franca and A. Azapagic, Journal of CO2 Utilization, 2015, 9, 82-102.
[3] A. Cherian, K. Robin, B. Jose and T. Roshith, Catalysis Surveys from Asia, 2015, 19, 223-235.
[4] Vidinha P, Augusto V, Almeida M, et al. Sol-gel encapsulation: An efficient and versatile immobilization technique for cutinase in non-aqueous media. J Biotechnol 2006, 121:23-33.