Cycloaddition of carbon dioxide to epoxides catalysed by supported ionic liquids. Issue 12 (30th May 2018) - Martínez-Ferraté, Oriol
Abstract : Simple hybrid silica-imidazolium based ILs as highly active and selective catalysts for the carbonation of epoxides in batch and continuous flow systems under mild reaction conditions. Abstract : Very simple and economical SiO2 supported ionic liquid phase (SILP) materials are efficient catalysts for the addition of CO2 to epoxides, producing cyclic carbonates in high yields (up to 99%) and selectivities (up to 99%). A range of ionic liquid (IL) concentrations (5–100 wt%), SiO2 -supported 1- n -butyl-3-methylimidazolium halides (SBMIm·X: X = Cl, Br and I) (1–7 ) and 1-ethyl-3-(3-(trimethoxysilyl)propyl)-imidazolium halides (SEPIm·X) (8, 9 ), were prepared and fully characterised. These hybrid materials are very active catalysts under mild reaction conditions (low temperature and atmospheric pressure or adsorbed CO2 ). Under the optimal reaction conditions ([S] = 3.34 mmol, [cat]/[S] = 0.50, P CO2 = 5 bar, T = 80 °C), the best SILP system yields maximum conversion in just 30 min and can be reused at least five times without a noticeable decrease in activity and selectivity. The catalytic system is also active when using a CO2 gas mixture from an industrial exhaust in both batch and continuous flow systems. A detailed structural and electronic analysis indicates that increasing the IL and water concentrations induces a solvation effect through the contact ion pair of the IL that drives the anions (Cl, Br and I) to the deeper regions of the confined space of SiO2 . The catalytic performance is directly related to the presence of the nucleophilic Br anion on the outermost exposed layer of the hybrid material.