Temperature-Controlled Reaction−Separation for Conversion of CO2 to Carbonates with Functional Ionic Liquids Catalyst
The combination of activity and recovery of homogeneous catalysts is recognized as a great challenge in catalysis research from an industrial point of view. The reported homogeneous catalysts are usually more efficient, while it is costly to reclaim them from reaction products.
By contrast, heterogeneous catalysts can be easily separated from the products and reused. But they are inefficient, on the same time, the high temperatures and pressures are often demanded, which make them practically excess costs.
In this work, carboxylic acid-based ionic liquids (CAILs) were synthesized. They displayed temperature-dependent dissolution-precipitation transitions in propylene carbonate (PC) by controlling the chain length of carboxyl group. Such an unique phase behavior was successfully used for the cycloaddition reaction of CO2 with epoxides, the optimal ILs could show a 92% yield of PC within 20 min and quickly precipitate out from homogeneous system at room temperature for easy recycle.
The reversible phase transition phenomenon supplied an efficient way to combine activity and recovery of homogeneous catalysts, which is benefit for the energy saving and industrial application.