Construction of trifloaluminate ionic liquid catalyst on the silica surface dedicated for continuous flow Diels-Alder synthesis

Supported ionic liquid phases (SILP) are efficiently use for the construction of highly active, heterogeneous and recyclable catalysts. In this study, three strategies towards chemical immobilization of trifloaluminate ionic liquid catalyst into microporous/mesoporous silica support were investigated. The order of silica surface modification with trifloaluminate ILs components had crucial influence on the catalytic activity and stability which was tested in the model Diels-Alder reaction between isoprene and maleic anhydride in acetonitrile at room temperature. The best catalytic performance (maleic anhydride conversion > 97% in ten reaction cycles) was achieved for catalyst created through the synthesis of trifloaluminate ionic liquid in the first step with further bounding to the silica surface using 25 wt% of ionic liquid loading. The effective transformation of the Diels-Alder reaction to continuous flow synthesis led to 97% maleic anhydride conversion over 432 h with a TOF of 104.3 h⁻¹ and significantly improved process sustainability.