Synthesis and Application of Encapsulating Metal/Sulfonic Dual‐Acid Based Phosphotungstic Acid Ionic Liquids

Abstract In recent years, ionic liquids have been widely used for industrial acid‐catalysis. The enhancements of the acidity and immobilization of ionic liquids have been drawing increasing attention from researchers. In this study, dual‐acid based phosphotungstic acid ionic liquids (PWILs) modified by a variety of metal ions (Fe 3+ , Cu 2+ , Al 3+ ) and sulfonic acid group (−SO 3 ) were synthesized. They were subsequently embeded into B‐SBA‐16 mesoporous molecular sieves with acidic sites to produce a plurality of encapsulating metal/sulfonic dual‐acid based phosphotungstic acid ionic liquids (M n PWIL/B‐SBA‐16s) composite catalysts. The structural properties, thermal stability, and encapsulation of the as‐fabricated composite catalysts were systematically investigated by FT‐IR, BET, SAXD, TEM, TG‐DSC and XPS. Moreover, the catalytic performances of the composite catalysts were evaluated using the ketalization of cyclohexanone with ethylene glycol as a model reaction. Among the different composite catalysts, Al 0.50 PWIL/B‐SBA‐16 showed the highest cyclohexanone conversion of 94.05 % and the maximum cyclohexanone glycol ketal yield of 83.45 %. Meanwhile, this catalyst still exhibited superior catalytic properties after five cycles of the catalytic reaction. These results demonstrate the high activity and durability of the novel ionic liquid composite catalyst.