Tunable Acid-Base Bifunction of Hierarchical Aluminum-Rich Zeolites for the One-Pot Tandem Deacetalization-Henry Reaction.

ABSTRACT

The development of bifunctional catalysts is important in the synthesis of materials for multiple sequential reactions in one-pot tandem catalytic processes. In this context, a dealuminated acid-base bifunctional catalyst with a hierarchical aluminum-rich faujasite structure (zeolite Y) has been successfully prepared by the solid-state dealumination of NaX nanosheets with ammonium hexafluorosilicate (AHFS). The characteristic properties of catalysts were examined by means of XRD, SEM, TEM, N2 physisorption technique, ICP-OES, NH3 -TPD, CO2 -TPD, 27 Al NMR, 29 Si NMR, Al K-edge XANES, and Pyridine-FTIR. The materials exhibit a superior catalytic performance for one-pot tandem catalysis, for example, the synthesis of trans-ß-nitrostyrene with a yield close to 100 % in a tandem deacetalization-Henry reaction of benzaldehyde dimethyl acetal with nitromethane. The high catalytic performance is attributed to the facile transfer of bulky molecules between acid and basic sites in the presence of hierarchical structures.