Mesoporous zeolite ZSM-5 synthesized via gel conversion with polyethyleneglycol as template and its catalytic performance

A simple strategy for synthesizing mesoporous zeolite ZSM-5 via gel conversion was successfully developed with polyethyleneglycol as mesopore directing agent. It is revealed that the gel obtained after 9-15 h evaporation of solvents could be transferred into mesoporous ZSM-5 zeolite after treatment at 160℃ for 24 h. However, pure ZSM-5 zeolite or mesoporous silica was achieved with too short or too long evaporation periods. The results indicate that the gelation process through solvent evaporation controls the hierarchical structure formation kinetically, which not only provides an appropriate amount of water for zeolite crystallization, but also prevents the phase-separation between zeolite and amorphous phases. Due to the introduction of the mesoporosity of several tens of nanometers in size, this hierarchical micro/mesostructured zeolite exhibits enhanced catalytic activities in the large molecules involved reactions, including aldol condensation of benzaldehyde with n-butyl alcohol and Pechmann reaction of resorcinol with ethylacetoacetate.