In situ polymerization of poly(vinylimidazole) into the pores of aEuroZhierarchical MFI zeolite as an acid-base bifunctional catalyst for one-pot aEuroZC-C bond cascade reactions

摘要

Poly(vinylimidazole)/hierarchical ZSM-5 has been prepared as a novel and efficient acid-base bifunctional catalyst by a simple method. First, the hierarchical ZSM-5 zeolite was synthesized by an indirect method from KIT-6 as a silica source. By this method, control of the zeolite crystallization was achieved due to the adjustment transformation processing of amorphous mesoporous silica to zeolite crystal. Then, vinylimidazole as a basic part was polymerized by an in situ method into the zeolite's pores. This acid-base bifunctional heterogeneous catalyst was characterized by FT-IR, TG-DTG, N-2 adsorption-desorption, TEM, SEM, NH3-TPD, and XRD. The catalyst has been applied to one-pot C-C bond formation tandem reactions including deacetalization-Henry reaction and deacetalization-Aldol condensation by the simple method at low temperature. Due to the uniform distribution of poly(vinylimidazole) in the micro-meso pores of the hierarchical zeolite reactants, the products easily pass through the catalytic active sites. The co-existence of acidic and basic sites in the structure of the catalyst has a crucial role in the superior activity of this catalyst. Moreover, the catalyst showed excellent recyclability and high activity even after 7 runs with aEuroZonly a 10% reduction in activity being detected.(sic).