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

• Published in: Research on chemical intermediates 2018, Vol.44 (5), p.3279-3291
• Main Authors: Javad Kalbasi, Roozbeh, Mansouri, Sanaz, Mazaheri, Omid
• Format: Article
• Language: English
• Subjects: Aldehydes; Ammonia; Cascade chemical reactions; Catalysis; Catalysts; Chemistry; Chemistry and Materials Science; Condensates; Crystallization; Inorganic Chemistry; Physical Chemistry; Polymerization; Polyvinylimidazoles; Porosity; Recyclability; Silicon dioxide; Zeolites
• ISSN: 0922-6168; 1568-5675
• DOI: 10.1007/s11164-018-3306-3

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, NH 3 -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 ‎only a 10% reduction in activity being detected.‎