Metal-bipyridine supported on 3-aminopropyl-functionalized MK10: effect of a metalating agent on the catalytic activity in the transesterification of β-keto ester

Abstract

The grafting of metal-bipyridine (Bpy-M, M = Mn or Zn) on aminopropyl-modified montmorillonite K10 (NH₂-MK10) synthesized via a functionalization-immobilization-metalation route was investigated. Formulated NH₂-MK10-Bpy-Mn and NH₂-MK10-Bpy-Zn were characterized using BET, FTIR, SEM, XRD, CHNS and NH₃-TPD techniques and tested for the synthesis of butyl acetoacetate (BAT) via the transesterification of β-keto ethyl acetoacetate (EAA) with butanol (BTL). The influence of reaction parameters on the BAT yield was investigated using the Taguchi optimization approach. According to characterization data, the samples were mesoporous materials with a considerable number of acidic sites and diverse inorganic and organic functional groups, making them inorganic–organic hybrid catalysts. Optimization results showed that catalyst loading had the most significant impact on the BAT yield, followed by the BTL : EAA molar ratio and temperature, whereas the conversion time had the least impact on the reaction process. NH₂-MK10-Bpy-Mn outperformed NH₂-MK10-Bpy-Zn in the transesterification of β-keto EAA, achieving 96.1 ± 0.79% conversion compared to 87.3 ± 0.94% at 110 °C for 7 h with a BTL : EAA molar ratio of 1.4 : 1 and catalyst loading of 2.0 wt%. Both catalysts were reusable and maintained good stability, which indicate their great potential for catalyzing the transesterification of β-keto ester.