Self-catalytic immobilization of choline-based ionic liquid on SiO2 and its application in transesterification for sec-butanol synthesis

Sec -butyl alcohol (SBA) is a crucial chemical intermediate and solvent in organic synthesis. The transesterification of sec -butyl acetate (SBAC) with methanol (MeOH) is a key SBA production process due to straightforward reaction conditions and raw materials easily available, but conventional catalysts suffer from high corrosivity and poor recyclability, increasing costs. Herein, we report a series of novel heterogeneous catalysts of TEOS-[Ch][Im]- x with differential loading amount of choline imidazolate ([Ch][Im]) supported on SiO 2 . [Ch][Im], for the first time, is employed not only as a basic catalyst to facilitate the formation of SiO 2 , but also as a catalytic moiety immobilized on the SiO 2 matrix via H-O hydrogen bonds, thus enabling the fabrication of efficient SiO 2 -based catalysts through a one-pot reaction. By optimization of catalytic conditions for optimal catalyst TEOS-[Ch][[Im]-12, over 50% SBAC conversion is achieved in 60 min, and the conversion rate reaches 61.58% under the reaction temperature of 67 ℃ , nMeOH: nSBAC = 8.8:1, and catalyst dosage 9 wt% conditions after response surface methodology (RSM) optimization. More importantly, the catalyst exhibits excellent reusability and cycling stability without any noticeable deactivation over five consecutive reaction cycles. Density functional theory (DFT) calculations and in situ diffuse reflectance infrared Fourier transform spectroscopy ( in situ DRIFTs) results further confirm that the functionalized [Im] − anions could activate methanol to form the key adsorbed CH 3 O* intermediate, which then undergoes a nucleophilic reaction with SBAC to yield SBA. This facile synthetic strategy thus endows the catalyst with considerable application potential for green catalytic transesterification processes.