Design and fabrication of choline-functionalized shaped polymer catalysts for efficient catalytic synthesis of sec-butanol

Sec-butanol (SBA) is an important industrial medium-polar solvent, mainly used as methyl ethyl ketone precursor and in coatings, fuels, fine chemicals. Transesterification is its dominant synthesis route for economical feedstocks and easy downstream separation. However, industrial homogeneous catalysts suffer from separation difficulties, equipment corrosion, and poor continuous operability, and heterogeneous catalysts often exhibit relatively low catalytic activity. To balance catalytic activity and industrial application, a heterogeneous catalyst was firstly prepared by anchoring choline-based ionic liquids on swellable Ps-Cl (optimized swelling enhanced active site accessibility). Then, choline-functionalized supported shaped catalyst (Ps-Ch[IM]) was obtained via quaternization of macroporous styrene-based polymers with N,N’ -dimethylethanolamine (DMEA) and ion exchange. Under reaction temperature of 60 o C, alcohol-to-ester molar ratio 5:1, catalyst dosage 5 % (mass) and reaction time 240 min, Ps-Ch[IM] achieved 26.60% sec-butyl acetate (SBAC) conversion, surpassing reported literature results. DFT calculation and in situ DRIFTS confirmed that Ps-Ch[IM] activates methanol (MeOH) via [IM] - and SBAC via the OH group in DMEA; subsequently, CH 3 O* attacks the C=O bond in SBAC and combines with CH 3 CO* to form MA, while the proton combines with *OCH(CH 3 )CH 2 CH 3 to yield the target product SBA. Moreover, Ps-Ch[IM] shown stable performance in continuous fixed-bed reaction with the yield of 20.86% after 1800 min, indicates industrial application potential.