Oxidation of 2,5-diformfylfuran to 2,5-furandicarboxylic acid catalyzed by Candida antarctica Lipase B immobilized in a cyclodextrin-templated mesoporous silica. The critical role of pore characteristics on the catalytic performance

摘要

Hypothesis: Porous silica has been extensively used as suitable carrier for the immobilization of various enzymes. Randomly Methylated 8-Cyclodextrin (RaMe8CD) has surface active properties and very high solubility in water and could therefore be used as template in the fabrication of silica particles with tunable pore size. Experiments: Silica particles were prepared by sol-gel process in alkaline medium with and without use of RaMe8CD. Lipase Bfrom Candida antarctica (CALB) was either incorporated within the pores of RaMe8CD-derived support or covalently attached on the surface of CD-free silica particles and its catalytic performance was assayed in the oxidation of 2,5-diformylfuran (DFF) to 2,5-furandicarboxylic acid (FDCA). Enzymatic reactors were characterized by N2-adsorption analysis, small angle XRD, TG/DSC experiments, ATR-FTIR spectroscopy, HRTEM and LSCM, while reaction products were determined based on 1H NMR spectroscopy combined with HPLC. Findings: Results showed that the use of RaMe8CD as structure directing agent led to mesoporous silica composed of uniform 8 nm-sized particles with 11 nm-sized mesopores compatible with the dimensions of CALB (3.0 nm ? 4.0 nm ? 5.0 nm). Incorporation of CALB within the pores of RaMe8CD-derived silica caused almost a two-fold increase in specific activity after 7 h at 40 ?C when compared to lipase immobilized on the surface of CD-free silica particles (33.2 ?mol g-1 min- 1vs. 14.4 ?mol g-1 min-1). Moreover, the RaMe8CD-derived biocatalyst demonstrated enhanced operational stability during the recycling experiments, retaining more than 90% of its initial activity after five 24 h-reaction cycles. These findings open up new avenues for future research on the use of cyclodextrins in the development of enzyme-based nanoreactors.