In this study, lipase A from Candida antarctica (CALA) was immobilized onto the macroporous resin NKA-9. Immobilization conditions (pH, time and CALA concentration) were studied, enzymatic activity and immobilization efficiency (IE) up to 968.89 U/g and 53.19% were respectively obtained under optimal conditions (immobilization pH 5.0, time 5 h and CALA concentration at 30 mg/mL). Then, the NKA-9 supported CALA (CALA@NKA-9) samples were used to catalyze glycerolysis in solvent-free system. With 0.25 g of the present CALA@NKA-9 (soybean oil 3.52 g and glycerol 0.184 g) and after 12 h reaction at 50 °C, diacylglycerols (DAG) content up to 64.37% and triacylglycerols (TAG) conversion at 83.33% were obtained. The relationship between temperature and TAG conversion was LnV 0 = 13.9310-6.4212/T for CALA@NKA-9. Meanwhile, the activation energy (Ea) of CALA@NKA-9 was calculated to be 53.39 kJ/mol. In addition, reusability in the glycerolysis reaction was also evaluated, and 57.82% of the initial glycerolysis activity was retained after 9 consecutive applications. Furthermore, the CALA@NKA-9 was also used to catalyze the esterification (esterification of fatty acids with glycerol), however, the present CALA@NKA-9 cannot initiate the esterification. Therefore, the present CALA@NKA-9 is shown to be potential for DAG production through glycerolysis reaction.
A composite hollow mesoporous MIL-101@Pd@ZIF-8-30min (HM-MIL@Pd@ZIF-30min) nanocatalyst with hollow core and stable shell was developed in this study. Hollow mesoporous MIL-101(HM-MIL) was hydrothermally synthesized and employed as the supports of Pd nanoparticles by adopting a facile HM-MIL-template strategy to make ZIF-8 crystals uniformly overgrew on HM-MIL-101@Pd microcrystal cores. The obtained core-shell catalyst possessed hollow mesoporous structure, and the shell layer of ZIF-8 had additional advantages of abundant Lewis basic sites for heterogeneous racemization reaction. Compared with unmodified HM-MIL@Pd and solid MIL-101(Cr)@Pd@ZIF-8 (S-MIL@Pd@ZIF-8), HM-MIL@Pd@ZIF-8-30min had higher racemic chemical activity (conv. 99%) and selectivity (sel. R-amide 94%) in one-pot dynamic kinetic resolution (DKR) reaction system of rac -1-phenethylamine. The catalyst showed excellent stability, and the conversion and selectivity reached 95% and 93% respectively after ten catalytic cycles.
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