Medium and reaction engineering for the establishment of a chemo-enzymatic dynamic kinetic resolution of rac-benzoin in batch and continuous mode

摘要

The effect of the reaction parameters water activity and reaction solvent was investigated for the dynamic kinetic resolution (DKR) of rac-benzoin with immobilized Lipase TL as biocatalyst for transesterification and the heterogeneous chemo-catalyst Zr-TUD-1 (Si/Zr = 25) for in situ racemization. Overall dry reaction conditions led to the best results for both catalysts. The immobilized lipase in a more environmentally benign solvent like cyclopentyl methyl ether (CPME) exhibited a 1.6-fold higher activity and an up to 1.5-fold higher half-life time than in the standard solvents such as toluene and 2-methyltetrahydrofuran (2-MeTHF). Among a variety of deep eutectic solvents (DESs) choline chloride:isosorbide (ChCI:lso) was found to be suitable for the reaction system. The activity was lower than in the aforementioned solvents, but the very low solubility of the product (S)-benzoin butyrate in ChCI:lso compared to the investigated organic solvents possesses great potential with respect to downstream processing. Optimized reaction parameters (dry CPME) were applied for DKR in batch and continuous mode yielding comparable or slightly better results than in toluene or 2-MeTHF. (C) 2014 Elsevier B.V. All rights reserved.