Catalytic performance of H-β nanozeolite microspheres in one-pot dynamic kinetic resolution of aromatic sec-alcohols

In this paper, uniform H-β nanozeolite microsphere (β-ZMS) prepared by polymerization-induced colloid aggregation, combined with an immobilized lipase B from Candida antarctica (commercially available Novozym® 435), is applied as a racemization catalyst to the one-pot dynamic kinetic resolution (DKR) of aromatic sec-alcohols. The DKRs of various aromatic sec-alcohols can be carried out with high selectivity and conversion under optimum conditions. Importantly, it is found that, compared to commercial zeolites β (C-β), β-ZMSs display high selectivity for small sec-alcohol molecules because their shorter microporous channels reduce the diffusion time of substrate/product in the three-dimensional framework, and thereby decrease the possibility of secondary reactions. However, the β-ZMSs show a high racemization rate in the DKR of large sec-alcohol molecules, such as racemic 1-(1-naphthyl)-ethanol, thanks to their abundant accessible active sites. This observation will not only benefit the performance of acidic zeolite catalysts in one-pot DKR systems but also provide a new perspective on the application of nanozeolites in catalysis.

Graphical abstractUniform H-β nanozeolite microsphere (β-ZMS) performs excellently in the racemization of aromatic sec-alcohols in DKR processes. It is found that β-ZMSs show different advantages for the one-pot DKR of small and large substrate molecules, owing to their special shorter micropore channels and more accessible acidic sites compared to commercial zeolites β.Figure optionsDownload full-size imageDownload high-quality image (165 K)Download as PowerPoint slideHighlights► β-ZMS is applied as racemization catalyst to one-pot DKR of various aromatic sec-alcohols. ► The use of β-ZMS greatly improves the performance of zeolite catalyst in one-pot DKR system. ► β-ZMS shows very different advantages for the DKR of small and large sec-alcohols molecules. ► β-ZMS displays high racemization selectivity for small aromatic sec-alcohols. ► β-ZMS shows high racemization rate for large aromatic sec-alcohols.