Lipase-catalyzed Continuous Ring-opening Polymerization of ε-Caprolactone in a Packed-bed Reactor

M. J. Zhang, E. Z. Su, J. P. Lin and D. Z. Wei

Abstract
A packed-bed reactor (PBR) system was developed for continuous lipase-catalyzed ring-opening polymerization of ε-caprolactone (ε-CL). The parameters affecting the poly(ε-caprolactone) (PCL) production in the PBR such as residence time, height to diameter (H/D) ratio, and monomer feed concentration were investigated. Monomer conversion of ε-CL increased with the increase of residence time, reached the highest (over 98 %) at the residence time of 12 min. And under this residence time it would almost not change even if the H/D ratio varied from 4 to 20 or the monomer concentration varied from 0.2 to 2.25 mol L–1. The number-average molecular mass (Mn) of PCL did not change in agreement with the monomer conversion, and approached the maximal values of 15600 g mol–1 with polydispersity index (PDI) of 2.1 under 20 min residence time, 12.0 H/D ratio and 1.75 mol L–1 monomer concentration. The Mn of PCL maintained around 15600 g mol–1 without appreciable loss during the long-term operation of 460 h with the PCL productivity of 19.15 g g–1 enzyme d–1).

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Keywords
Packed-bed reactor (PBR), lipase, ring-opening polymerization, poly (ε-caprolactone)