Scale-up of a Pervaporation Membrane Reactor for the Transesterification Production of Butyl Acetoacetate

The use of pervaporation membranes assisted reactors for chemical reaction processes has attracted much attention. Since pervaporation membranes permit selective removal of a component from a mixture, the membrane reactor systems have the potential to significantly increase the product yield and the reaction rate of equilibrium-limited reactions via controlled removal of the byproduct from the reaction mixture. Thermodynamically limited reactions, such as transesterification reactions, have alcohol byproduct generated. If the alcohol byproduct is selectively removed, enhanced yield over that conventionally achieved is possible. Thus, transesterification reactions are well-suited for the use of a membrane reactor system.

β-Keto esters are versatile intermediates in organic synthesis, and have extensive uses in the construction of natural products and other biologically active heterocyclic molecules. n-Butyl acetoacetate is an important β-keto ester and it can be synthesized by the transesterification of methyl acetoacetate with n-butanol using acid catalysts. In this study, a series of membrane reactor systems with various scale and complexity was developed for the transesterification of methyl acetoacetate with n-butanol to n-butyl acetoacetate and methanol catalyzed by immobilized lipase Novozym 435. All hybrid systems consisted of a stirred tank reactor and an external membrane module. The membrane systems investigated include flat sheet membranes and hollow fiber modules. The employed perfluorinated membrane modules are commercially available and are manufactured by Compact Membrane Systems. Our results indicate that the enhanced membrane reactor can selectively remove the byproduct methanol and achieve a 100% conversion, nearly 55% in excess of that achieved in the conventional system. All membrane modules have a high permselectivity of methanol over butanol. This presentation will discuss the performance of different scales of membrane reactors for transesterification at temperature of 30°C. We will also discuss the stability of membrane modules employed in the presence of aggressive reaction chemicals.