CARRIER-MEDIATED TRANSPORT IN MEMBRANE REACTORS: DEACYLATION OF BENZYLPENICILLIN

A membrane reactor is potentially superior to conventional reactors such as, plug flow, continuous stirred tank, and batch reactors. Both, catalysis and product enrichment, can be effected by the use of an appropriate set of permselective and catalytic membranes. Previous membrane reactor experiments have employed synthetic membranes which are most suitable for mild operating conditions, such as those found in biological and biochemical processes. For this reason, a relevant enzymatic reaction was sought to demonstrate the practical application of membrane reactors. Because of its industrial importance in the preparation of semisynthetic penicillins, the enzymatic deacylation of benzylpenicillin to produce 6-aminopenicillanic acid was chosen as a candidate reaction system.; The membrane reactor studied consists of a two-layer composite of permselective and catalytic membranes. Reactant diffuses from a feed compartment through the permselective film into the catalytic membrane. The reaction product exits the membrane composite through a product compartment adjacent to the catalytic film. The permselective membrane is chosen such that it rejects the backdiffusion of product into the feed compartment. An immobilized liquid membrane (ILM) is used as the perm-selective film. Permeation of anionic species through the ILM is achieved by introducing a carrier species capable of forming ion-pairs which are soluble in the organic solvent confined in the liquid membrane. The use of this mode of transport has been incorporated into an integral membrane reactor model to predict reactor performance. The analysis leads to the realization that this permeation mode is also capable of increasing catalyst effectiveness by the proper modulation of the carrier species concentration on either side of the membrane composite.; The deacylation of benzylpenicillin was successfully conducted in a membrane reactor consisting of a composite of immobilized liquid and catalytic membranes. The permeation properties of the permselective membrane and enzymatic activity of the catalytic film were also characterized. Product concentrations almost five times greater than the feed reactant concentration were attained in reactor runs in which conversion was as low as 50%.