Organic solvent recovery and reuse in pharmaceutical purification processes by nanofiltration membrane cascades

Abstract

The recovery and posterior reuse of organic solvents is a very important aspect to be taken into account during the production processes by chemical, petrochemical, food, and pharmaceutical industries. Organic solvent nanofiltration is becoming more relevant and appears as a very promising way to carry out solute fractionation, concentration and purification, which can be considered exigent separation operations in organic media. Under optimal design conditions, organic solvent nanofiltration can be also an effective unit process to reduce organic solvent consumption by incorporation of closed-loop solvent recycling systems. Usually, single stage organic solvent nanofiltration processes can only be applied to relatively easy separations, so, most of the times, multiple membrane processes have to be integrated to carry out more complex separations. This research group has previous experience with the design of counter current membrane cascades to purify chemicals and has decided to make use of the acquired knowledge to advance in the design of continuous OSN membrane cascades with solvent recovery and reuse. The purification of an intermediate API precursor in methanol medium has been selected as case study. After the formulation of a valid simulation model for the membrane cascade, the design of the process has been pointed to find the best cascade configuration in terms of sustainable solvent consumption. The proposed solution is based on solvent recovery from one extreme of the cascade, purification, and recirculation of the recovered solvent to the other extreme of the cascade in order to improve its performance by avoiding too concentrated streams, which could cause solubility problems, without any additional fresh solvent stream.