The Importance of Acetonitrile in the Pharmaceutical Industry and Opportunities for its Recovery from Waste

Acetonitrile is regarded as a key solvent in the pharmaceutical
industry. However, the volatility in acetonitrile supply in recent
years, coupled with its relatively poor environmental profile, has
presented significant challenges to its use in manufacturing processes
and laboratories. This study investigates the importance of acetonitrile
in the pharmaceutical industry and critically examines several options
for reducing the exposure of the industry to future supply problems
whilst also improving its life cycle management. The physicochemical
properties of acetonitrile were compared with other typical process
solvents and the Conductor-like Screening Model (COSMO) surfaces and
sigma profiles were used to help explain the favorable solvation behaviour
of acetonitrile. Several options for the replacement or recovery and
recycle of acetonitrile were critically examined in the contexts of
environmental, technical, and economic feasibility. Azeotropic distillation
was found to be the most likely approach to recovering acetonitrile
from aqueous waste streams. Several potential breaking agents were
assessed against a range of selection rules based on residue curve
maps, determined using the Universal Functional Activity Coefficient
(UNIFAC) method, and potential processing issues. A range of ionic
liquids were screened via the predictive Conductor-like Screening
Model for Realistic Solvation (COSMO-RS) approach and several promising
candidates were identified. Experimental vapor–liquid equilibria
studies were carried out, confirming the feasibility of ionic liquid-enhanced
azeotropic distillation as a novel approach to acetonitrile recovery.