Alternative Integrated Distillation Strategies for the Purification of Acetonitrile from Ethanol Ammoxidation

The feasibility and performance of different strategies to purify a complex mixture of H2O/CH3CN/NH3/HCN from bioethanol ammoxidation are compared. Dichloromethane as entrainer is taken as a base case and compared with more sustainable molecules, such as ethyl acetate (EA), ethylene glycol (EG) and glycerol (G). The thermodynamic behavior of the homogeneous or heterogeneous mixtures is first discussed. Then, the separation and purification section is designed accordingly. To yield high-purity acetonitrile a low-boiling entrainer (EA) is preferable. If economic issues prevail, then EG grants a lighter sizing of the equipment and lower heat duties. Similar recoveries of acetonitrile, ranging from 90 (EG and G) to 92% (DCM and EA) were achieved when comparing the different entrainers. Higher purities are obtained with the lower-boiling additives with respect to acetonitrile, leading to purity >99.99% for DCM and EA, >99.6% for EG and >99% for G. This acetonitrile purification section is part of a full integrated plant, newly designed for the production of this commodity from renewable sources, since no commercial examples of bioethanol-to-acetonitrile plants are disclosed in the literature.