Green Acetonitrile

In 2008, the wheels fell off the supply train for acetonitrile, a key solvent used in high-performance liquid chromatography, synthesis of pharmaceuticals, and extraction of butadiene in refineries. The dire shortage, which lasted about a year, came about when the global economic downturn depressed acrylonitrile demand. Acetonitrile is typically derived as a minor coproduct of the process to make acrylonitrile, a building block for making fibers and resins used in automobiles and appliances. To help prevent the acetonitrile shortage from happening again, a team led by Rasmus Fehrmann at the Technical University of Denmark has devised an alternative acetonitrile synthesis (Green Chem., DOI: 10.1039/c3gc36513a). Chemists have been working toward producing the solvent by starting with ethanol and ammonia to make ethylamine, followed by oxidation of ethylamine to acetonitrile. The formation of ethylamine is already a commercial process, but the oxidation step is a work in progress that suffers from low conversion rates and unwanted by-products. Fehrmann and coworkers found a ruthenium oxide-alumina catalyst that facilitates the O₂ oxidation of ethylamine, rather than relying on a stoichiometric oxidizing reagent. The oxidation works under batch or continuous-flow conditions with up to 85% conversion rates and 90% acetonitrile selectivity. The catalytic O₂ oxidation route starting from bioethanol is a promising green, petrochemical-independent route to acetonitrile, the researchers say.