Green aniline breakthrough claimed

Researchers at the University of Glasgow have published a paper demonstrating a new and more environment-friendly method of creating anilines at room temperature and pressure using a redox mediator. This builds on over a decade of work on mediators, said project lead Dr Mark Symes (pictured) in Cell Reports Physical Science.

Anilines, which are widely used in dyes, plastics, insulation and pharmaceuticals, including paracetamol, have traditionally been made by reacting nitrobenzenes with hydrogen at high temperatures and pressures, often using precious metal catalysts. “These processes …are energy-intensive, frequently inefficient, and can create chemical waste by-products,” the team stated.

The newly developed method involves passing an electrical current through water, into which a redox mediator has been dissolved. This collects the protons and electrons produced by electrolysis of water and deliver these to the nitrobenzenes, while also preventing direct electro-reduction of nitrobenzenes at the electrode surface and thus reducing the generation of by-products.

The paper, ‘High Yield and Selective Electrocatalytic Reduction of Nitroarenes to Anilines using Redox Mediators’, also demonstrates the effectiveness of their technique by reducing 12 different types of nitrobenzenes to form anilines, ranging from those commonly used in industry to more unusual products, like ortho-iodides, which are difficult to create by other methods. Yields of >99% were achived in four cases

“Electrochemistry is inherently scalable, so we believe that it would be possible to stack mediator modules to enable industrial production of anilines,” Symes said. “If those large-scale reactions were powered using renewable sources of electricity, it could go a long way towards making the $11 billion aniline production industry more environmentally-friendly.”