Sustainable electro-organic synthesis of dicarboxylic acids from biogenic shellac

Abstract

Shellac, a bioresin secreted by insects on trees is used as a coating in various applications. However, due to transesterification and polymerization, shellac and in particular its solutions have a limited shelf life. This work demonstrates the electrochemical degradation of this shellac waste stream to value-added dicarboxylic acids using activated nickel anodes. After optimisation of the shellac hydrolysis and electrolysis, we obtained up to 51% pimelic acid and 71% azelaic acid, with respect to the maximum theoretical amount. The reaction was successfully scaled to 12.5 g of shellac and isolated using distillation of the corresponding methyl esters. A green metrics comparison with the ozonolysis of oleic acid shows that our method is significantly safer.