Hydrolysis of amide bonds in dipeptides and nylon 6 over a ZrO2 catalyst†

Hydrolysis of amide bonds is expected as a promising technology, namely in the fields of biorefinery using proteins and chemical recycling of plastics. For the model reaction of glycylglycine hydrolysis, ZrO₂ was found to work as an effective catalyst and afforded glycine in up to 97%-C under the optimum conditions, while acidic oxides and basic oxides were inferior to ZrO₂. The characterization using N₂ physisorption, XRD, NH₃-TPD, and CO₂-TPD revealed that the weight-basis activity of ZrO₂ correlated with its acidic and basic properties. ZrO₂ was demonstrated to be applicable to the hydrolysis of amide bonds: dipeptides with acidic or basic side chain into amino acids; small organic amides into both amines and carboxylic acids with their equivalent amounts; and nylon 6 into ε-caprolactam and ε-aminocaproic acid.