Influence of Brønsted acid sites on chemoselective synthesis of pyrrolidones over H-ZSM-5 supported copper catalyst

Cu(0)/H-ZSM-5 was identified as a chemoselective catalyst in the reductive amination of levulinic acid for the synthesis of pyrrolidones at ambient pressure and in aqueous media. The chemoselective nature of Cu was explained by carbonyl interaction with surface Brønsted acid sites deduced by pyridine and acetone adsorbed in situ infrared (IR) spectroscopic studies in conjunction with N2O titration. A strong polarization of band at 1685 cm−1 and an increase in its intensity with a decrease in Si/Al ratio of the H-ZSM-5 was found to be a key factor in the reductive amination activity. Structure activity relationship was established using the physicochemical characteristics of the catalysts analyzed by XRD, BET-SA, H2-TPR, NH3-TPD and XPS analyses.