Green Nitration of Toluene Catalyzed by Lewis Acids Immobilized on Hβ Zeolite

In this study, we have successfully developed an environmentally benign methodology for synthesizing para -nitrotoluene ( p -NT) via catalytic nitration of toluene using nitrogen dioxide (NO 2 ) as the nitrating agent, with molecular oxygen (O 2 ) serving as an efficient promoter in the reaction system. The experimental results demonstrate that the Hβ zeolite-supported Lewis acid catalyst (AlCl 3 ) exhibits remarkable catalytic performance in the developed NO 2 –O 2 –Ac 2 O system, achieving a toluene conversion of 78.5% with a p -NT selectivity of 62.5%. To elucidate the structure–activity relationship, the physicochemical properties of various catalysts were systematically characterized using multiple analytical techniques, including nitrogen physisorption (BET), x-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), temperature-programmed desorption of ammonia (NH 3 -TPD), and scanning electron microscopy (SEM). On the basis of comprehensive catalytic characterization and density-functional theory (DFT) calculations, we propose a plausible reaction mechanism that accounts for the enhanced para -selectivity in the toluene nitration process within the NO 2 –O 2 –Ac 2 O catalytic system.