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

ABSTRACT 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.