Highly selective vapor phase nitration of toluene to 4-nitro toluene using modified and unmodified H3PO4/ZSM-5

The nitration of toluene has been studied in the vapor-phase at various temperature over a series of surface modified and unmodified ZSM-5 (Si/Al = 60-170) loaded with H3PO4, differing in the external surface treatment of the zeolites. All samples were characterized by element chemical analysis, X-ray diffraction, N2 physisorption, thermal analyses and FT-IR.. When the external surface of the zeolite is blocked with a surfactant before loading it with H3PO4, the selectivity to form the 4-nitrotoluene was higher. This superior performance of the externally blocked catalysts, relative to the unmodified H3PO4/ZSM-5 catalyst, shows that by blocking the external surface area of the ZSM-5 support, it exhibits a superior catalytic selectivity than the unmodified catalyst. Catalysts containing 0–4.9 wt.% P were prepared using modified and unmodified ZSM-5 zeolites, and their catalytic performance for vapor phase nitration of toluene to 4-nitrotoluene (4-NT), 2-nitrotoluene (2-NT) and oxidation products was determined. The effect of reaction temperature, H3PO4 content, feed ratio of HNO3 to toluene, WHSV and carrier gas flow rate was also investigated.