Regioselective nitration of o-xylene to 4-nitro-o-xylene using nitric acid over solid acid catalysts

Abstract

The regioselective nitration of o-xylene to 4-nitro-o-xylene (4-NOX) has been studied in the liquid and vapor phase over zeolites H-beta, H-ZSM-5 and silica supported molybdenum oxide (MoO3/SiO2) catalysts. Zeolite H-beta showed the maximum conversion of 28% and 63% selectivity for 4-NOX in liquid phase nitration at 70 °C with 70% HNO3. The conversion increased to 65% when the reaction was carried out in vapor phase at 150 °C using dilute 30% HNO3. The formation of α-methylphenyl nitromethane by alkyl nitration in liquid phase was decreased in vapor phase reaction. The formation of oxidation products was also decreased in vapor phase reaction with minor amounts of dinitro and ipso-products. The influence of experimental parameters such as temperature, nitric acid concentration and WHSV on conversion and selectivity has been investigated. The use of dilute nitric acid and the selective formation of 4-NOX using dilute HNO3 makes this process environmental friendly with a potential for commercialization