Acid‐free and highly efficient one‐step nitration of naphthalene with NO2 promoted by O2‐Ac2O in Fe‐ and Cu‐modified S2O82−/ZrO2 catalyst to 1,5‐dinitronaphthalene under mild conditions

Abstract

AbstractIt is crucial to develop an acid‐free, mild, and efficient strategy for preparing 1,5‐dinitronaphthalene (1,5‐DNN) from naphthalene (NT). This work presented a one‐step NT nitration method using NO2 conjugated to an O2‐Ac2O system over Fe‐/Cu‐modified S2O82−/ZrO2 catalyst (). The effects of different nitration systems and Fe‐/Cu‐modified ZrO2 with various sulphur sources on NT nitration have been studied. Under optimal conditions, 99.5% of the NT conversion with 56.9% selectivity to 1,5‐DNN was obtained. Synergistic catalysis between the strong acid site and the current nitration system remarkably improved the 1,5‐DNN selectivity. The characterization results demonstrated that the appropriate Fe/Cu metals loadings combined with the covalent persulphates promoted the formation of more active tetragonal ZrO2. Chemical bonding of Zr4+ with S2O82− species allowed S6+ more electrons to withdraw than in SO42− species, which led to stronger acidity and better catalytic activity in the catalyst. Moreover, a plausible catalytic nitration reaction mechanism was proposed. The findings revealed that mild reaction conditions, combined with a solid superacid catalyst and NO2‐O2‐Ac2O system, offer significant advantages in reducing acid wastewater discharge and increasing target product selectivity.