Environment-Friendly Nitration Of O-xylene

Aromatic nitro-compounds are kind of important intermediates for organic synthesis, which have being widely utilized in the fields like pharmaceuticals, pesticides, dyes, spices, explosives and plastics industry. The intensive-processing products produced from their derivatives are obtaining high added value, therefore, further development and application of aromatic nitro-compounds could obtain significant benefits both in economic and social aspects.Several nitration chemical methods, as well as research progress of catalysts, which have been used for clean nitration of aromatic compounds in recent decades and indicated with high industrialization potentials, have been reviewed in this paper. Furthermore, o-xylene generated in petrochemical industry with a lower added value, has been employed to prepare higher value-added3-nitro-o-xylene as a nitration model substrate, and it also shows up great significance in the aspect of green environment protection.1. Several laboratory commonly-used Lewis acids have been used as catalysts to convert o-xylene to3-Nitro o-xylene through catalytic nitration reactions, and the reaction parameters like reaction time, reaction temperature, solvents and dosage of catalyst have been experimentally optimized, thereinto, Cu(NO3)2involved as a catalyst. A optimum reaction condition has been indicated by the experimental results:o-xylene and concentrated nitric acid with a molar ratio of1:3,1,2-dichloromethane as solvent, phase transfer catalyst (PTC) charging quantity with5mol-%, and reacting8hours under reflux. Corresponding conversion rate could exceed99%, and additionally, there were no multiple-nitro products generated.2. Four mixed metallic oxides catalysts (C1-C4) were prepared by using a co-precipitation method, and their catalytic effectiveness on nitration of o-xylene were compared, and C3catalysts represented a best catalytic performance. Under using of same C3catalytic system, reaction substrates were extended, including polycyclic aromatic compounds, and they could be effectively converted into corresponding nitro-compounds with yields between75%-98%.3. Through using mixed metallic oxides catalyst, nitration reaction indicated some obvious advantages like mild reaction conditions, simplified operation, easy post-treatment and environment-friendly etc., and it is becoming an important supplement to the existing nitration methods. Meanwhile, with the use of such catalytic system, some remarkable disadvantages which originated in the traditional nitration methods, like generating large quantity of waste acids, extreme reaction conditions, non-convenient operation and high requirements on equipments, could be fundamentally avoided, and a good commercial application prospect is highly expected.