Mechanism of 2,4-dinitrotoluene hydrogenation over Pd/C

Hydrogenation of 2,4-dinitrotoluene (DNT) to 2,4-diaminotoluene (DAT) has been carried out over a 5% Pd/C catalyst. Gas chromatography and liquid chromatography have been used to detect the reaction intermediates. 4-Hydroxylamine,2-nitrotoluene (4HA2NT) is the main reaction intermediate. The two amino-nitro compounds 4-amino,2-nitrotoluene (4A2NT) and 2-amino,4-nitrotoluene (2A4NT) are the other relevant intermediates found. 4HA2NT decomposes by exposure to air and in the GC injector thus complicating the analysis of the reaction mixture. A simple procedure has been developed to perform the GC analysis without interference of the hydroxylamine. A kinetic study has been also carried out and a reaction pathway has been proposed. Intermediates are formed from DNT through three parallel reactions. They are then hydrogenated to the final product DAT by a series of consecutive reactions.