Nitric acid continued purification

A mixture of 21 g 2,3-methylenedioxytoluene and 1 g Hg(OAc)2 in 59 mL acetic acid was stirred and heated to 80 °C. To this there was added, dropwise, 12.8 g of concentrated nitric acid. Heating and stirring was continued for 2 h. The reaction mixture was quenched by pouring it into ice-H20, and extracted with Et20. The extracts were pooled, dried with anhydrous MgS04, and the volatiles removed under vacuum. The orange solid residue was recrystallized from to provide 20 g (58%) of a mixture of the ortho- and meta-products, 2,3-methylenedioxy-5-nitrotoluene and 2,3-methylenedioxy-6-nitrotoluene, with a mp 65-67 °C. This unresolved mixture was employed in the next step without further purification. 

Serious consideration was given to the continuous manuf of TNT in the USA in 1953 (Ref 2). The known European continuous processes, seven in all, were studied and compared, and the Bofors Norell process was selected as clearly the best. This procedure entailed nitric acid crystn for purification of the crude TNT, as discussed below under Purification . A second study group again compared available continuous processes in 1967 (Ref 6). They selected the Swedish Nobel-Chematur Process as modified by Canadian Industries Ltd, using Na sulfite for the purification step. After still further modification, three lines based on this concept were installed at Radford AAP, and operation was... 

In one purification process (U.S Patent 3,202,481) potassium or sodium permanganate is used to oxidize the impurities Other oxidizing agents also can be used, such as persulfates or chlorates Molybdenum trioxide is used to form a complex with the oxidized phosphorus impurities. The nitric acid is contacted with the oxidizing agent and the molybdenum compound at the boiling point of the acid, and the acid is continuously removed by distillation. The oxidized impurities remain in the residue. As a result, the purified acid will contain less than 0.5 ppb by weight of arsenic and phosphorus. 

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