PROCESSO PARA A RECUPERACAO DE ACIDO NITRICO

摘要

This invention relates to an improved process for the recovery and regeneration of nitric acid from spent acid obtained from the mixed acid nitration of aromatic compounds. In that process a mixed acid of sulfuric acid and nitric acid is contacted with an aromatic composition at a temperature and pressure sufficient for producing a nitroaromatic composition and a spent acid containing unreacted nitric acid, sulfuric acid and solublized nitroaromatic compounds in said spent acid. The improvement comprises initially heating the spent acid to a temperature of from about 120 to 200 DEG C for a time sufficient to convert said nitroaromatics in said spent acid to a nitroaromatic composition having a boiling point greater than 300 DEG C at atmospheric pressure and then flash distilling the hot spent acid containing nitroaromatics compositions at a pressure from about 5 to 15 psia and temperature of 150 to 200 DEG C. Nitric acid is removed as an overhead vapor fraction in preselected concentration and sulfuric acid and nitroaromatics are obtained as a bottoms liquid stream from said flash distilling step. The nitroaromatics are then removed from the liquid stream. Sulfuric acid obtained from this process is essentially free of color and suited for concentration.