David A Parks

US Patent:

50063251, Apr 9, 1991

Filed:

Aug 28, 1989

Appl. No.:

7/399654

Inventors:

David L. Parks - Houston TX
Carl J. Martin - Houston TX

Assignee:

Air Products and Chemical, Inc. - Allentown PA

International Classification:

C01B 2146
C07C 7910

US Classification:

423390

Abstract:

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 solubilized nitroaromatic compounds in said spent acid. The improvement comprises initially heating the spent acid to a temperature of from about 120. degree. to 200. degree. C. for a time sufficient to convert said nitroaromatics in said spent acid to a nitroaromatic composition having a boiling point greater than 300. degree. 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. degree. to 200. degree. 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.