Process for the production of 4-nitrotoluene-2-sulfonic acid
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A process for the preparation of 4-nitrotoluene-2-sulfonic acid by sulfonating 4-nitrotoluene with oleum or liquid SO.sub.3 is described. The sulfonation is carried out continuously with oleum of at least 50% concentration or liquid 100% SO.sub.3 while keeping the conversion of 4-nitro-toluene in the reaction mixture at .gtoreq.90% during the entire reaction course.
The process is inherently non-polluting, and provides the product in high yield and low sulfuric acid content in a form usable for 4,4'-dinitrostilbene-2,2'-disulfonic acid production without further purification.