The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Nov. 22, 1994
Filed:
Aug. 20, 1992
Eberhard Ritter, Morfelden-Walldorf, DE;
Hans Schafer, Bad Soden am Taunus, DE;
Thomas Vollheim, Hanau, DE;
Martin Schottler, Wiesbaden, DE;
Hoechst Aktiengesellschaft, Frankfurt am Main, DE;
Abstract
Process for the preparation of 2,5-di(phenylamino)terephthalic acid and dialkyl esters thereof in high purity. The invention relates to a process for the preparation of dialkyl 2,5-di(phenylamino)terephthalates of the formula (I) ##STR1## in which R is a hydrogen atom or a methyl group and R' is a methyl group or ethyl group, by dehydrogenation (oxidation) of the corresponding dialkyl 2,5-di(phenylamino)-3,6-dihydroterephthalate with oxygen, which comprises blanketing with oxygen a solution or suspension of the dialkyl 2,5-di(phenylamino)-3,6-dihydroterephthalate in aromatic hydrocarbons in a stirred vessel, circulating this reaction mixture via a spraying device, so that the sprayed reaction mixture is distributed over the reaction mixture present in the stirred vessel, the sprayed reaction mixture being mixed with the circulating gas. The process has the advantage of a short reaction time, combined with favorable space-time yields and simplicity in terms of apparatus.