Dynamit Nobel Aktiengesellschaft

Heinrich Bunger

Rudolf Cordes

Otto W Bleh, Deceased

Gerhart Hoffmann

Gerhard Hoffmann

A process for the recovery and reuse of heavy metal oxidation catalyst from residues in the Witten DMT process by extraction, which involves mixing and settling of the residue with water or dilute aqueous solutions of water-soluble, low-molecular, aliphatic monocarboxylic acids at 70.degree.-160.degree. C. and recycling of the extract of the high-boiling distillation residues into the DMT process. The high-boiling distillation residue and the extractant are used in a quantitative ratio of 1:0.9 to 1:0.1, preferably 1:0.5 to 1:0.3.

Process for the recovery and reuse of heavy metal oxidation catalyst

A process for effecting the recovery and use of a heavy metal oxidation catalyst from a high-boiling distillation residue obtained during the Witten process for the production of dimethyl terephthalate involves the extraction of the high-boiling distillation reside with water or dilute aqueous solution of low molecular weight aliphatic monocarboxylic acids or alcohols and recycling of the extract into the oxidation stage of the Witten process. In the extract the quantitative ratio of the sum of the amount of trimellitic acid and monomethyl ester of trimellitic acid to the amount of heavy metal catalyst is controlled to be at a value of no more than 1.8:1 and in the oxidation stage of the Witten process the catalyst concentration (c), expressed in p.p.m., is represented by the formula:

Method for obtaining and reusing of oxidation catalyst in the Witten DMT

A process for producing dimethyl terephthalate from high-boiling tarry residues from the combined oxidation of p-xylene and p-toluate in the liquid phase, esterification of the resulting acids with methanol and separation of the resulting dimethyl terephthalate which include the steps of subjecting the high-boiling residues to treatment with methanol at temperatures above 250.degree. C. and thereafter separating the resulting dimethyl terephthalate in accordance with conventional separation techniques.

Process for the preparation of dimethyl terephthalate

A process for the production of dimethyl terephthalate and intermediate products of the dimethyl terephthalate manufacture from the high-boiling by-products obtained during the air oxidation of p-xylene and methyl p-toluate in the liquid phase, subsequent esterification of the thus-formed acids, and separation of the thus-produced esters, which comprises treating said high-boiling by-products with methanol at an elevated temperature and then separating the resultant product rich in dimethyl terephthalate by distillation with the addition of a carrier gas or a carrier vapor.

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Siegburg, Germany

Heinrich Bunger