| 摘要 |
A process of manufacturing dimethyl terephthalate by oxidising para-xylene or mixtures containing para-xylene and para-toluic methyl ester in a reaction zone with oxygen or an oxygen containing gas at an elevated temperature, preferably in the presence of an oxidation catalyst, esterifying the oxidation mixture with methanol at an elevated temperature, preferably under pressures of from about 20 to 250 atmospheres and further oxidising the esterification products of the crude esterification mixture, possibly after it is freed from dimethyl terephthalate, by recycling to the said process or by oxidising the products per se with oxygen or an oxygen-containing gas, esterifying the oxidation mixture and isolating the dimethyl terephthalate comprises the improvement of distilling the esterification products, before they are further oxidised, with methanol vapour from the crude esterification mixture and separating them by removing methanol and water and possibly dimethyl terephthalate from the distillate of this condistillation. The term condistillation is employed to mean the distillation method wherein methanol vapour, preferably superheated is passed through a liquid crude esterification mixture, thereby volatilizing two or more components of the mixture. The mixture obtained from the condensate after separation of the methanol is oxidised with oxygen or oxygen containing gases preferably after the addition of fresh para-xylene and an oxidation catalyst such as lead or zinc acetate, cobalt naphthenate, manganese cumate, cobalt or manganese bromide optionally with the addition of hydrogen peroxide or dibenzoyl peroxide and in the presence of methanol. Examples are furnished in which cobalt ethyl hexanoate is employed as catalyst. Apparatus for carrying out the processes is described with reference to Figures (not shown). Specification 727,989 is referred to. |
