Hoechst Aktiengesellschaft

Josef Alfranseder

Siegfried Rebsdat

Sigmund Mayer

Josef Riedl

Iwo Schaffelhofer

A method for improving the activity of a used supported silver catalyst, used for the manufacture of ethylene oxide by reaction of ethylene with oxygen or air, which method consists essentially of:

Process for improving the activity of used supported silver catalysts

A method for making a silver catalyst by applying a promoter and a complex formed between a silver salt and a mixture of a tert.-alkyl amine and a sec.-alkyl amine to a heat resistant porous support and then thermally decomposing said complex to metallic silver.

Silver catalysts, and a process for their preparation

Silver catalysts, useful for the oxidation of ethylene to ethylene oxide, contain 3-20 percent by weight of silver and 0.003-0.05 percent by weight of potassium, rubidium, cesium, or a mixture thereof as a promoter present on a heat-resistant porous support to which they have been applied by several impregnating steps.

Silver catalysts, a process for their preparation, and their use in

Ethylene oxide and water are reacted in a reactor and the reaction product is subjected to distillation in a plurality of distillation columns, in the first columns water and components having a boiling point below that of monoethylene glycol and higher ethylene glycols, if any, being distilled off. To obtain extremely pure monoethylene glycol alkali metal compounds are added at a point between the reactor and the monoethylene glycol distillation column in an amount to adjust the pH of the product entering the latter column to a value of from 7 to 10. The monoethylene glycol obtained in this manner is especially pure and has very low UV absorption values. It is, therefore, especially suitable for the manufacture of polyester fibers.

Process for the manufacture of extremely pure monoethylene glycol

Supported silver catalysts, which should have as high an activity as possible, are employed for the manufacture of ethylene oxide by oxidizing ethylene by means of oxygen or air. A process is described for improving the activity of supported silver catalysts which have already been used, in which the used catalyst is first washed with an inert liquid containing ammonia and/or aliphatic amines and 1 to 1,000 parts, per 1 million parts of catalyst, of cesium, rubidium or a mixture thereof is then deposited on the washed catalyst. The deposition is generally effected with the aid of an impregnating solution containing the cesium and/or rubidium compounds in a suitable quantity. This process makes it possible to improve considerably the activity of supported silver catalysts which have already been in use for the oxidation of ethylene by means of oxygen or air.

Process for improving the activity of supported silver catalysts

The activity of supported silver catalysts, which have been used for the direct oxidation of ethylene to ethylene oxide with molecular oxygen or air and to which from 1 to 1,000 parts, per 1 million parts of catalyst, of cesium and/or rubidium have been applied, is improved by washing the catalyst with an inert liquid prior to the application of cesium and/or rubidium.

The activity of supported silver catalysts for the direct oxidation of ethylene to ethylene oxide with molecular oxygen or air is improved by applying to the catalyst from 1 to 1,000 ppm, preferably 20 to 500 ppm, of cesium and/or rubidium in two or more than two steps and using the catalyst after each impregnation step again for the production of ethylene oxide by direct oxidation of ethylene with molecular oxygen or air.

The activity of supported silver catalysts used up in the direct oxidation of ethylene with molecular oxygen or air is improved by impregnating the catalyst arranged in a fixed bed with a solution of a caesium and/or rubidium compound in an inert organic solvent, optionally together with up to 40% by weight of water, calculated on the total liquid, as dissolving intermediary, so as to produce a concentration gradient of from 0.3 to 20 parts of caesium and/or rubidium per 1 million parts of catalyst and per meter of fixed bed, counter to the direction of flow of the gas to be reacted. In this manner the activity of the catalyst is considerably improved which results in an increased selectivity of the oxidation of ethylene to ethylene oxide.

The efficiency of silver carrier catalysts having reduced activity for the manufacture of ethylene oxide by reacting ethylene with oxygen or air is improved by impregnating the used catalyst with a solution containing cesium and/or rubidium compounds, an aliphatic alcohol and at most 10% by weight of water. After impregnation the alcohol and optionally the water are evaporated. The cesium and/or rubidium content of the impregnating solution and the number of impregnations are adjusted to obtain on the carrier a cesium and/or rubidium concentration of from 1 to 1,000 ppm.

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Hofschallern, Germany

Josef Alfranseder