| abstract |
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. |