Production of alkylene oxides and catalysts thereof

A catalyst for the production of an alkylene oxide by oxidation of the corresponding olefine with oxygen which comprises silver supported on a porous heat resisting support which has a specific surface area in the range 0.05 to 10 m.sup.2 /g as measured by the Brunauer Emmett and Teller method, the catalyst also comprising more than 16 .mu.gram equivalents of potassium per square meter of surface area of the catalyst, the said amount being also more than 1.5.times.10.sup.-5 gram equivalents per gram of catalyst, together with at least one other alkali metal selected from rubidium and cesium, the said potassium and rubidium and/or cesium being present in a form which is extractable by contact with water.