| 摘要 |
Ethylene and other ethylenic hydrocarbons are oxidized to ethylene oxide and other oxides in the presence of a silver catalyst, e.g. as described in Specifications 663,257 and 728,821, [both in Group III], which has been activated or reactivated by treatment with an aqueous alkaline solution of a hydrate or salt of the following:-hydrazine, an alkyl or aryl hydrazine, hydroxylamine, or an alkyl or arylhydroxylamine (see Group III). In examples, a mixture of air and ethylene is passed at 250 DEG C. over a silver-calcium catalyst which has been intentionally poisoned with a gas containing a halogen, a hydrogen halide, hydrogen sulphide, or sulphur dioxide and then reactivated with alkaline solutions of hydrazine sulphate, phenylhydrazine sulphate, and hydroxylamine sulphate.ALSO:A silver catalyst for the oxidation of ethylenic hydrocarbons is activated or reactivated by treatment with an aqueous alkaline solution of a hydrate or salt of the following:- hydrazine, an alkyl or aryl substituted hydrazine, hydroxylamine, or an alkyl or aryl substituted hydroxylamine Suitable compounds are the hydrate nitrate, formate, oxalate, or sulphate of hydrazine or of its methyl, ethyl, benzyl, phenyl, tolyl, or p-tolyl derivatives, or the hydrates or salts of hydroxylamine or of its methyl, ethyl, propyl, benzyl, phenyl, or p-tolyl derivatives. The preferred concentration of the treating solution is 0..1-0.2M and the excess of alkali (e.g. sodium hydroxide) 0.02-0.1M. Treatment may be for 30 minutes to 1 hour at about 50 DEG C., after which the catalyst is washed and dried. Before treatment, the catalyst may be intentionally poisoned by contact with a gas containing a halogen, a hydrogen halide, hydrogen sulphide, or sulphur dioxide. The silver catalysts may be as described in Specifications 663,257 and 728,821 and may consist of alloys of silver with one or more of the metals calcium, magnesium, barium, and strontium, some of which metal has been removed by treatment with water or dilute acid. In examples alkaline solutions of hydrazine sulphate, phenylhydrazine sulphate, and hydroxylamine sulphate are used to reactivate a silver-calcium catalyst used in the oxidation of ethylene to ethylene oxide. |
