Size effects in ethylene oxidation on silver catalysts. Influence of support and Cs promoter

✍ Scribed by S.N. Goncharova; E.A. Paukshtis; B.S. Bal'zhinimaev

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 966 KB
• Volume: 126
• Category: Article
• ISSN: 0926-860X
• DOI: 10.1016/0926-860x(95)00036-4

✦ Synopsis

A new method for preparing supported silver catalysts with a narrow particle size distribution has been developed. For crystals with a diameter ranging from 100 to 1000 ,~ the dependencies of reaction rates on size have been studied for epoxidation and deep oxidation of ethylene. For particles 300-500 in size the reaction rate was found to increase sharply. The concentration of ethylene ~--complexes with Ag + cations increased proportionally to the reaction rate. These w-complexes are assumed to be the only intermediates directing the reaction towards epoxidation. The ratio of the reaction rate to the concentration of zr-complexes was found to remain constant within a wide range of Ag crystal sizes including bulk silver samples. The influence of the support (a-A1203, SiO2) on the size effect relates to the secondary processes of ethylene oxide conversion. The factors that cause the catalytic size effect and the promoting effect of Cs are discussed.