Hisao Kanoh

Supported silver catalysts for the oxidation of ethylene: The effects of thermal treatment of alumina as catalyst support

Silver (40Vertical Bar3< by wt) was supported on alumina prepared from hydrogel by heat treating at 300/sup 0/-1800/sup 0/C. With increasing alumina treating temperature, the catalyst surface area decreased from 171 to 0.37 sq m/g. The activity for ethylene oxidation at 250/sup 0/C increased with increasing surface area from approx. 70Vertical Bar3< conversion (0.37 sq m/g) to 100Vertical Bar3< approx. 10 sq m/g, 1150/sup 0/C pretreatment temperature), and the selectivity for ethylene oxide decreased with increasing surface area (0.37-10 sq m/g) from approx. 60Vertical Bar3< to zero. Pulsed kinetic studies on the oxidation of ethylene, ethylene oxide, and acetaldehyde, and of ethylene isomerization to acetaldehyde at 230/sup 0/-270/sup 0/C showed that ethylene oxide isomerization occurred on the alumina support as well as on silver and was always slower than acetaldehyde oxidation to carbon dioxide on the silver; that direct oxidation of ethylene to carbon dioxide occurred and that it was the predominant reaction on catalysts pretreated at high temperature and unsupported silver; and that the formation of carbon dioxide via ethylene oxide was the preferred path on catalysts pretreated at lower temperatures.

Gas chromatographic determination of the products of degradation of polyethylene over a silica—alumina catalyst

Abstract The degradation products of polyethylene, especially a liquid fraction, formed over a silica-alumina catalyst were analyzed by glass capillary column gas chromatography. The liquid fraction contains large amounts of the same isoalkanes and aromatics as are present in the gasoline fraction of petroleum. Most of the isoalkanes are monobranched with a methyl group at the 2- or 3-position. The aromatics consist mainly of those with one or more methyl groups and are produced highly selectively at carbon numbers higher than 7. The degradation products are distributed in a narrow range of carbon number compared with those obtained by thermal degradation. The relative yield Of C 3 C- 5 fractions was greater than 70 wt. % at the initial stage of the reaction. Isomerization, aromatization and hydrogen transfer reactions seem to play an important role in the secondary degradation of the primary products of polyethylene.

Epoxidation of ethylene over silver catalysts modified by sodium chloride

the selectivity of epoxide synthesis in the direct oxidation of ethylene is increased to 85–87% by addition of sodium chloride to the silver catalyst; this selectivity corresponds to the maximum expected by mechanistic studies.