REACTIONS BETWEEN HYDROCARBONS AND DEUTERIUM ON CHROMIUM OXIDE GEL. I. GENERAL
Sites for hydrogenation of olefins and for isotopic exchange between alkanes and deuterium are simultaneously developed by heating chromium oxide gel to higher temperatures. Above 470 deg C, the rate of loss of surface exceeds the rate of site production. There is little interaction among sites. Chromium oxide gel also catalyzes double bond migration but on sites which, at least in part, differ from those involved in hydrogenation and exchange. The major processes, simple isotopic exchange of one atom per adsorption step and simple cis-addition of deuterium atoms to the double bond, involve a monoadsorbed alkane which cannot revert to a diadsorbed alkane at temperatures below 300 deg C. 1t seems probable that olefin reacts with a surface hydrogen atom to form monoadsorbed alkane without proceeding through diadsorbed alkane. The preference for exchange of primary hydrogen atoms and the relative rates of exchange of a series of hydrocarbons suggest that the transition state separating alkane and monoadsorbed alkane involves some small contribution from carbanion. The very rapid exchange of cyclopropane probably results not only from this but also from isovalent hyperconjugation with surface sites in which a d-p pi -bond is involved. The minor processes, multiple deuteration in isotopic exchange and the spreading of isotopic distribution patterns in the addition of deuterium to olefin, cannot, in general, involve gas phase olefin as an intermediate. Because of the absence of the minor processes in ethane exchange and in the deuterogenation of ethylene, it seems probable that an adsorbed allylic species is the intermediate. (auth)
- Research Organization:
- Northwestern Univ., Evanston, Ill.
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-15-007255
- OSTI ID:
- 4118608
- Journal Information:
- Journal of the American Chemical Society (U.S.), Vol. Vol: 82; Other Information: Orig. Receipt Date: 31-DEC-61
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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