Abstract
Parahydrogen enrichment on eleven first transition series metal oxides has been investigated at 77 and 90 °K over the pressure range 1 to 200 Torr (1 Torr = 133.3 N m
-2
). The order of activity at 77 °K and 10 Torr was found to be: Fe
2
O
3
> Co
3
O
4
> CoO > MnO > NiO > V
2
O
3
> Cr
2
O
3
> CuO > ZnO > V
2
O
5
> TiO
2
. This activity series is interpreted in terms of the paramagnetic mechanism in which the rate is dependent upon the magnetic properties of the metal ions arising from their 3
d
electronic configuration. Comparison of the pressure dependencies for enrichment with those of hydrogen adsorption isotherms at 77 and 90 °K suggests that enrichment occurs on a small fraction of the oxide surface. The rates of hydrogen–deuterium equilibration at 10 Torr have been measured on the eleven oxides at 297°K, and at 77 and 90°K both before and after exposure to hydrogen at 297°K. The order of activity at 297°K was found to be: Co
3
O
4
> CoO > NiO > Cr
2
O
3
> V
2
O
3
> ZnO > CuO > Fe
2
O
3
> MnO > TiO
2
> V
2
O
5
. This activity series confirms, at a single reaction temperature on well-sintered oxides, the twin-peaked activity pattern previously found for this reaction (Dowden, Mackenzie & Trapnell 1956). At 77 and 90 °K the simple twin-peaked activity pattern was not observed and high activity was confined to V
2
O
3
, Co
3
O
4
and NiO, and to CoO after exposure to hydrogen at 297°K.
Cited by
18 articles.
订阅此论文施引文献
订阅此论文施引文献，注册后可以免费订阅5篇论文的施引文献，订阅后可以查看论文全部施引文献