HIGH-TEMPERATURE ADSORPTION OF CARBON-MONOXIDE AND HYDROCARBON GASES OVER NICKEL AND PLATINUM CATALYSTS

The high-temperature (573 K) adsorption of ethene, propene, propyne, c arbon monoxide, and the high temperature co-adsorption of propyne-carb on monoxide have been studied over Pt/alumina and Ni/silica catalysts. The Pt catalyst was found to retain hydrogen from the reduction proce ss, this hydrogen being released by ethene adsorption at 573 K, wherea s when propene was adsorbed on the Pt catalyst no hydrogen was liberat ed, indicating that the adsorption of propene did not affect the surfa ce in the same manner as that of ethene. Equally, the deposit formed f rom ethene and propene adsorption, on the Pt catalyst, is not the same in nature or reactivity. However, the deposits formed from both prope ne and ethene adsorption on the Ni catalyst were very similar in natur e and reactivity. Propyne adsorption on the Pt catalyst was examined b y FTIR and revealed a totally different surface species than that deri ved from alkene adsorption. In general it was found that, with the Ni system, regeneration of adsorptive capacity could be achieved to some extent (dependent upon the gas being adsorbed) by treatment with dihyd rogen at 573 K, whereas such a treatment of the platinum catalyst had no obvious effect. Go-adsorption studies revealed that single adsorpti on behaviour was not reproduced in the presence of a second adsorbing gas. The extent of adsorption and the nature of the deposit from propy ne on the Pt system was modified, even though no carbon monoxide adsor ption was detected, while on the Ni system, although carbon monoxide w as adsorbed, the propyne adsorption was similar to that found in the a bsence of carbon monoxide.