High-temperature adsorption of carbon monoxide and hydrocarbon gases over nickel and platinum catalysts
The high-temperature (573 K) adsorption of ethene, propene, propyne, carbon monoxide, and the high temperature co-adsorption of propyne–carbon monoxide have been studied over Pt/alumina and Ni/silica catalysts. The Pt catalyst was found to retain hydrogen from the reduction process, this hydrogen being released by ethene adsorption at 573 K, whereas when propene was adsorbed on the Pt catalyst no hydrogen was liberated, indicating that the adsorption of propene did not affect the surface in the same manner as that of ethene. Equally, the deposit formed from ethene and propene adsorption, on the Pt catalyst, is not the same in nature or reactivity. However, the deposits formed from both propene and ethene adsorption on the Ni catalyst were very similar in nature and reactivity. Propyne adsorption on the Pt catalyst was examined by FTIR and revealed a totally different surface species than that derived 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 dihydrogen at 573 K, whereas such a treatment of the platinum catalyst had no obvious effect. Co-adsorption studies revealed that single adsorption behaviour was not reproduced in the presence of a second adsorbing gas. The extent of adsorption and the nature of the deposit from propyne on the Pt system was modified, even though no carbon monoxide adsorption was detected, while on the Ni system, although carbon monoxide was adsorbed, the propyne adsorption was similar to that found in the absence of carbon monoxide.