The Interaction of the Oxides of Carbon, Hydrogen and Water With Unsupported Copper Catalysts

[摘要] An investigation of the adsorption and reaction of carbon monoxide, carbon dioxide, water and hydrogen on polycrystalline copper is presented. These studies were carried out by (i) the use of [14-C] radiotracers in a static adsorption system and (ii) mass spectrometric analysis of adsorption and reaction in a flow microreactor. Carbon monoxide was found to interact with the copper surface in two distinct forms. The bulk of the adsorbate was relatively weakly adsorbed (AH ads = ca. 43 KJ mol-1, while 7% of the carbon monoxide monolayer had an activation energy of desorption of ca. 100 KJ mol-1 Carbon dioxide readily chemisorbed on polycrystalline copper. This process involved a limited oxidation of the copper surface by carbon dioxide decomposition. The adsorbed oxygen generated by this dissociative chemisorption allowed further, extensive, molecular carbon dioxide adsorption. The carbon monoxide species formed by carbon dioxide dissociation had an activation energy of desorption of ca. 100 KJ mol -1. The presence of preadsorbed oxygen on the copper surface allowed carbon dioxide to adsorb in a partially dissociated form and, by this means, promoted direct interconversion of carbon monoxide and carbon dioxide. The interaction of water with copper readily produced 8% of a monolayer of oxygen, together with molecularly adsorbed water (Ah ads = 46 KJ mol -1) and a more strongly held hydroxyl species, Hydrogen was found to exist on the copper surface in a variety of adsorbed states. The most strongly held species were not removed from the surface until temperatures in excess of 100

[发布机构] University:University of Glasgow

[关键词] Physical chemistry, Inorganic chemistry