Development of next generation methanol synthesis catalysts

The main aim of this project was to re-visit the area of copper and cerium containing catalysts for use in the methanol industry. The goals were not only to prepare more robust copper/cerium catalysts, but also to further investigate the species that contributed to the high activity of the copper/cerium intermetallic catalysts. Initially a series of copper and cerium catalysts supported on silica or alumina were prepared. The preparation method was chosen so as to maximise the metal dispersion over the support. Methanol decomposition was used to investigate the activity of the prepared catalysts. Ideally, for the catalyst to behave similarly to the Cu/Ce alloy catalysts, they would have to decompose methanol to produce predominantly carbon monoxide and hydrogen. However, on closer examination of these catalysts it was found that the presence of cerium in the catalysts led to an increase in the carbon dioxide:carbon monoxide ratio. A cerium hydride was prepared and a number of its properties were examined using small highly reactive molecules. The results showed that adsorbed hydrogen was reactive, readily available for exchange with deuterium and able to catalyse hydrogenation reactions. The cerium hydride selectively hydrogenated carbon to oxygen multiple bonds. Moreover, the presence of carbon monoxide or carbon dioxide did not poison the cerium hydride. The hydride reacted irreversibly with methanol to produce methane and hydrogen. Due to increasing interest in the water-gas shift reaction for the production of hydrogen for fuel purposes and its uses in industry, the copper/cerium mixed catalysts were examined for use in the water gas shift reaction. In general the mixed metal catalysts were found to be highly active for conversion of carbon monoxide from the reaction mixture. However on closer examination, surface oxygen appeared to have a strong influence on catalytic activity. Further experiments were used to determine the extent to which surface oxygen influenced the reaction products. Addition of cerium to copper-containing catalysts reportedly has the advantage of reducing the ‘pyrophoricity’ observed when reduced shift catalysts are exposed to air/oxygen. As a result of this investigation, it was found that the addition of cerium to copper-containing catalysts was treated with oxygen. During the course of the study, changes in reactivity of the silica-supported catalysts were observed which led to re-examination of a selection of the catalysts for their activity towards methanol decomposition and the hydrogenation of 1,3-butadiene. The changes in activity were attributed to aging of the catalysts