Effect of the oxidation state of gold on the complete oxidation of isobutane on Au/CeO2 catalysts

Catalysts of highly dispersed gold supported on ceria were prepared by deposition precipitation method. Au is dispersed as Au-0, Au+ and Au3+ species on ceria. The content of Au+ and Au3+ was highest on catalyst prepared on uncalcined ceria, which possess least ordered surface. It is inferred that oxygen vacancy on disordered ceria surface is essential for the preparation of highly dispersed gold catalysts and in stabilizing monolayer surface Au+ clusters while cationic vacancies are sites for substitutional Au3+. Au/CeO2 catalysts showed low-temperature isobutane oxidation activity with maximum conversion at 150-180 degrees C. Ex-situ XPS results demonstrated that the low temperature isobutane oxidation activity was closely related to the content of Au+ which we interpreted as surface gold oxide formed under reaction conditions. Isobutane oxidation activity associated with ceria at temperature above 300 degrees C was enhanced by substitutional Au3+.