Effect of Storage Time On the Catalytic Activity of Gold for Selective CO Oxidation

Gold supported alumina catalysts were studied for selective CO oxidation, in order to provide appropriate H₂ for PEM fuel cell. The catalysts were prepared by deposition-precipitation method using HAuCl₄ as precursor of gold. The catalysts showed high activity at lower temperatures. The fresh catalysts were tested and after 1 year the activity tests were repeated. A considerable loss in the catalytic activity was observed, the maximum CO conversion decreased and the temperature to reach this conversion was higher. The loss of gold catalytic activity was attributed to the agglomeration of gold particles, which occurred spontaneously at room temperature, and may be favored to the presence of residual chloride from the preparation of the catalysts. The catalysts promoted with copper showed higher activity and a smaller loss of activity after 1 year of storage time. The interaction between gold and copper seemed to decrease to gold mobility, avoiding the agglomeration of gold particles.