We varied the cobalt loading (10, 15, 25, 35 wt%) to determine the optimum loading in a Co–CeO2 catalytic system used for the high temperature water–gas shift (WGS) reaction. Severe reaction conditions were used to compare the catalytic performances including a very high gas hourly space velocity (142,663 h−1) and a high CO concentration (~38%). Among the prepared catalysts, 15% Co–CeO2 exhibited excellent catalytic activity in the temperature range of 350–550 °C without promoting the methanation reaction. In addition, this catalyst showed relatively stable activity for 50 h at 400 °C. The outstanding performance of 15% Co–CeO2 catalyst is mainly due to the highest amount of dispersed cobalt atoms on the catalyst surface. Additionally, the WGS activity was affected by the oxygen vacancy concentration.
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