Long-term durability of Ni/TiO2 and Ru–Ni/TiO2 catalysts for selective CO methanation

• Durability Ni/TiO2 and Ru–Ni/TiO2 for selective CO methanation was studied.
• Ni/TiO2 showed the long-term durability for 7000 h at a GHSV of 2500 h−1.
• Ru–Ni/TiO2 also exhibited high stability for 5500 h at a GHSV of 10,000 h−1.
• NiO reduction was related with CO methanation activity and catalytic stability.

Selective CO methanation was carried out over 10 wt%Ni/TiO2 and 0.5 wt%Ru–10 wt%Ni/TiO2, and the durability was examined. During the long-term test, both catalysts abated CO concentration from 0.25% (dry base) to less than 0.05% above ca. 175 °C with CO2 methanation suppressed. Ru–Ni/TiO2 exhibited the high activity of CO methanation compared to Ni/TiO2 during the test. Furthermore, for more than 5500 h, Ru–Ni/TiO2 maintained a wide temperature window for selective CO methanation (>50 °C), where CO and CH4 concentrations were <0.05% and <1%, respectively, at a high gas hourly space velocity of 10,000 h−1. Over Ni/TiO2 and Ru–Ni/TiO2, CO2 methanation activity was initially enhanced, and then stabilized. The initial promotion of CO2 methanation activity is possibly due to the reduction of NiO which remained unreduced after the prereduction by H2 at 450 °C.

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