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

Abstract

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.