Enhanced direct methanation of CO2 using Ni-based catalysts supported on ZrO2, CeO2-ZrO2, and La2O3-ZrO2: The effect of support material on the reducible NiO-interacted species and catalytic activity
Radwa A. El‐Salamony, Kenit Acharya, Ahmed S. Al‐Fatesh, Ahmed I. Osman, Salwa B. Alreshaidan, Nadavala Siva Kumar, Hamid Ahmed, Rawesh Kumar
Abstract
The lack of reducible NiO-interacted species in ZrO2-supported Ni catalyst at reaction temperature (350 °C) renders it inactive towards CO2 conversion. However, the addition of 2.5 wt.% Ce to the catalyst (Ni/Ce-ZrO2) promotes the formation of reducible NiO-interacted species at around 350 °C, resulting in 23–18.5% CO2 conversion, 60% CH4 selectivity, and 40% CO selectivity during 13 h of time on stream. The lanthana-zirconia support features size-optimized stable Ni sites, the highest population of oxygen vacancy/interacted CO2 species and oxide diminution, leading to constant 38–36% CO2 conversion with 100% CH4 selectivity up to 13 h of time on stream through the direct methanation route (without involving the CO intermediate step). In the longer time on stream (11–13 h), the formate species destabilizes over Ni/CeO2 catalyst, CO2 conversion drops (from 33 to 24%), and CO selectivity increases (from 0.5% to 5.3%) at the expense of CH4 selectivity (from 99.5% to 94.7%).