CH 4 Synthesis From CO 2 and NH 3 Over Oxide‐Supported Ru Catalysts
Katsutoshi Sato, Hiroki Ishikawa, Yuji Ueda, Ryosei Murata, Hiroshi Yamada, Katsutoshi NagaokaABSTRACT
Carbon dioxide (CO 2 ) methanation using H 2 is a promising route for carbon capture and utilization (CCU), but securing green H 2 remains a critical challenge for carbon‐neutral implementation. Here, we propose a CO 2 + NH 3 methanation approach, in which NH 3 serves as a hydrogen source in place of H 2 , and develop oxide‐supported Ru catalysts for this process. Activity evaluation of the prepared catalysts revealed that Ru/ZrO 2 exhibited the highest CH 4 yield of 55.3% at 425°C among the catalysts tested. Coupled mass spectrometry (MS) and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis revealed that surface isocyanate species (NCO*) act as reaction inhibitors, and that the basic character of the oxide support strongly affects the stability of NCO*. The basic character of the oxide support also governs NH 3 decomposition activity, which constitutes an elementary step for H 2 supply and plays an important role in promoting CH 4 formation. Based on these findings, we propose that oxide supports with moderate basic character, such as ZrO 2 and TiO 2 , are well‐suited for CO 2 + NH 3 methanation. Further optimization of the Ru–oxide interface should enable the development of more active catalysts, facilitating progress toward carbon‐neutral fuel production processes utilizing NH 3 as a direct hydrogen source.