| Summary: | In this study, the Taguchi experimental design method using an L16 orthogonal array was attempted in order to investigate the optimal operating conditions for the CO<sub>2</sub> methanation process in Ni-based catalysts. The relative influence of the main factors affecting CO<sub>2</sub> conversion and CH<sub>4</sub> yield was ranked as follows: reactor pressure > space velocity > reaction temperature. The optimal combination of operating conditions was a reactor temperature of 315 °C, a pressure of 19 bar, and a space velocity of 6000 h<sup>−1</sup>. The effect of the H<sub>2</sub>/CO<sub>2</sub> ratio on CO<sub>2</sub> conversion and CH<sub>4</sub> yield was further considered under these optimal operating conditions. Moreover, the catalyst was characterized in order to investigate the production of coke through Brunauer–Emmett–Teller analysis, thermogravimetric analysis, and scanning electron microscopy. The amount of coke produced after the reaction for approximately 24 h was ~2 wt.%. Therefore, the desired CH<sub>4</sub> yield and long-term operational stability were successfully obtained using the Taguchi design method and catalyst characterization.
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