Methanation of carbon dioxide over Ni-based carbon nanotubes monolith catalysts

Nickel based catalyst has been a potential catalyst in CO2 methanation. However, the challenges of the existing catalyst including carbon deposition and catalyst stability need to be addressed for more efficient performance of CO2 methanation. The objective of the study is to synthesize the CNT monolith at optimum condition, to fabricate monometallic and bimetallic supported onto CNT monolith, to investigate the performance of the catalysts in CO2 methanation reaction at optimum condition and to predict the suitable kinetic and model fitted the catalyst behavior. The experimental studies conducted to grow CNT onto cordierite monolith at optimum condition using direct liquid injection chemical vapor deposition after immersion in Ni/citric acid solution. The CNT monolith catalyst was fabricated via impregnation method and the catalytic CO2 methanation reaction was performed in a fixed bed reactor at optimum condition. The optimization studies were designed by Taguchi method based on L9(34) orthogonal array and characterization analysis was determined using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and others. About 96.45% of CNT’s growth onto monolith was sized in the range of 32 to 34 nm. The performance of monometallic CNT monolith catalysts achieved about 77-86% of CO2 conversion, 76-98% of CH4 selectivity and 1-23% CO selectivity. Meanwhile, bimetallic CNTs monolith catalyst accomplished above 90% for CO2 conversion and CH4 selectivity and less than 10% of CO selectivity. The kinetic behaviour of 10 wt.% Ni CNT and 1/10 wt.% Co/Ni CNT monolith catalyst were fitted based on the Langmuir-Hinshelwood (L-H) models that showed only reactant adsorbed with the dual-site mechanisms and all reactants and products were adsorbed through a single-site mechanism, respectively. As the conclusion, the CNT monolith provides a potential as a catalytic support due to its mesoporous active catalytic site. Furthermore, this study shows that bimetallic CNTs monolith catalyst of 1/10 wt.% Co/Ni gave the highest performance compared to the other catalysts.

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