Development of mesoporous Ni-zeolites for carbon dioxide conversion to methane

Date

2024-6

Author

Kızıl, Asena

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CO2 methanation was investigated over various zeolite-supported (BEA, ZSM-5, US-Y, FER) Ni-catalysts to develop a promising catalyst. After optimizing the operating conditions and catalyst properties, mesoporous zeolites with La2O3 and CeO2 promotions, one-pot Ni/zeolites with La and Ce additions, and amine-functionalized nanosized and microsized zeolites with different extra-framework cations (Na+, Li+, Mg2+, Ca2+) were prepared as supports of Ni-catalysts for CO2 methanation. Prepared samples were characterized by XRD, ICP-OES, N2 physisorption, SEM, TEM, EDS, H2-TPR, CO2-TPD, TPSR, XPS and Raman spectra. The catalytic activity tests were performed in a fixed bed reactor at atmospheric pressure and GHSV of 12,500 h-1 (H2:CO2=4:1) at 300−400 °C. Mesopore addition prevented Nickel sintering because of the encapsulation of Ni nanoparticles, and La2O3 and CeO2 promotions improved the low-temperature catalytic activity of mesoporous zeolites due to improved surface basicity, Ni dispersion and reducibility. Si/Al molar ratio and Ni0 particle size of catalysts had more influence on activity than the crystal size of amine-functionalized zeolites. Additionally, Ca2+-exchanged zeolite-supported Ni-catalyst showed higher catalytic performance among other extra-framework cations. Among all catalysts, Ni-CeO2/Na+-BEA exhibited the best performance with 69% CH4 yield at 300 °C, showing 30-hour stability while preserving Ni0 size. The superior performance was attributed to its optimum Ni0 size (8 nm), low-temperature reducibility of NiO, and nickel-promoter interactions such as Ni−O−Ce sites.

Subject Keywords

CO2 methanation, Nickel, Mesoporous zeolite, La2O3, CeO2

URI

https://hdl.handle.net/11511/110149

Collections

Graduate School of Natural and Applied Sciences, Thesis