Carbon dioxide methanation over Ni catalysts prepared by reduction of NixMg3‒xAl hydrotalcite-like compounds: Influence of Ni:Mg molar ratio. (26th June 2022)

• Record Type: Journal Article
• Authors: Yang, Xinru; Huang, Min; Huang, Hongyang; Li, Dalin; Zhan, Yingying; Jiang, Lilong
• Is Part Of: International journal of hydrogen energy. Volume 47:Number 53(2022)
• Page Start: 22442
• Page End: 22453
• Publication Date: 2022-06-26
• Subjects: Hydrogenation -- Carbon dioxide -- Methanation -- Nickel catalyst -- Hydrotalcite-like compounds; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2022.05.076
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: A series of supported Ni catalysts have been prepared from Ni x Mg3‒ x Al hydrotalcite-like compounds (HTlcs) and the influence of Ni:Mg molar ratio on the structural property and catalytic activity for CO2 methanation is investigated. The catalysts were characterized by N2 physical adsorption, X-ray powder diffraction (XRD), temperature-programmed reduction (H2 -TPR), temperature-programmed desorption (CO2 -TPD), H2 chemisorption, scanning electronic microscopy (SEM), scanning transmission electronic microscopy (STEM), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). By reducing HTlcs at 800 °C, well dispersed Ni particles with average size of 5–10 nm are formed. The Ni crystal size decreases with the decrease of Ni:Mg ratio, attributable to the strong interaction between nickel and magnesium oxides. Among the catalysts, Ni2 Mg1 Al-HT shows the highest activity, giving ∼93% CO2 conversion and >99% CH4 selectivity at 275 °C and SV = 5000 mL g −1 h −1 . Meanwhile, this catalyst exhibits good stability without obvious sintering and coking. The high activity is related to the large amount of surface Ni 0 species and medium basic sites. From CO2 -TPD and DRIFTS, it is inferred that CO2 adsorbs on the medium basic sites, i.e., Ni–Mg(Al)O interface, forming monodentate carbonate. In situ DRIFTS reveals that monodentate carbonate, monodentate formate, and adsorbed CO are the main intermediate species, suggesting that the reaction may proceed via the formate formation route. Highlights: Ni particles with size of 5–10 nm are obtained by reducing NiMgAl HTlcs at 800 °C. The presence of Mg enhances the metal-support interaction and Ni metal dispersion. The catalyst with Ni:Mg ratio of 2:1 shows higher activity and good stability. High activity is linked to the large amount of surface Ni 0 and medium basic sites. Monodentate carbonate and formate are key intermediates of the reaction.