Dynamic transformation of small Ni particles during methanation of CO2 under fluctuating reaction conditions monitored by operando X-ray absorption spectroscopy

16th International Conference on X-ray Absorption Fine Structure

Mutz, B.^1,2 ; Carvalho, H.W.P.^1 ; Kleist, W.^1,2 ; Grunwaldt, J.-D.^1,2

Institute for Chemical Technology and Polymer Chemistry (ITCP), Karlsruhe Institute of Technology (KIT), Karlsruhe

D-76131, Germany^1

Institute of Catalysis Research and Technology (IKFT), Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen

D-76344, Germany^2

关键词: Catalytic process;    Deactivation phenomena;    Dynamic reactions;    Dynamic transformation;    Increased temperature;    Ni/Al2O3 catalyst;    Reaction atmospheres;    Reaction conditions;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/712/1/012050/pdf
DOI  :  10.1088/1742-6596/712/1/012050

来源: IOP

【 摘 要 】

A 10 wt.-% Ni/Al2O3catalyst with Ni particles of about 4 nm was prepared and applied in the methanation of CO2under dynamic reaction conditions. Fast phase transformations between metallic Ni, NiO and NiCO3were observed under changing reaction atmospheres using operando X-ray absorption spectroscopy (XAS). Removing H2from the feed gas and, thus, simulating a H2dropout during the methanation reaction led to oxidation of the active sites. The initial reduced state of the Ni particles could not be recovered under methanation atmosphere (H2/CO2= 4); this was only possible with an effective reactivation step applying H2at increased temperatures. Furthermore, the cycling of the gas atmospheres resulted in a steady deactivation of the catalyst. Operando XAS is a powerful tool to monitor these changes and the behavior of the catalyst under working conditions to improve the understanding of the catalytic processes and deactivation phenomena.