Ni/LnOx Catalysts (Ln=La, Ce or Pr) for CO₂ Methanation

Abstract

The effect of the LnOx support has been studied for Ni‐based CO2 methanation catalysts. 10 wt.% nickel catalysts with LaOx, CeO2 and PrOx supports have been prepared, characterized by N2 adsorption, XRD, XRF, TG‐MS (N2‐TPD and H2‐TPR) and XPS, and have been tested for CO2 methanation. The catalytic activity follows the trend Ni/CeO2>Ni/PrOx≫Ni/LaOx, all catalysts being very selective towards CH4 formation. The activity depends both on the nature of the catalytic active sites and on the stability of the surface CO2 and H2O species. Ni/CeO2 is the most active catalyst because (i) the Ni2+‐ceria interaction leads to the formation of the highest population of active sites for CO2 dissociation, (ii) the reduced Ni0 sites where H2 dissociation takes place are the most electronegative and active, and (iii) the stability of surface CO2 and H2O species is lowest. Ni/LaOx achieves lower activity because of the strong chemisorption of H2O and CO2, which poison the catalyst surface, and because this support is not able to promote the formation of highly active sites for CO2 and H2 dissociation. The behavior of Ni/PrOx is intermediate, being slightly lower to that of Ni/CeO2 because the formation of active sites is not so efficient and because the stability of chemisorbed CO2 is slightly higher.

Continuous selective deoxygenation of palm oil for renewable diesel production over Ni catalysts supported on Al2O3and La2O3–Al2O3

“…Two additional thermal processes should also be taken into consideration; decomposition of the La(OH) 3 and LaO 2 CO 3 phases that take place at around 350 C and 750 C, respectively, as carbonates are more stable than the hydroxides. 83 The nature and structure of the carbonaceous species deposited on to the spent catalysts was also investigated using Raman spectroscopy and as can be observed in Fig. 10a and b, both catalysts show two well resolved bands around 1340 cm À1 and 1580 cm À1 .…”

The Role of Alkali and Alkaline Earth Metals in the CO2 Methanation Reaction and the Combined Capture and Methanation of CO2

“…The adsorbed hydrogen atoms on the Pd surface were then proposed to spillover to Mg carbonates, hydrogenating the CO 2 -adsorbed phases and forming the CH 4 final product. This bifunctional character of CO 2 methanation reaction that requires the presence of a catalyst componentent capable of activating the CO 2 (Supporting Material: even the commonly considered "inert" Al 2 O 3 acts in this way; support doping is often used for further enhancing this role), and a metallic component typically active in H 2 dissociation has been well established in the literature [60][61][62].…”

Enhancing the CO2 methanation activity of Ni/CeO2 via activation treatment-determined metal-support interaction

“…Cárdenas-Arenas and co-workers, examining the CO 2 methanation mechanism over Ni/CeO 2 and Ni/Al 2 O 3 by isotopic and in situ DRIFTS, proposed the synergistic cooperation of Ni-CeO 2 interface and Ni 0 phase responsible for the activation of CO 2 and H 2 enhanced the methanation activity and selectivity over Ni/CeO 2 [18]. Alcalde-Santiago et al linked the highest activity of Ni/CeO 2 (relative to Ni/PrO x and Ni/LaO x ) to the MSI that generated the highest population of active sites for CO 2 /H 2 activation and the lowest stability of surface CO 2 and H 2 O species [23]. A structure sensitivity was reported that the turnover frequency (TOF) increased with an increase of Ni particle size in the reaction over Ni/CeO 2 [24].…”