Lanthanum partial substitution by basic cations in LaNiO3/CeO2 precursors to raise DFM performance for integrated CO2 capture and methanation

Abstract

The influence of the adsorbent nature on the CO2 capture and in situ methanation efficiency of novel Dual Function Materials (DFMs) is studied. Several 20% La0.7A0.3NiO3/CeO2–type precursors, with La3+ partially substituted by basic metal oxides (Na, K, Ca and Ba) are prepared. Samples are deeply characterized before and after catalytic tests by XRD, N2 adsorption-desorption, H2-TPR, H2-TPD, STEM-EDS, XPS, CO2-TPD and H2-TPSR. Characterization results show that Ca2+ and Ba2+ cations accommodate better inside the perovskite structure, due to their similarity in oxidation state and ionic radius to La3+. Corresponding DFMs result in enhanced textural properties, more homogenous phase distribution and promoted surface basic sites accessibility and concentration. Finally, the higher proximity and interactions between CO2 adsorption and active sites enhances CH4 formation in a wider temperature window. The order of reactivity has been observed in terms of CH4 production: Ca-doped ≥ Ba-doped > non-doped ≫ Na-doped > K-doped. The 20% La0.7Ca0.3NiO3/CeO2-derived DFM improves methane production of the conventional 15% Ni-15% CaO/Al2O3 DFM (128.0 vs. 118.0 μmol CH4 g−1 at 400 ºC) in the presence of CO2 during the adsorption period, whereas the incorporation of O2 and/or NOx during the adsorption period shows similar detrimental effect in both cases. However, the partial confinement of Ni nanoparticles (NPs) on Ni-La2O3, Ni-CaO or La-Ce-O interfaces prevents synthesized DFM from deactivation and promotes its regenerability related to the conventional formulation. Thus, Ca doping emerges as the more effective way of tailoring CO2 adsorption and in-situ hydrogenation to CH4 efficiency of 20% LaNiO3/CeO2-derived DFMs.