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An advanced catalyst, Ni/ZrSn${}_{0.90}$Ce${}_{0.10}$O₄/$\gamma$-Al₂O₃, was synthesized for the methanation of CO₂ under moderate conditions of atmospheric pressure and low H₂ concentration (4 vol%). The use of scrutinyite-type ZrSn${}_{0.90}$Ce${}_{0.10}$O₄ improved the catalytic activity, likely because of abundant oxygen vacancies for CO₂ adsorption and good redox properties for cleavage of the C-O bond of adsorbed CO₂. The CH₄ yield of 18 wt.% Ni/20 wt.% ZrSn${}_{0.90}$Ce${}_{0.10}$O₄/$\gamma$-Al₂O₃ reached 61.0% with high CO₂ conversion (58.4%) at $350^{\circ }$C using 1 vol% CO₂-4vol% H₂-95 vol% Ar at atmospheric pressure.

Sintering of the active metallic nanoparticles and carbon deposition are the key problems faced for CO methanation catalysts. For overcoming those problems, bimetallic nanocatalyst is a promising route. In this work, a series of Al₂O₃ supported Ni-Co alloy catalysts were prepared by reducing NiCoAl layered double hydrotalcite (LDHs), and characterized with X-ray diffraction (XRD), temperature programmed reduction TPR, N₂ adsorption-desorption, transmission electron microscopy (TEM) and temperature programed oxidation (TPO) techniques. The resultant catalysts were mesoporous with nanoparticles of Ni-Co alloy ranging from 7.9nm to 9.2nm which were highly dispersed in alumina matrix. The sample Ni₇Co₃-Al₂O₃ catalysts showed very good catalytic performance during the stability test at 500/600${}^{\circ }$C for 300h, meanwhile exhibited excellent anti-sintering ability and anti-carbon deposition ability, owing to the formation of Ni-Co alloy and the feature of LDHs. This strategy for improving anti-sintering and anti-carbon deposition should be extendable for catalysts of other reactions.

The supported bimetallic Ni-Co alloy catalysts modified with La₂O₃ were prepared by using the perovskite composite oxide of LaNi${}_{1-x}$Co${}_x$O₃/SiO₂ as the precursor, which were obtained by the impregnation method combined with the citrate complex method. The samples were characterized through using XRD, BET, H₂-TPR, CO-TPD, TG and XPS, and the catalytic performances for CO methanation was investigated. The component among the bimetallic (Ni-Co) alloy-La₂O₃/SiO₂ catalyst would be mutually diluted, consequently exhibiting pretty good resistance to metal sintering. The carbon deposition on the catalyst surface mainly depends on the adsorption form of CO, the doping of Co changed the adsorption form and adsorption strength of Co, thereby, the bimetallic Ni-Co catalyst showed strong resistance to carbon deposition. Comparing with the mono-metallic nickel catalyst, the supported bimetallic Ni-Co alloy catalysts exhibited good catalytic activity, selectivity and stability for CO methanation, especially excellent resistance to carbon deposition and metal sintering.

This work reports on the fundamental properties of nanostructured catalysts active in the main carbon oxides’ conversion processes for sustainable energy supply: methanation and co-methanation of CO₂. Transition metals (e.g. Ni, Pd, Pt, Co, Ru, Rh) are active species in both reactions. Ni has been the most studied because of its cheapness. Monometallic and bi-metallic Ni and Ni₃Fe catalysts supported on Gadolinia-doped ceria (GDC) have been synthesized, characterized and tested in the temperature range 200–600${}^{\circ }$C. In the methanation reaction, the monometallic catalyst showed higher performance with respect to the bi-metallic catalyst. At 400${}^{\circ }$C, the CO₂ conversion overcomes 90% with CH₄ selectivity of 100%. In co-methanation, the highest CO₂, CO and H₂ conversion values over monometallic Ni/GDC catalyst were obtained at 300${}^{\circ }$C; at higher temperatures, conversion decreases. The GDC support plays a pivotal role in both reactions, enhancing the basicity of the catalyst and improving the dissociation of carbon oxide species adsorbed on Ni sites.

Natural gas consists mainly of methane (CH₄) and ethane (CH₃CH₃) and other hydrocarbons in small quantities. Depending on the source it may also contain CO₂, nitrogen (N₂), hydrogen sulfide (H₂S) and helium (He). It is very abundant and its combustion contributes to the increase of the CO₂ content in the biosphere. Natural gas is a non-renewable fuel (Section 5.1). It is widely used to produce electricity, heat, chemicals including hydrogen, and hydrocarbons (liquid fuels) and as a fuel for motor vehicles…

In this study, catalytic filter with controlled pore size and structure was fabricated with nano sized particles and used in CO₂ methanation reaction. The catalytic filter was made by using press and thermal treatment of the mixed powder. Ni/Fe-YSZ catalytic filter showed a shrinkage phenomenon because of sintering effect, on the contrary, Ni-YSZ and Ni/Ce-YSZ catalytic filter has not been observed sintering effect. From mercury porosimeter analysis, there was no difference in Ni/Ce-YSZ catalytic filter, however, due to effect of Fe, Ni/Fe-YSZ catalytic filter showed slighty decreased. Also, it observed 70 % of CO₂ conversions at 400°C.