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Bulk La x NiO y and supported La x NiO y /MgAl 2 O 4 (with x = 1 or 2 and y = 3 or 4) catalysts have been prepared respectively by sol-gel and impregnation methods The elaborated materials have been characterized by XRD, BET, H 2 -TPR, H 2 -chemisorption and TPO. The catalytic activity was evaluated in dry reforming of methane (DMR) with an equimolar ratio of CH 4 and CO 2 . XRD analysis shows the presence of LaNiO 3, La 2 NiO 4 and MgAl 2 O 4 phases. Higher specific surface areas and nickel dispersions were obtained for the supported catalysts. H 2 -TPR analysis revealed a low reducibility of the nickel in the supported solids. Supported catalysts were found more active and stable than bulk one in DMR in good agreement with higher Ni dispersion and the beneficial role of the basic support. The XRD analysis performed on the spent catalysts (after 65 h of catalytic test) revealed the presence of the initial phases with metallic nickel species. The TPO analysis showed a low carbon deposition for the supported catalysts. A kinetic study based on the reaction mechanism points out the participation of the reverse water gas shift reaction (RWGS) for the conversion of CO 2 and of the produced H 2 as well as contribution of steam methane reforming reaction for the conversion of CH 4 , with water produced from (RWGS), for temperatures over 1023 K. [ABSTRACT FROM AUTHOR]

Ni Mg Al–based catalysts were synthesized by coprecipitation, sol–gel, and impregnation methods, calcined at 700 °C for 4 h and tested in partial oxidation of methane in a temperature range of 500–800 °C. The fresh and used unsupported and supported samples were characterized by X-ray diffraction, nitrogen physisorption with Brunauer-Emett-Teller (BET) analysis, and H 2 –temperature-programmed reduction. X-ray diffraction analysis showed, for all samples, the formation of spinel phases MgAl 2 O 4 and/or NiAl 2 O 4 with crystallite sizes of 6–14 nm. H 2 –temperature-programmed reduction analysis showed reduction of two Ni 2+ species (in octahedral and tetrahedral sites of a spinel structure) into metallic nickel known to be responsible for the methane activation. The 10 wt % Ni/MgAl 2 O 4 impregnated catalysts exhibited the highest activity and stability in the partial oxidation of methane reaction, which led mainly to syngas (CO + H 2 ) at 800 °C with a methane conversion close to the thermodynamic equilibrium (95%). A kinetic model revealed that the oxidation of methane occurs on a thin layer of the catalytic bed in which oxygen is consumed and is followed by the production of CO and H 2 by methane steam reforming and water gas shift reactions. [ABSTRACT FROM AUTHOR]

Sintering of nickel particles is a well-known path of deactivation for Ni/Al2O3 catalysts. Considering the CO2 methanation in the context of Power-to-Gas, a sintering study for up to 300 h was performed in a controlled atmosphere between 450 and 600 °C. Since water is a product of the methanation reaction and is known to favor the particle sintering, the H2O:H2 molar ratio was varied in the range 0–3.2. Characterization of the post mortem samples showed sintering of both nickel and support particles. The absence of carbon oxides in the gas feed allows us to rule out other causes of deactivation such as carbon deposits. A sintering law is derived from the loss of metallic surface area with time-on-stream according to local temperature and H2O:H2 molar ratio. An excellent fit of the experimental data was obtained allowing the prediction of the metallic surface area within 15%. [ABSTRACT FROM AUTHOR]

• Nanostructured Ce x Zr 1-x O 2 materials prepared by the continuous supercritical solvothermal sol-gel like synthesis. • Nanostructured Ce x Zr 1-x O 2 as supports of Ni impregnated dry reforming of methane (DRM) catalysts. • High TOF and small selectivity of coke formation in DRM. The nanostructured Ce x Zr 1-x O 2 systems (0 ≤ x ≤ 0.75) were prepared combining alkoxide and nitrate precursors in an ethanol/water mixture by the continuous supercritical solvothermal sol-gel like synthesis. They were subsequently used as supports for nickel impregnation (10 wt.%) to obtain catalysts for dry reforming of methane (DRM) reaction. A reference Ce x Zr 1-x O 2 (x = 0.50) system prepared via conventional coprecipitation method was used as a support for nickel impregnation in the comparative study of the nanostructured materials' catalytic potential. The morphological and structural properties of the prepared nanostructured supports and Ni-containing catalysts were investigated by numerous techniques as XRD, Raman spectroscopy, SEM, TEM, EDS, chemisorption and others. The conditions of DRM reaction were chosen in order to compare the activity, the stability as well as the selectivity of coke formation in the presence of the prepared catalytic materials. It was found that the industrial catalyst leads to heavy coking in the chosen conditions with a rapid loss of activity. While the nanostructured Ce x Zr 1-x O 2 (0 ≤ x ≤ 0.75) materials are found to be promising supports for Ni dispersion and coke control in DRM. In this study the nanostructured Ce 0.50 Zr 0.50 O 2 material impregnated with nickel shown the highest TOF and the smallest selectivity of coke formation in DRM among other nanostructured materials. The continuous supercritical solvothermal method allows to prepare nanostructured mixed oxide materials that could be promising supports for different active metals dispersion and for coke control in the reactions where coking may be abundant. [ABSTRACT FROM AUTHOR]