Influence of lanthanum carbonate phases of Ni/La0.98Sr0.02O x catalyst over the oxidative transformation of methane

Abstract

This work combines the advantages of $2 mol.% Sr/La 2 O 3 (i.e. La 0.98 Sr 0.02 O x ) for OCM (oxidative coupling of methane) with welldispersed nickel over metal oxides for POM (partial oxidation of methane) to efficiently transform methane to desirable products. The catalysts were prepared by sequential impregnation and characterized by X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, temperature-programmed reduction, temperature-programmed decomposition of carbonates and BET surface area measurements. The aim of this work is to find out not only the effect of the catalyst compositions over the formation and growth of carbonate phases, but also their influence over the transformation oxidative of methane.The La 0.98 Sr 0.02 O x -supported Ni catalyst precursors show a strong nickel oxide-lanthana interaction, involving anionic vacancies or structural defects that induce the formation of island-like structure of La 2-x Sr x NiO 4 -type mixed oxide for 2 mol.% Ni/La 0.98 Sr 0.02 O x . Higher nickel composition facilitates the formation of LaNiO 3 . Surface lanthanum hydroxycarbonate formation is probably associated with a conjugated effect between lanthanum oxide and oxidized nickel phases. For high-nickel amount containing catalysts, carbonate-enriched La 2 (OH) 6-2x (CO 3 ) x as intermediate phase in methane reforming reaction is proposed. For low nickel composition (i.e. 2%), partial oxidation of methane could follow predominantly the pyrolysis mechanism. In which, carbon monoxide is the direct product and carbon dioxide is subsequently formed from carbon monoxide oxidation.

Synthesis of lanthanum silicate oxyapatite materials as a solid oxide fuel cell electrolyte

“…(4)) would increase with the time of exposition to air. 23 Fig. 3(a and b), an experimental weight loss ( M/M 0 ) of about 13.5 wt.% occurred during heating, which proceeded in three steps.…”

CO2 Reforming of Methane over LaNiO3 Perovskite Supported Catalysts: Influence of Silica Support

“…These species are present on the perovskite surface. Rudolfo et al also reported a peak of reduction at 573 K, which is attributed to NiO on the surface [33]. The second step is observed at ~ 500 °C, due to the reduction of Ni 3+ in the perovskite to Ni 2+ which generates the formation of the La2Ni2O5 phase, this last being reduced at ~ 630 °C as indicates the third peak.…”

Methane reforming over Ni-based pyrochlore catalyst: deactivation studies for different reactions

“…Figure 1 also shows the reduction of nickel oxide under four different peaks. The peak at 305°C can be attributed to the reduction of bulk NiO [22,23]. The peaks at 352°C [24].…”