LaNi_xFe_1–xO_3−δ as a Robust Redox Catalyst for CO₂ Splitting and Methane Partial Oxidation

Abstract

The current study reports LaNi0.5Fe0.5O3−δ as a robust redox catalyst for CO2 splitting and methane partial oxidation at relatively low temperatures (∼700 °C) in the context of a hybrid redox process. Specifically, perovskite-structured LaNi x Fe1–x O3−δ (LNFs) with nine different compositions (x = 0.05–0.5) were prepared and investigated. Among the samples evaluated, LaNi0.4Fe0.6O3−δ and LaNi0.5Fe0.5O3−δ showed superior redox performance, with ∼90% CO2 and methane conversions and >90% syngas selectivity. The standalone LNFs also demonstrated performance comparable to that of LNF promoted by mixed conductive Ce0.85Gd0.1Cu0.05O2−δ (CGCO). Long-term testing of LaNi0.5Fe0.5O3−δ indicated that the redox catalyst gradually loses its activity over repeated redox cycles, amounting to approximately 0.02% activity loss each cycle, averaged over 500 cycles. This gradual deactivation was found to be reversible by deep oxidation with air. Further characterizations indicated that the loss of activity resulted from a slow accumulation of iron carbide (Fe3C and Fe5C2) phases, which cannot be effectively removed during the CO2 splitting step. Reoxidation with air removed the carbide phases, increased the availability of Fe for the redox reactions via solid-state reactions with La2O3, and decreased the average crystallite size of La2O3. Reactivating the redox catalyst periodically, e.g., once every 40 cycles, was shown to be highly effective, as confirmed by operating the redox catalyst over 900 cumulative cycles while maintaining satisfactory redox performance.

High-throughput oxygen chemical potential engineering of perovskite oxides for chemical looping applications

“…[100][101][102] 4 additional previously reported compositions were covered by the loose criteria (Table S7, ESI †). [103][104][105][106][107] The lack of literature reports compared to CLAS materials is largely due to relatively few studies on this subject. Of the 81 DFT predicted materials that have not been reported previously, we synthesized 7 for experimental validation.…”

Ce stabilized Ni–SrO as a catalytic phase transition sorbent for integrated CO2 capture and CH4 reforming

“…28–30 Overall, the key lies in the design of bifunctional materials for lattice oxygen storage/release and catalysis that should have a good reaction affinity with both CO 2 and CH 4 . 30–35…”

Ru-promoted perovskites as effective redox catalysts for CO2 splitting and methane partial oxidation in a cyclic redox scheme

“…As such, syngas from the POx step is suitable for the synthesis of methanol and liquid fuels, whereas CO from the splitting step can be used separately as a feedstock for chemical production, without the need for complex syngas conditioning and separation steps. 20,23…”

“…[10][11][12][13][14][15][16][17] A key challenge involved in thermochemical methods is that the decomposition of the RC requires a very high temperature (≥1100 °C), 10,18 which can be lowered to ≤950 °C by introducing reducing agents such as hydrogen (H 2 ) and methane (CH 4 ) to facilitate CO 2 splitting in an open-loop hybrid redox process (HRP). [19][20][21][22][23][24] Using CH 4 is attractive since inherently separated CO and syngas with a H 2 /CO ratio of ∼2 can be obtained via the HRP (Fig. 1).…”