Methane partial oxidation using FeO(x)@La(0.8)Sr(0.2)FeO(3-δ) core-shell catalyst--transient pulse studies

Area of Science:

• Chemical Engineering
• Catalysis
• Materials Science

Background:

• Chemical looping reforming (CLR) offers an efficient method for methane valorization, avoiding energy-intensive air separation by using lattice oxygen from redox catalysts.
• Iron oxide-based core-shell catalysts, like Fe2O3@La0.8Sr0.2FeO3-δ (LSF), show promise by combining catalytic selectivity with oxygen capacity.

Purpose of the Study:

• To investigate the dynamic reaction mechanisms of methane partial oxidation over a Fe2O3@LSF redox catalyst using transient pulse injection.
• To elucidate how catalyst surface properties and lattice oxygen availability influence the reaction pathways.

Main Methods:

• Utilized a transient pulse injection approach to study methane partial oxidation.
• Employed isotope exchange experiments to confirm transitions between different reaction mechanisms.
• Analyzed the interplay between oxygen evolution and methane conversion pathways.

Main Results:

• The Fe2O3@LSF catalyst facilitates methane partial oxidation through distinct reaction regions with varying mechanisms.
• Oxygen evolution follows a modified Mars-van Krevelen mechanism, with O(2-) conduction as the rate-limiting step.
• Methane conversion mechanism shifts from Eley-Rideal to Langmuir-Hinshelwood-like as the reaction progresses, controlled by surface oxygen availability.

Conclusions:

• The study demonstrates that surface oxygen availability dictates the catalyst's reduction scheme and the underlying reaction mechanism in CLR.
• Understanding these dynamic mechanistic shifts is crucial for optimizing CLR processes for efficient methane conversion.