Lithium carbonate-promoted mixed rare earth oxides as a generalized strategy for oxidative coupling of methane with exceptional yields

Abstract

The oxidative coupling of methane to higher hydrocarbons offers a promising autothermal approach for direct methane conversion, but its progress has been hindered by yield limitations, high temperature requirements, and performance penalties at practical methane partial pressures (~1 atm). In this study, we report a class of Li2CO3-coated mixed rare earth oxides as highly effective redox catalysts for oxidative coupling of methane under a chemical looping scheme. This catalyst achieves a single-pass C2+ yield up to 30.6%, demonstrating stable performance at 700 °C and methane partial pressures up to 1.4 atm. In-situ characterizations and quantum chemistry calculations provide insights into the distinct roles of the mixed oxide core and Li2CO3 shell, as well as the interplay between the Pr oxidation state and active peroxide formation upon Li2CO3 coating. Furthermore, we establish a generalized correlation between Pr4+ content in the mixed lanthanide oxide and hydrocarbons yield, offering a valuable optimization strategy for this class of oxidative coupling of methane redox catalysts.

Data-driven Design of Catalytic Materials in Methane Oxidation Based on a Site Isolation Concept

“…This will be a topic for future more targeted studies. On the other hand, since the OCM reaction contains also the gas phase part (recombination of methyl radicals), very important are such factors as reactor geometry, CH 4 /O 2 ratio, the concentration of inert gas, cofeeding, ,, especially with water. , Also replacement of oxygen with more soft oxidant N 2 O can promote higher yields . Highest C 2 -yields of about 30% have been reported for Mn–Na 2 WO 4 /SiO 2 at 750 °C and for Li–MgO at 770 °C (Table S10).…”

Heterometallic Rare-Earth Complexes: A Review on Magnetism, Catalysis and Transformation to Nanomaterials

“…Despite being non-sesquioxides, these compounds can, under specific conditions, adopt structures isostructural to other REs. Within catalysis, they stand out as highly active and selective catalysts, facilitating processes such as the oxidation coupling of CH4 to higher hydrocarbons [19], isomerization of 1-butene [20], acetone aldol addition [21], hydrogenation of 1,3-butadiene [22], and the dehydration of alkanediols into unsaturated alcohols [23]. The distinctive magnetic and optical properties of glasses derived from rare-earth metal oxides position them as ideal candidates for applications in optics and electronics.…”

Electrocatalytic Conversion of Methane to Ethanol via Promoted •OH Generation in Aqueous Electrolyte

“…Consequently, CH 4 utilization is both ecologically responsible and urgently needed . Traditionally, methane is transformed into liquid fuels in two steps: generation of synthesis gas from methane, and then conversion of syngas into liquid fuels using the Fischer–Tropsch synthesis. − However, it requires harsh conditions to activate the C–H bond in methane (i.e., at temperatures over 700 °C and a pressure of about 20 bar) because of the high C–H bond energy, high ionization energy, and low polarizability of methane. − Recently, a few direct methane conversion pathways, such as oxidative coupling, partial oxidation, and nonoxidative coupling aromatization, have been suggested. − Nevertheless, they still require high temperatures (500–700 °C), so many efforts have been undertaken to inhibit the overoxidation of products to promote the high selectivity of the intended oxygenated products during the methane conversion. − …”