This study proposes an integrated oxidative coupling of methane (OCM) process for the co-production of ethylene and hydrogen, aiming to overcome the limitations of conventional single-reactor OCM and improve system-level performance while addressing resource sustainability in ethylene production. The proposed processes employ a two-stage isothermal reaction system to improve methane conversion and C 2 selectivity, combined with an alternative separation strategy and on-site energy recovery via combined heat and power integration. Rigorous process simulations were conducted to establish mass and energy balances, followed by comprehensive techno-economic and environmental analysis. The optimal configuration achieved an ethylene unit production cost of 0.97 USD/kg, representing a 55.9% reduction relative to a conventional single-reactor OCM benchmark (2.2 USD/kg), driven by staged conversion, elimination of methane recycles, and hydrogen coproduction. Net CO 2 -equivalent emissions were reduced by 66.2% to 4.50 kg CO 2 per kg C 2 H 4 . Sensitivity analysis identified hydrogen value, methane price, and the methane/oxygen ratio as key determinants of economic feasibility. A multi-metric assessment incorporating energy use, carbon efficiency, feedstock availability, and price elasticity shows that methane-based direct conversion pathways exhibit favorable structural characteristics, particularly in terms of feedstock robustness. These results provide practical solutions to cost-competitively diversify resources for ethylene production, while leveraging emerging hydrogen markets. • Two-stage OCM reactors improve methane conversion and ethylene selectivity. • A developed process enables co-production of ethylene and hydrogen. • Ethylene unit production cost reaches 0.97 $/kg, 55.9% lower than benchmark. • Net CO 2-eq emissions reduced to 4.50 kg CO 2 per kg of ethylene, 66.2% improvement. • Multi-metric assessment supports methane-based routes for sustainable ethylene production.

ConspectusThe direct oxidation of methane, which is the main component of natural gas, shale gas, methane clathrates, and biogas, to value-added products is an economically attractive and environmentally friendly alternative to strongly endothermic methane steam reforming to synthesis gas (CO/H2). Among the different routes, the oxidative coupling of methane (OCM) to ethylene/ethane (C2-hydrocarbons) is the most promising one. A key limiting factor is insufficiently high selectivity to C2-hydrocarbons due to their overoxidation to carbon oxides (COx) at industrially relevant degrees of methane conversion. Although it is generally agreed that both selective and unselective reactions are initiated by oxygen species on the surface of catalysts, the kind, role, and origin of these species remain elusive, which hampers the tailored design of catalysts.In this Account, we summarize our recent progress in understanding how product selectivity in the OCM reaction can be tuned by controlling the type of oxygen species through catalyst composition or reaction conditions. The combination of in situ time- and temperature-resolved catalyst characterization with transient kinetic methods, i.e., temporal analysis of products (TAP) and steady-state isotopic transient kinetic analysis (SSITKA), has been proven to be effective for understanding the origin and role of oxygen species involved in selective and unselective pathways. We also present strategies for regulating the concentrations of selective and unselective oxygen species. For the Mn-M(M = Na, K, Rb, or Cs)2WO4 system, the electronegativity of the alkali metal was found to influence the ability of the catalysts to form selective oxygen species from gas-phase oxygen. The binding strength of atomic oxygen species is a key parameter for hindering the oxidation of methane to COx over Gd2O3-based catalysts. This property can be adjusted by using a metal oxide promoter. The nature and concentration of different oxygen species can also be controlled through the use of steam or an alternative oxidizing agent, N2O, and by performing the OCM reaction in a chemical looping mode, i.e., by alternating between CH4- and air-containing feeds. Using steam in the latter option enabled us to largely enhance the productivity of C2-hydrocarbons, thus making this technology more attractive for large-scale applications. The knowledge summarized in this Account is expected to present insights for further studies in the development of selective catalysts for various alkane oxidation reactions and in the optimization of reactor operation.

Oxygen Defect Engineering of SrTiO ₃ Catalysts for Oxidative Coupling of Methane

ABSTRACT The photocatalytic oxidative coupling of methane (OCM) offers a sustainable pathway for converting methane into valuable C2 compounds under ambient conditions. We explore the movement of oxygen species in photocatalytic OCM, particularly the cooperative effects between inert supports loaded with Au and semiconductor compounds (ZnO/TiO 2 , ZTO). The experimental results demonstrate that the coexistence of Au and ZTO is essential for C 2 H 6 production, even without any direct interfacing between the two components. EPR characterization indicates that superoxide radicals (·O 2 − ) may migrate from ZTO to Au sites, forming active Au─O species which activate methane into methyl radicals (·CH 3 ) for subsequent coupling into C 2 H 6 . Interestingly, in the photocatalytic OCM system, the C 2 H 6 yield remained stable upon progressive reduction of the semiconductor content before eventually declining. This trend suggests saturation of ·O 2 − intermediates likely arising from the kinetic balance between generation and quenching of ·O 2 − , where the semiconductor mediates the conversion of O 2 and lattice oxygen to ·O 2 − . We interpret this self‐regulating phenomenon as an Oxygen‐Mediated Self‐Buffering (O‐MSB) mechanism.

Oxidative coupling of methane (OCM) over Ce-loaded CaO catalysts: Investigating the active sites

Abstract Photocatalytic oxidative coupling of methane (POCM) is a promising strategy for the production of sustainable C 2+ hydrocarbons; however, it typically relies on large quantities of noble metals, such as gold, to serve as active sites for methyl coupling. In this study, we demonstrate that ZnO-supported gold nanoclusters with an average diameter of 1.1 nm provide a robust alternative to conventional gold nanoparticles, enabling efficient POCM even at ultralow gold loadings of 0.1 wt%. The optimized photocatalyst affords a C 2 –C 4 hydrocarbon production rate of 3.89 mmol/(g h) with 94.8% selectivity under 365 nm irradiation in a batch reactor. Results reveal that the abundant interfaces between highly dispersed gold nanoclusters and ZnO substrates facilitate charge carrier separation and promote a light-induced Mars–van Krevelen reaction pathway. Methyl adsorption causes gold nanoclusters to exhibit a more intense d- σ hybridization state compared to gold nanoparticles, enhancing electron transfer interactions and substantially reducing the transition-state energy barrier for methyl coupling.

• Introduced a new optimization framework for staged adiabatic reactors using OCM. • Distributed O 2 feeding with interstage cooling improves reactor safety and control. • C 2 yield enhanced 8 times higher with staged reactor zoning and cooling. • Framework can be extended for other highly exothermic catalytic systems. Managing heat is a major challenge for oxidative coupling of methane (OCM) because of its high exothermicity. While recent innovations have mainly focused on reactor design, most studies assume isothermal operation, which is often impractical for scale-up. Adiabatic operation better reflects industrial conditions but remains underexplored. Additionally, little attention has been given to distributing O 2 along the reactor or using interstage cooling to smooth temperature variations inside the OCM reactor and improve performance. In this work, we address those gaps by optimizing a multi-zone reactor design with distribution feeding of O 2 . Using Simulated Annealing, we model up to 30 reactor zones, each treated as a fixed-bed, one-dimensional and pseudo-homogeneous system. Our results show that distributing oxygen across multiple zones with interstage cooling increases the C 2 yield by almost 8 times, from 5.7% in a single zone to 46.5 % across 30 zones, achieving smoother temperature profiles without changing the catalyst.

Unraveling the evolution of oxygen species and its role in adjusting catalytic performance over LaAlO3-based catalysts in oxidative coupling of methane

Chemical looping (CL) technologies have emerged as transformative approaches for energy conversion, carbon capture, and sustainable chemical production. Based on cyclic redox reactions of solid oxygen or nitrogen carriers, CL processes enable inherent separation of CO2, high thermal efficiency, and reduced pollutant formation compared with conventional combustion and reforming methods. This review provides a comprehensive assessment of the current status and recent advances across multiple CL applications, including combustion of gaseous, liquid, and solid fuels, hydrogen generation via reforming, gasification, and water splitting, and novel extensions for ammonia synthesis, air separation, oxidative coupling of methane, and oxidative dehydrogenation of light hydrocarbons. Key developments in oxygen carrier (OC) materials, ranging from Ni-, Cu-, Fe-, Mn-, and Co-based oxides to natural ores, mixed oxides, perovskites, and composites, are critically evaluated in terms of redox activity, stability, cost, and environmental impact. Various reactor configurations and pilot-scale demonstrations worldwide are reviewed, highlighting progress in scaling CL from laboratories to MWth pilot units. Techno-economic and life cycle assessments consistently point to CL’s potential for achieving low-carbon power and chemical production, although challenges remain in oxygen carrier durability, reactor scale-up, and system integration under industrial conditions. Collectively, these advances position chemical looping as a versatile pathway for decarbonized energy generation, negative-emissions bioenergy systems, hydrogen production, and sustainable chemical manufacturing.

Photocatalytic methane coupling represents a promising strategy for the production of valuable C2+ chemicals. Herein, the rational design of an Au24Zn1 nanocluster-embedded ZnO catalyst was demonstrated to enhance photocatalytic performance, and the resultant Au24Zn1/ZnO catalyst exhibited a C2+ selectivity of 93.5% and a yield of 663.1 μmol·gcat-1·h-1 (510.1 mmol·gAu-1·h-1) in a batch reactor. X-ray photoelectron spectroscopy (XPS) and diffuse reflectance infrared Fourier transform spectroscopy-CO adsorption (CO-DRIFTS) revealed that the clusters functioned as hole acceptors, thereby accelerating the separation of photogenerated carriers. Radical experiments and isotope-labeling studies confirmed that the •OH radical derived from water serves as the primary reactive oxygen species responsible for activating methane to •CH3 radicals under the coexistence of H2O and O2, which demonstrates a significant discrepancy compared to the reported photogenerated hole activation pathway. Additionally, the •OOH radical generated via oxygen reduction played a supporting role both in modulating the concentration of •OH radicals and promoting the catalytic cycle. The cooperation contributed to the high yield and excellent selectivity of the C2+ products. This work provides valuable insights into the mechanistic pathway of methane conversion and highlights the potential of metal nanocluster-based materials in photocatalysis.

ABSTRACT The catalytic transformation of natural gas (primarily C 1 –C 3 light alkanes) into value‐added chemicals represents a fundamental research frontier in the energy and chemical industry, yet conventional approaches typically demand elevated temperatures to achieve considerable C–H bond activation and conversion. The utilization of molecular oxygen as an oxidant presents significant thermodynamic benefits, enabling the potential for low‐temperature aerobic conversion of light alkanes. However, oxidants also introduce challenges in inhibiting overoxidation and enhancing product selectivity. Photocatalysis, leveraging the distinctive capacity of photogenerated high‐energy charge carriers to selectively cleave strong C–H bonds, further circumvents reaction kinetics and selectivity limitations for converting inert light alkanes under mild conditions. In this Perspective, we focus particularly on the selective C–H bond activation in oxygen‐containing environment for the photocatalytic oxidation coupling of methane, while also reviewing recent advances in photocatalytic dehydrogenation of ethane and propane. We conclude by critically analyzing the current challenges and future opportunities in low‐temperature aerobic photocatalytic conversion of light alkanes.

A review on advances in oxidative coupling of methane (OCM) for industrial use and prospects of CO2–H2O splitting integration

Systematic study on oxidative coupling of methane over La2O3 under external electric fields

Abstract Oxidative coupling of methane reaction in an electric field at low temperatures was investigated using alkaline-earth-metal-cation-doped LaAlO3 perovskite catalysts. Results demonstrate that reaction activity depends on the amount of surface oxygen species on the perovskite phase, which are activated by direct current applied to the catalysts and function as active sites, selectively promoting C2 production rather than the complete oxidation of methane.

The incorporation of fluoride anions into oxide catalysts can modify their structural and surface properties, consequently influencing their catalytic performance. In this work, a series of rare-earth oxyfluorides (REOF; RE = La, Sm, Eu, Dy, Y, and Yb) was investigated for their catalytic activity in the oxidative coupling of methane (OCM). All REOFs crystallize in a trigonal structure, except YbOF, which adopts either monoclinic (YbOF-m) or tetragonal (YbOF-t) polymorphs. The CH4 conversion and C2 selectivity on the REOF catalysts at 600 and 800 °C exhibit systematic increasing or decreasing trends that correlate with the ionic radii of the RE3+ cations. Among the trigonal REOFs, YOF shows the highest CH4 conversion and C2 selectivity at 800 °C, with values of 24.8% and 44.9%, respectively. CO2- and O2-temperature-programmed desorption (TPD) analyses reveal that OCM activity, lattice size, basicity, and surface oxygen species follow similar trends, indicating correlations among these factors. Larger lattice parameters and longer RE-(O,F) bond lengths are associated with a higher density of moderate basic sites and moderately bound surface oxygen species. Finally, YbOF-m exhibits superior CH4 conversion and C2 selectivity compared to its tetragonal polymorph, YbOF-t. At 700 °C, the C2 selectivities are 45.2% and 14.5% for the monoclinic and tetragonal phases, respectively.

ABSTRACT The commercialization of the oxidative coupling of methane (OCM) process is hindered by its low C 2 hydrocarbon yield and C 2 H 4 /C 2 H 6 product ratio. In this work, a dual‐bed catalytic system comprising a SrCl 2 additive layer packed above the classic Na 2 WO 4 ‐MnO x /SiO 2 catalyst has been proposed. The promoting effect of the introduced SrCl 2 additives is revealed. On one hand, SrCl 2 undergoes in situ oxidative dehalogenation to generate chloromethane active intermediates, which trigger chlorine radical chain transfer reactions in the OCM catalyst layer, significantly reducing the energy barriers of methane activation and ethane dehydrogenation. On the other hand, SrCl 2 , with a high melting point, prevents the metal chlorides from evaporating and covering the catalyst active sites, but still releases abundant chloromethane intermediates to participate in the OCM reaction at a moderate rate. Consequently, a more reactive and stable OCM reaction was achieved, with a C 2 yield up to 25% and a C 2 H 4 /C 2 H 6 ratio around 5 in 20 h of continuous operation. This work provides an efficient strategy for a highly active and stable OCM process.

The role of highly uniform, diverse experimental data in catalyst informatics is examined using an oxidative coupling of methane dataset measured by a single researcher under consistent devices and conditions....

Dual heterojunction engineering on TiO2 enables the spatial decoupling of active sites, where holes mediate C-H activation and electrons drive O2 activation. This synergistic strategy achieves a remarkable C2 hydrocarbon production rate of 1.7 mmol g-1 h-1 with 83% selectivity and a remarkable 45-hour stability in the photocatalytic oxidative coupling of methane.

The identification of active catalytic species and reaction mechanisms remains a challenging obstacle in catalyst design for the Oxidative Coupling of Methane (OCM), as reaction pathways are dependent on a catalyst's chemistry, structure, and reaction conditions, and characterization during operation is not feasible in most cases. Machine Learning (ML) has emerged as a recent addition in the catalyst design toolbox, since the construction of regression models able to predict catalytic activity as a function of catalyst composition and operating conditions facilitates the design of potential catalyst compositions. This work introduces the use of engineered compositional features reflecting both catalyst active metal and support information to aggregate multiple regression models to discover potential metal-support combinations with high OCM activity. As a result, three combinations are found to hold a C2 yield greater than 20%: (Na, K, W)/CeO2, (Cs, Ba, W)/TiO2, and (Na, Cs, W)/SiO2. These results show how an automated framework to generate and search for suitable catalyst features can discover active catalyst formulations within a large materials space.

Atomic-level control in catalyst synthesis is critical for optimizing the catalytic performance. Here, we have developed a generalizable and scalable liquid atomic layer deposition (L-ALD) technique using stoichiometric injections of metal alkoxide precursors to deposit lanthanum on Al2O3 nanoparticles, with precise control over surface chemistry and catalyst properties. Quantitative gas chromatography revealed distinct stoichiometric reaction stages during lanthanum deposition, showing initial ligand exchange with surface hydroxyl groups and transition to sterically hindered saturation due to limited hydroxyl utilization. Optimized acidic hydrolysis conditions (1 mM HNO3, 40 °C) ensured a nearly complete counter-reaction with unreacted ligands, regenerating hydroxyl sites effectively and promoting consistent deposition cycles. Cyclic L-ALD systematically modulated the surface acidic and basic sites, influencing the catalytic behavior. As a model reaction, an La thin-film coating of Al2O3 was demonstrated for enhanced and selective catalytic performance in oxidative coupling of methane (OCM), with a C2+ hydrocarbon selectivity of 32% with a stable (90 h) CH4 conversion (∼35 to 40%) after five deposition cycles. Structural and spectroscopic characterizations (X-ray diffraction (XRD), TEM, X-ray photoelectron spectroscopy (XPS), and CO2/NH3TPD) confirmed the formation of uniform, conformal lanthanum aluminate layers, controlled lanthanum dispersion, and optimized electronic interactions at the catalyst surface. This work demonstrates how atomic-scale deposition techniques can precisely tune surface and electronic properties, enabling enhanced catalytic selectivity and stability for complex environmentally and energy-related reactions such as OCM.