Direct Conversion of Methane to C₂Hydrocarbons in Solid-State Membrane Reactors at High Temperatures

Abstract

Direct conversion of methane to C2 compounds by oxidative and nonoxidative coupling reactions has been intensively studied in the past four decades; however, because these reactions have intrinsic severe thermodynamic constraints, they have not become viable industrially. Recently, with the increasing availability of inexpensive “green electrons” coming from renewable sources, electrochemical technologies are gaining momentum for reactions that have been challenging for more conventional catalysis. Using solid-state membranes to control the reacting species and separate products in a single step is a crucial advantage. Devices using ionic or mixed ionic–electronic conductors can be explored for methane coupling reactions with great potential to increase selectivity. Although these technologies are still in the early scaling stages, they offer a sustainable path for the utilization of methane and benefit from the advances in both solid oxide fuel cells and electrolyzers. This review identifies promising developments for solid-state methane conversion reactors by assessing multifunctional layers with microstructural control; combining solid electrolytes (proton and oxygen ion conductors) with active and selective electrodes/catalysts; applying more efficient reactor designs; understanding the reaction/degradation mechanisms; defining standards for performance evaluation; and carrying techno-economic analysis.

Fisher–Tropsch Synthesis for Conversion of Methane into Liquid Hydrocarbons through Gas-to-Liquids (GTL) Process: A Review

“…Figure 2 represents natural gas's direct and indirect conversion into higher-value chemicals. Syngas has become the industrially favored method for the indirect conversion of natural gas into higher-value chemicals and fuels because it is more efficient than the direct conversion methods that are currently available [24].…”

“…The reaction mixture will be close to equilibrium at high methane conversion [28]. This process uses pure oxygen that is produced using low-temperature separation vessels; therefore, it has a high cost because pure oxygen production comprises about 40% of the total syngas plant cost [24]. Other methods for producing pure oxygen at lower costs, such as using membrane technology, are still in the research stage [26,28].…”

Catalytic Processes to Accelerate Decarbonization in a Net‐Zero Carbon World

“…Switching to methane‐based ethylene production could lower operating temperatures and enhance energy efficiency. This transformation is considered a grand challenge in catalysis and could occur via conventional thermochemical, [87] chemical looping, [88] membrane, [89] electrochemical, [90] or plasma‐based approaches [91] . An emerging and much more effective ethylene decarbonization pathway is emerging via CO 2 hydrogenation reaction and via the eCO 2 RR approach described above.…”

Highly active and selective Li/MgO catalysts for methane transformation to C2 hydrocarbons: experimental and DFT study

“…13,14 Earlier studies were carried out to maximize C 2 yield by varying the composition of catalyst and reaction parameters, but economic evaluation revealed that the selectivity of C 2 hydrocarbons is more important than C 2 yields. 8,15 Studies say that catalysts play the primary role in producing C 2 hydrocarbons that affect methane conversion and C 2 selectivity in OCM. To date, several catalysts have been developed; including lanthanide series oxides [16][17][18] , Na-W-Mn mixed metal oxides 19 , and alkaline-earth metal oxides [20][21][22] for OCM reaction.…”