Low-Temperature Non-Oxidative Coupling of Methane on Atomically Dispersed Titanium-Aluminum-Boron Nanopowder

Nonoxidative coupling of methane represents a long-standing challenge in heterogeneous catalysis, as it requires activation of the carbon-hydrogen (C-H) bond, controlled carbon-carbon (C-C) bond formation, and effective hydrogen management without relying on oxidants. Here, we report a low-temperature C-H activation and nonoxidative C-C coupling of methane over atomically dispersed titanium-aluminum-boron nanopowder (Ti-Al-B NP) utilizing a catalytic microreactor coupled to synchrotron single-photon photoionization reflectron time-of-flight mass spectrometry. The soft-ionization, in situ probing method detects the nascent reaction products and radical intermediates under operando conditions, including methyl radical, C2 hydrocarbons, and molecular hydrogen. Methane activation is initiated at 800 K, approximately 700 K below the gas-phase decomposition threshold, leading predominantly to ethylene formation with selectivity reaching up to 78% among the C-C coupled products. Electronic structure calculations on model Ti-Al-B clusters elucidate a cooperative catalytic mechanism in which titanium enables methane adsorption and C-H activation, boron acts as a reversible hydrogen reservoir, and aluminum stabilizes methylene intermediates, thereby facilitating selective C-C coupling and dehydrogenation. These findings establish a distinct catalyst architecture for nonoxidative methane coupling based on earth abundant elements alternative to expensive platinum and other noble metal-containing conventional catalysts and provide molecular-level design principles for controlling dehydrogenation and subsequent C-C bond formation in challenging light alkane conversions.