High-temperature parallel screening of catalysts for the oxidative coupling of methane

The oxidative coupling of methane (OCM) was investigated with a specifically designed multi-channel device operating fixed-bed reactors at high temperature and atmospheric pressure. The device allows precise temperature measurement in each channel selected for analysis and possesses a quench cooling unit right after the reaction zone. Analysis is based on a mass spectrometer allowing a time resolution of only 3 s per analysis and 30 s per reactor channel. Successful screening is demonstrated using a reactant feed of O₂ and CH₄ diluted in Ar at flows between 100 and 166 mL/min per reactor channel. As expected, Li/MgO-based catalysts showed good initial performance, but rapid deactivation at 800 °C excludes their use in high-temperature applications. Good C₂ selectivity up to 80% and high yields up to 20% were observed for La/Sr/CaO catalysts. Even more interesting, no decline in performance was observed for those formulations identifying 10% La/20% Sr/CaO as best catalyst in an initial library. Screening of various La and Sr loadings at different operating conditions identified a optimal content of 5–10% for La and 20% for Sr. The exploration of operating conditions showed increasing C₂ productivities with increasing reactant partial pressure, reaching at 800 °C values up to 1.3 × 10⁻⁵ mol (C₂) s⁻¹ g(cat)⁻¹.