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 O(2) and CH(4) 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 degrees C excludes their use in high-temperature applications. Good C(2) 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 C(2) productivities with increasing reactant partial pressure, reaching at 800 degrees C values up to 1.3 x 10(-5) mol (C(2)) s(-1) g(cat)(-1). (C) 2008 Elsevier B.V. All rights reserved.