Operando Raman Spectroscopic Studies on Propane Dehydrogenation Over Co‐Based Catalysts

ABSTRACT The development of cost‐effective and eco‐compatible nonnoble metal oxide catalysts for large‐scale propene production via nonoxidative propane dehydrogenation (PDH) is a key topic of current research in heterogeneous catalysis. Cobalt‐based catalysts show remarkable catalytic performance and are promising alternatives to industrially established platinum‐ or chromium oxide‐based catalyst systems. The formation of coke deposits under the reaction conditions has a significant influence on their performance. Time‐resolved operando Raman spectroscopic experiments have been performed during the PDH reaction using a catalyst system containing 3‐wt.% Co on silicalite‐1 as a support (3Co/S‐1) to elucidate the role of carbon‐containing species. Three stages during the PDH process were identified. During the initial 5 min on propane stream, propane is preferentially oxidized to carbon oxides and water. This indicates the removal of lattice oxygen from Co 3 O 4 , whereby this species is reduced to metallic cobalt (Co 0 ). With increasing time on propane stream, the formation of C 1 –C 2 hydrocarbons was observed, pointing to the occurrence of cracking and deep dehydrogenation reactions of propane. Subsequently, intense G and D bands appeared in the Raman spectrum due to the formation of carbon deposits. Simultaneously, there was a substantial enhancement in propene formation, which indicates that carbon‐containing species are necessary for the selective dehydrogenation of propane to propene. The catalyst showed high activity and durable operation in a series of seven dehydrogenation/reoxidation cycles under relevant conditions. The induction period observed for the fresh catalyst was shortened for the catalyst system in course of the PDH/reoxidation cycles.