Key roles of formyl insertion mechanism and C-O scission of oxygenates on cobalt carbide in syngas Conversion: A detailed reaction network analysis

Direct conversion of syngas to olefins and oxygenates provides nonpetroleum routes for producing value-added chemicals. Cobalt carbides (Co2C) exhibit great potential in both Fischer-Tropsch to olefins (FTO) process and higher alcohols synthesis (HAS). Among which, the morphology-specific Co2C nanoprisms have shown remarkable performance in producing lower olefins, with limited selectivity towards oxygenates. However, the underlying mechanisms for product formation on Co2C nanoprisms remain elusive, especially why olefins are abundant but oxygenates are rare is unclear. In this work, through detailed reaction network analysis and microkinetic modeling, based on first principles simulations, we demonstrate the important roles of C-O scission and CHO insertion in Co2C nanoprisms catalyzed FTO process, revealing its unique catalysis behavior. A previously neglected CHO insertion mechanism followed by hydrogenation and C-O scission opens a new pathway for ethylene formation and carbon chain growth. And oxygenate intermediates are proved unstable on Co2C(020) facet, leading to suppressed oxygenate selectivity. (C) 2022 Elsevier Inc. All rights reserved.