Tailoring Carbon Deposits on a Single-Crystal Cobalt Catalyst for Fischer–Tropsch Synthesis without Further Reduction: The Role of Surface Carbon and Penetrating Carbon

• Published in: ACS catalysis 2023-07, Vol.13 (13), p.8551-8560
• Main Authors: Qin, Chuan, Hou, Bo, Wang, Jungang, Ma, Zhongyi, Chen, Congbiao, Jia, Litao, Li, Debao, Ding, Mingyue
• Format: Article
• Language: English
• ISSN: 2155-5435; 2155-5435
• DOI: 10.1021/acscatal.3c01016

The preparation of Fischer–Tropsch synthesis (FTS) catalysts that exhibit excellent catalytic performance and are suitable for direct use in a fixed-bed reactor without further reduction is crucial in industrial applications. However, only marginal progress has been made with respect to the preparation of cobalt-based FTS catalysts owing to tendency of metallic cobalt to oxidize easily; this tendency necessitates the activation of these catalysts via reduction despite having undergone reduction treatment during their preparation. Herein, this problem has been addressed by tuning the carbon deposits (surface C and penetrating C) on the surface of a single-crystal cobalt catalyst. Screen-like surface C on a catalyst pretreated with 5% CO (p-Co–CO) exhibits diffusion suppression and chemical inertness to oxidizing gas, thus preventing the oxidation of metallic cobalt and resulting simultaneously in high activity and low CH4 selectivity (7.2%) without requiring further reduction. Moreover, the exact role of surface C and penetrating C deposited on cobalt catalysts in the FTS performance is explored. Both surface C and penetrating C enhance the activity of the cobalt catalyst but with opposite effects on the FTS selectivity. Surface C improves the adsorption ability of bridged-type CO and the formation of long-chain hydrocarbons, whereas penetrating C is conducive to adsorbing linear CO and increases undesired CH4 selectivity. This study clarifies the effect of deposited carbon on the FTS reaction and provides insights into the design of high-performance nonconventional FTS catalysts that do not require further reduction.