Fischer–Tropsch Synthesis to Olefins: Catalytic Performance and Structure Evolution of Co 2 C-Based Catalysts under a CO 2 Environment

作者：Tiejun Lin, Kun Gong, Caiqi Wang, Yunlei An, Xinxing Wang, Xingzhen Qi, Shenggang Li, Yongwu Lu, Liangshu Zhong, Yuhan Sun · 发表于：ACS Catalysis · 年份：2019 · DOI：10.1021/acscatal.9b02513 · 被引用次数：90 · 研究领域：Catalysts for Methane Reforming、Catalytic Processes in Materials Science、Catalysis for Biomass Conversion

Cobalt carbide (Co 2 C) nanoprisms derived from CoMn composite oxides exhibit promising catalytic performance for Fischer–Tropsch to olefins (FTO) synthesis via H 2 -lean syngas conversion, but with nearly 45 C% of CO 2 selectivity. The work herein was aimed to investigate the effect of CO 2 in the feed on the structure–performance relationship of Co 2 C-based catalysts during a realistic FTO process. An obvious negative effect of CO 2 was observed on the catalytic performance, and the presence of CO 2 greatly decreased the catalytic activity and olefin formation rate, while it facilitated methane formation. In addition, the product distribution shifted toward light components at increasing CO 2 content, and a typical methanation regime with low selectivity to olefins was observed for CO 2 hydrogenation. A structural characterization suggested that the Na-promoted Co 2 C nanoprisms remained stable under FTO working conditions, and weak linearly and bridge adsorbed CO molecules were observed when the temperature reached 250 °C in a flow of CO-containing gas. However, the CO 2 environment hindered CO adsorption, and the strong CO 2 adsorption ability led to decreased CO coverage and a high local H 2 /CO ratio on the catalyst surface. The as-obtained CO-lean and H-rich surface microenvironment gradually changed the morphology of Co 2 C nanostructures from nanoprisms to nanospheres. Some of the Co 2 C was even transformed into metallic Co. The change of the catalyst structure and...