Elucidating the Copper–Hägg Iron Carbide Synergistic Interactions for Selective CO Hydrogenation to Higher Alcohols

• Published in: ACS catalysis Vol. 7; no. 8; pp. 5500 - 5512
• Main Authors: Lu, Yongwu, Zhang, Riguang, Cao, Baobao, Ge, Binghui, Tao, Franklin Feng, Shan, Junjun, Nguyen, Luan, Bao, Zhenghong, Wu, Tianpin, Pote, Jonathan W., Wang, Baojun, Yu, Fei
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society (ACS) 04.08.2017
• Subjects: biomass; catalytic activity; CO hydrogenation; coal; commercialization; copper; density functional theory; electron transfer; feedstocks; Hagg iron carbide; higher alcohols; hydrogenation; natural gas; reaction mechanism; shale gas; synergistic effect; value added
• ISSN: 2155-5435; 2155-5435
• DOI: 10.1021/acscatal.7b01469

CO hydrogenation to higher alcohols (C(2+)OH) provides a promising route to convert coal, natural gas, shale gas, and biomass feedstocks into value-added chemicals and transportation fuels. However, the development of nonprecious metal catalysts with satisfactory activity and well-defined selectivity toward C(2+)OH remains challenging and impedes the commercialization of this process. Here, we show that the synergistic geometric and electronic interactions dictate the activity of Cu(0)–χ-F(e)5C(2) binary catalysts for selective CO hydrogenation to C(2+)OH, outperforming silica-supported precious Rh-based catalysts, by using a combination of experimental evidence from bulk, surface-sensitive, and imaging techniques collected on real and high-performance Cu–Fe binary catalytic systems coupled with density functional theory calculations. The closer is the d-band center to the Fermi level of Cu(0)–χ-Fe(5)C(2)(510) surface than those of χ-Fe(5)C(2)(510) and Rh(111) surface, and the electron-rich interface of Cu0–χ-Fe(5)C(2)(510) due to the delocalized electron transfer from Cu0 atoms, facilitates CO activation and CO insertion into alkyl species to C2-oxygenates at the interface of Cu(0)–χ-Fe(5)C(2)(510) and thus enhances C(2)H(5)OH selectivity. Starting from the CHCO intermediate, the proposed reaction pathway for CO hydrogenation to C(2)H(5)OH on Cu0–χ-Fe(5)C(2)(510) is CHCO + (H) → CH(2)CO + (H) → CH(3)CO + (H) → CH(3)CHO + (H) → CH(3)CH2O + (H) → C(2)H(5)OH. This study may guide the rational design of high-performance binary catalysts made from earth-abundant metals with synergistic interactions for tuning selectivity.