Oxygen Vacancy over CoMnO<sub><i>x</i></sub> Catalysts Boosts Selective Ethanol Production in the Higher Alcohol Synthesis from Syngas
Shaoxia Guo, Zhuoshi Li, Rui Yin, Jianbao Li, Zhuang Zeng, Zhiwei Hu, Guangyuan Luo, Jing Lv, Shouying Huang, Yue Wang, Xinbin Ma
Abstract
Higher alcohol synthesis (HAS) from syngas is highly attractive but still challenging due to the complexity of the reaction system and the difficulty in modulating the carbon number distribution of products, especially in improving the selectivity toward ethanol or short-chain alcohols over a single catalyst. Herein, we propose a CoMnO x nanocomposite catalyst with the Co/Mn molar ratio of 1/2 prepared by the facile sol–gel method and found that it could selectively produce short-chain alcohols in the HAS. The C 2 - 5 OH proportion in the total alcohol reached 75.5 C%, in which the ethanol proportion was as high as 48.0 C%, breaking through the Anderson-Schulz–Flory distribution and outperforming most of the reported cobalt-based catalysts for HAS. Multiple characterizations and contrast experiments indicated that oxygen vacancies in MnO x that formed during reduction and reaction can dissociate CO but are inactive in C–C coupling, thus generating lots of CH x * monomers. The CH x * intermediates could react with the CO* species adsorbed on the neighboring Co 2 C species, greatly stimulating the production of ethanol. It is also demonstrated that the oxygen vacancies possibly facilitated the carbonization of cobalt and enhanced the alcohol selectivity, while the untransformed Co x Mn 1– x O was not active in the reaction. These findings may provide potentials in designing catalysts for highly selective production of ethanol and short-chain products in HAS from syngas.