Higher alcohols (C₂₊ alcohols) are important raw materials and have been used as the intermediates of valued products. They are also widely applied in various fields of fuel, food, fine chemicals, pharmaceuticals and energy.

With the gradual depletion of petroleum resources, direct synthesis of higher alcohols from syngas has become a sustainable and potential process because of its wide source of raw materials and high atomic utilization. However, the low yield of higher alcohols restricts industrial application.

Recently, a research team led by Prof. SUN Jian and Prof. GE Qingjie from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) has realized direct synthesis of higher alcohols from syngas and achieved highly selective production of higher alcohols from CO hydrogenation over synergistic iron carbides catalysts.

This study was published in Chem Catalysis on March 24.

"The proposed synergistic Ca-Fe series catalysts could realize a oxygenate selectivity of 69.7 wt% under mild conditions, alongside the alcohols fraction of 86.4 % in oxygenates," said Prof. SUN. "The total oxygenates and alcohols selectivity outperformed the results of previously reported catalysts."

By using multiple characterizations, the researchers found that Ca loading enabled Ca-Fe catalyst to obtain high surface iron carbides with a proper Fe₂C/(Fe₅C₂+Fe₃C) ratio. The Fe₅C₂ and Fe₃C as CO dissociative sites could be assisted by synergistic effect with Fe₂C (CO non-dissociative sites) to produce higher alcohols.

Therefore, the proper Fe₂C/(Fe₅C₂+Fe₃C) ratio facilitated the balance of CO dissociative and non-dissociative abilities, and boosted better cooperation of *CO and *CH_x to form the *CH_x-*CO species, further promoting higher alcohols formation.

"This study extends our understanding of the important role of Ca and provides a new strategy for the design of catalysts in CO hydrogenation to higher alcohols," said Prof. SUN.