Directly Converting Carbon Dioxide to Linear α-Olefins on Bio-Promoted Catalysts

Directly converting carbon dioxide to linear α-olefins on bio-promoted catalysts

Lisheng Guo^{1, 2}, Jian Sun²*, Qingjie Ge², Noritatsu Tsubaki¹*

¹Department of Applied Chemistry, School of Engineering, University of Toyama, Gofuku 3190, Toyama 930-8555, Japan

²Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China

Corresponding authors: sunj@dicp.ac.cn; tsubaki@eng.u-toyama.ac.jp

Higher olefins and in particular linear α-olefins (LAOs), which contain a terminal carbon-carbon double bond, are important and expensive industrial feedstocks for producing highly-value-added chemicals, such as lubricants, detergents, and polyolefins. However, no related reports concerning LAO production from CO₂ have been reported to our knowledge, in spite of the fact that CO₂ conversion to heavy hydrocarbons has been demonstrated in recent years.

Recently, we design an enzyme-like integrated catalyst comprising iron carbides and alkali promoters from calcined corncob (CC) ash, accomplishing direct conversion of CO₂ hydrogenation into LAO with selectivity in hydrocarbons of higher than 40% and total olefin selectivity in hydrocarbons of 72%. Contrary to the introduction of potassium (K) from a chemical promoter, K derived from biopromoters (CC) shows stronger migration ability than chemical promoters during the CO₂ hydrogenation process. According to the results from ⁵⁷Fe Mössbauer spectra and X-ray photoelectron spectroscopy, we learn that these surface enriched K ions could promote the formation of carbides (Fe₅C₂) and further enhance the activity of C-C coupling. Besides, the surface-enriched alkali K from CC ash suppresses the hydrogenation of alkenes and leads to more formation of higher alkenes based on a propylene pulse experiment. The synergetic effect from enhanced C-C coupling and subdued hydrogenation ability led to a high selectivity of linear α-olefins. Thus, this design of biopromoters-modified catalyst provides a new strategy for selective hydrogenation of CO₂ into high value-added products, and sheds a light on the rational design of highly efficient catalysts referenced from biocatalysis in nature.