Progress in Engineering the Isomerization during the Propagation of Carbon-Carbon Chain

Recently, the research group of Prof. Zeng has made great progress in engineering the isomerization during the transformation of C₃ to C₄ molecules based on Rh/CoO single-atom catalysts. Researchers successfully constructed CoO-supported Rh single-atom catalysts and evaluated their catalytic properties in the transformation of C₃ to C₄ molecules. Further mechanistic studies revealed that a structural reconstruction of Rh single atoms in Rh/CoO occurred during the catalytic process, facilitating the adsorption and activation of reactants. This work has been published on Nature Communications with the title of “Atomic-level Insights in Optimizing Reaction Paths for Hydroformylation Reaction over Rh/CoO Single-atom Catalyst” [Nature Commun. 2016, 7, 14036]. Doctor Liangbing and Master Wenbo Zhang Wang contributed equally.

 

Rh/CoO single-atom catalysts and their catalytic mechanism

 

In the current energy fields, liquid fuels mainly came from the petroleum cracking. With regard to the gradual depletion of oil resources and the ever-increasing demand for new energy resources all over the world, Fischer-Tropsch synthesis represents one of the most potential approach to solve the shortage of petroleum resources. In Fischer-Tropsch synthesis, isomerization occurs during the propagation from small carbon-based molecules to long-chain molecules. It is well established that octane value serves a pivotal descriptor for the quality of petroleum. The isomerization of low molecular olefins/alkanes can not only increase the octane value for high quality petroleum, but also yield value-added products such as butyraldehyde to improve the economic efficiency. Accordingly, great attention has been focused on searching for low-cost, remarkable activity and high selectivity catalysts towards the isomerization during the propagation of carbon-carbon chains.

The isomerization in the propagation of carbon-carbon chain starts from the transformation from C₄ to C₄ molecules. Herein, we demonstrated the isomerization during the transformation of C₃ to C₄ molecules based on CoO-supported Rh single-atom catalysts. Rh/CoO single-atom catalysts exhibited remarkable catalytic activity and high selectivity for the linear products towards the chain propagation. By increasing Rh mass loadings, isolated Rh atoms switched to aggregated nanoclusters with different atomicity. Among the obtained Rh-based catalysts, Rh/CoO achieved the highest turnover frequency number of 2065 h⁻¹ with the selectivity as high as 94.4% for linear products, butyraldehyde. According to mechanistic studies, the chemical field originating from the interaction between CO and the catalyst surface induced the structural reconstruction of Rh single atoms on CoO nanosheets. This field also coupled with that deriving from the reactants and intermediates. As such, the linear products, butyraldehyde, were kinetically favored, thus influencing the isomerization during the transformation of C₃ to C₄ molecules.

 

This work was supported by CAS, MOST of China, and the National Natural Science Foundation of China.

 

http://www.nature.com/articles/ncomms14036?WT.feed_name=subjects_physical-sciences.