Recently, a research group led by Prof. ZHANG Tao and Prof. QIAO Botao from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences proposed a novel approach to selectively obtain linear aldehydes in hydroformylation of styrene and its derivatives by coupling with a water-gas shift reaction on Rh single-atom catalyst supported by CeO₂ without using any ligands. 

Hydroformylation of olefins is one of the most important homogeneously catalyzed industrial reactions for aldehyde synthesis. Various ligands are usually used to obtain desired linear aldehydes in aliphatic olefin hydroformylation. 

However, in the hydroformylation of aromatic substrates, branched aldehydes are formed preferentially with common ligands. To obtain high selectivity to linear aldehyde, steric hindrance ligands have to be used, following with high cost and complex synthetic procedure. 

New approaches to manipulate the regioselectivity of styrene hydroformylation are needed. 

The researchers found that the in situ H generated from the water-gas shift played a critical role in determining the high regioselectivity to linear products. 

Besides, compared with Rh single-atom catalyst, Rh homogeneous catalysts were much less active due to the inability to catalyze water-gas shift reaction, and Rh nanoparticle catalysts mainly generated corresponding phenylpropanols rather than aldehydes, resulting in the decrease of chemoselectivity.  

In traditional hydroformylation condition (CO+H₂) low liner/branch ratio (L:B) was obtained while by coupling with water gas shift (CO + H₂O) a much higher L:B ratio was obtained. (Image by DICP)