Researchers uncover mechanism behind high performance of cobaltosilicate zeolite catalyst in propane dehydrogenation

Propane dehydrogenation is a key industrial route to produce propylene without relying on oil. However, its current production processes rely heavily on precious-metal catalysts such as Pt-based materials. Developing efficient alternatives using earth-abundant metals has remained a challenge.

In a study published in Nature Catalysis, Prof. XIAO Jianping's group from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences, and the collaborators, developed a high-performance cobaltosilicate zeolite catalyst (CoS-1) via a hydrothermal synthesis method. The catalyst has solely tetrahedral cobalt sites and none of the unstable cobalt species, achieving a propylene productivity as high as 9.7 kg_C3= kg_cat^–1 h^–1, surpassing that of industrial PtSn/Al₂O₃ catalyst.

The synthesis method involved a gel composed of cobalt salts, tetraethyl orthosilicate, tetrapropylammonium hydroxide (TPAOH), urea, and water, followed by crystallization at 180 °C. After calcination to remove the organic template and triple nitric acid washing at 80 °C to eliminate excess cobalt species, the resulting CoS-1 catalyst contained only tetrahedral cobalt sites without unstable Co species. 

Through density functional theory calculations and ab initio molecular dynamics simulations, researchers studied the stability of different active centers, and uncovered the mechanism behind the high performance of CoS-1 catalyst. They revealed that the flexible zeolite framework obviously lowered the dehydrogenation barriers at isolated cobalt sites due to entropic effects, resulting in a lower barrier of propane dehydrogenation than Pt₃Sn alloy.

Microkinetic simulations further showed that while CoS-1 had a lower dehydrogenation barrier, its overall reaction rate at initial conversions was slightly lower than that of Pt₃Sn, due to reduced propane concentration at isolated Co sites—an effect of entropy loss during diffusion into the zeolite channels.

The CoS-1 developed in this study exhibits excellent long-time stability. Researchers proved that this can be attributed to the non-bonding adsorption of propylene within the zeolite, which enables rapid product desorption and reducing coke formation.