Delving deep into regulation of cobalt active sites to enhance selectivity of propylene to improve production

Chemical reactions are not always naturally optimized to yield the products in the quantities needed, especially on the scale needed for the amount of industry in the world today.

Researchers from East China University of Science and Technology explored the options available to develop a more cost-effective, scalable and straightforward method to increase specificity towards a certain pathway to maximize selectivity for propylene, an important building block for the preparation of gasoline and other chemicals that are found in a wide range of products.

This was done through the synthesis of a cobalt-antimony (CoSb) intermetallic catalyst, which is a highly ordered structure achieved by combining at least two metallic elements, providing unique properties to the material that gives it enhanced catalytic abilities.

The results were published in the journal Carbon Future.

Propyne semihydrogenation selectively adds hydrogen to carbon-carbon triple bonds to reduce them to double bonds. Propyne is a popular chemical intermediate and is also used as a specialty fuel. For such a necessary chemical, little effort has been put towards finding a way to optimize the cobalt reaction sites for configuration matching for this given scenario.

Researchers saw an astounding 97% selectivity for propylene which significantly outperforms the reference cobalt catalyst. This notable percentage of selectivity can be attributed to the unique properties the CoSb intermetallic catalyst gives to the reaction thanks to the well-defined and highly organized geometric and electronic structure.

“Temperature-programmed surface reaction and desorption measurements, along with theoretical calculations, unravel that this exceptional selectivity arises from the kinetically preferred desorption of propylene over its further hydrogenation to undesired propane byproduct on the finely regulated Co sites of the CoSb intermetallic catalyst,” said Xuezhi Duan, author and researcher of the study.

The CoSb catalyst is used to optimize the process of propyne semihydrogenation. Its selectivity can be attributed to a reaction’s preference for ease: energetically, the desired product of propylene is yielded in larger quantities than the undesired product of propane, which can save time and resources while reducing the amount of “junk” products at the end of the reaction.

In many reactions, two or more products will be yielded in varying percentages, and it’s not always the case that the desired product is yielded in a higher quantity than the undesirable product. Achieving a highly selective pathway for a chemical reaction can help ensure the proper product is yielded in the desired quantities while minimizing the percentage of undesired products, creating a more efficient reaction that can lead to an overall reduction of the amount of materials used.

With the impressive selectivity rate of the CoSb catalyst, it is possible that Co catalysts can be tuned with near-perfect precision by Sb. Not only does this provide a positive outlook for the subject of this study, but other substrates could be tested and observed for their effectiveness as an alternative for selective hydrogenation.

Xiaohu Ge, Ziyue Kou, Nina Fei, Yueqiang Cao, Xinggui Zhou and Xuezhi Duan of the State Key Laboratory of Chemical Engineering at East China University of Science and Technology and Hao Jiang of the School of Materials Science and Engineering at the East China University of Science and Technology contributed to this research.