Recently, Hong Yang Liu and Lin Min Zhao, a researcher at the National Research Center for Materials Science in Shenyang, CAS, in collaboration with Professor Martin from Peking University, Professor Ning Wang from Hong Kong University of Science and Technology, and Professor Ruifeng Lu from Nanjing University of Science and Technology, have achieved efficient and selective hydrogenation of styrene from phenylacetylene by precisely constructing sub-nanometer-scale, atomic-level dispersed magnetically separable metal Pd catalysts. The research results were recently published online in Advanced Materials. 
 
Styrene, as an important chemical intermediate, is widely used in agriculture, medicine, textile, rubber and other fields. The industrial preparation methods of styrene include ethylbenzene dehydrogenation, cracked petroleum extraction, and propylene oxide - styrene co-production, etc. Among them, styrene extraction from cracked petroleum is one of the important production processes. The main problem facing this process at present is that the extracted styrene contains a small amount of impurity phenylethynyl, which can lead to severe poisoning of the catalyst for the next styrene polymerization reaction. Therefore, selective hydrogenation of phenylacetylene is needed to remove phenylacetylene from styrene in an efficient manner. Since the reaction environment is in a styrene-rich liquid phase system, how to achieve high selectivity of the catalyst and effective separation of the catalyst while maintaining high activity of the catalyst is the key to this reaction. 
 
Liu Hongyang's research team has been working on the controlled design and application of sub-nanometer scale metal catalytic materials in recent years. Based on the previous research work, the research team has precisely constructed single-atom catalysts (Pd1/Ni@G) and cluster catalysts (Pdn/Ni@G) on layer less graphene-coated nickel nanoparticles (Ni@G), and systematically characterized them by spherical difference electron microscopy and CO adsorption infrared spectroscopy. The results showed that the Pd species on Pd1/Ni@G existed as the majority of single atoms (Figure 1); the Pd species on Pdn/Ni@G existed as clusters. After a systematic comparison of the activity and selectivity of Pd1/Ni@G and Pdn/Ni@G catalyzed selective hydrogenation of phenylacetylene, it was found that the single-atom catalyst Pd1/Ni@G has excellent hydrogenation activity, selectivity, cycling stability and magnetic fractionability (Figure 2). Combined with in situ infrared spectroscopy experiments, adsorption energy calculations, comparison experiments and color development reactions (Figure 3), it was inferred that the catalytic reaction process is the activation of hydrogen on Pd monoatom, the activation of phenylacetylene by adsorption on Ni@G, and the overflow of activated hydrogen atoms to the carrier surface for hydrogenation reaction with phenylacetylene adsorbed on the Ni@G surface. This organic coupling of magnetically separable carriers and sub-nanometer scale, atomically dispersed metal catalysts provides new design ideas for the development of highly efficient liquid phase selective hydrogenation catalysts. 
 
The above work was supported by the Ministry of Science and Technology of China, the National Science and Technology Foundation of China, the Liaoning Xingliao Talent Program, the Establishment Research Program of the Chinese Academy of Sciences, the Young Talent Program of the National Research Center, the Incubation Program of the Institute of Innovation Fund, the Postdoctoral Fund of China in cooperation with Sinopec and other enterprises, and the Shanghai Synchrotron Radiation Light Source. 

Translated with www.DeepL.com/Translator (free version)