Researchers Develop Dynamic Trimer Catalyst for Efficient Hydrogenations (Chemistry)

A team led by Prof. LU Junling and Prof. WEI Shiqiang from University of Science and Technology of China (USTC) of the Chinese Academy of Sciences (CAS) developed a dynamic trimer catalyst for highly efficient hydrogenations by synergizing metal-support interactions and spatial confinement. This catalyst showed good activity, selectivity and stability in selective hydrogenation of acetylene and 1,3 butadiene in olefin rich atmosphere. The study was published in Nature Nanotechnology.

Supported atomic dispersion catalysts (SADCs) have attracted extensive attention due to their high atomic utilization efficiency and unique catalytic performance. Compared with those of traditional metal nanoparticle catalysts, the active sites of SADCs are isolated from each other. They have uniform structures, which makes these catalysts show high selectivity and good anti-carbon deposition performance in hydrocarbon selective hydrogenation.

However, due to the rapid increase in surface free energy, it is a great challenge to obtain catalysts with high loading and high stability under reaction conditions. Among the two standard methods, strong metal-support interactions (MSIs) may lead to a significant reduction in reaction activity, while microporous confined active metals may affect the mass transfer of the reaction. Therefore, the rational design of high loading, high stability and high activity SADCs is in urgent.

The research team led by Prof. LU prepared high loading Ni1Cu2 trimer catalyst on g-C3N4 support, utilizing the strong metal-support interaction between Cu, Ni and rich nitrogen on g-C3N4 support, as well as the confinement of pre-deposited Cu to Ni atoms. The loading of Ni and Cu were 3.1 wt.% and 8.1 wt.% respectively.

In the selective hydrogenation of acetylene in ethylene rich atmosphere, the prepared Ni1Cu2 trimer structure catalyst showed excellent catalytic performance in activity, selectivity and stability. The catalyst realized the complete conversion of acetylene at about 170 ℃, maintains 90% ethylene selectivity, and can maintain stability for more than 350 hours.

The excellent carbon deposition resistance of the above catalyst was further proved by in situ synchrotron radiation technology. Prof. WEI revealed the coordination structure information of Ni in hydrogen and acetylene hydrogenation atmosphere with the help of in-situ X-ray absorption spectroscopy (XAFS).

In-situ synchrotron radiation vacuum ultraviolet photoionization mass spectrometry and in-situ thermogravimetry showed that there was no carbon deposition in the reaction process. These characterizations indicated that the possible structure of the catalyst is Cu-OH-Ni-OH-Cu. In-situ diffuse reflectance infrared Fourier transform spectroscopy (DIRTFS) of acetylene hydrogenation reaction showed that OH groups were directly involved in the catalytic reaction.

Furthermore, a team led by Prof. LI Weixue from Dalian Institute of Chemical Physics of CAS determined the spatial configuration of Cu-OH-Ni-OH-Cu structure through theoretical calculation. They revealed that the covalent bond interaction between the three atoms of Ni1Cu2 and the support, and the confinement of Cu atoms on both sides to the intermediate active Ni atom, are the internal reasons for the high stability of the catalyst, and the isolated active Ni site limits the co-adsorption of acetylene and ethylene, making it have excellent carbon deposition resistance.

The coordination of metal-support interaction and atomic confinement brings new insights into dynamic structural changes in the catalytic process, which can not only improve the adsorption of reaction molecules and catalytic activity, but also maintain high stability. The single Ni site makes the catalyst show high selectivity and high carbon deposition resistance.

Featured image: Structural characterization: A representative HAADF-STEM image of Ni1Cu2/g-C3N4 with atomic resolution, where isolated atoms, triangular trimers and linear trimers are highlighted by dashed yellow circles, red triangles and green rectangles, respectively. © Authors

Reference: Gu, J., Jian, M., Huang, L. et al. Synergizing metal–support interactions and spatial confinement boosts dynamics of atomic nickel for hydrogenations. Nat. Nanotechnol. (2021).

Provided by Chinese Academy of Sciences

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