Acetylene-Selective Hydrogenation Catalyzed by Cationic Nickel Confined in Zeolite

Abstract

The selective hydrogenation of alkynes to alkenes is an important type of organic transformation with large-scale industrial applications. This transformation requires efficient catalysts with precise selectivity control, and palladium-based metallic catalysts are currently employed. Here we show that four-coordinated cationic nickel­(II) confined in zeolite can efficiently catalyze the selective hydrogenation of acetylene to ethylene, a key process for trace acetylene removal prior to the polymerization process. Under optimized conditions, 100% acetylene conversion and an ethylene selectivity up to 97% are simultaneously achieved. This catalyst system also exhibits good stability and recyclability for potential applications. Spectroscopy investigations and density functional theory calculations reveal the heterolytic dissociation of hydrogen molecules and the importance of hydride and protons in the selective hydrogenation of acetylene to ethylene. This work provides an efficient strategy toward active and selective zeolite catalysts by utilizing the local electrostatic field within the zeolite confined space for small-molecule activation and by linking heterogeneous and homogeneous catalysis.

Single‐Atom Catalysts Supported by Crystalline Porous Materials: Views from the Inside

“…[97] Furthermore, this result was verified from the XANES spectra of Zn-UiO-67-BPY ( Figure 13B), which showed the high oxidation state of Zn. Similarly, Chai et al [77] combined the information from Ni K-edge XANES and XPS measurements to confirm the presence of Ni 2+ in dehydrated Na-Ni@CHA. Another nonnoble metal-based SAC used in Figure 12.…”

“…XAS has also been widely used in the structural analysis of nonnoble metal SACs that are more easily incorporated into zeolites and MOFs. Chai et al [ 77 ] reported the synthesis of isolated Ni atomic sites confined within chabazite zeolite ( CHA ). By using the combination of XAS analysis and DFT calculations, the existence of single‐atom sites and the evolution of cationic nickel species confined within chabazite zeolite was revealed.…”

“…[ 97 ] Furthermore, this result was verified from the XANES spectra of Zn‐UiO‐67‐BPY (Figure 13B), which showed the high oxidation state of Zn. Similarly, Chai et al [ 77 ] combined the information from Ni K‐edge XANES and XPS measurements to confirm the presence of Ni 2+ in dehydrated Na‐Ni@ CHA . Another nonnoble metal‐based SAC used in such studies is a Co‐based catalyst, such as that synthesized by Zhang et al [ 83 ] who reported a Co single‐site MOF that integrated Zr 6 clusters and porphyrin‐based molecular units into a 3D network.…”

Effect of IB-metal on Ni/SiO2 catalyst for selective hydrogenation of acetylene

“…The supported Ni catalysts were applied to the selective hydrogenation of acetylene in the literature. Recently, Chai et al [20] reported that the cationic nickel confined in zeolite showed high ethylene selectivity and stability. Felix et al [21,22] synthesized a series of Ni-Zn alloy catalysts on the MgAl2O4 spinel support.…”

Recent developments in the control of selectivity in hydrogenation reactions by confined metal functionalities

“…The semihydrogenation of acetylene was also performed on Ni@CHA, with CHA acting as an inorganic ligand for the Ni cationic complex and contributing to the heterolytic dissociation of H 2 . 60 Using Na-Ni@CHA as a catalyst, ethylene was produced in 97% yield. To understand this selectivity, the authors performed temperatureprogrammed desorption experiments (TPD), FTIR, DRIFT studies, and DFT calculations.…”