Effect of pore size and nickel content of Ni-MCM-41 on catalytic activity for ethene dimerization and local structures of nickel ions

Masashi Tanaka, Atsushi Itadani, Yasushige Kuroda, Masakazu Iwamoto

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56 Citations (Scopus)

Abstract

The catalytic activity of nickel ion-loaded mesoporous silica MCM-41 (Ni-M41) for ethene dimerization was investigated as a function of the pore size and the amount of nickel. In addition, the silica wall and the loading of the nickel species were characterized. The Ni-M41 samples with smaller pore size and higher Si/Ni ratio exhibited greater reaction rate constants. The Fourier transform infrared (FT-IR) spectra indicated the formation of 2:1 nickel phyllosilicate-like species along the pore wall. Furthermore, the IR band at approximately 570 cm -1 and the X-ray absorption fine structure (XAFS) spectra indicated the existence of five-membered rings consisting of Si-O on the M41 pore wall in addition to the typical six-membered ones. On the basis of the UV-vis-NIR diffuse reflectance (UV-vis-NIR DR), FT-IR, and XAFS data, we propose that the three- and four-coordinated Ni 2+ ions lie on the five- and six-membered Si-O rings of silica, respectively. Nitrogen monoxide was employed as a probe molecule in the FT-IR and UV-vis-NIR DR experiments and revealed that NO adsorbed as di- and mononitrosyl species on the three- and four-coordinated Ni 2+ ions. The intensity of the dinitrosyl species on the three-coordinated Ni 2+ ions correlated with the catalytic activity for ethene dimerization. Therefore, the three-coordinated Ni 2+ ions are proposed to act as the active site for the reaction.

Original languageEnglish
Pages (from-to)5664-5672
Number of pages9
JournalJournal of Physical Chemistry C
Volume116
Issue number9
DOIs
Publication statusPublished - Mar 8 2012

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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