Physico-chemical characterization of Ni/MCM-41 synthesized by a template ion exchange approach

A template ion exchange approach has been employed to prepare Ni/MCM-41 with varying nickel loadings. The synthesized samples were studied by nitrogen physisorption, X-ray diffraction, atomic absorption spectroscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed reduction and Fourier transform infrared spectroscopy. Extensive compound formation was found to result from the adopted preparation method. The Ni(II) phase was elucidated to be a nickel silicate with layer structure. Corresponding layers were comprised of an octahedral Ni(II) sheet in between two tetrahedral SiO4 sheets. Nickel compound formation was accompanied by simultaneous dissolution of the support material. The nickel phase was most likely deposited onto the external surface of the MCM-41 particles. Temperature-programmed desorption of ammonia was used to investigate the influence of nickel content on acidity. Moderate acidity was found for the undoped support material. Introduction of nickel led to the formation of two additional types of acid sites with weak and moderate acidity characteristics.

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► Strong interaction between nickel and MCM-41 with corresponding compound formation.
► Resultant Ni(II) phase is a 2:1 nickel phyllosilicate.
► Silicate generation is accompanied by dissolution of the mesoporous support.
► Template-protected deposition–precipitation instead of template ion exchange.
► Both nickel- and support-related acid sites with weak and moderate strength.