The deposition−precipitation (DP) method, which was extensively developed for the preparation of Ni/SiO2, is applied here to the preparation of Ni/Hβ zeolite catalysts. The Ni/Hβ samples prepared at different deposition−precipitation times (1−4 h) were characterized by BET, XRD, TPR, FTIR, SEM, and TEM. The results indicate that as in the case of the deposition−precipitation of Ni on silica of low surface area, for short DP times (=2 h), nickel hydroxide is the main Ni(II) phase deposited on Hβ zeolite whereas, for longer DP times (3 and 4 h), the Ni(II) phase is a mixture of nickel hydroxide and 1:1 nickel phyllosilicate. The behavior of the OH groups of the Hβ zeolite indicates that the Ni(II) phase species are formed mainly on the external surface of the zeolite. After reduction at 450 °C, the samples contain well-dispersed Ni metal particles with sizes between 9.5 and 120 Å and with average particle sizes between 29 and 44 Å, depending on the DP time.

The deposition-precipitation (DP) method was used for the preparation of Ni/SiMCM-41 and Ni/AlMCM-41 catalysts with different DP times (1-4 h), and the catalysts were characterized by BET, XRD, TPR, FTIR spectroscopy, and TEM. On both types of catalysts, the Ni(II) phases formed are a mixture of 1:1 nickel phyllosilicate and Ni(OH) 2 . The quantity of each phase at the end of the deposition process determines the final Ni particle size; i.e., greater amounts of Ni(OH) 2 lead to larger Ni particles. In addition, it was found that the presence of aluminum in the framework of MCM-41 delays the formation of the nickel hydrosilicate phase. As a result of the consumption of the siliceous pore walls during DP, the long-range order of the MCM-41 hexagonal pore structure is gradually lost. Catalytic activity in the hydrogenation of naphthalene was higher for Ni/SiMCM-41 catalysts and was a linear function of the exposed area of Ni particles.

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