Ni/Hβ-Zeolite Catalysts Prepared by Deposition−Precipitation

Abstract

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.