Metal Particle Size in Ni/SiO₂Materials Prepared by Deposition−Precipitation:  Influence of the Nature of the Ni(II) Phase and of Its Interaction with the Support

Abstract

The influence of the parameters of the deposition−precipitation method used to prepare Ni/SiO2 samples on the size of nickel metal particles was investigated by temperature-programmed reduction, transmission electron microscopy, and thermogravimetry. The results show that the average metal particle size, which varies between 27 and 79 Å, depends on the nature and the reducibility of the supported Ni(II) phase (nickel hydroxide or 1:1 nickel phyllosilicate), and on the extent of the interface between the supported Ni(II) phase and silica. These parameters themselves depend on the characteristics of the silica support (surface area and morphology) and on the preparation parameters (urea and silica concentrations). At the interface, a nickel phyllosilicate is detected whatever the nature of the supported Ni(II) phase. The metal particles are smaller and the size distribution is narrower when the supported phase is a 1:1 nickel phyllosilicate (d̄ ≤ 50 Å, 10−100 Å) than when it is a nickel hydroxide (d̄ ≈ 80 Å, 20−280 Å). The metal particles are smaller when the extent of the Ni(II) phase−silica interface increases. This arises from the comparison of Ni/SiO2 samples prepared from silicas of high and low surface area, and from nonporous and porous silica.

Surface Oxidation of Supported Ni Particles and Its Impact on the Catalytic Performance during Dynamically Operated Methanation of CO2

“…These values are comparable with those reported in the literature for supported Ni catalysts that were prepared using the same preparation technique [37,38].…”

“…In Figure 2, the values obtained from Equation (1) distribution and a Ni dispersion of 21%. These values are comparable with those reported in the literature for supported Ni catalysts that were prepared using the same preparation technique [37,38]. As an additional characterization tool, temperature programmed reduction (TPR) experiments were used, which showed H2 consumption in a small temperature range (peak maximum at 565 °C, cf.…”

Design, Synthesis, and Mechanistic Evaluation of Iron-Based Catalysis for Synthesis Gas Conversion to Fuels and Chemicals

“…These results indicate that the surfactant removal process and the prevention of the re-oxidation of small metallic Co clusters during this process are essential to form small supported Co metal clusters via colloidal methods. Homogeneous deposition-precipitation (HDP) techniques provide another approach to synthesize high loadings of dispersed metal oxide clusters on supports [45,46]. This method allows the deposition of a soluble metal salt exclusively onto a support surface via gradual and homogeneous introduction of a precipitation agent, for example, hydroxyl ions, to prevent the nucleation of the precursor away from surfaces in the homogeneous phase.…”

Support Materials and Characterization Tools for Nanostructured Catalysts

“…With silica, the extensive work by Louis and co-workers [18,19] has proven that a mixed compound of support and metal hydroxide is formed under most circumstances. This mixed compound displays a lower solubility of nickel than bulk nickel hydroxide thus providing a thermodynamic driving force for selective precipitation onto the oxidic support material.…”