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.

Importance of Size and Distribution of Ni Nanoparticles for the Hydrodeoxygenation of Microalgae Oil

“…Then, the pH of mixture reached a maximum at 5.6 and stabilized at a slightly lower value of 5.5 due to the dynamic equilibrium between the formation of OH À ions and their consumption for precipitation of Ni II hydrooxoaqua species on the surface of HBEA ( Figure S2, the Supporting Information). The Ni loadings at different DP duration and the shape of the pH variation curve are similar to the DP cases with Ni II on both silica and HBEA zeolite, [6,9] demonstrating that DP is a controllable and reproducible method for synthesizing Ni/HBEA catalysts. In the fourth case, the synthetic strategy with Ni NPs involved firstly the preparation of soluble Ni NPs by reducing [Ni-A C H T U N G T R E N N U N G (acac) 2 ] (acac = acetylacetonate) with borane tributylamine (BTB) in the presence of oleylamine (OAm) and oleic acid at 90 8C, followed by grafting the as-synthesized NPs onto the zeolite under stirring at ambient temperature in hexane.…”

“…[5] However, the Ni/zeolite bifunctional catalyst prepared by conventional incipient wetness impregnation method as reported [4] suffers from large and non-uniform Ni particles, leading to relatively low Ni dispersion and resultantly low hydrogenation activity. [6] In addition to impregnation, supported Ni catalysts are usually prepared by ion-exchange and sol-gel techniques, both of which have limitations. For instance, the sol-gel method can generate homogeneously dispersed Ni particles at higher metal content, but the resulting particle size increases with the increasing Ni content (typically larger than 10 nm, when the Ni content exceeds 10 wt %).…”

Enhanced catalytic stability through non-conventional synthesis of Ni/SBA-15 for methane dry reforming at low temperatures

“…All the catalysts present the broad diffraction peak of FWHM circa 20 • , located at 2Â between 20 • and 30 • , typical of the low angle diffractions of the short-range ordered structure of SBA-15. In the case of the catalyst prepared by impregnation, IM, the X-ray pattern [33][34][35]. However, the discrimination between these two species depends upon the presence of an additional reflection at 2Â around 20 • for the nickel phyllosilicate [34,35], which unfortunately overlaps with SBA-15 wide diffraction peaks.…”

“…In the case of the catalyst prepared by impregnation, IM, the X-ray pattern [33][34][35]. However, the discrimination between these two species depends upon the presence of an additional reflection at 2Â around 20 • for the nickel phyllosilicate [34,35], which unfortunately overlaps with SBA-15 wide diffraction peaks. Table 1 shows the results of the textural characterization by means of N 2 adsorption for both the SBA-15 support and the IM, PM and RM catalysts.…”

Precipitation and growth of magnesium hydroxide nanopetals on zeolite 4A surfaces

“…The method involves the addition of ammonia to an aqueous solution of magnesium chloride (MgCl 2 ) containing dispersed zeolite 4A particles. The addition of a weak base results in the precipitation of small crystallites of magnesium hydroxide [11][12][13][14][15][16], which interact with specific sites on the zeolite surface [17]. In particular, bridging hydroxyl groups on the zeolite directly interact with ions present in solution, leading to the formation of a highly dispersed active phase after thermal treatment [18,19].…”