Synthesis optimization, structural evolution and optical properties of hierarchical nanoporous alumina microspheres prepared by continuous soft chemistry method

Beiknejad, Davoud

doi:10.1007/s10934-013-9689-z

Cited by 14 publications

(9 citation statements)

References 33 publications

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“…In the oil-molding route, the starting broth, a dispersion of precursors (with controlled acidity) and a gelling agent such as hexamethylenetetramine (HMTA) or a mixture of HMTA and urea (organic monomer) [3,15], is introduced dropwise into hot oil (~90 • C), resulting in the generation of gel droplets due to surface tension as they enter the oil bath [3,16]. The sol congeals through neutralization with ammonia ions upon the decomposition of the HMTA and/or urea, while the droplets age in the hot oil [3,13].…”

Section: Introductionmentioning

confidence: 99%

“…Finally, spherical ceramic carriers are obtained after washing filtration (using organic solvents, ammonia solution, and deionized water), drying, and a heat treatment [3,13,15]. The oil molding route has been primarily used to prepare γ-Al 2 O 3 spherical granules [3,[16][17][18] and CeO 2 -stabilized-ZrO 2 (CSZ) [15], Al 2 O 3 -CeO 2 [19], Y 2 O 3 -stabilized ZrO 2 [20], and CeO 2 -Nd 2 O 3 [21] fuel kernels and pellets (referred to as internal gelation). Despite the achieved uniformity of the processed spheres, major drawbacks of this method include the toxic nature of the reagents, the requirements of the use and disposal of hot oil together with by-products, and the necessity to maintain the granules under severe processing conditions to complete the decomposition of HMTA and urea [13].…”

Section: Introductionmentioning

confidence: 99%

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Effects of Processing Conditions on the Properties of Porous Diatomite Granules Prepared by Sodium Alginate Gelation

Sosa Lucio,

Oh,

et al. 2023

Applied Sciences

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The proper application of millimeter-sized spherical porous ceramic supports in catalytic operations relies on their ease of handling, convenient separation, recyclability, high-catalyst-solid loading, and the optimum mass transfer of reactants and products. However, common granulation techniques of spherical carriers entail complex liquid-phase-based processes under severe conditions and the use of toxic or expensive reagents. The present study discusses the manufacturing of porous ceramic granules derived from an inexpensive silica source (diatomite, solid network) and a biopolymer cross-linked by ion exchange (sodium alginate, patterning structure). The results indicated that, with fixed granulation conditions, porous diatomite granules with a sphericity of approximately 0.9 could be successfully obtained by optimization of the diatomite/sodium alginate dispersion to a 30.07 wt.% solid content and 1560 mPa·s viscosity (at ~0.3 s−1). Moreover, the described manufacturing process was proven effective in developing hierarchically porous diatomite granules that were heat-treated at 1200 °C with high sphericity (~0.9), acceptable compressive strength (5.17 ± 0.31 MPa), and porosity features (total porosity: 69.0 ± 2.9%, macropore size: 2.777 μm, mesopore size: 35.34 nm), establishing them as well-matched support materials for either catalytic or adsorption applications.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effects of Processing Conditions on the Properties of Porous Diatomite Granules Prepared by Sodium Alginate Gelation

Sosa Lucio,

Oh,

et al. 2023

Applied Sciences

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“…Because of the mentioned disadvantages, an alternative method is needed for the spray drying method. In recent years, alumina microgranules have been prepared by using a combination of sol–gel methods as the base of synthesis routes and a hardware design process for shaping microgranules. − Most academic research in the field of catalysts uses only small quantities of powders without regarding the influence of the scale-up. Owing to the importance of the porous alumina structure as the support of catalysts, an innovative scalable hybrid method has been reported for the production of microgranules of alumina in the present study.…”

Section: Introductionmentioning

confidence: 99%

Morphology Engineering of γ-Alumina Microgranules as Support of Cobalt Catalysts Used for Fischer–Tropsch Synthesis: An Effective Strategy for Improving Catalytic Performance

2021

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As a catalyst skeleton, the morphological design of support materials is definitely important since the performance of the catalyst is strongly influenced by the structural and textural properties of the support. Herein, an innovative scalable synthesis of γ-alumina microgranules was performed by designing a setup to combine sol−gel, oil-drop, and electrospray methods in order to study the effects of alumina microgranule morphology on cobalt catalyst performance for Fischer−Tropsch synthesis (FTS). Different drying conditions were applied to prepare γ-alumina support with different crystalline phases and morphological structures. Depending on the drying method of the hydrogel precursor, the structural and textural properties of the microgranules were improved. Cobalt catalysts were prepared by incipient wetness impregnation on alumina microgranules for FTS in the slurry phase and in a fixed bed reactor. The results showed that the change in the morphological properties of alumina affects its oxidation state in addition to affecting the distribution of cobalt nanoparticles. The two-dimensional structure aerogel nanosheets provide uniform distribution of the cobalt particles, while alumina xerogels exhibit significant shrinkage during the drying process, resulting in predominance of aggregation behavior on cobalt particles. This research focused on the development of ambigel as an effective intermediate of aerogel and xerogel for catalytic applications.

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“…However, there have been few studies concerning the synthesis of γ-alumina microspheres with particle sizes ranging from 0.1 to 1 mm. Beiknejad prepared γ-alumina microspheres by a modified oil-drop method, which controlled the dimensions of microspheres to 10–1000 μm, but the particle size was extremely nonuniform under these conditions . In addition, the pore volumes of the spheres are usually lower than 1.0 mL/g because the sol is generally prepared by the hydrolysis of organic or inorganic aluminum salts, which is uncontrollable .…”

Section: Introductionmentioning

confidence: 99%

Preparation of Uniform γ-Alumina Microspheres with Large Pore Volumes in a Coaxial Microchannel

Wan

Wang

et al. 2018

Ind. Eng. Chem. Res.

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A novel and effective method is proposed to prepare uniform γ-alumina microspheres with large pore volumes using a coaxial microchannel. In this process, the so-called “temperature/pH-induced gelation” method, in which methylcellulose (MC) and hexamethylenetetramine (HMTA) are added to accelerate gelation of Al(OH)3 sol, is combined with microfluidics technology to ensure sphericity and dimensional homogeneity of the prepared microspheres. The influences of the sol concentration, the properties of pseudoboehmite (PB) used to obtain the sol, and the two-phase flow rates were investigated. By controlling the sol concentration at 10 wt % and the continuous to dispersed phase flow ratio at 14–50, 750–380-μm-diameter γ-alumina microspheres with uniform pore structures were synthesized using an Al(OH)3 sol obtained from PB3. The pore volume was 1.20 mL/g, and the crushing strengths were 8.19–16.67 N/mm2. Prepared at the maximum two-phase flow ratio, sample S9 exhibited the most uniform particle size of about 380 μm.

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Synthesis optimization, structural evolution and optical properties of hierarchical nanoporous alumina microspheres prepared by continuous soft chemistry method

Cited by 14 publications

References 33 publications

Effects of Processing Conditions on the Properties of Porous Diatomite Granules Prepared by Sodium Alginate Gelation

Effects of Processing Conditions on the Properties of Porous Diatomite Granules Prepared by Sodium Alginate Gelation

Morphology Engineering of γ-Alumina Microgranules as Support of Cobalt Catalysts Used for Fischer–Tropsch Synthesis: An Effective Strategy for Improving Catalytic Performance

Preparation of Uniform γ-Alumina Microspheres with Large Pore Volumes in a Coaxial Microchannel

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