Influence of synthesis parameters on the properties of nanostructured γ-Alumina using plackett-burman experimental design (original) (raw)
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A Facile Strategy for the Preparation of Highly Mesoporous γ‐Alumina
European Journal of Inorganic Chemistry, 2017
A new, rapid, and very facile strategy for the large‐scale preparation of highly porous γ‐Al2O3 was developed. Defined γ‐alumina microparticles with a narrow mesopore‐size distribution, specific surface area of 400 m2 g–1, and a pore volume of 0.65 mL g–1 were obtained by merely employing an aqueous aluminum chloride solution.
Synthesis, Characterization and Phase Transition of Highly Porous γ - Alumina Nanoparticles
Vandana Publications, 2020
Alumina is an important metal oxide used in a wide range of applications. It is a challenge to synthesize stable γ-alumina nanoparticles because; γ-phase of alumina is not as stable as α phase of alumina. But γ-alumina owns a higher surface area making it a good candidate for many industrial applications such as catalyst, catalytic support for petroleum refining, absorbent, alcohol dehydration, catalytic reduction of automotive pollutants like NOx, CO and hydrocarbons. This research focuses on synthesis, characterization and study of phase identification of pure γ-alumina nanoparticles. Modified "Pechini method" (Danks, Hall, and Schnepp (2016); Huízar-Félix, Hernández, de la Parra, Ibarra, & Kharisov, 2012; Naskar, 2010; Zaki, Kabel, & Hassan, 2012) was used for the synthesis. Transesterification of citrate and ethylene glycol makes a covalent polymer network with trapped Al atoms. Continuous stirring of the reaction mixture while maintaining an optimum temperature is an important factor affecting this reaction. Calcination was carried out at different temperatures to identify phase transitions of alumina nanoparticles. In order to further reduce the particle size and increase the surface area, reactant ratio of citric acid: aluminum acetate was modified to 1:1, volume of ethylene glycol was increased up to 90% of volume of the solution and Triton X was used as a surfactant. PXRD confirmed the pure γ-alumina phase (JCPDS No. 00-010-0425) in samples calcined at 900 °C. At 1000 °C γ-alumina is conve+rted to α-alumina (JCPDS No. 00-083-2080). After the modifications, γ-alumina was identified at 700 °C. FTIR-ATR analysis shows peaks around 1127 cm-1 indicating the presence of Al-O-Al asymmetric bending modes and the peaks around 500 cm-1-750 cm-1 correspond to γ-AlO 6 octahedral sites and 800 cm-1 correspond to AlO 4 tetrahedral sites in γ alumina spinel structure. Resulted product of low temperature, pure γ-alumina nanoparticles will facilitate the industrial development in various applications.
2019
In the present study, the gamma alumina (γ-Al2O3) nano powders have been prepared with addition of 1%mol Co using an aqueous sol-gel method at lower temperature than the pure gamma alumina. The synthesis process accomplished by partial hydrolysis of the aqueous solution of metallic ions Al3+ and Co2+, with ammonia. The Al(NO3)3.9H2O and Co(NO3)2.6H2O salts were used as cations sources. The obtained gel at 40 ˚C dried at 120°C and calcined at different temperatures. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and BET method of surface analysis were applied for powders characterization. The results indicated that the well crystallization of the gamma phase occurred at about 700°C for the Co doped samples while it was 900 °C for the pure sample. The specific surface area and particle sizes of the powders varied from 186 to 140 m2/g and 8 to 11 nm for pure and cobalt added γ-Al2O3, respectively. Both powders have the meso-porous st...
A Novel Synthesis Route of Mesoporous γ-Alumina from Polyoxohydroxide Aluminum
Materials Research
Mesoporous gamma-aluminas (γ-Al 2 O 3) were synthesized starting from an unusual precursor of polyoxohydroxide aluminum (POHA). This precursor was obtained from aluminum oxidation in alkaline water-ethanol solvent in the presence of d-glucose that induces the formation of a gel, which leads to the POAH powder after ethanolic treatment. Precipitated POHAs were calcined at different temperatures (300, 400, 700 and 900 °C) resulting in the metastable γ-Al 2 O 3 phase. Whereas at 300 °C no γ-Al 2 O 3 phase was formed, unexpectedly, mesoporous γ-Al 2 O 3 was obtained at 400 ºC having a high specific surface area (282 m 2 /g) and a narrow pore size distribution. At higher temperatures, the aluminas had the expected decrease in surface area: 166 m 2 /g (700 °C) and 129 m 2 /g (900 °C), respectively. The structural change from POHA to alumina calcined at 400 ºC occurs directly without the need to isolate the hydroxide or oxyhydroxide aluminum precursors. Both POHA and transition aluminas were characterized by Fourier Transform Infrared spectroscopy (FTIR), X-ray diffraction (XRD), N 2 sorption and Scanning Electron Microscopy (SEM). These findings show an alternative route to produce high standard aluminas.
Preparation of functionalized porous nano-γ-Al2O3 powders employing colophony extract
Biotechnology Reports, 2014
This study reports the synthesis of porous nano alumina employing carboxylato-alumoxanes [Al(O) x (OH) y (O 2 CR) z ] n as precursors for controlling the pore size, pore size distribution and porosity of the alumina, using a new process ecofriendly. The carboxylato-alumoxanes was prepared by the reaction of boehmite with carboxylic acids. The boehmite was obtained by the hydrolysis of aluminum alkoxide in an aqueous solution. The colophony extract is employed as a source of carboxylic acids. The materials were characterized, using XRD, TGA, N 2 physical adsorption, SEM, TEM, NMR and FTIR. A mechanism was proposed for the formation of the synthesized structures. TEM measurements confirmed particle size ranged from 5 to 8 nm.
2018
In the present work, nano-sized γ-alumina powders have been successfully synthesized by control precipitation path using aluminum chloride as forerunner and water and ammonium solution as precipitating agents and at 70 °C. The synthesized γ-alumina samples have been characterized by XRD, AFM, SEM, and N2-adsorption/desorption isotherm at -196 °C by the BET method. Different initial concentrations of aluminium chloride precursor in ethanol solvent were studied on the particle size and surface area of the prepared γ-alumina. Results indicates that the sample prepared by this method gave nano-sized particle with crystallite shape in the range 70-91 nm, surface area 260-291 m/g and pore volume 0.467-0.36 cm/g. Copyright © 2018 International Energy and Environment Foundation All rights reserved.
2013
Mesoporous γ-alumina is the most extensively used catalysts support in a wide range of catalytic processes. The usefulness of γ-alumina relies on its favorable combination of physical, textural, thermal, and chemical properties. Pore structure properties are among the most important properties, since high surface area and large pore volume enable higher loading of active catalytic phases, while design of pore size and pore size distribution is critical to optimize pore diffusional transport and product selectivity. In addition, accurate determination of surface area (SA), pore volume (PV) and pore size distribution (PSD) of porous supports, catalysts, and nanomaterials is vital to successful design and optimization of these materials and to the development of robust models of pore diffusional resistance and catalyst deactivation. In this dissertation, we report a simple, one-pot, solvent-deficient process to synthesize mesoporous γ-alumina without using external templates or surfactants. XRD, TEM, TGA and N 2 adsorption techniques are used to characterize the morphologies and structures of the prepared alumina nanomaterials. By varying the aluminum salts or the water to aluminum molar ratio in the hydrolysis of aluminum alkoxides, γ-alumina with different morphologies and pore structures are synthesized. The obtained alumina nanomaterials have surface areas ranging from 210 m 2 /g to 340 m 2 /g, pore volumes ranging from 0.4 cm 3 /g to 1.7 cm 3 /g, and average pore widths from 4 to 18 nm. By varying the alcohols used in the rinsing and gelation of boehmite/bayerite precursors derived from a controlled hydrolysis of aluminum alkoxides, the average pore width of the γ-aluminas can be tuned from 7 to 37 nm. We also report improved calculations of PSD based on the Kelvin equation and a proposed Slit Pore Geometry model for slit-shaped mesopores of relatively large pore size (>10 nm). Two structural factors, α and β, are introduced to correct for non-ideal pore geometries. The volume density function for a log normal distribution is used to calculate the geometric mean pore diameter and standard deviation of the PSD. The Comparative Adsorption (α s) Method is also employed to independently assess mesopore surface area and volume.
Molecules
γ-Alumina with incorporated metal oxide species (including Fe, Cu, Zn, Bi, and Ga) was synthesized by liquid-assisted grinding—mechanochemical synthesis, applying boehmite as the alumina precursor and suitable metal salts. Various contents of metal elements (5 wt.%, 10 wt.%, and 20 wt.%) were used to tune the composition of the resulting hybrid materials. The different milling time was tested to find the most suitable procedure that allowed the preparation of porous alumina incorporated with selected metal oxide species. The block copolymer, Pluronic P123, was used as a pore-generating agent. Commercial γ−alumina (SBET = 96 m2·g−1), and the sample fabricated after two hours of initial grinding of boehmite (SBET = 266 m2·g−1), were used as references. Analysis of another sample of γ-alumina prepared within 3 h of one-pot milling revealed a higher surface area (SBET = 320 m2·g−1) that did not increase with a further increase in the milling time. So, three hours of grinding time were s...