Ordered Mesoporous Alumina Research Articles

Ordered Mesoporous Alumina with Ultra-Large Pores as an Efficient Absorbent for Selective Bioenrichment

Alumina has recently turned out to be effective in enrichment of biomacrolecules like phosphopeptides due to its good affinity to phosphor groups. Ordered mesoporous alumina (OMA) materials with high surface areas, regular porous structures, and large pore size are an ideal absorbent for the enrichment of phosphopeptides. Herein, a ligand-assisted solvent evaporation induced coassembly route is developed to synthesize OMA materials with an ultralarge pore size (16.0–18.9 nm) using a high-molecular-weight poly(ethylene oxide)-b-polystyrene (PEO-b-PS) as a soft template, aluminum acetylacetonate as a precursor, and tetrahydrofuran as a solvent. The obtained ordered mesoporous alumina shows high surface area (114–197 m2/g), large pore volume (0.16–0.34 cm3/g), and high thermal stability (up to 900 °C). The OMA materials show crystalline γ-Al2O3 frameworks with crystal size of ∼11 nm after calcination at 900 °C in air. Because of their high surface area, ultralarge pore size, and rich Lewis acid sites, the ob...

Structural and surface properties of highly ordered mesoporous magnesium-aluminium composite oxides derived from facile synthesis

Highly ordered mesoporous magnesium-aluminium composite oxides (denoted as OMMA-x) with a variety of nAl/nMg ratios have been successfully synthesized via a facile strategy, and a salt effect was proposed to explain the formation mechanism. The incorporation of Mg can significantly improve the structural and surface properties of ordered mesoporous alumina (OMA) material. The resultant OMMA-x exhibited a much more ordered 2-D hexagonal mesostructure, a narrower pore size distribution, a higher specific surface area and pore volume, and a stronger basicity than those of OMA. More importantly, the highly homogeneous incorporation of Mg at the atomic level and the formation of framework MgOAl bonds could effectively suppress the formation of crystalline alumina during the calcination process. As a result, OMMA-x demonstrated a superior thermal stability. For example, the ordered mesostructure of OMMA-8 could be well maintained with a high surface area of 182 m2/g even after thermal treatment at 1000 °C.

Enhanced Stability of Spatially Confined Copper Nanoparticles in an Ordered Mesoporous Alumina for Dimethyl Ether Synthesis from Syngas

A spatial confinement effect of copper nanoparticles in an ordered mesoporous γ-Al2O3, which is synthesized by an evaporation induced self-assembly (EISA) method, was investigated to verify the enhanced catalytic activity and stability with less aggregation of copper crystallites during direct synthesis of dimethyl ether (DME) from syngas. The surface acidity of the mesoporous Al2O3 and the metallic copper surface area significantly altered catalytic activity and stability. The ordered mesopore structures of Al2O3 were effective to suppress the aggregation of copper nanoparticles even under reductive CO hydrogenation conditions through the spatial confinement effect of the ordered mesopores of Al2O3 as well as the formation of strongly interacted copper nanoparticles with the mesoporous Al2O3 surfaces by partial formation of the interfacial CuAl2O4 species. The aggregation of copper nanoparticles on the bifunctional Cu/meso-Al2O3 having an ordered mesoporous structure was effectively suppressed due to the...

Carbon Dioxide Reforming of Methane over Cobalt‐Nickel Bimetal‐Doped Ordered Mesoporous Alumina Catalysts with Advanced Catalytic Performances

AbstractCo‐Ni bimetal‐doped ordered mesoporous Al2O3 composite oxides with different Co/(Co+Ni) ratios were designed and fabricated by a one‐pot evaporation‐induced self‐assembly method. The obtained materials, which had an ordered mesostructure and outstanding thermal stability, were investigated as catalysts for the CO2 reforming of CH4. The effects of the Co/(Co+Ni) molar ratios and ordered mesostructure on the catalytic performances were investigated systematically. The ordered mesoporous Co‐Ni bimetallic catalysts exhibited both higher catalytic activities and better anticoke properties than the corresponding monometallic materials because of the Co‐Ni synergistic effect. Furthermore, the ordered mesostructure could promote the catalytic performances significantly by providing gaseous reactants with enough accessible metallic active centers and stabilizing the metallic nanoparticles through the confinement effect of the mesoporous framework. As a result, these mesoporous Co‐Ni bimetallic catalysts had more enhanced catalytic properties and anticoke ability than traditional supported catalysts toward the CO2 reforming of CH4, which promises a series of potential catalyst candidates.

Synthesis and application of highly dispersed ordered mesoporous silicon-doped Pd-alumina catalyst with high thermal stability

Employing P123 as a structure directing agent and acetic acid as an interfacial protector, ordered mesoporous silicon-doped γ-alumina with high thermal stability was synthesized through a modified sol–gel process by adding aluminum isopropoxide in batches to control the hydrolytic and condensation rate of Al3+. When the silicon content was 10–25wt%, the specific surface area of the as-obtained samples were higher than others. Especially when the silicon content up to 20wt%, the sample still maintained ordered mesoporous γ-Al2O3 phase with a large specific surface area of 139.8m2g−1 and narrow pore size distribution even the calcination temperature up to 1100°C. Taking as-synthesized ordered mesoporous alumina (OMA) as carrier, the catalysts with high thermal stability supported by Pd were obtained by a facile process of thermal incipient wetness impregnation, which shows highly dispersed nano-particles and ordered mesostructure. When applied the catalysts in the catalytic converters of simulated exhaust automobile gases, it was found that the ordered mesostructure and high surface area showed significant effects in promoting catalytic activity. The as-synthesized ordered mesoporous Pd-alumina catalyst exhibited an excellent catalytic activity for gas mixture including CO, NO and hydrocarbon (HC).

Assembly of ordered mesoporous alumina-supported nickel nanoparticles with high temperature stability for CO methanation

The high-temperature methanation of CO is an important reaction in the processes used to produce substitute natural gas, while the Ni-based catalysts prepared using the conventional impregnation method tend to deactivate under high-temperature reaction conditions. This paper describes the design and assembly of ordered mesoporous alumina (OMA) using highly disperse ∼5 nm nickel nanoparticles (Ni NPs), via a one-pot, evaporation-induced self-assembly (EISA) method. Small-angle X-ray diffraction (XRD), transmission electron microscope (TEM), and N2 adsorption and desorption results revealed that this catalytic material had highly ordered mesopores, which were retained even after long-term stability tests. The catalyst exhibited excellent sintering-resistant and anti-coking properties in high-temperature CO methanation reactions (60% CO conversion after 50 hours of accelerated deactivation at 700°C). The improved catalytic performance was attributed to the matrix of the OMA, which effectively improved the dispersion of the nickel particles, and prevented the Ni NPs from sintering, via a particle migration and coalescence mechanism. The Ni-OMA catalyst demonstrated here shows promise for high-temperature methanation.

Rapid adsorption of binary dye pollutants onto the nanostructred mesoporous alumina

In this study ordered mesoporous alumina (OMA) with pore size of about 5nm has been used for removal of dye pollutants from binary systems including methyl orange+bromothymol blue, methyl orange+reactive yellow and methyl orange+methyl violet. Derivative spectrophotometry was used for simultaneous determination of the dyes concentrations. The results show that OMA is a good adsorbent for rapid removal of dyes (especially anionic ones) from aqueous solution. Characterization of OMA has been performed by TEM and XRD techniques. The adsorption kinetic data of binary dye mixtures follows the competitive statistical rate theory (SRT) model well.

Effect of p-aminobenzoic acid on synthesizing ordered mesoporous alumina via the sol–gel method

Ordered mesoporous alumina (OMA) samples were prepared via the sol–gel method. The triblock copolymer P123 and aluminum isopropoxide were chose as the template and aluminum source, respectively. The p-aminobenzoic acid (PABA) worked as both the interfacial protector and the assisted template. Different techniques, including X-ray diffractions, N2 physisorption measurement and transmission electron microscope, were employed to study the structural properties of the prepared samples. The results showed that the mesostructure ordering and specific surface area of the samples highly depend on the quantity of the added PABA. The samples after calcinated at 800 °C with the n(PABA)/n(Al3+) molar ratio lying in 0.30 exhibited high specific surface areas (301 m2 g−1) and retained an ordered mesostructures. It was indicated that the carboxyl groups of PABA have multiple functions in the formation of OMA with a long-range ordering and high specific surface area. The carboxyl groups of PABA can slow down the hydrolysis-condensation reaction of aluminum isopropoxide, reduce the influence of chloride ions on self-assembly process. The amino groups of PABA can also react with the hydrogen ions to form quaternary ammonium salt, which can neutralize the charges of the chloride ions, protect the balance of inorganic–organic interface, further to improve the mesostructure ordering and specific surface area of the prepared OMA.

Chemical and biological treatment of waste water with a novel silver/ordered mesoporous alumina nanocomposite

One of the serious problems in the present century is chemical and biological pollution of the environment. Nanocomposites are multiphase solid materials that have been used as adsorbent of pollutants such as dyes, pesticides, anions and etc. in the last decades. In this study, a novel nanocomposite including silver nanoparticles and ordered mesoporous alumina (OMA) has been synthesized and used for the removal of dyes pollutants (methyl orange, bromothymol blue and reactive yellow) from aqueous solution. The characterization of synthesized nanocomposite has been performed by TEM, N2 adsorption/desorption, XRD and energy dispersive X-ray spectroscopy analysis. The adsorption kinetic and equilibrium data have been obtained by UV–vis spectroscopy. The results show that the silver/OMA nanocomposite (Ag/OMA nanocomposite) is good adsorbent for the removal of anionic dyes from aqueous solution, and also this nanocomposite has a biocidal action against both Gram-negative and Gram-positive bacteria.

Adsorption and structural properties of ordered mesoporous alumina synthesized in the presence of F127 block copolymer

A facile one-pot evaporation induced self-assembly synthesis of ordered mesoporous alumina (OMA) was explored by using Pluronic ® F127 nonionic triblock copolymer (structure directing agent), aluminum alkoxide (alumina precursor), nitric acid (pH adjustor) and ethanol (solvent). A series of OMA samples with highly ordered cage-like structures, large spherical mesopores, high specific surface area and large pore volume were obtained and studied by nitrogen adsorption, small angle X-ray scattering, and transmission electron microscopy.

Facile Synthesis of Ordered Mesoporous Alumina and Alumina-Supported Metal Oxides with Tailored Adsorption and Framework Properties

The evaporation-induced self-assembly (EISA) in ethanolic solution of a triblock copolymer (Pluronic P123) is explored for the synthesis of ordered mesoporous alumina (MA) and MA-supported metal oxides, using aluminum isopropoxide, aluminum chloride, and aluminum nitrate nonahydrate as aluminum precursors, and nickel, magnesium, iron, chromium, copper, cerium, lanthanum, yttrium, calcium, tin chlorides, or nitrates as metal precursors. The as-synthesized mesoporous oxides were characterized by a variety of techniques, such as thermogravimetry, Fourier transform infrared spectroscopy, nitrogen adsorption, small- and wide-angle X-ray diffraction, high-resolution transmission electron microscopy, energy-dispersive X-ray spectrometry, elemental mapping, and CO2 and NH3 temperature-programmed desorption. It is shown that the EISA strategy in the presence of polymeric template not only is well-suited for the synthesis of ordered MAs and MA-supported metal oxides with tailored adsorption and framework properties, but also ensures a homogeneous distribution of metal species within inorganic framework with the aluminum/metal atomic ratio close to this used in the synthesis mixture. The aluminum and other metal precursors used in EISA have a significant impact on the pore structure, surface area, and basic and acidic properties of the resulting mixed oxides. For instance, the use of inexpensive aluminum nitrate nonahydrate in the synthesis leads to the significantly enlarged mesopores (ranging from ∼7 nm to 16 nm), improved ordering of the oxides, and enhanced adsorption affinity toward CO2, while the aluminum chloride precursor affords MA-supported metal oxides with a bimodal pore size distribution, with peaks located in the ranges of 2−4 nm and 5−9 nm, respectively. It is also shown that the use of inexpensive aluminum and metal salts as precursors instead of aluminum alkoxides affords MA-supported metal oxides with tailorable properties, in terms of the surface area, porosity, and surface basicity and acidity, which determine the performance of these materials in various applications, including adsorption and catalysis.

Ordered Mesoporous Crystalline γ-Al2O3 with Variable Architecture and Porosity from a Single Hard Template

In this paper, an efficient route is developed for controllable synthesis of ordered mesoporous alumina (OMA) materials with variable pore architectures and high mesoporosity, as well as crystalline framework. The route is based on the nanocasting pathway with bimodal mesoporous carbon as the hard template. In contrast to conventional reports, we first realize the possibility of creating two ordered mesopore architectures by using a single carbon hard template obtained from organic-organic self-assembly, which is also the first time such carbon materials are adopted to replicate ordered mesoporous materials. The mesopore architecture and surface property of the carbon template are rationally designed in order to obtain ordered alumina mesostructures. We found that the key factors rely on the unique bimodal mesopore architecture and surface functionalization of the carbon hard template. Namely, the bimodal mesopores (2.3 and 5.9 nm) and the surface functionalities make it possible to selectively load alumina into the small mesopores dominantly and/or with a layer of alumina coated on the inner surface of the large primary mesopores with different thicknesses until full loading is achieved. Thus, OMA materials with variable pore architectures (similar and reverse mesostructures relative to the carbon template) and controllable mesoporosity in a wide range are achieved. Meanwhile, in situ ammonia hydrolysis for conversion of the metal precursor to its hydroxide is helpful for easy crystallization (as low as approximately 500 degrees C). Well-crystallized alumina frameworks composed of gamma-Al(2)O(3) nanocrystals with sizes of 6-7 nm are obtained after burning out the carbon template at 600 degrees C, which is advantageous over soft-templated aluminas. The effects of synthesis factors are demonstrated and discussed relative to control experiments. Furthermore, our method is versatile enough to be used for general synthesis of other important but difficult-to-synthesize mesoporous metal oxides, such as magnesium oxide. We believe that the fundamentals in this research will provide new insights for rational synthesis of ordered mesoporous materials.

Homogeneously Dispersed Ceria Nanocatalyst Stabilized with Ordered Mesoporous Alumina

Homogeneously dispersed ceria nanocatalyst can be synthesized and stabilized with ordered mesoporous alumina by a one-step sol–gel method. This novel material possesses high thermal stability and exhibits 100% conversion at room temperature for CO oxidation when loaded with Au. This established approach can be expanded to the controlled synthesis and stabilization of other nanocatalysts with wide applications. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Ceria Nanocatalysts: Homogeneously Dispersed Ceria Nanocatalyst Stabilized with Ordered Mesoporous Alumina (Adv. Mater. 13/2010)

Ceria Nanocatalysts: Homogeneously Dispersed Ceria Nanocatalyst Stabilized with Ordered Mesoporous Alumina (Adv. Mater. 13/2010)

Synthesis of Mesoporous Alumina from Boehmite in the Presence of Triblock Copolymer

Mesoporous alumina was synthesized using commercial boehmite in the presence of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer Pluronic P123. Its calcination at 400 degrees C yielded gamma-alumina, in contrast to the ordered mesoporous alumina (OMA) obtained by hydrolysis of aluminum alkoxide in the presence of the same triblock copolymer. This synthesis afforded boehmite-based mesoporous alumina (BMA) with better adsorption properties and higher thermal stability in comparison to the alkoxide-based OMA, which remained amorphous after calcination below 900 degrees C. The BMA materials also exhibited higher amount of acidic and basic sites as evidenced by ammonia (NH(3)) and carbon dioxide (CO(2)) temperature programmed desorption (TPD), respectively. Dispersion of commercial boehmite precursor under microwave irradiation afforded BMA materials with similar surface characteristics as those of the corresponding BMA samples obtained under conventional conditions, but showing slightly lower acidity and better basic properties. Thus, the dispersion method of boehmite can be used to modify the surface properties of the resulting BMA samples without sacrificing their porosity.

Synthesis, Characterization and Catalytic Applications in Propane Dehydrogenation of Ordered Mesoporous Alumina

Alumina is the most frequently employed catalyst or catalytic support in the chemical industry. The catalytic performances of alumina-supported catalysts are largely dependent on the textural properties of the alumina supports. Therefore, any improvement of the alumina properties significant for their catalytic applications is extremely challenging. Ordered mesoporous aluminas with high thermal stability have been successfully prepared by a facile synthesis method. Using the ordered mesoporous aluminas as support, V/Ni-catalysts mesoporous materials also have been prepared by vacuum impregnation method and the coprecipitation method. The mesoporous structures are characterized by XRD, TEM, N2 adsorption -desorption and TG-DTA. Preliminary catalytic tests showed that the ordered mesoporous aluminas prepared in such a way exhibited superior performance in the oxidative dehydrogenation of propane to propylene when they were used as the supports for V and Ni catalysts.