Synthesis Of Mesoporous Alumina Research Articles

Mesoporous aluminas synthesis using carboxylic acids to enhance performance in CO2 adsorption

This work evaluated for the first time the effect of carbon chain size of different carboxylic acids (stearic and caprylic acid) and crystallization temperatures (60, 120, and 180 °C) on the structural, textural, morphological, basic, and mechanism properties of reaction in the synthesis of mesoporous aluminas (meso-Al2O3). Regarding the structure-directing agents (SDA) traditionally used in the synthesis of meso-Al2O3 (i.g. strong acids, strong bases, and synthetic polymers), carboxylic acids are non-toxic, biodegradable compounds of low commercial value, and can be obtained from renewable sources. The physical-chemical characterizations performed, including low and high-angle X-ray diffractometry (XRD), Fourier-transform infrared spectroscopy (FT-IR), thermal analysis (TG/DTG), nitrogen adsorption-desorption, temperature-programmed desorption of carbon dioxide (CO2-TPD), scanning electron microscopy (SEM), and transmission (TEM), confirmed the formation of mesostructured γ-Al2O3. No pore organization was observed, but a system of interconnected channels was provided by the wormhole-like structure. Mesoporous aluminas synthesized at 180 °C showed an increase in structural, textural (higher of 68 % in pore volume and 36% in pore diameter), and basic properties (around 19 %) about materials synthesized at 60 °C. This can be attributed to the increased degree of coordination of the carboxylic acid with aluminum during the hydrolysis-condensation reactions. Furthermore, stearic acid (longer carbon chain carboxylic acid) tends to bend during micellar aggregation, leading to pore sizes 33% smaller than caprylic acid (shorter carbon chain acid). Therefore, the best condition for meso-Al2O3 synthesis was obtained at 180 °C and using caprylic acid (CAP-180 °C) as SDA. The results of CO2 adsorption showed that all materials correlate better with the pseudo-first order model in the entire temperature range studied (10 – 50 °C), suggesting that diffusion through the interface gas-solid (external diffusion) is the limiting step of the adsorption process. The adsorbent CAP-180 °C showed high adsorption capacity (around 134.45 mgCO2/gads at 10 °C under atmospheric pressure) and elevated stability after eight cycles of adsorption-desorption, reaching adsorption capacity superior to other meso-Al2O3.

Pristine and modified-mesoporous alumina: molecular assistance-based drug loading and sustained release activity

The present article reports on the synthesis of mesoporous alumina and its modification through $$\upbeta $$ -cyclodextrin (BCD) incorporation for loading and release studies of amoxicillin. The drug loading in the mesoporous matrices was found to be activated upon providing molecular assistance by amino acids, L-methionine, L-proline and L-phenylalanine. The effect of molecular assistance has been attributed to intermolecular interactions between the drug and the individual amino acids which have been further confirmed by different spectroscopic studies. The drug-loaded material with BCD modification was found to exhibit a sustained release mechanism in physiological pH and is suggested as a proposed material for hip joint prosthesis.

Synthesis of mesoporous alumina: an impact of surface chemistry on release behavior

The present investigation describes the successful synthesis of mesoporous alumina (MeAl) nanoparticles for controlled drug delivery via a soft template route have been adopted using hexadecyltrimethyl ammonium bromide as template and aluminum chloride as precursor. The obtained Langmuir type II isotherm for MeAl showed P/Po 0.1 at 10 cm3/G STP. The Brunauer-Emmett-Teller study revealed the formation of uniform morphology and mesoporous structure. The fourier transform infrared spectroscopy study confirmed the presence of characteristic peaks of mesoporous alumina. Elemental analysis demonstrated the substantial Al and O peak supported with nanosized crumb with cluster by field emission scanning electron microscopy. The transmission electron microscopy indicates wormhole strikingly inter connected pore system assigned to functionalized MeAl. X-ray diffraction pattern suggests the formation of γ-Aluminum oxide. The particle size and surface charge of synthesized MeAl were successfully analyzed to assess the surface charge. The drug loading was confirmed by spectroscopic study with eloquent extension in drug release was found to be 74.44% attributed to release by control manner. In present study, synthesized MeAl holds an excellent compassionate impact on particle size and exterior chemistry for sustained release of model drug.

The Effect of Time and H2O/CTAB Ratio in Synthesis of Mesoporous Alumina from Bauxite Residue

Mesoporous alumina has been successfully synthesized from bauxite residues (red mud) as raw material and cetyltrimethylammonium bromide (CTAB) as template at room temperature. The effects of crystallization time and molar ratio of H2O/CTAB on structural and textural properties of mesoporous alumina were investigated. The synthesized product was characterized by XRD, FTIR, SEM-EDX, TEM, N2 adsorption-desorption and acidity test using pyridine adsorption. The XRD pattern and SEM micrograph showed that the synthesized product possessed an amorphous phase and irregular shapes. From obtained results, it could be observed that crystallization time and H2O/CTAB ratio influenced the surface acidity of mesoporous alumina.

Synthesis of mesoporous alumina with tunable structural properties

Mesoporous aluminas (MAs) with tunable structural properties including BET surface area, pore volume and pore size were successfully synthesized. The synthesis method was based on a sol–gel process via hydrolysis of aluminium isopropoxide associated with non-ionic block copolymer P123 as the structure-directing template in an acidic aqueous system. The MAs were characterized using thermogravimetry – differential thermal analysis (TG-DTA) for decomposition and mass loss characteristics during calcination, X-ray diffraction (XRD) for bulk crystallinity, transmission electron microscopy (TEM) for nano-scale morphology, selected area electron diffraction (SAED) for local crystallinity and N2 adsorption–desorption techniques for porous structural properties. By tailoring the amount of P123 and HNO3 addition, inorganic aluminium precursor Al(NO3)3 doping ratio and calcination temperature, MAs with controllable structural properties were obtained, leading to regular variations in the surface area (up to 409 m2g−1), pore volume (0.4 cm3g−1 ∼ 2.8 cm3g−1) and pore size (5.0 nm ∼ 33.1 nm). Bovine serum albumin (BSA) was employed to evaluate the adsorption capability of the synthesized MAs. It was found that the structural properties of MA had a crucial effect on the BSA adsorption capability, increasing dramatically with increasing surface area, pore volume and pore size. For the sample MA4P15AlN (surface area 287 m2g−1, pore volume 2.8 cm3g−1 and pore size around 33.1 nm), the BSA adsorption amount reached 182.7 mgg−1 in 2 h, higher than other MA samples as well as a silicon based reference sorbent material, SBA-15 (133.3 mgg−1).

Understanding the role of tetramethyl urea for the synthesis of mesoporous alumina

Mesoporous alumina was synthesized by hydrothermal method at 150 °C for 6–24 h using tetramethyl urea followed by their calcination at 500–1100 °C. The samples were characterized by XRD, FTIR, N2 adsorption–desorption, FESEM and TEM. The γ-Al2O3 was found to be stable up to 1000 °C for the samples prepared at 150 °C/6 h, and up to 900 °C for the samples prepared at 150 °C/12–24 h. The BET surface area values of 500 °C treated samples were 428 m2 g−1, 393 m2 g−1, and 366 m2 g−1 for the reaction time of 6 h, 12 h and 24 h, respectively. FESEM and TEM showed the formation of alumina nanoparticles at 150 °C/6 h, which ripened to flake-shaped alumina comprising of alumina nanoflakes (70–100 nm) at 150 °C/12–24 h. To understand the role of tetramethyl urea, a tentative formation mechanism was illustrated.

Synthesis of mesoporous alumina through photo cross-linked poly(dimethylacrylamide) hydrogels

Catalysis plays a central role in many fields of life, e.g., in biochemical processes, to reduce energy costs and resources in chemical industry and to decrease or even avoid environmental pollution and in energy management. Porous alumina (Al2O3) is an essential material in various applications, especially as a support material for catalysts. It is often prepared by nanocasting using porous carbon materials that serve as rigid structure matrices. In this work, an alternative way to synthesize mesoporous Al2O3 by using hydrogels as porogenic material is presented. Hydrogels can easily be patterned by light and used to imprint their structure onto alumina opening a new approach to fabricate patterned Al2O3. The hydrogels used in this work are based on poly(dimethylacrylamide) and were photo-chemically cross-linked. Followed by a nanocasting process, mesoporous alumina samples were synthesized and characterized by N2 physisorption and X-ray diffraction. The cross-linker amount in the polymer network was varied and the influence on the properties of the Al2O3 is analyzed.

Synthesis of mesoporous alumina with CO2 expanded carbonation and its catalytic oxidation of cyclohexanone

A CO2 expanded carbonation technique is proposed for direct synthesis of alumina powders that does not require structure directing substances or templates. Mesoporous amorphous flower-like alumina was synthesized at relatively low volume expansions (lower ethanol to water volume ratio), whereas mesoporous crystalline honey-comb-like alumina was synthesized at high volume expansions. The alumina powders exhibited high surface area and pore size with small crystallite sizes. The alumina structures were stable from 400 to 800°C. Experimental tests showed that the alumina powders could catalytically convert cyclohexanone to ɛ-caprolactone efficiently. The use of the calcined catalysts (at 400 and 800°C; flower-like alumina) at equal ethanol to water volume ratio avoids the usual and inevitable hydrolysis of ɛ-caprolactone to ɛ-hydroxyhexanoic acid. The catalyst was recyclable and stable for up to five reaction cycles.

Simplified sol–gel method for synthesis of mesoporous alumina

In the present investigation, a simplified method for the synthesis of mesoporous alumina using a sol–gel strategy is reported. Formation of the mesoporous structure is supported by the results of a Brunauer-Emmett-Teller study. The Fourier transform infrared spectroscopy spectra confirmed its primary characteristic peaks. Elemental analysis and X-ray diffraction revealed the formation of γ-Al 2 O 3 , after calcination at 700°C. Particle size and zeta potential were measured to assess the size and the surface charge of the synthesised mesoporous material.

A template-free synthesis of mesoporous crystalline γ-alumina through partial hydrolysis of aluminum nitrate aqueous solution

The synthesis of mesoporous alumina with large surface area and crystalline nature is still a great challenge because of the susceptibility to hydrolysis of aluminum precursors. Here, we first report a preparation of NH4NO3 and Al species hybrids containing Keggin-Al13 [Al13O4(OH)24(H2O)127+] through a simple condensation of Al(NO3)3 aqueous solution partially hydrolyzed with (NH4)2CO3. Thermal treatment at a low temperature of 200°C could successfully transform the hybrid to γ-alumina, which exhibited a wormhole-like mesoporous structure with high surface area of 380–450m2/g and narrow PSD after completely removing NH4NO3 at 300°C.

Synthesis of Mesoporous Alumina: Effect of Preparation Variables on the Textural Properties

Synthesis of mesoporous alumina has received attention of researchers due to its application, as support for heterogeneous catalysts. In order to use mesoporous alumina as support, it should have a desired surface area, pore size, and pore volume. Generally, mesoporous alumina is synthesized using sol-gel method. This article reviews the influence of different parameters during the synthesis on the textural properties of mesoporous alumina from recent works and patents. The effect of variables during the synthesis route such as types of surfactant, pH of reaction medium, water concentration in hydrolysis reaction, as well as calcination temperature are reviewed and discussed.

Synthesis of Mesoporous Alumina: Effect of Preparation Variables on the Textural Properties

Synthesis of Mesoporous Alumina: Effect of Preparation Variables on the Textural Properties

Sucrose-Template Synthesis of Mesoporous Alumina from Aqueous Systems

Mesoporous alumina was prepared by using sucrose as a structure-directing template in an aqueous system. The resultant samples were characterized by using different methods such as x-ray diffraction, transmission electron microscopy, nitrogen adsorption-desorption analysis, and thermogravimetric and differential thermal analyses. The results showed that the prepared mesoporous gamma alumina has high surface area, uniform pore size distribution and excellent thermal stability.

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.

Investigation of the Surfactant Role in the Synthesis of Mesoporous Alumina

Mesoporous alumina with a narrow pore size distribution can be synthesized by hydrolysis of aluminum alkyl ethers in an organic solvent in the presence of an ionic or nonionic surfactant. However, the pores are not ordered and the role of the surfactant as a possible template is not clear as it is in the synthesis of the mesoporous silica of the M41S family and of the SBA-15, 16 type materials. In this work we use continuous wave electron paramagnetic resonance (CW-EPR) spectroscopy, in combination with electron spin−echo envelope modulation (ESEEM) measurements, to provide experimental evidence for the interaction between the surfactant and the alumina species during synthesis. This is achieved by using spin-labeled analogs of the surfactants and following their interaction with 27Al at different stages of the alumina formation. The results show that in sec-butanol solutions the surfactants do not form micellar aggregates. Instead, the anionic surfactant, lauric acid, has a strong tendency to bind to alumina precursors, hydrolysis products of the aluminum alkyl ethers in the starting solution, and remains bound until the final product. Here the surfactant decorates the surface of the alumina particles with an average extended configuration with the carboxylate being the closest to the alumina surface. The interaction with aluminum increases during precipitation as the density of the alumina increases. By contrast, the nonionic polyethyleneoxide type surfactants: Tergitol 15-S-12 and Pluronics P123 and L64 seem to remain unbound even in the as-synthesized precipitates. In this last case, EPR spectra of a small, hydrophobic spin probe have shown that solvent evaporation by room temperature drying brings about the formation of liquid-like “organic zones” confined in the alumina structure, which presumably are at the origin of the pores.

Cation–anion double hydrolysis derived mesoporous γ-Al2O3as an environmentally friendly and efficient aldol reaction catalyst

Parameters, such as crystallization temperature, pH, P123 content and aluminium source in the synthesis of mesoporous aluminas using the cation–anion double hydrolysis method (P. Bai, P. Wu, G. Zhao, Z. Yan and X. S. Zhao, J. Mater. Chem., 2008, 18, 74) were examined. With the assistance of characterization techniques, such as N2 adsorption, X-ray diffraction (XRD), transmission electronic microscopy (TEM), selected area electron diffraction (SAED) and 27Al magic-angle spinning (MAS) nuclear magnetic resonance (NMR), it was found that the parameters studied all have an influence on both the textural properties and the crystalline structure of the resultant solid materials. Dependence of the catalytic activity of the mesoporous alumina materials on the synthesis parameters was observed. The observed remarkably high catalytic activity of the mesoporous alumina materials is attributed to the high surface area, surface basicity, pure γ-Al2O3 phase and absence of anion residues, such as SO42−.

New Templating Route for Synthesis of Mesoporous Alumina

Synthesis of mesoporous alumina made by nanocasting using polymer spheres matrix is reported. In contrast to all other recipes described in the literature so far, mesoporous alumina prepared by the nanocasting method consists of irregularly ordered particles exhibiting pores of ca. 25 nm in size. The void volume among the particles constitutes a porous system with narrow pore size distribution in the mesopore region.

Synthesis of mesoporous alumina using polyvinyl alcohol template as porosity control additive

The effects of polyvinyl alcohol (PVA) template and calcinations temperatures on the characteristics of the alumina films were investigated. The samples were prepared by sol-gel method using aluminium triisopropylate precursor. The variation of microstructure, pore size and pore volume, were determined by nitrogen adsorption/ desorption analysis and the macropore size distribution was determined using mercury porosimetry. TEM and SEM were used to observe the texture of these samples and the particle morphology. Experimental observation after drying and annealing shows that it is possible to produce crack free nanoporous alumina films using polyvinyl alcohol template. The obtained alumina samples have macroporous microstructure (with the average pore diameter dav = 34.9 ?m, for sample prepared with 42.5 wt% of PVA addition and annealed at 1000?C) with high portion of mesopores (with the average pore diameter Dav = 14.0 nm for the same sample).

Synthesis of Mesoporous Alumina Using Carboxyl Functional, Hyperbranched Polyesters as Templates

A series of mesoporous aluminas have been synthesized using commercial hyperbranched polyesters of the second to fourth generation as porogens. To achieve a suitable interaction between the polymer and the aluminium source, aluminium sec‐butoxide, the terminal hydroxyl groups of the hyperbranched polymer were first reacted by succinic anhydride. The mesoporous aluminas were analyzed by nitrogen adsorption/desorption, X‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). No dependence of the generation of the hyperbranched template on pore size was found in this study. Instead the pore size appears to depend on the amount of water added to the reaction mixture as well as the concentration of the hyperbranched polymer.

Synthesis of mesoporous alumina with highly thermal stability using glucose template in aqueous system

Mesoporous alumina materials prepared from precursors of Al[O iPr] 3/HNO 3 in the presence of glucose in aqueous system, exhibit high specific surface areas, narrow pore size distributions and excellent thermal stability.