Mesoporous γ-Al2O3 Research Articles

Comparative study of the catalytic performance of physically mixed and sequentially utilized γ-alumina and zeolite in methanol-to-propylene reactions.

This study aimed to investigate the catalytic performance of H-ZSM-5 zeolite compared with physically mixed and sequentially used synthesized γ-alumina and zeolite in the methanol-to-propylene (MTP) reaction. A facile, green and cost-effective method was first applied to prepare a mesoporous γ-Al2O3 support using a combination of sol-gel and hydrothermal methods via a few consecutive steps. This process was carried out using aluminium nitrate and polyethylene glycol with different molecular weights as non-ionic surfactants. X-ray diffraction, transmission electon microscopy, thermogravimetric analysis, ammonia temperature programmed desorption and Brunauer-Emmett-Teller analysis were then used to characterize the prepared γ-Al2O3 catalyst. Afterwards, the catalytic activity of the commercial H-ZSM-5 zeolite (Si/Al = 200) and the effect of the presence of the γ-alumina physically mixed and unmixed with the zeolite were also researched in the MTP reaction. Accordingly, methanol conversion and product selectivity were monitored via gas chromatography. The physically mixed mesoporous γ-Al2O3 and H-ZSM-5 zeolite exhibited the highest catalytic activity in terms of both conversion and selectivity at 400°C. To our knowledge, this research represents the first documented use of γ-alumina and zeolite simultaneously as catalysts in the MTP reaction within the English literature. It is hoped that this work will offer valuable insights for advancing the development of catalytic systems in methanol conversion processes.

Hydrolysis of carbonyl sulfide using non-ionic surfactant-modified mesoporous γ-Al2O3 catalysts with high efficiency

Carbonyl sulfur (COS) was difficult to be removed by conventional desulfurization technologies because of its stable chemical properties. Mesoporous γ-Al2O3 (MA) showed excellent potential for hydrolysis of COS, but the catalyst life was greatly shortened with the progress of the reaction. Therefore, improving the catalyst life is the key to MA which can apply to hydrolysis of COS. In this study, P123 modified mesoporous γ-Al2O3 (P-MA) catalyst was prepared by sol–gel method, and it was regulated by template agent and acidity regulator. These preparation conditions of P-MA were optimized to improve the hydrolysis efficiency of COS. The effects of temperature, space velocity, relative humidity and oxygen concentration for the hydrolysis efficiency of COS were studied. The results show that the optimized P-MA catalyst is suitable for COS low-temperature hydrolysis reaction, and it can maintain 99 % for 10 h under the tough reaction conditions. The only crystal of P-MA was γ-Al2O3 with large specific surface area and uniform distribution pore, which are beneficial to the COS hydrolysis. In addition, the hydrolysis efficiency of COS can also remain 97 % for 10 h in the O2 and CO2 atmosphere, indicating that the P-MA catalyst has a specific anti-poisoning ability. The kinetics and reaction mechanism of COS catalytic hydrolysis were studied, which showed that the adsorption of H2S was the key to hindering the continuous reaction. The P-MA can effectively inhibit the adsorption of H2S, which greatly improved COS hydrolysis life of P-MA. This study provided a theoretical basis for the application of Al2O3 catalyst in the COS hydrolysis.

Extraction and green template-free synthesis of high-value mesoporous γ-Al2O3 and SiO2 powders from coal gangue

The study successfully demonstrated an eco-friendly approach for synthesizing mesoporous alumina and mesoporous silica from coal gangue, in line with green chemistry rules. By employing natural breakdown and increased dissolution of coal gangue through specific chemical treatments, along with optimal leaching conditions, this study achieved a dissolution efficiency of over 98% for aluminum. This process, which includes leaching, separation, simultaneous precipitation, selective dissolution, gel formation, and calcination, produced mesoporous alumina and mesoporous silica without the need for templates. The results presented that the synthesized mesoporous alumina and silica had purities of 98.81% and 99.08%, respectively. Additionally, the synthesized mesoporous alumina and silica had specific surface areas of 340.15 and 392.85 m2/g, and average pore sizes of 7.27 and 3.25 nm, confirming the desirable physical properties of the synthesized γ-Al2O3 and SiO2. These products offer a sustainable solution to environmental issues caused by coal accumulation, with promising applications across various industries.

The key role played by mesoporous alumina as binder for obtaining ultra-hard CaO based pellets for thermochemical heat storage leveraging the CaO/CaCO3 cycle

The synthesis of CaO-based pellets with high energy storage and suitable mechanical resistance after prolonged cycling is pivotal for the successful implementation of the Calcium looping (CaL) technology for energy storage in CSP plants. In this work, CaO-based spherical pellets (CAA) were prepared made up of 60 wt % Ca(OH)2 and varying ratios (0–40 wt %) of commercial γ-Al2O3 and mesoporous γ-Al2O3 (m-Al2O3). They were tested in TG in several CO2 carbonation/decarbonation cycles (15 and 50 for selected pellets) and their respective average crushing strengths measured. After 15 cycles, the optimum pellet CAA 20-20 (60 wt % Ca(OH)2/20 wt % γ-Al2O3/20 wt % m-Al2O3) exhibits a remarkable energy storage density of 1030 kJ/kg with a superb crushing strength of ∼29 N. This was ascribed to the enhanced formation of the calcium aluminate mayenite (Ca12Al14O33), since the high BET surface area (384 m2 g−1) of mesoporous γ-Al2O3 promotes the interaction with calcium oxide. Additionally, CAA 20-20 showed meaningful porosity that favored CO2 mass transport. Interestingly, after 50 cycles, the optimum CAA 20-20 pellet maintained a high carbonation yield (0.46), representing an 84 % of the initial value and corresponding to an energy storage density of ∼873 kJ/kg. Additionally, the optimum CAA 20-20 pellet was coated with an external layer of Al-MCM-41 silica that augmented its crushing strength up to 37 N, with a concurrent slight abatement in the carbonation yield and energy storage density after 50 cycles (0.43 and ∼824 kJ/kg). Consequently, both uncoated and coated CAA 20-20 pellet are promising for the successful implementation of CaL in CSP plants.

Copper and zinc-impregnated mesoporous gamma-alumina catalyst for hydrothermal liquefaction of alkali lignin

The complete utilization of lignocellulose is a sustainable key for bio-refineries, where the utilization of evitable lignin is a great challenge owing to its structural complexity. Here, the effect of Cu and Zn-loaded mesoporous γ-Al2O3 catalysts was examined for the first time for the hydrothermal liquefaction of alkali lignin in an ethanol/water solvent system. It showed excellent performance towards the liquefaction as compared to that of (commercial) com-5Cu/γ-Al2O3 catalyst. Here, the bio-oil yield was observed to be 47.7 wt% for com-5Cu/Al catalyst which was increased to 59.1% for syn-5Cu/Al. It was increased substantially to 65.4 wt% for syn-10Cu/Al. However, only a 40 wt% bio-oil yield was found for the non-catalytic (NC) reaction. Additionally, a further significant improvement to 74.7 wt% was noticed for Zn (5 wt%) modified syn-10Cu/Al catalyst. Here, the screening of the water-ethanol mixture, and reaction parameters were also evaluated which showed a small increase in bio-oil yield to 77.4 wt% for ethanol/water (75/25, v/v). The GC-MS analysis of bio-oil exhibited the high specificity of vanillin (69.3%) for syn-10Cu-5Zn/Al. The 1H NMR and FT-IR investigation also validate the diverse functionality of bio-oils. The reusability of the optimum catalyst (syn-10Cu-5Zn/Al) was also tested for three successive catalytic cycles that exhibited the good performance of the catalyst up to the second cycle.

Nitridation-activated Al flakes for hydrogen generation on-demand

The on-demand generation of hydrogen from aluminium particles can be a promising approach to alleviate air pollution from town gas production facilities during peak operation periods. Overcoming the challenges of disrupting the protective alumina film on aluminium particles without using highly corrosive alkaline solutions, energy-intensive processes, or expensive metal additives is crucial. This study reports the hydrolysis of aluminium flakes with gamma-alumina (γAl2O3) and aluminium nitride (AlN) nano inclusions in distilled water. We optimised the growth of these active inclusions via calcination of aluminium flakes in a semi-permeable steel chamber at temperatures ranging from 843 to 903 K. The optimal activation process triggers hydrogen release by hydrolysing AlN within the activated flakes at moderate temperatures (313−353 K). Additionally, we study the synthesis of mesoporous γAl2O3 particles from hydrolysis by-products and explore the potential for harnessing waste heat and ammonium solution in town gas production.

Preparation of high permeability γ-Al2O3 ultrafiltration membranes from pseudo-boehmite industrial precursor

To obtain γ-Al2O3 ultrafiltration membranes, AlOOH sols which were usually derived from aluminum alkoxide were used as the top layer precursor. However, the colloidal sols obtained by this process were complex, high cost and time-consuming. Pseudo-boehmite, an industrial product with characteristics of high purity, excellent gelation and strong caking property, was widely used to prepare γ-Al2O3 products. In this work, mesoporous γ-Al2O3 ultrafiltration membranes were prepared conveniently and quickly by using pseudo-boehmite powder as precursor with colloidal sol-gel route at room temperature. The effects of H+/Al3+ molar ratio and polyvinyl alcohol (PVA) content on the properties of AlOOH sols and γ-Al2O3 ultrafiltration membranes were analyzed. Results showed that the viscosity and hydrodynamic particle diameter of the AlOOH sols can be controlled by changing the H+/Al3+ molar ratio, and the pore size of the prepared γ-Al2O3 ultrafiltration membranes could be varied by adjusting the PVA content in the AlOOH sols coating slurry. The pore size increased from 6.98 nm to 11.34 nm by increasing PVA content from 1.25% to 1.50%. Additionally, the γ-Al2O3 ultrafiltration membranes derived from the pseudo-boehmite exhibited a relatively high permeability (＞94.5 L m−2 h−1⋅MPa−1), which was higher than that of the aluminum alkoxide derived.

Catalytic upgrading of bio-oil model mixtures in the presence of microporous HZSM-5 and γ-Al2O3 based Ni, Ta and Zr catalysts

Bio-fuel production from bio-oil was investigated in the presence of microporous HZSM-5 and Al2O3 (MA) based catalysts. This study focused on the catalytic upgrading of a model bio-oil compound with ethanol for bio-fuel production. The model compound containing hydroxypropanol/furfural/formic acid: 4/6.5/5 by volume was used as a bio-oil mixture. Activity tests were performed under atmospheric pressure with a volumetric feed ratio of 30/70 bio-oil mixture/ethanol using a 0.5 g catalyst. In the reaction studies performed on the commercial microporous HZSM-5 catalyst, the optimum co-cracking temperature was determined as 400 °C. Mesoporous γ-Al2O3 support was synthesized by the evaporation-induced self-assembly (EISA) synthesis method, and Ni, Ta, and Zr metals were incorporated into the structure of the catalyst by the impregnation method to improve the surface acidity. The synthesized catalysts were characterized by X-ray diffraction (XRD), X-ray absorption near edge spectroscopy (XANES), N2 adsorption–desorption, scanning electron microscopy energy dispersive spectroscopy (SEM/EDS), X-ray fluorescence (XRF), Fourier-transformed infrared spectroscopy (FTIR), pyridine adsorbed diffuse reflectance FTIR spectroscopy (DRIFTS), and thermogravimetric/differential thermal analysis (TGA-DTA). Monometallic and pure alumina catalysts indicated an ordered mesoporous structure with surface area values 106–389 m2/g. Lewis and Brønsted acid sites associated with mild acidity were observed in the DRIFTS results of the 10 wt% Zr-containing alumina catalyst (10Zr@MA). The highest oil phase selectivity and isoparaffin selectivity in oil phase values were obtained in the presence of 10Zr@MA as 17.22% and 80.96%, respectively. 10Zr@MA catalyst showed the best catalytic activity compared to other catalysts, with 9.54% coke formation.

Catalytic decomposition sensing mechanism of mesoporous gamma alumina for freon R134a detection

Freon R134a is a widely used refrigerant that can cause a severe greenhouse effect and should be detected on site. However, it is a big challenge for semiconductor gas sensors to detect the inert Freon R134a molecules. Herein, mesoporous γ-Al2O3 is synthesized and loaded on top of ZnO sensing materials to form a bilayer microsensor to realize high-performance detection of Freon R134a. The mesoporous γ-Al2O3 material first decomposes the inert R134a molecule into a large number of active radicals. The generated reactive radicals are then easily sensed by the ZnO material. The limit of detection (LOD) of the bilayer sensor reaches the ppm level, which meets the requirements for on-site detection of Freon R134a leakage. The online mass spectrum (online MS) is used to identify the produced radicals qualitatively. According to the online MS results, the catalytic mechanism of mesoporous γ-Al2O3 for Freon R134a molecules has been clearly revealed.

Surface engineering of γ-Al2O3 nanosheets with highly dispersed poly(ionic liquids) for selective CO2 adsorption

An efficient CO2 adsorbent (γ-Al2O3 @PAVIMBr) was constructed by means of graft copolymerization with mesoporous γ-Al2O3 nanosheets served as the host material and amino-functionalized imidazolium based poly(ionic liquids) (PAVIMBr) as the guest material. Thereinto, mesoporous γ-Al2O3 could provided abundant hydroxyl groups for loading PAVIMBr uniformly via chemical bonding interaction, while PAVIMBr was able to tailor suitable pore size and expose amino-groups adsorption active sites that was contributed to chemisorb with CO2. It was observed that the general topography of γ-Al2O3 @PAVIMBr composite was almost unchanged after PAVIMBr loaded, and its mesoporous structure and crystalline form was still maintained. Moreover, the content of PAVIMBr in our composite could be calculated from the TGA results before and after its grafting. The obtained γ-Al2O3 @PAVIMBr presented a good CO2 adsorption performance, its CO2 adsorption capacity increased obviously. Meanwhile, the CO2/N2 selectivity of γ-Al2O3 @PAVIMBr was 15.3 times higher than that of γ-Al2O3 at room temperature and the pressure of 100 kPa, while the CO2 uptake of γ-Al2O3 @PAVIMBr was almost 13 and 3 times higher than that of PAVIMBr and γ-Al2O3 at 10 kPa and 25 °C, respectively. It was mainly attributed to that the maintaining mesoporous channels in γ-Al2O3 @PAVIMBr could accelerate the CO2 diffusion, while chemisorption of those exposed adsorption active sites from loaded PAVIMBr could improve the adsorption performance at lower CO2 partial pressure and CO2/N2 selectivity of our composite. Furthermore, the excellent CO2/N2 selectivity, renewability and physicochemical stability of γ-Al2O3 @PAVIMBr might employ it as one of the potential CO2 adsorbents.

Advances in the understanding of mesoporous transition aluminas: Unveiling the correlation between morphology and thermostability

The thermostabilities of mesoporous γ-Al2O3 samples with similar initial surface areas and average pore radii, but significantly different pore volumes, were studied in detail. The results show that γ-Al2O3 with highest initial pore volume converts to α-Al2O3 at a significantly higher temperature, along with larger residual surface area and pore volumes after aging. These observations are directly related to the morphologies of the individual particles and the resulting aggregate structures, which were studied by automated crystallite orientation mapping (ACOM-TEM). Large particles with well-developed plate-like morphologies preferentially form dense stacks by assembly via the {110} main basal planes (pseudo-cubic lattice). This arrangement favors sintering and the formation of α-Al2O3 at comparatively low temperatures. Aluminas with higher proportions of the lateral {100} and {111} facets tend to form aggregate structures with higher porosities and lower interparticle contact areas, thus explaining their superior thermostabilities. These findings highlight the importance of the aggregate structure for the purposeful development of alumina-supported catalysts.

Spray pyrolysis synthesis of mesoporous γ-AlOOH and γ-Al2O3 microspheres and their properties for Cr (VI) adsorption

ABSTRACT In this work, mesoporous spherical γ-AlOOH and γ-Al2O3 particles were rapidly prepared by spray pyrolysis (SP) at different temperatures (400°C–700°C) without the use of template materials. A sol-gel-derived colloidal solution of boehmite was ultrasonicated to generate fine droplets, which were continuously and rapidly transferred into a quartz reactor heated at a specific temperature by a constant flow of N2 gas. Under ultrasonication-assisted spray conditions, a phase change from boehmite to γ-alumina occurred at a temperature of 500°C, leading to a decrease in the surface area and surface hydroxyl group density of the products. At 400°C, the produced γ-AlOOH microspheres exhibited the highest surface area values of ca. ~ 510 m2/g and a surface hydroxyl group density of ca. ~ 2.92 mmol/g, surpassing those of commercial boehmite. The Cr (VI) removal experiments revealed that γ-AlOOH and γ-Al2O3 microspheres have good adsorption performance towards Cr6+. The optimal γ-AlOOH spheres exhibited the highest Cr(VI) adsorption capacity of ca.~ 44.5 mg/g (~74%) at 27 °C and pH = 5.5. After five adsorption-desorption cycles, the synthesised boehmite powder remained a Cr6+ adsorbing capacity of ~ 78%. Notably, the fabricated SP-γ-AlOOH was capable of simultaneously removing Cr6+ and textile dye from the solution. This study provides a facile, rapid, and scalable approach for producing boehmite powder with improved properties for Cr (VI) adsorption.

Preparation of high pore volume γ-Al2O3 nanorods via “gibbsite-AACH” precursor route in a membrane dispersion microreactor

In this work, several mesoporous γ-Al2O3 nanorods with high pore volume and narrow pore size distribution were controllable prepared via “gibbsite-AACH (ammonium aluminum carbonate hydroxide)” precursor route in a membrane dispersion microreactor. The effects of reaction temperature, (NH4)2CO3 concentration and calcination temperature on the samples were intensively studied. The highly uniformed morphology was assured due to the high mixing intensify in the membrane dispersion microreactor and the successful conversion of the precursor in the slurry. Under optimal conditions, these as-prepared γ-Al2O3 nanorods behaved high pore volume of 1.65 mL/g and narrow pore size distribution of 3–20 nm with a length and width of 150–200 nm and 30–60 nm, respectively. Furthermore, the adsorption experiment of the prepared samples were carried out under natural pH value, and the as-prepared sample of AACH-500 exhibited favorable adsorption performance for Congo red (CR) solution. The maximal adsorption capacity was up to 2006.7 mg/g, thus indicating that the as-prepared mesoporous γ-Al2O3 nanorods are in adsorption and other application potential of the field.

Role of zeolite properties in bio-oil deoxygenation and hydrocarbons production by catalytic cracking

A comparison between the behavior of Y and ZSM-5 zeolites having the same Si/Al ratio was established in the catalytic cracking of bio-oil for producing fuels and platform chemicals. The catalysts were prepared by agglomerating each zeolite with a mesoporous γ-Al2O3 matrix. Properties of the zeolites and the catalysts were characterized by N2 ads/desorption, SEM-EDX, pyridine-FTIR, tBA-TPD, and NH3-TPD techniques. The experiments were conducted in a continuous two-step catalytic cracking system (TS-CC) at 450 °C. Both catalysts are highly selective to C5-C12 hydrocarbons, with a composition strongly affected by the porous structure and acidity of the zeolite. The HZSM-5 catalyst (high acid strength and Brønsted/Lewis ratio) promotes cracking and deoxygenation reactions that lead to C2−C4 olefins which condensate into aromatics, yielding 9% of 1-ring aromatics (3% BTX) and 4% of naphthalenes for a feed conversion of 85%. These reactions are less favored over the HY catalyst, which promotes olefins oligomerization and hydrogen-transfer reactions, yielding 14% of highly aliphatic gasoline (> 30% linear paraffins) and 5% of C13−C20 diesel fraction (> 90% long chain paraffins). The remaining upgraded bio-oil obtained with both catalysts is composed of light oxygenates, with ketones, acids and esters as main components and low concentration of phenolic compounds.

Synthesis of Mesoporous γ-Alumina Support for Water Composite Sorbents for Low Temperature Sorption Heat Storage

The efficiency of thermochemical heat storage is crucially determined by the performance of the sorbent used, which includes a high sorption capacity and a low regeneration temperature. The thermochemical salt hydrate– γ-alumina composite sorbents are promising materials for this application but lack systematic study of the influence of γ-alumina structural properties on the final storage performance. In this study, mesoporous γ-Al2O3 supports were prepared by solvothermal and hydrothermal synthesis containing a block copolymer (F-127) surfactant to design thermochemical CaCl2 and LiCl composite water sorbents. Altering the solvent in the synthesis has a significant effect on the structural properties of the γ-Al2O3 mesostructure, which was monitored by powder XRD, nitrogen physisorption, and SEM. Solvothermal synthesis led to a formation of mesoporous γ-Al2O3 with higher specific surface area (213 m2/g) and pore volume (0.542 g/cm3) than hydrothermal synthesis (147 m2/g; 0.414 g/cm3). The highest maximal water sorption capacity (2.87 g/g) and heat storage density (5.17 GJ/m3) was determined for W-46-LiCl containing 15 wt% LiCl for space heating, while the best storage performance in the sense of fast kinetics of sorption, without sorption hysteresis, low desorption temperature, very good cycling stability, and energy storage density of 1.26 GJ/m3 was achieved by W-46-CaCl2.

Single-Atom Ru on Al2O3 for Highly Active and Selective 1,2-Dichloroethane Catalytic Degradation.

1,2-Dichloroethane (1,2-DCE) is a toxic volatile organic compound, which is harmful to the environment and human health. Herein, we develop a single-atom Ru catalyst anchored on the mesoporous schistose γ-Al2O3 (Ru SACs/m-γ-Al2O3) to enhance the catalytic activity and selectivity toward 1,2-DCE degradation. The Ru SACs/m-γ-Al2O3 shows low T50 and T90 (the temperature for 50 and 90% conversion) of 215 and 289 °C, which are lower than those for Ru NPs/m-γ-Al2O3 (291 and 374 °C) and pristine m-γ-Al2O3 (323 and 386 °C). The degradation products are mainly CO2 (>94%) and HCl (>90%) by using the Ru SACs/m-γ-Al2O3 catalyst, and almost no byproducts are detected. Furthermore, Ru SACs/m-γ-Al2O3 also presents excellent anti-chlorine poisoning effect and water resistance during the stability test. This work may shed light on the development of efficient single-atom catalysts for the degradation of industrial pollutants.

Practicality of hierarchically macro/mesoporous γ-Al2O3 as a promising sorbent in the preparation of low specific activity 99Mo/99mTc generator

Hierarchically macro-/mesoporous γ-Al2O3 (HMMA) was synthesized and characterized by various analytical techniques. The results indicated that HMMA possessed macropores (∼0.45 μm) and mesopores (∼10.6 nm) with a large surface area (∼542 m2 g−1). The absorption behaviors of Mo and Re with HMMA were investigated. The maximum static absorption capacity could reach about 250 mg Mo per g HMMA. The absorption equilibrium can be attained quickly within 10 mins. At initial Mo ions concertation of 10,000 mg L−1, the breakthrough capacity was determined to be around 200 mg Mo per g HMMA. Additional, absorption mechanism results indicated that Mo ions reacts strongly with a hydroxyl on the surface of γ-Al2O3 and an adjacent Al atom, simultaneously. A 9.15 mCi (339 MBq) 99Mo generator was prepared and evaluated its performance for over one week. The recovery of 99mTc could reach about 89% with favorable radionuclidic, radiochemical and chemical purity for nuclear medicine application. HMMA has a potential application prospect for the preparation of low specific activity (LSA) 99Mo/99mTc generator.

Coke-resistance enhancement of mesoporous γ-Al2O3 and MgO-supported Ni-based catalysts for sustainable hydrogen generation via steam reforming of acetic acid

Highly ordered mesoporous γ-Al2O3 particles and MgO materials were synthesized by evaporation induced self-assembly (EISA) and template-free hydrothermal co-precipitation routes, respectively. Ni, Ni–MgO, and Ni–La2O3-containing catalysts were prepared using a wet-impregnation method. The synthesized catalysts were characterized by N2 adsorption–desorption, XRD, SEM-EDS, DRIFTS, XPS, TGA-DTA, and Raman spectroscopy analysis. The mesoporous γ-Al2O3 catalyst support exhibited a high surface area of 245 m2/g and average pore volume of 0.481 cm3/g. The DRIFTS results indicate the existence of large Lewis's acid regions in the pure γ-Al2O3 and metal-containing catalysts. Catalytic activity tests of pure materials and metal-containing catalysts were carried out at the reaction temperature of 750 °C and a feed molar ratio of AA/H2O/Ar:1/2.5/2 over 3 h. Complete conversion of acetic acid and 81.75% hydrogen selectivity were obtained over the catalyst 5Ni@γ-Al2O3. The temperature and feed molar ratio had a noticeable impact on H2 selectivity and acetic acid conversion. Increasing the water proportion in the feed composition from 2.5 to 10 considerably improved the catalytic activity by increasing hydrogen selectivity from 81.75% to 91%. Although the Ni-based γ-Al2O3-supported catalysts exhibited higher activity performance compared to the Ni-based MgO-supported catalysts, they were not as resistant to coke formation as were MgO-supported catalysts. The introduction of MgO and La2O3 into the Ni@γ-Al2O3 and Ni@MgO catalysts' structures played a significant role in lowering the carbon formation (from 37.15% to 17.6%–12.44% and 12.17%, respectively) and improving the thermal stability of the catalysts by decreasing the agglomeration of acidic sites and reinforcing the adsorption of CO2 on the catalysts' surfaces. Therefore, coke deposition was reduced, and catalyst lifetime was improved.

Ordered Mesoporous Alumina with Tunable Morphologies and Pore Sizes for CO2 Capture and Dye Separation.

We describe a versatile and scalable strategy toward long-range and periodically ordered mesoporous alumina (Al2O3) structures by evaporation-induced self-assembly of a structure-directing ABA triblock copolymer (F127) mixed with aluminum tri-sec-butoxide-derived sol additive. We found that the separate preparation of the alkoxide sol-gel reaction before mixing with the block copolymer enabled access to a relatively unexplored parameter space of copolymer-to-additive composition, acid-to-metal molar ratio, and solvent, yielding ordered mesophases of two-dimensional (2D) lamellar, hexagonal cylinder, and 3D cage-like cubic lattices, as well as multiscale hierarchical ordered structures from spinodal decomposition-induced macro- and mesophase separation. Thermal annealing in air at 900 °C yielded well-ordered mesoporous crystalline γ-Al2O3 structures and hierarchically porous γ-Al2O3 with 3D interconnected macroscale and ordered mesoscale pore networks. The ordered Al2O3 structures exhibited tunable pore sizes in three different length scales, <2 nm (micropore), 2-11 nm (mesopore), and 1-5 μm (macropore), as well as high surface areas and pore volumes of up to 305 m2/g and 0.33 cm3/g, respectively. Moreover, the resultant mesoporous Al2O3 demonstrated enhanced adsorption capacities of carbon dioxide and Congo red dye. Such hierarchically ordered mesoporous Al2O3 are well-suited for green environmental solutions and urban sustainability applications, for example, high-temperature solid adsorbents and catalyst supports for carbon dioxide sequestration, fuel cells, and wastewater separation treatments.

Preparation of mesoporous γ-Al2O3 with high surface area from an AlOOH extract of recycling biomass ash

This study explores the potential application of recycled materials extracted from arboreal ABA (ABA); this waste is used as an alternative source of aluminium oxyhydroxide for the synthesis of γ-Al2O3 with high surface area-based mesoporous materials with interesting applications in environmental remediation. The aluminium present in ABA was extracted by desilication and reflux in acid and subsequently converted to mesoporous γ-Al2O3 via a sol–gel process with Pluronic P-123 as surfactant. The surface of that material was successfully functionalized with racemic glycine (GLY) and N,N-dimethylacetamide (DMAC) by liquid impregnation in order to study and compare their applications in capture of Fe3+ cations. All the materials were unambiguously characterized by adsorption-desorption isotherms of N2 at 77 K, X-ray fluorescence (XRF), elemental analysis (EA), X-ray diffraction (XRD), diffuse reflectance infrared fourier transform spectroscopy (DRIFTS), scanning electron microscopy with dispersive energy detector of X-ray (SEM-EDS), transmission electronic microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). This process afforded γ-Al2O3 with high purity and the surface area of the mesoporous materials ranged from 115 m2 g−1 for AlOOH to 230 m2 g−1 for γ-Al2O3. The achieved surface functionalization was of 2 and 3 wt% with glycine and DMAC, respectively. The effective performance of these materials (both pristine and functionalized) in the removal of Fe3+ ions from an aqueous solution was evaluated in batch systems. In particular, the materials presented extraction capacities of about 78.2% for bare γ-Al2O3, 83.2% for Al-GLY and 93.9% for Al-DMAC.