Ammonium Aluminum Carbonate Hydroxide Research Articles

Structure evolution of porous alumina during aging process and its support effect on PtSn/Al2O3 catalyzed propane dehydrogenation

Precise control of porous alumina microstructures is always challenging due to the diversity and complexity of the growth process-related alumina crystalline phase and surface properties. In this work, we established a bottom-up synthesis route with a combination of rapid precipitation at high supersaturation and high-temperature aging in terms of enhancing particle aggregation kinetics. Surprisingly, we discovered that there were two distinct growth stages of alumina precursor (ammonium aluminum carbonate hydroxide) during the aging procedure, that is, oriented attachment at the early stage of crystallization and subsequent Oswald ripening. High-temperature aging can effectively strengthen the aggregation kinetics between the particles and produce large mesoporous (∼16 nm) and a remarkable number of defect sites with the exposure of up to 14 % unsaturated pentacoordinate aluminum ions. Owing to the presence of strong metal-support interactions, the alumina-supported PtSn catalyst exhibited excellent catalytic activity in the propane dehydrogenation reaction with propylene formation with 99 % selectivity and superior stability with a low deactivation rate of 0.007 h−1 over 24 h. These results suggested that it was feasible and instructive to achieve precise control of the structure and surface properties of alumina by manipulating the aggregation process of the initial particles during the aging stage.

Precursor-oriented design of nano-alumina for efficient removal of antibiotics

Rapid and efficient removal of environmental antibiotics is vital to curb bacterial resistance. Through rational precursors-oriented design, we attain the best Al2O3 absorbent by 500 °C calcination of ammonium aluminium carbonate hydroxide (AACH) precursor from NH4HCO3 route (AACH-NH4HCO3-500) for fast and efficient removal of tetracycline (TC) and other antibiotics from environmental waters including high-salinity wastewater. AACH-NH4HCO3-500 (0.25 g·L−1) can remove (69.92 ± 1.78)% of aqueous TC (0.025 g·L−1) within 5 min and (97.62 ± 2.75)% within 2 h, and the adsorption capacity is 444.4 mg·g−1, which is the highest qmax of TC for the 2 h-adsorptions among numerous adsorbents. AACH-NH4HCO3-500 has fine tolerance to the coexisting substances, and can be easily regenerated and reused, and has no harm even discarded. The relations among the synthetic methods, the structural features, and the adsorption functions of Al2O3 are disclosed through a systematic comparison of the commercial Al2O3 and different Al2O3 nanomaterials attained from three precursors produced by five different routes. The reasons behind the exceptional adsorption performance are discussed throughout. Our findings would facilitate the development of excellent adsorbents for removal of other pollutants.

СИНТЕЗ И СВОЙСТВА ОКСИДОВ АЛЮМИНИЯ И ИТТРИЯ ДЛЯ КЕРАМООБРАЗУЮЩИХ МАТЕРИАЛОВ

Effect of hydroxide precursor nature on the morphology of alumina derived by heat treatment of ammonium aluminium carbonate hydroxide NH4AlCO3(OH)2 was investigated. It was found that the use of aluminum hydroxide as the precursor leads to the formation of needle-like particles of the product, while during synthesis using hydrated alumina, alumina particles of isometric shape were obtained. The effect of ammonia sulfate (NH4)2SO4 on the BET surface area of ammonium aluminium carbonate hydroxide powders was shown.

Влияние природы гидроксидного прекурсора на морфологию порошков Al2O3

Effect of hydroxide precursor nature on the morphology of alumina derived by heat treatment of ammonium aluminium carbonate hydroxide NH4AlCO3(OH)2 was investigated. It was found that the use of aluminum hydroxide as the precursor leads to the formation of needle-like particles of the product, while during synthesis using hydrated alumina, alumina particles of isometric shape were obtained. The effect of ammonia sulfate (NH4)2SO4 on the BET surface area of ammonium aluminium carbonate hydroxide powders was shown.

Features of the Hydrosulfate Method for Processing Alumina-Containing Raw Materials in a Closed Reagent Cycle

The decrease in the availability of high-quality bauxites makes the processing of high-silica raw materials inevitable, and in this regard, it is necessary to develop acid–salt methods suitable for these ores. The purpose of the work was to study various stages of the hydrosulfate method for processing alumina-containing raw materials on the example of nepheline concentrate in order to investigate the possibilities of their improvement. A. The distribution of various macro- and meso-components of leaching between phases at the stage of isolation of ammonium alum depending on sulfate concentration were experimentally and theoretically studied. It was shown that, with an increase in the total concentration of sulfate in the equilibrium mother liquor, the concentration of main impurity components, including iron, in a solid phase decreases significantly. To obtain relatively pure alum, it was recommended to use ammonium hydrosulfate with a concentration of at least 4 mol/L. B. Different embodiments for further purification of alum were explored. It was found that the use of the recrystallization process in the presence of small additions of sodium thiosulfate reduces the content of iron impurities in alum by almost an order of magnitude. C. A method for isolating purer final product was demonstrated. Isolation of ammonium aluminum carbonate hydroxide (ASACH), as a precursor of high-purity alumina, using ammonium bicarbonate is currently the most promising method in the hydrosulfate technology. In combination with the process of recrystallization, the preparation of AACH makes it possible to eliminate the need for expensive methods of selective sorption or extraction for deep purification of aqueous solutions of alum.

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.

PURIFICATION OF TAN RAI ALUMINUM HYDROXIDE WITH ACETIC ACID AND PREPARATION OF HIGH PURE NANOSIZE α-ALUMINA

Gibbsite is the most common form of aluminum hydroxide (AH) as commercial product of Bayer process. However, it usually contains some impurities such as sodium, iron, calcium, and silicon compounds that may not meet requirements for preparation of advanced materials or functional ones which need very high pure raw materials. In this paper, we present some results on the purification of commercial AH from Tan-rai alumina company (Vietnam) using dilute acetic acid solution. The removal yields of 93.19, 91.75, 100, and 86.03% are obtained for Na2O, CaO, Fe2O3, and SiO2 respectively, whereas the recovery of clean AH is almost quantitative. The clean AH is then used for preparation of high pure nanosize α-alumina via chemical processes of dissolution, precipitation ammonium aluminium carbonate hydroxide (AACH) with ammonium carbonate solution. After washing the excess reagents, the precipitate of AACH is then decomposed at elevated temperature to get high pure nanosize α-alumina. The obtained product rather regular and most of particles are not agglomerated. The laser scattering data on the prepared sample show that the particle sizes of the prepared α-alumina from 60 – 90 nm are obtained which are in good agreement with the data from XRD and morphology measurements. The α-alumina structure of the final product is confirmed by the XRD measurement data.

Изучение фазообразования при гетерогенном синтезе гидроксокарбоната алюминия-аммония

Synthesis of ammonium aluminium carbonate hydroxide NH4AlCO3(OH)2 from hydrated alumina received by ammonization of ammonia alums NH4Al(SO4)2·12H2O was studied. It was found the synthesis of NH4AlCO3(OH)2 occurs without the formation of intermediate phases.

Preparation of rod-like γ-alumina/volcanic rock porous material and the adsorption property of Congo red

The porous materials of rod-like γ-alumina interlaced in pores of volcanic rock were prepared by in-situ growth using volcanic rock as matrix material, aluminum nitrate and ammonium bicarbonate as raw materials. The structure and properties of the materials were characterized by XRD, SEM, N2 adsorption-desorption and TG-DSC technology. The adsorption performance of Congo red was also studied. It was found that the aluminum nitrate solution filled the pores of volcanic matrix materials by diffusion and adsorption, and amorphous alumina was formed after calcination. During hydrothermal treatment and calcination, the formed alumina was transformed into ammonium aluminum carbonate hydroxide and γ-alumina. The optimal reaction conditions for the preparation of rod-like γ-alumina/volcanic rock porous materials were as following: the concentration of ammonium bicarbonate solution was 0.8 mol/L, the reaction temperature was 140°C, and the reaction time was 4 h. The rod-like γ-alumina stacked in the channels of volcanic rock with a diameter of 50–150 nm and length of 3–10 μm. The specific surface area and pore volume of the porous material was 0.1 mL/g and 47 m2/g, respectively. When the concentration of Congo red solution was 500 mg/L and the dosage of porous material was 2 g/L, the removal rate was 96% with the adsorption amount of 243 mg/g.

Preparation of Al<sub>2</sub>O<sub>3</sub> Whiskers from AACH Using Hydrothermal Method and its Use for the Removal of Lead Ions by Adsorption

This work explores the potential of adsorption of Pb2+ by hydrothermally synthesized alumina. In comparison to other heavy ion removal techniques, adsorption is preferred in the current study as it has the edge of ease of operation and environment friendly characteristics. Synthesis of high surface area alumina whiskers was achieved by hydrothermal route which were subsequently employed for the active adsorption of lead ions. AACH (Ammonium Aluminum Carbonate Hydroxide), used as precursor for alumina, was calcined at three different temperatures i.e. 700, 900 and 1100 °C to form alumina whiskers. These whiskers were characterized by XRD, SEM, BET and FTIR. Various adsorption parameters such as contact time, pH, initial metal concentration were studied for lead ions. Maximal removal efficiency was obtained for the specimen having pH 4 and calcined at 700 °C for 60 minutes. Kinetic data was best described by pseudo second order model, whereas the adsorption equilibrium data obeyed the Langmuir adsorption isotherm model.

Facile Hydrothermal Fabrication of Eu Doped Alumina for Potential Bioluminescent Imaging and Drug Delivery System

The aim of this study is to investigate the photoluminescence (PL) properties of europium (Eu) doped alumina as potential platform for simultaneous bio Imaging and drug delivery. Synthesis of Eu doped alumina is done by a facile two step method. In the first stage, hydrothermal synthesis is used to prepare the Eu doped ammonium aluminum carbonate hydroxide which is then calcined to get a crystalline Eu doped alumina. Structural characterization of the prepared sample is done through XRD and SEM. Photoluminescence spectroscopy is performed in order the study the PL response. The SEM images of the Eu doped sample revealed whisker shaped morphology, the porosity in the inter and intra whisker region is beneficial for the high drug loading capacity. The length of the bundle after annealing was about 5 µm with the bundle diameter of 0.45 µm. XRD patterns of the prepared sample has sharp peaks, showing a high degree of crystallinity corresponding to the α-alumina phase. Finally PL response was checked at an excitation wavelength of 393 nm. A dominant peak was observed at a wavelength of 613 nm corresponding to the 5D0 to 7F2 transition.The3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide MTT assay confirms the cell viability of more than 100% at even a concentration of 500 nano molar alumina in phosphate-buffered saline (PBS). These results show that the Eu doped alumina having optimum PL response, high biocompatibility and drug loading capacity which makes it a promising candidate for theranostic applications.

Effect of composite additives on phase transition and dispersibility of α-Al2O3

α-Al2O3 nanoparticles are easy to agglomerate in the preparation, thereby leading to adverse effects during the applications. This paper reported the preparation of α-Al2O3 nanoparticles with good dispersity and controllable morphology by lowering temperature calcination of the precipitated precursor powders. The composite composed of PVP and ammonium sulfate is used to control the morphology and improve the precursor's dispersion. The influences of R ((NH4)2CO3/Al3+, molar ratio) and PVP-ammonium sulfate composite were studied thoroughly. It was found that an urchin-shaped ammonium aluminum carbonate hydroxide (AACH) precursor can be formed under the conditions of R = 3, and the ammonium sulfate and PVP are 20 wt% and 5 wt%, respectively. After calcination at 1000 °C for 2 h, such urchin-like precursor particles were converted to quasi-spherical and well crystallized α-Al2O3 nanoparticles, which possessed a narrow size distribution of 110 nm and a specific surface area of 12.13 m2/g. The resultant α-Al2O3 nanoparticles prepared by such a simple method were expected to be applied in transparent ceramics and high-performance catalysts.

The synthesis of urchin-like γ-Al2O3 hierarchical microspheres from Al foils and its rapid adsorption ability towards Congo red

In this paper, we present a convenient hydrothermal method to synthesize hierarchical microspheres consisting of ammonium aluminum carbonate hydroxide (AACH) nanowires with a diameter of about 400 nm and length ∼50 μm on aluminum foils. After calcination at 900 °C, hierarchical γ-Al2O3 microspheres with mesoporous structures were obtained successfully, which possess a high specific surface area of 124 m2 g−1 and high porosity of 0.71cm3 g−1. The possible formation mechanism was discussed. The as-prepared mesoporous γ-Al2O3 hierarchical nanostructures exhibited improved adsorption performance towards Congo red in aqueous solution, 90% CR could be removed rapidly in 20 min, and its saturation adsorption capacity in 80 mg l−1 Congo red can reach to 180 mg g−1, it suggests that the hierarchical γ-Al2O3 microspheres with unique microstructure have potential in wastewater treatment.

Preparation of γ-Al2O3 via Hydrothermal Synthesis Using ρ-Al2O3 as Raw Material for Propane Dehydrogenation

γ-Al2O3 was prepared by hydrothermal synthesis using ρ-Al2O3 and urea as raw materials. In this work, the effects of the molar ratio of CO(NH2)2/Al and reaction temperature were investigated, and a Pt–Sn–K/γ-Al2O3 catalyst was prepared. The ammonium aluminum carbonate hydroxide (AACH), γ-Al2O3, and Pt–Sn–K/γ-Al2O3 were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N2 adsorption–desorption, thermogravimetry–differential thermal analysis, and NH3 temperature-programmed desorption techniques. The reactivity of Pt–Sn–K/γ-Al2O3 for propane dehydrogenation was tested in a micro-fixed-bed reactor. The results show that γ-Al2O3 with a specific surface area of 358.1 m2/g and pore volume of 0.96 cm3/g was obtained when the molar ratio of CO(NH2)2/Al was 3:1 and the reaction temperature was 140 °C. The alumina obtained by calcination of AACH has a higher specific surface area and larger pore volume than the industrial pseudo-boehmite does. The catalyst prepared from AACH as precursor showed high selectivity and conversion, which can reach 96.1% and 37.6%, respectively, for propane dehydrogenation.

A novel green synthesis of γ-Al2O3 nanoparticles using soluble starch

In this research, nanocrystalline [Formula: see text]-[Formula: see text] powders have been synthesized by a novel mechanochemical method, through thermal decomposition of the ammonium aluminum carbonate hydroxide (AACH) precursor. The route involved using low-cost [Formula: see text] and [Formula: see text] as raw materials and environmental-friendly soluble starch as an effective dispersant. The precursor and product were characterized by simultaneous thermogravimetric and differential thermal analysis (TG-DTA), X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The results show that spherical [Formula: see text]-[Formula: see text] nanoparticles without hard agglomeration and with particle size in the range of 20–30 nm can be obtained. The crystallite size of products measured from XRD, SEM and TEM were in good agreement. This novel mechanochemical method combined with the use of environmentally benign starch has the advantages of simple operation, low calcination temperature and environmental safety, and will have good prospects for commercial production.

Effect of the Ammonium Aluminium Carbonate Hydroxide Preparation Method on Morphological Properties of Aluminium Oxide

Ammonium aluminium carbonate hydroxide is synthesized by three different ways. The prepared samples and the products of their heat treatment (aluminium oxides) are studied by physicochemical methods. It is shown that the synthetic method used to prepare ammonium aluminium carbonate hydroxide has a significant effect on the structure, porosity, and dispersion of the resulting γ- and α-forms of aluminium oxide.

Understanding Li-Al-CO3 layered double hydroxides. (I) Urea-supported hydrothermal synthesis

In the current work, Li-Al-CO3 layered double hydroxides (LDHs) were synthesized by a hydrothermal method using LiCl, AlCl3, and urea as raw materials. The effect of LiCl/AlCl3 molar ratio (RLi/Al) on the composition of products was investigated. Special emphasis was placed on the formation process of Li-Al-CO3 LDHs. It was found that the RLi/Al has a significant impact on the types of products. Only at the RLi/Al being higher than unity, the pure LDHs phase with a chemical formula of [LiAl2(OH)6](CO3)0.5·2H2O can be formed. Low RLi/Al values (≤0.25) lead to the formation of an ammonium aluminum carbonate hydroxide phase. The formation of the LDHs is essentially via a Li+-intercalation mechanism. Amorphous Al(OH)3 is first formed, and Li+ ions are then intercalated into the vacancies in the Al(OH)3-layers to form crystalline Li-Al-CO3 LDHs. To the best of our knowledge, this is the first report on the hydrothermal formation process of Li-Al LDHs. This work provides a better understanding for the features of Li-Al LDHs.

One Step Conversion of Glucose into 5-Hydroxymethylfurfural (HMF) via a Basic Catalyst in Mixed Solvent Systems of Ionic Liquid-Dimethyl Sulfoxide.

A simple solid base catalyst, ammonium aluminum carbonate hydroxide (AACH), was prepared and its structure was characterized by many technologies, including XRD, FT-IR, SEM, BET and Elemental Analysis. The prepared catalyst was used to catalyze the conversion of glucose into 5-hydroxymethylfurfural (HMF) in ionic liquid 1-butyl-3-methylimidazolium chloride ([Bmim]+Cl-) and dimethyl sulfoxide (DMSO) mixtures. Various reaction conditions, including catalyst loading, reaction temperature, reaction duration and solvent, were investigated. A moderated HMF yield of 52.17 % was obtained at the mild reaction conditions (120°C for 4 h). More importantly, the catalyst could be reused for several times without the loss of its significant catalytic activities. After five reaction runs, a HMF yield about 49.34 % was also obtained.

Controlling the acid-base properties of alumina for stable PtSn-based propane dehydrogenation catalysts

The surface properties of catalyst supports are important in regulating the catalytic properties of heterogeneous catalysts. Herein, we studied the effect of acid-base properties of alumina on metal-support interaction and coke deposition, and investigated the stability of catalysts in propane dehydrogenation (PDH) using PtSn/Al2O3. We prepared γ-Al2O3 (A750) from ammonium aluminum carbonate hydroxide (AACH) and compared it with a commercial sample (Sasol Puralox SBA-200; P200). We loaded 0.5 wt% Pt and 0.9 wt% Sn on alumina then conducted propane dehydrogenation at 590 °C (WHSV = 5.2 h−1). PtSn/A750 and PtSn/P200 showed compatible initial activity (conversion = ˜50%) and selectivity (> 95%). After 20 h of reaction, PtSn/A750 showed a slight decrease in activity (39.9%) while the activity of PtSn/P200 dropped significantly (28.4%). Spent catalysts showed different metal sintering behavior and coke deposition which are well known causes for catalyst deactivation. A high strength of Lewis acid sites in A750 (higher Td in ethanol TPD) prevented the sintering of metal by strong metal-support interaction. Also, the lower number of Lewis acid sites in A750 than that of P200 reduced deposited coke on the catalysts (PtSn/A750: 1.8 wt% and PtSn/P200: 8.6 wt%). Furthermore, diffuse reflectance infrared Fourier-transform spectroscopy after CO adsorption at -150 °C clearly demonstrated that coke deposition was initiated from Lewis acid sites on the alumina surface, but then aromatization occurs at these sites. These results suggested that strong metal-support interactions to hold metal particles and less residual Lewis acid sites after metal loading to reduce coke deposition are important factors for designing stable and coke-resistant PtSn on alumina catalysts. Furthermore, precise characterization and understanding of the acid-base properties of alumina will contribute in developing catalysts with high stability.

Formation of porous α-alumina from ammonium aluminum carbonate hydroxide whiskers

Ammonium aluminum carbonate hydroxide (AACH) whiskers prepared by hydrothermal technique were employed as precursor material for development of porous alumina. After compaction of AACH whiskers at 8 bars, calcination was performed at 650 °C followed by sintering at different temperatures. The sintered samples were characterized by XRD, FTIR, SEM and mercury intrusion porosimetry. Mechanical strength was determined by compression testing. At sintering temperatures of 1200 °C to 1400 °C, the % age porosity was around 80%. At 1500 °C, the percentage porosity decreased to 71%. The as-prepared AACH consisted of bundles of whiskers with diameters as thick as 0.7 µm, while an individual whisker had a diameter of about 100 nm with an aspect ratio of about 33. A two-phase mixture consisting of θ- and α-alumina was obtained at 1100 °C, while at 1200 °C and above, single phase α-alumina was formed. θ-alumina retained the bundle-like morphology. However, transformation to α-alumina was accompanied by formation of bead-like morphology. These beads were joined together through necks/stems within the whiskers as well as across the parallel-lying whiskers. These necks grew at 1300 °C to form aggregates with smooth surfaces. At 1400 °C, these aggregates started joining with each other by neck formation and at 1500 °C, a three-dimensional network was formed. For sintering temperatures of up to 1400 °C, pores with sizes around 260 nm were very stable. At 1500 °C, significant pore growth took place along with an overall densification. Therefore, number of pores with sizes of around 260 nm decreased and those with sizes around 10 µm, 1 µm and 5 nm increased. The compression strength of samples sintered at 1100 °C to 1300 °C was in the range of 3.4–4.3 MPa. At 1400 °C, the strength increased to 5.2 MPa, while at 1500 °C, it jumped to 10.8 MPa due to the formation of three-dimensional network.