Activated Alumina Research Articles

Oxidation of residual methane from VNG vehicles over Co3O4-based catalysts: Comparison among bulk, Al2O3-supported and Ce-doped catalysts

Cobalt oxide based catalysts with three different active phase configurations, namely bulk, alumina supported and cerium-doped Co3O4 samples were examined for the complete oxidation of methane under conditions similar to those found in the exhaust of VNG engines. The structural and redox properties of the resulting catalysts were determined by N2 adsorption-desorption, WDXRF, ICP-AES, X-Ray diffraction, temperature-programmed reactions, UV–vis-NIR DRS, XPS and Raman spectroscopy. Alumina-supported catalysts (10–40%wt. Co) were found to be less active, since the strong interactions between the alumina and the Co3O4 active phase were highly detrimental for the redox properties of these catalysts. On the other hand, doping with cerium (10%wt.) led to an increased inherent activity of the Co3O4 phase by distorting the spinel lattice, which resulted in improved structural and redox properties and enhanced mobility of the oxygen species within the spinel lattice. These catalysts were also stable over a prolonged period of time under both dry and humid conditions (150 h).

Properties of coral waste-based mortar incorporating metakaolin: Part II. Chloride migration and binding behaviors

This study investigated the mechanical properties, chloride migration and binding mechanisms of marine mortars with coral waste powder (CP) incorporating metakaolin. Due to the synergetic effect of carboaluminate formation and pozzolanic reaction, the compressive strength and chloride resistance of CP mortars are dramatically improved by metakaolin incorporation. When exposed to 0.5 M NaCl solution, more than 75% of the total bound chloride is bound by the hydrated mortars within 24 h. Friedel’s salt (Fs) is the main chloride-uptaking phase and its X-ray diffraction peak area is well consistent with bound chloride content. The thermodynamic analyses indicate that carboaluminate has great capacity to form Fs, and SO4-AFm can transform to Fs and release gypsum in temperatures below 21 °C. The released gypsum further reacts with SO4-AFm to form additional SO4-AFt after exposed to chloride solution. Besides, nearly linear relationship between bound chloride content and active alumina content in binder is found.

Effect of Aluminum Hydroxide Addition on Properties of Fired Refractory Clay Brick

The pottery of Ratchaburi is very famous especially dragon jar which was fired by using dragon kiln. The kiln was made of unfired clay bricks, which its properties including high refractoriness, low thermal shrinkage and durable are desired. Aluminum hydroxide is an interesting material for improving brick’s properties, providing high active alumina (gamma-alumina) content after decomposition, high melting point and also reasonable cost. The study evaluated the effect of an additive, Al (OH)3, on the fried properties of refractory clay brick. In this study, four difference proportions of Al (OH)3 to clay , including 0:100, 25:75, 49:51 and 76:24 were studied. The specimens of 5x5x5 cm3 were formed by hand molding, then were fired at 1200, 1300 and 1400°C. The properties including refractoriness, volume shrinkage, strength, bulk density, water absorption, and slaking time were investigated. The samples of 25:75 ratio of Al (OH)3 to clay, which was fired at 1300°C exhibited high in refractoriness, low volume shrinkage of 5% and relatively low density of 1.69 g/cm3 as compared to those of 1400°C fired. Moreover, the moderate water adsorption of 15 % and useable compressive strength of 12.4 MPa was also observed. As a result, these properties suitable for using in firebox of dragon kiln of Ratchaburi province.

Studies on performance characteristics of calcium and magnesium amended alumina for defluoridation of drinking water

Two variants of amended activated alumina named CMAA 650 and CMAA 850 were prepared using activated alumina (AA) granules. AA was successfully coated with calcium and magnesium in the form of calcium magnesium aluminum oxide (Ca0.965Mg2Al16O27), calcium aluminum oxide (Ca9(Al6O18)) and magnesium aluminum oxide (MgAl2O4). CMAA 850 had a highly crystalline porous leaf like structure and higher adsorption capacity than CMAA 650, with surface distribution of Ca & Mg at 30.96 and 3.29 wt% respectively. AA, CMAA 650 and CMAA 850 followed Langmuir and Temkin adsorption isotherms with maximum defluoridation capacity of 2.48, 2.61, and 2.74 mg/g respectively for treating a 10 mg/L of fluoride solution at neutral pH. CMAA 650 had a homogenous surface and CMAA 850 had a heterogeneous surface while both followed second order rate kinetics implying chemisorption. Fluoride adsorption equilibrium was attained in 120 min–180 min for all three adsorbents. Regeneration of CMAA 650 and CMAA 850 was carried out effectively by ultrasonication for 2 min using 1.5 M sodium hydroxide and after the second adsorption cycle, adsorption capacity dropped by 12.41% and 12.15% respectively. The adsorption capacity of CMAA 850 was unaffected in presence of other co-existing ions except that it got reduced by 21.4% in the presence of nitrate ions. No residual aluminum was detected in treated water samples of both CMAA 650 and CMAA 850. However, CMAA 850 was found to be more favorable with a higher capacity over a wider pH range of 4–9 for defluoridation of water.

Defluoridation of reject water from a reverse osmosis unit and synthetic water using adsorption

Many parts of the world have excess fluoride in drinking water. At some locations, nitrate is also in excess. Hence, reverse osmosis (RO) units have been installed at several villages in India. Reverse osmosis is a good technique, but it has the disadvantage of discarding a considerable amount of the inlet water as a reject stream. This is an unsustainable way of using water. Two adsorbents, namely, a hybrid anion exchange resin embedded with zirconium oxide nanoparticles (HAIX-Zr), and activated alumina (AA) were used in column experiments. For water containing only F−, HAIX-Zr had a better capacity than AA. The same trend was observed with synthetic water samples containing other ions in addition to F-. However, for RO reject, the converse was true, and the capacities of AA and HAIX-Zr decreased significantly. For AA, the presence of a small concentration of HCO3− increased the uptake of F- by 100% compared to water containing only F-. For HAIX-Zr, the adsorption capacity decreased as the concentration of co-ions increased. The cost of treated water varied from ▪ 0.1–1.5/L (US $ 0.002–0.03/L) for AA and ▪ 0.2–11.5/L (US $ 0.004–0.23/L) for HAIX-Zr.

Preparation and characterization and application of activated alumina (AA) from alum sludge for the adsorption of fluoride from aqueous solutions: new approach to alum sludge recycling

Abstract Activated alumina (AA) prepared from alum sludge (AS) was used in removal of fluoride from aqueous solutions. The capacity of AA in the adsorption of fluoride from water was found to be 17.75 mg/g. The maximum efficiency of fluoride adsorption was 96% at the optimum condition (C = 5 mg/L, pH = 7, t = 20 min and adsorbent dosage = 5 g/L). Based on the results, it can be concluded that conversion of AS to AA can be a method for recycling of AS. Also AA can be used for adsorption of fluoride from aqueous solutions. So AS as a substance harmful to the environment turns into AA as a usable material in water treatment.

Buffered delivery of phosphate to Arabidopsis alters responses to low phosphate.

Arabidopsis has been reported to respond to phosphate (Pi) stress by arresting primary root growth and increasing lateral root branching. We developed a system to buffer Pi availability to Arabidopsis in gel media systems by charging activated aluminum oxide particles with low and sufficient concentrations of Pi, based on previous work in horticultural and sand culture systems. This system more closely mimics soil chemistry and results in different growth and transcriptional responses to Pi stress compared with plants grown in standard gel media. Low Pi availability in buffered medium results in reduced root branching and preferential investment of resources in axial root growth. Root hair length and density, known responses to Pi stress, increase in low-buffered Pi medium. Plants grown under buffered Pi conditions have different gene expression profiles of canonical Pi stress response genes as compared with their unbuffered counterparts. The system also eliminates known complications with iron (Fe) nutrition. The growth responses of Arabidopsis supplied with buffered Pi indicate that the widely accepted low-Pi phenotype is an artifact of the standard gel-based growth system. Buffering Pi availability through the method presented here will improve the utility and accuracy of gel studies by more closely approximating soil conditions.

Hydrocracking of Vacuum Gasoil on NiMo/AAS-Al2O3 Catalysts Prepared from Citric Acid: Effect of the Catalyst Heat Treatment Temperature

Ni-Mo bimetallic catalysts are prepared by impregnating a carrier containing amorphous aluminosilicate (AAS) and aluminum oxide using a solution with Ni, Mo, and citric acid. The temperature of the catalysts ranges from 120 to 550°С. The physicochemical properties of the catalysts are studied via XPS, TEM, and HCNS analysis, and they are tested in hydrocracking of vacuum gasoil. The particles of the sulfide active component (NiMoS phase) are localized predominantly on surfaces of aluminum oxide, and only some are on surfaces of AAS. When the temperature of catalyst calcination is raised, the average number of the layers in particles of the NiMoS phase grows as well, due to the removal of citric acid. This indicates strengthening of the interaction between the sulfide active component and aluminum oxide. The content of Ni-Mo massive sulfide particles also grows along with the temperature of calcination. The morphological characteristics of the sulfide active component affect the activity of the catalysts in hydrodesulfurization and hydrodenitrogenation, but not in hydrocracking. The optimum heat treatment temperature for NiMo/AAS-Al2O3 catalysts prepared with citric acid is 120°C. Recommendations are given for the heat treatment of catalysts under industrial conditions.

Engineering Investigations and Durability Problems of the Construction Materials of the Roman Babylon of Egypt

The Babylon of Egypt was constructed in the Roman period (300 AD), in the old Cairo area. It is one of the most distinguished monuments in the universal architectural heritage. The present study introduces the characteristics of roman and byzantine bricks and their joining structural mortars used in the roman fortress in order to risk assessment and to define the necessary characteristics of the intervention retrofitting new materials, which will be used in the ongoing preservation work of this fortress. To achieve such, several analyses and laboratory tests like ultra-sonic pulse method testing (ultrasonic pulse velocity, dynamic modulus of elasticity), uniaxial compression test and Brazilian splitting tension test, were carried out to determine their basic, mechanical and engineering properties, along with the microstructural properties determination using Mercury porosimeter. On the other hand, the morphological description, petrography, mineralogical and microstructural properties were determined using scanning electron microscope equipped by EDS, polarizing light microscopy, XRD and XRF. The obtained results indicated that the joining structural mortars are ranging from medium to stiff, low compacted, having hydraulic properties due to the use of natural furnace slag, brick powder, brick fragments and aggregates that match with the pozzolanic properties and also rich in active silica and alumina. The examinations reveal the use of limestone fractions as coarse aggregates or fillers. On the other hand, the Roman bricks consist mainly on quartz and feldspars embedded in a matrix of iron oxide and burnt clays. Also the obtained results indicated that old bricks were of low apparent specific density (1.4 - 1.7), medium absorption (10% - 20%) and low uniaxial compressive strength (2 - 10 MPa), with Young’s modulus 1.2 to 3 GPa. The ultra-sonic wave velocity is 1.7 to 2 km/s, with dynamic modulus of elasticity 2.4 to 4 MPa. The shear modulus is 917 to 1500 MPa. These results may be due to large pores and cracks into their matrix. Due to their surface roughness, the adhesion with the lime mortars was relatively high.

Условия получения активного оксида алюминия, отвечающего требованиям перспективной хлорной технологии

Условия получения активного оксида алюминия, отвечающего требованиям перспективной хлорной технологии

Arsenic(V) Removal Using Activated Alumina: Kinetics and Modeling by Response Surface

AbstractArsenic(V) removal using activated alumina (AA) was carried out in batch mode and was modeled using response surface method. The Doehlert design of experiment (DOE) was used to model the ex...

Acetylation of Glycerol over Highly Stable and Active Sulfated Alumina Catalyst: Reaction Mechanism, Kinetic Modeling and Estimation of Kinetic Parameters

ABSTRACTThe Langmuir–Hinshelwood–Hougen–Watson (LHHW) kinetic model was developed for acetylation of glycerol over highly stable and active 2 M SO42−/γ‐Al2O3 catalyst. The apparent reaction rate constants were determined by numerically solving the differential rate equations using ode23 tool in MATLAB coupled with the genetic algorithm optimization technique. The estimated rate constants were used to obtain the activation energy and pre‐exponential factor by using the Arrhenius equation. The estimated activation energy for direct acetylation of glycerol to monoacetylglycerol and diacetylglycerol was 7.2 kJ mol−1, for acetylation of monoacetylglycerol to diacetylglycerol was 37.1 kJ mol−1, and for acetylation of diacetylglycerol to triacetylglycerol was 26.6 kJ mol−1, respectively.

Exceptional selectivity for dissolved silicas in industrial waters using mixed oxides

The removal of silica, ubiquitous in produced and industrial waters, by novel mixed oxides is investigated in this present study. We have combined the advantage of high selectivity hydrotalcite (HTC, (Mg6Al2(OH)16(CO3)·4H2O)), with large surface area of active alumina (AA, (Al2O3)) for effective removing of the dissolved silica from cooling tower water. The batch test results indicated the combined HTC/AA is a more effective method for removing silica from CTW than using each of HTC or AA separately. The silica uptake was confirmed by Fourier transform infrared (FTIR), and Energy dispersive spectroscopy (EDS). Results indicate HTC/AA effectively removes silica from cooling tower water (CTW), even in the presence of large concentrations of competing anions, such as Cl−, NO3− HCO3−, CO32− and SO42−. The Single Path Flow Through (SPFT) tests confirmed to rapid uptake of silica by combined HTC/AA during column filtration. The experimental data of silica adsorption fit best to Freundlich isotherm model.

Ethylene Formation from Ethanol Dehydration Using ZSM-5 Catalyst

Catalysts prepared for ethanol dehydration in a fixed-bed reactor acted as strong active acidic catalysts under reaction conditions at lower temperatures. Experimental conditions including the catalyst type [active aluminum oxide (γ-Al2O3) and ZSM-5 zeolite catalyst modified using two-stage through dealumination or desilication and by using the impregnation method with phosphorous and lanthanum], weight hourly space velocity (WHSV), ethanol concentration, and reaction temperature were investigated to obtain optimal reaction conditions. The catalysts were characterized using the Brunauer–Emmett–Teller method, temperature-programmed desorption of ammonia gas, thermogravimetric analysis, X-ray photoelectron spectroscopy, and X-ray diffraction. The results revealed that the ethylene yield and selectivity were 98.5 and 100%, respectively, for the ZSM-5 zeolite catalyst modified through dealumination at a temperature of 220 °C and WHSV of 2.5 h–1 when the ethanol concentration was 95%. The ethylene yield and selectivity were 94.3 and 94.4%, respectively, for the ZSM-5 zeolite catalyst modified using phosphorous at a temperature of 240 °C and WHSV of 1.5 h–1 when the ethanol concentration was 20%. Both of these catalysts were the most favorable among all prepared catalysts.

Influence investigation of the type and amount of the new active aluminas addition on the properties of products from low-cement corundum chromium-containing castable mass

The influence of new active aluminas addition (NABALOX NO 635 and NABALOX NO 713-10 MF) and its amount on the properties of non-burning and fired at 1580 оC samples has been studied. It was established that, the compressive strength of non-burning samples, depending on the type and amount of the active alumina addition, is maximal when 5 % of the active alumina NABALOX NO 635 is added. After high-temperature firing, the densest structure is formed in the samples of this composition, as evidenced by their indices properties: open porosity of 23.3 %, apparent density of 3.03 g/cm3, compressive strength of 115 N/mm2. As a result of the carried out researches, the technology of products manufacturing by vibrocasting method from the low-cement corundum chromium-containing castable mass has been improved by adding the new active alumina of NABALOX NO 635 instead alumina grade of CTC-40. This technology provides manufacturing of products with higher compressive strength (115 vs. 104 N/mm2) and a larger apparent density (3.03 vs. 3.02 g/cm3) with substantially equal open porosity values compared to those of earlier manufactured products containing of active alumina addition grade of CTC-40. Based on the economic feasibility, as well as the availability and the possibility of purchasing NABALOX NO 635 alumina in small batches on the domestic raw materials market (“Nabaltec AG”, Germany, has a representative office in Ukraine), its use for manufacture of the low-cement corundum chromium-containing castable mass is more preferable compared to with the previously used active alumina grade of CTC-40 produced by “Almatis GmbH” (Germany). As a result of the carried out researches, normative documentation has been developed. According to this documentation, in the conditions of PJSC “UKRNIIO NAMED AFTER A. S. BEREZHNOY” full-scale samples of products characterized by high properties were produced: compressive strength after hardening in humid conditions for 7 days of 63 N/mm2, open porosity of 23.3 %, an apparent density of 3.03 g/cm3, compressive strength after firing at a temperature of 1580 оC of 94 N/mm2.

A Facile Green Synthetic Route for the Preparation of Highly Active \u03b3-Al2O3 from Aluminum Foil Waste

A novel green preparation route to prepare nano-mesoporous γ-Al2O3 from AlCl3.6H2O derived from aluminum foil waste and designated as ACFL550 is demonstrated, which showed higher surface area, larger pore volume, stronger acidity and higher surface area compared to γ-Al2O3 that is produced from the commercial AlCl3 precursor, AC550. The produced crystalline AlCl3.6H2O and Al(NO3)3.9H2O in the first stage of the preparation method were characterized by single-crystal XRD, giving two crystal structures, a trigonal (R-3c) and monoclinic (P21/c) structure, respectively. EDX analysis showed that ACFL550 had half the chlorine content (Cl%) relative to AC550, which makes ACFL550 a promising catalyst in acid-catalysed reactions. Pure and modified ACFL550 and AC550 were applied in acid-catalysed reactions, the dehydration of methanol to dimethyl ether and the total methane oxidation reactions, respectively. It was found that ACFL550 showed higher catalytic activity than AC550. This work opens doors for the preparation of highly active and well-structured nano-mesoporous alumina catalysts/supports from aluminum foil waste and demonstrates its application in acid-catalysed reactions.

Core–Shell Zeolite Y@γ‐Al2O3 Nanorod Composites: Optimized Fluid Catalytic Cracking Catalyst Assembly for Processing Heavy Oil

AbstractCompositions, structures, and distributions of the active phases in fluid catalytic cracking (FCC) catalysts have an essentially important impact on their porosities, acidities, and thus cracking capabilities for processing heavy oil fractions. Here, we report a facile approach for fabrication of core–shell zeolite Y@γ‐Al2O3 nanorod composites by controlling the attachment of boehmite nanorods on the external surface of zeolite crystals, and thus regulating the dispersion and combination of the active alumina matrix on zeolite components in the FCC catalyst. The synthesized discrete boehmite nanorods possess a large quantity of positive charges and can directly electrostatically interact with the negative surface of zeolite crystals, leading to the formation of core–shell zeolite Y@γ‐Al2O3 nanorod composites (nY@Al2O3). The optimized 4Y@Al2O3 composite (Y/γ‐Al2O3 weight ratio of 4) with zeolite crystals fully embedded by alumina nanorods shows enhanced textural properties, acidity accessibilities, and improved cracking ability of 1,3,5‐triisopropyl benzene. Taking it as the main active component, the produced FCC catalyst shows better contaminant resistant ability and especially higher gasoline yield in the cracking of heavy oil, which could potentially bring practical economic profits for the oil‐refining industry.

A novel sort of porous ceramic foam ball with modified surface for arsenic removal from aqueous solution

A sort of lightweight porous ceramic foam ball that can float on the water was recently made from the natural zeolite. The diameters of porous ball and its macroscopic pores are around 5 and 1 mm, respectively. Such ball surface could be modified to activate in different ways, i. e. loading the active alumina or desilicating the ball. Both of modified products have been investigated to adsorb the toxic ion of arsenic (As) in water effectively. This kind of porous ceramic ball was prepared by powder sintering, using natural clinoptilolite powder as the primary raw material. An active-alumina-loaded porous ceramic product was generated by sol-gel method with pseudoboehmite (AlOOH) as the main composition. The active Al atom on the porous ball surface could also be achieved by desilicating the ceramic ball in the NaOH solution. Such a desilicated product exhibited a good activity to adsorb the arsenic ion although carrying no active alumina. With this effective porous structure, the present products can be expected to become practically advantageous.

A novel approach to synthesize in-situ crystallized zeolite/kaolin composites with high zeolite content

We present an alkali solution aided (ASA) activation approach to activate kaolin microspheres and its application to synthesize in-situ crystallized zeolite/kaolin composite materials. Compared with conventional thermal activation methods, the ASA activation can high-effectively convert silicon and aluminum species in kaolin microspheres into active silica and alumina for synthesizing zeolite/kaolin composites, leading to a successful synthesis of zeolite/kaolin composites with high zeolite content and outstanding attrition resistance. When used as a fluid catalytic cracking catalyst, the resulting zeolite Y/kaolin composite gave high conversion efficiency of vacuum oil and high selectivity to valuable products.

Effect of temperature on the synthesis of active alumina by flash calcination of gibbsite

In this paper, activated aluminas were synthesized directly using cheap precursor via a simple thermal process and short time using no sacrificial templates. The dehydration of gibbsite has been studied at different temperatures (350–1150 °C) by flash calcination. The synthesized materials were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and N2 adsorption measurements. According to the obtained results, the temperature appeared to be the key parameter at activation process. The changes of the specific surface area affected on the average pore size because the amounts of pore volume were nearly constant. The powders prepared by the flash calcination method had a monomodal pore distribution with mesopores. FE-SEM images showed particle growth in nanodimensional. The optimum temperature for powder synthesized by flash calcination was 650 °C, which the surface area, pore volume, and average pore size were 262 m2/g, 0.22 cm3/g, and 33 A, respectively. The synthesized powder had smaller nanoparticles for 650 °C in comparison of other temperatures.