Alumina Catalysts Research Articles

Pyrolysis of waste plastics-derived carbon nanomaterials on nickel foam for utilization as an efficient binder-free electrode: Effect of catalyst loading on capacitive performance

The pyrolytic liquid and gas products are extensively analyzed for practical applications, but, few applications exist for solid product from waste plastics pyrolysis. This study investigates energy storage potential of waste plastics-derived carbon nano-materials (CNMs), pyrolyzed directly on nickel foam (NF) coated with nickel alumina catalyst, in a two-stage fixed bed reactor. Effect of increasing nickel to aluminum molar ratio (0.05, 0.1, 0.2) in energy storage capacity is studied. Galvanostatic charge-discharge curves, at 0.125 A g−1, show highest specific capacitance of 153.75 F g−1 for 0.1 molar ratio. The reason for such high performance is mainly because of a) greater metal-support interaction by using NF substrate, b) formation of CNMs according to base-growth mechanism, providing metal free surface at the top, and c) the presence of equal amounts of disordered and ordered carbons, resulting in meso- and micro-porous structures, providing high electrolyte availability at the electrode surface. The retained rectangle shape of cyclic voltammetry (CV) curve after 5000 cycles, with 98.5 % capacitance retention, also exhibits stability and durability of produced electrode. Though the fabricated electrode involved no post-treatment, yet, it showed higher performance than commercial CNMs. Therefore, this study open new ways to fabricate environment friendly and economically effective supercapacitors.

Effect of Basic Promoters on Porous Supported Alumina Catalysts for Acetins Production

A facile strategy for the design of porous supports was obtained by modifying the sol-gel method followed by the wet impregnation technique. In this respect, herein, the acidity of the γ-Al2O3 phase was modulated by adding basic MgO, La2O3 or ZnO promoters to form binary supported catalysts. The Ni and Co dispersion on the supports associated with their tunable acidity and morphologies resulted in highly porous supported alumina-based catalysts. The physicochemical properties of the solids were comprehensively investigated by XRD, textural properties, Raman and FTIR spectroscopy, SEM-EDS, TEM, EPR and XPS analyses. The catalytic performances in the esterification of glycerol in the presence of acetic acid (EG) for the acetins production were evaluated. The highly dispersed NiO and Co3O4 active species on binary porous supports produced synergistic effects appearing to be the reason for the activity of the solids in the EG reaction. Under the optimized reaction conditions, NiCo/MgO-Al2O3 was found to be a robust solid with superior catalytic performance and improved stability in four reaction cycles with 65.0% of glycerol conversion with an exclusive selectivity of 53% for triacetin. The presence of Co2+/Co3+ and Ni2+ strongly interacting with the spinel γ-Al2O3 and MgAl2O4 phases, the latter having a large number of lattice oxygen species, was considered another active component besides those of Ni and Co in the esterification of glycerol.

Multidisciplinary green approaches (ultrasonic, co-precipitation, hydrothermal, and microwave) for fabrication and characterization of Erbium-promoted Ni-Al2O3 catalyst for CO2 methanation

The dispersion of nickel catalysts is crucial for the catalytic ability of CO2 methanation, which can be influenced by the fabrication method and the operation process of the catalysts. Therefore, a series of fabrication methods, including ultrasonic, hydrothermal, microwave, and co-precipitation, have been applied to prepare 25Ni-5Er-Al2O3 catalysts. The fabrication method can partially influence the structural and catalytic activity of the nickel aluminate catalysts. Among the catalysts modified by Erbium prepared with various methods, the catalyst fabricated by ultrasonic pathway exhibited better catalytic performance and CH4 selectivity especially, at a temperature (400 ℃). The impact of the temperature of the reaction (200–500 °C) was examined under a stoichiometric precursor ratio of (H2:CO2) = 4: 1, atmospheric pressure, and space velocity (GHSV) of 25000 mL/gcath. The results demonstrate that the ultrasonic method is strongly efficient for fabricating Ni-based catalysts with a high BET surface area of about 190.33 m2g−1. The catalyst composed via the ultrasonic technique has 69.38 % carbon dioxide conversion and 100 % methane selectivity at 400 °C for excellent catalytic performance in CO2 methanation reactions. The fabrication effect can be associated with its high surface area, which is achieved via the hot spot mechanism. Besides, the addition of Erbium promotes the Ni dispersion on the supports and stimulates the positive reaction because of the erbium oxygen vacancies.

Biogasoline Obtained Using Catalytic Pyrolysis of Desmodesmus sp. Microalgae: Comparison between Dry Biomass and n-Hexane Extract

The present work deals with the production of hydrocarbons in the C5–C12 range obtained from the fast micropyrolysis of a laboratory-grown Desmodesmus sp. microalgae. It compares the properties of this specific fraction of hydrocarbons using or not using transition alumina catalysts during pyrolysis in experiments with both pure dried microalgae and its n-hexane extract. The microalgae were characterised using thermogravimetry (TG) and CHN analysis; the n-hexane extract was analysed through Fourier transform infrared spectroscopy (FTIR). The pyrolysis experiments were performed in a multi-shot pyrolyser connected online with a gas chromatograph coupled to a mass spectrometer (GC/MS). The composition of the C5–C12 fraction was compared to that of an industrial pyrolysis gasoline. The results of pyrolysis at 600 °C show that the alumina catalyst increases the quantity of C5–C12 hydrocarbon families when compared to purely thermal pyrolysis, representing about 40% of all the dry microalgae pyrolysis products. In the case of n-hexane extract, the C5–C12 area fraction corresponds to 33.5% of the whole products’ area when pyrolysis is conducted with an alumina catalyst. A detailed analysis shows that linear molecules, mainly unsaturated, are predominant in the products. Dry biomass formed more aromatic but less cyclic and alkylated molecules in relation to the n-hexane extract. Nitrogen products, essentially alkylated pyrroles, were produced in large quantities when dry biomass was used but were below the detection limit when pyrolysing the extracts. Thus, the extraction with hexane proved to be an effective way to remove nitrogen compounds, which are undesirable in fuels. The estimated low heating values of the present C5–C12 pyrolysis hydrocarbon fractions (between 43 and 44 MJ/kg) are quite comparable to the reported values for reformulated and conventional industrial gasolines (42 and 43 MJ/kg, respectively).

Template-free hydrothermal synthesis of hollow alumina microspheres and its excellent catalytic properties for thiolation

In view of the important industrial application value of alumina supports in the field of oil refining and reforming, it is of great significance to develop a simple and economical synthesis method for the hierarchical porous alumina. Herein, the hollow microsphere alumina was hydrothermally synthesized without template. The surface of the hollow microsphere alumina supports has a raised fluffy structure, the microsphere diameter is about 5 ∼ 8 μm, and the thickness of the shell is about 1 μm. The morphology evolution process from solid microspheres to core–shell microspheres with spindle-shaped nanoclusters, and then to hollow fluffy microspheres with protruding surface was observed by investigating the effect of hydrothermal synthesis temperature on the morphology of microspheres. Because of its specific morphology and surface characteristics, the microsphere can better disperse the active component KW to prepare KW/Al2O3 catalyst and used in the thiolation to methyl mercaptan. Compared with our previously used catalysts prepared from commercial alumina, this KW/Al2O3 catalyst was not only able to greatly reduce the amount of active component, but also exhibited higher CH3SH selectivity. On the 10KW/Al catalyst, the CH3SH selectivity reached 66.2 % at 340 °C, which was about 10 % higher than that of the previous commercial alumina catalyst. This work can provide theoretical basis and practical guidance for the reasonable design of new alumina support and high efficiency methyl mercaptan catalyst.

Catalytic pyrolysis behavior of heavy crude oil over acid-base composite catalysts

Direct pyrolysis of crude oil to petrochemical feedstocks (light olefins and aromatics) is a trend for the transformation of refineries. In order to combine the advantages of solid base and acid catalysts to boost the yields of light olefins and BTX (benzene, toluene and xylene), catalytic pyrolysis behavior of heavy crude oil over acid, base and composite catalysts were studied using Py-GC/MS. The results showed that maximum content of alkenes was obtained over the calcium aluminate (CaAl) catalyst due to the inhibited hydrogen transfer reactions, but its catalytic activity was lower than ZSM-5 with Si/Al ratio of 40 (Z-40). For different composite catalyst ratios, maximum light olefins and BTX content of 65 % was obtained with 40Z catalyst (60 %CaAl + 40 %Z-40), which was higher than that obtained with pure Z-40 and CaAl catalysts. Compared to commercial ZSM-5 based and USY based catalysts, the 40Z catalyst demonstrated superior catalytic cracking performance, with the highest content of light olefins and BTX, while significantly higher content of C9+ aromatics were obtained over FCC catalyst. This revealed that catalyst type and appropriate composite catalyst blend ratio all play important role in enhancing the generation of light olefins and aromatics.

A path to a dynamic hydrogen storage system using a liquid organic hydrogen carrier (LOHC): Burner-based direct heating of the dehydrogenation unit

Liquid organic hydrogen carrier (LOHC) systems offer a promising way to store and transport hydrogen in a safe and dense form at ambient conditions. Compared to other chemical hydrogen storage systems such as ammonia, formic acid, and methanol, LOHC systems enable reversible storage of hydrogen. For the endothermic hydrogen release reaction, heat and a suitable catalyst are needed. In this work for the first time, the exhaust gas enthalpy of a porous media burner is utilized to supply the heat for dehydrogenation of the LOHC compound perhydro dibenzyltoluene (H18-DBT). This approach significantly increases the system dynamics and the power density of the dehydrogenation unit compared to conventional heating via a heat transfer fluid. A dynamic hydrogen release is important to satisfy the fluctuating hydrogen demand, especially in hydrogen refuelling stations (HRS) or in stationary heating applications, e.g., for buildings. Our setup utilized methane as fuel source for the burner. The key challenge is the precise temperature control of the direct heating of the LOHC in the dehydrogenation unit. This is required as hot spots may result in thermal decomposition of the LOHC compounds, while cold spots limit the rate of the dehydrogenation reaction. With our laboratory-scale setup, we demonstrate a hydrogen release from H18-DBT of up to 450 mlN min−1 with 8.2 g of Pt on alumina catalyst (0.3 mass % Pt loading, i.e., 25 mg of Pt). Hydrogen is released within 10 min after a cold start of the entire system. The system exhibits a catalyst productivity of up to 1.5 gH2 gPt−1 min−1 and a power density relative to the reactor volume of about 3.6 kWtherm L−1 based on the lower heating value of hydrogen. Our findings show the strong potential of the direct heating concept in hydrogen release from LOHC systems and represent a significant step towards LOHC-based technical hydrogen provision systems.

Bio-template fabrication of nanoporous Ni@Al2O3: Durable catalyst for biogas reforming reaction

Following green chemistry principles and the significant role of catalysts in chemical transformations, in this study, for the first time, Ni@Al2O3 nanoparticles were prepared via a green, a sustainable, and practical approach using the waste management concept. To achieve this goal, the eggplant skin was employed as an abundant and green bio-template to synthesize desired materials, applying for biogas reforming (CH4/CO2 = 1:1) at four temperatures (600–750 °C). Synthesized materials were fully characterized and according to the findings, the bio-template was able to induce its structure on prepared materials and had a considerable effect on the activity of nickel-based alumina catalysts thanks to the high dispersion of Ni nanoparticles on the prepared materials. This catalyst could tolerate the reaction conditions even after 30 h of the catalytic run at 650 °C, along with a remarkable coke resistance (less than 4% carbon deposition).

Defining Stereochemistry in the Polymerization of Lactide by Aluminum Catalysts: Insights into the Dual-Stereocontrol Mechanism.

Aspects of the proposed pathway combining chain-end and enantiomorphic site control for the stereospecific polymerization of lactide (LA) were investigated through studies of aluminum complexes supported by enantiopure and racemic bipyrrolidine-based salan ligands, Lig1AlOBn and Lig2AlOBn. Spectroscopic analysis of stoichiometric initiation reactions and the definition of the stereochemistry of the selective formation of the "match" single-insertion products by X-ray crystallography led to key conclusions about the observed stereocontrol. Notably, it was determined to rely heavily on the preference for the trio of stereocenters around the metal to have a "match" formation (RR-ligand + S-polymer), which works synergistically with the enantiomorphic site preference of the catalyst to ring-open next to a stereocenter of a monomer of the same chirality as that of the ligand, resulting in highly heterotactic or syndiotactic PLA from rac- or meso-LA, respectively.

Novel 3D-Printed Alumina Monolith Catalysts for Hydroconversion of Tar

This paper reports on a novel method for the preparation of monolith catalysts using a 3D-printed matrix. The development included an investigation into potential approaches to improving the strength of alumina catalysts, 3D printing of a polymer matrix (template) with a specific channel structure, preparation of templated monolith catalysts, an examination of their physicochemical properties, and testing of these catalysts in hydroconversion of tar. Using an indirect template method, this study is the first to prepare a Al2O3 monolith catalyst with a Schwartz surface microstructure. The extrudate drying rate was found to be the most important parameter for the synthesis of high-strength catalysts. The activity of the monolith catalyst proved to be comparable—and in some parameters even markedly superior—to that of similar granular samples. The tar hydroconversion product consisted of super heavy oil with 2.8 wt % of sulfur.

Adsorption of asphaltenes on multiscale porous alumina

Alumina catalysts are frequently used in refineries for the hydrotreatment of heavy petroleum fraction that are enriched in asphaltenes. The transport of real and model asphaltenes molecules through powder and alumina’s extrudates treated or not at 150 °C to remove or not surface-adsorbed water was studied. The kinetics and isotherms of adsorption at 298 K were obtained by the solution depletion method. Calorimetric experiments were also investigated. The kinetic is faster on the powder than on the alumina extrudates where the equilibrium is reached after 24 h (against 1 h for the powder) due to mass transfer limitation. The capacity of adsorption of model asphaltenes on untreated powder and extrudates is comparable around 1.1 and 1.2 mg.m− 2 and increases with the heat treatment due to water removal. Both adsorption strength and capacity of real asphaltenes on alumina is lower compared to the model asphaltene molecule which could be explained by the strong interaction between the acidic function of the model molecule and the alumina surface. The calorimetric study in absence of alumina shows the dimerization of model asphaltene molecules. In presence of alumina, the enthalpy of adsorption of model and real asphaltenes on alumina is determined. The enthalpy of adsorption of model asphaltenes on treated powder is higher than on untreated powder meaning that more energetic sites are available (probably due to the release of water-occupied sites) and the curve obtained for treated powder suggests different adsorption sites. The enthalpy of adsorption of model asphaltene is higher for the treated extrudates but these results must be taken carefully because the kinetic of adsorption is very slow (24 h) for extrudates. The effect of flow rate was studied by saturating an extrudate column with model asphaltene molecules. The adsorption increases as the flow rate decreases which could be explained by higher friction in the macropores leading to the release of weakly retained asphaltenes as the flow rate increases or by less intermediate pore blocking by asphaltenes as the flow rate and thus the pressure increases. This study shows that the transport of asphaltenes through porous alumina supports is a complex process depending on many parameters.

Oxygen deficient Ce doped CO supported on alumina catalyst for low-temperature CO oxidation in presence of H2O and SO2

The carbon monoxide (CO) oxidation has been carried out using Ce doped Co/Al2O3 prepared by coprecipitation followed by deposition precipitation. The 0.1 mol Ce doped Co supported on alumina showed maximum CO oxidation activity compared to the undoped catalyst at a low temperature. The physicochemical characteristics of synthesized catalysts were investigated by FTIR, XRD, Raman, XPS, 27Al solid-state NMR, H2-TPR, HR-TEM, etc. Ce doping promoted a distortion in the cobalt lattice structure. The distortion leads to an increase in reactive oxygen and the number of oxygen vacancies. In addition, Ce modification prevents the generation of the cobalt aluminate phase and stimulates the production of the Co3O4 active phase for CO oxidation. The presence of hexa and penta-coordinated alumina increases the defect and oxygen vacancy formation, which was responsible for a higher CO oxidation rate. The Ce doped Co/Al2O3 catalyst showed maximum water and SO2 tolerance due to the Ce doping. The mechanistic and kinetic details for CO oxidation have been explained by correlating with characterization.

Synthesis of cerium and bismuth doped nickel aluminate for the photodegradation of methylene blue, methyl orange and rhodamine B dyes.

In the current research, NiAl2O4, NiAl1.98Bi0.02O4 and NiAl1.98Ce0.02O4 are fabricated by the sol-gel method. Doping of larger ions (Ce3+ and Bi3+) into smaller aluminium ion lattice increased the lattice constant from 8.0091Å to 8.9732Å and 8.0272Å respectively. XPS spectra of NiAl1.98Ce0.02O4 confirmed the existence of Ce ion in Ce3+ and Ce4+. Spherical shaped particles with visible pores are noticed in the Transmission Electron Microscopy (TEM). The bandgap of the tailored materials has decreased to 2.25eV and 2.98eV and increased the catalytic efficiency due to the decrease in electron-hole pair recombination rate. The photocatalytic efficiency of the materials was tested against methylene blue (MB), methyl orange (MO) and rhodamine B (RhB) dyes. In the case of MB degradation, the efficiency of nickel aluminate (0.5mg/mL) was 54% under UV light irradiation after 60min, which was increased to 94% and 89% through cerium doped and bismuth doped nickel aluminate catalyst respectively. A drastic increase from 31% to 94% (NiAl1.98Ce0.02O4) and 91% (NiAl1.98Bi0.02O4) was noticed against MO degradation. Doping of cerium and bismuth in nickel aluminate enhanced the photocatalytic activity against the selected coloured organic pollutants.

Cobalt promoted molybdenum carbide supported on γ-alumina as an efficient catalyst for hydrodesulfurization of dibenzothiophene

The development of new hydrodesulfurization (HDS) catalysts with suitable electronic structure and metal-support interaction are critical for the efficient removal of sulfur from oil. In this work, cobalt-promoted molybdenum carbide supported on mesoporous alumina (CoxMo2C/MA) catalysts were prepared by a simple one-step hydrolysis method combined with a temperature programmed carbonization process, and the effects of Co on the physicochemical properties and HDS performance of the catalysts were systematically investigated. The results show that the appropriate Co addition can reduce the interaction between Mo species and alumina support, which is beneficial for the carbonization of Mo. Besides, the introduction of Co makes Mo species electron-rich, causing the C–S bond is vulnerable to attack. Taking dibenzothiophene (DBT) as a probe, Co0.3Mo2C/MA shows significant high sulfur removal efficiency (about 100%) and effective direct desulfurization selectivity. Furthermore, the density functional theory calculations further prove that the activation energy barrier of DBT HDS at the Co–Mo2C site is lower than that of Mo2C, confirming its reaction is easier to proceed. This work may provide a strategy for accessing new efficient modified molybdenum carbide catalysts for the HDS field.

Steam reforming of tar in hot syngas cleaning by different catalysts: Removal efficiency and coke layer characterization

AbstractSyngas produced by biomass and waste gasification processes must be adequately clean of tar compounds before being utilized in value‐added applications. Syngas cleaning by tar cracking at high temperatures is a promising technique that can utilize different kinds of catalysts. However, their use is limited by the deposition of coke layers, which induces a masking phenomenon on the active surface, and, consequently, the rapid deactivation of the catalyst. This study addresses how the temperature (750 and 800°C) and the steam concentration (0% and 7.5%) can affect the extent of water–gas and reforming reactions between steam and coke deposits. Two catalysts were used: a market‐available activated carbon and an iron‐based alumina catalyst. The tests showed better performance of the Fe/γ‐Al2O3 catalyst. A mass increase of the bed was measured in tests with both the catalysts, which confirms the deposition of the coke layer produced by tar dehydrogenation and carbonization. Scanning electronic microscopy‐energy‐dispersive X‐ray analysis (SEM‐EDX) and Raman spectroscopy were utilized to investigate the nature of coke layers over the catalyst surface, with the aim of acquiring information about their reactivity towards the water gas reaction. SEM‐EDX observations indicate that the thickness of these carbon layers is less than 2 μm. Raman spectra suggest a negligible effect of the reaction temperature in the tested range and, in particular, that the amorphous nature of coke layers deposited in the presence of steam is relatively more graphitic than that obtained without steam.

Production of carbon nanomaterials and syngas from biogas reforming and decomposition on one-pot mesoporous nickel alumina catalysts

Biogas, a renewable energy source, is primarily composed of CH4 and CO2. It is a promising alternative to fossil fuels and can be used directly for electricity production as well as heat generation via combustion. Concerns about climate change and a greater emphasis on renewable energy sources have recently increased interest in biogas utilization. In this context, biogas reforming and decomposition (BRD) into synthesis gas and carbon nanofibers (CNFs) is viewed as a new and attractive way of efficiently valorising biogas. In this study, Ni-loaded (i.e., 20, 50 wt%) mesoporous alumina materials were prepared using one-pot evaporation-induced self-assembly method for BRD. Synthesized materials were characterized by various techniques: N2-physisorption, X-ray diffraction, temperature-programmed reduction, scanning electron microscopy, and thermal gravimetric analysis. Results showed that textural and structural properties of synthesised materials differed with Ni loading. High Ni-loaded catalyst displayed higher surface area, pore volume, pore size distribution, and average particle size which is the result of deposition of Ni species outside alumina grains creating thus, surface defects. BRD results were greatly influenced by Ni content with Ni50%Al2O3 reflecting catalytic behaviour similar to those expected for pure methane decomposition. Most importantly, this catalyst was also capable of generating, selectively, interesting carbon nanofibers.

Understanding the effects of feedstock blending and catalyst support on hydrotreatment of algae HTL biocrude with non-edible vegetable oil

The performance of cobalt-molybdenum (CoMo) on hydrotreating of algae HTL biocrude and carinata oil was investigated. Commercial CoMo/Al2O3 (CoMo/Al) and synthesized CoMo supported on Douglas fir biochar (CoMo/DF), sulfided or unsulfided catalysts, were compared for hydrodeoxygenation (HDO), hydrodenitrogenation (HDN), hydrodesulfurization (HDS) and hydrodemetallization (HDM) reactions. Results showed that there lies a synergistic effect when HTL algae biocrude and carinata oil blends are hydrotreated. The yield of the upgraded blend (UB) oils retrieved over alumina catalyst was higher than the individual hydrotreated parent oils. For example, a 9% and 5% increase in yield was noted compared to the average of individual hydrotreated parent oils. The UB produced from sulfided CoMo/Al exhibited superior HDO activity primarily by decarbonylation. This was apparent in increased heating value, carbon addition, higher octane number, and lower total acid number than the oils obtained from the biochar-supported catalysts. Sulfided CoMo/DF catalyzed cracking reactions which lowered the viscosity, followed by high HDN and HDS activity compared to the commercial catalyst. The two supports showed different sorption behaviors. Interestingly, CoMo/DF had an effective sorption mechanism that helped in higher metal removal from the oil. Additionally, presulfiding and DF support exhibited positive results in term of less coke formation. In brief, biochar supports have higher acidic sites, inorganic mineral oxides, ion exchange capacity, high surface area, pore structure and connectivity. All of these make a substantial contribution to its unique catalytic behavior.

Effect of extrusion-spheronization granulation and manganese loading on catalytic ozonation of petrochemical wastewater.

The petrochemical secondary effluent (PSE) is typical refractory wastewater derived from the petrochemical industries, which requires advanced treatment due to the strict environmental protection policies. Catalytic ozonation is one of the most widely used advanced oxidation technologies in wastewater treatment because of its high mineralization rate, in which the alumina-based catalyst usually plays an important role. Extrusion-spheronization is a promising technique for the preparation of alumina spheres because the synthesized alumina particles have high sphericity, high specific surface aera and narrow particle size distribution. In this paper, two kinds of alumina-based catalysts (catalyst A: manganese nitrate added after alumina granulation and catalyst B: manganese nitrate added into alumina powder before granulation) were prepared by the extrusion-spheronization method and used for PSE treatment by catalytic ozonation. The prepared alumina samples were characterized by Brunauer-Emmett-Teller (BET) method, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM), while the wastewater samples were analyzed for Total organic carbon (TOC), UV254 and fluorescence spectroscopy. Results showed that manganese was uniformly distributed in both catalysts, and the specific surface area of two catalysts was 318.36 m2/g and 354.95 m2/g, respectively. Catalytic ozonation experiments were repeated nine times with each catalyst under the same conditions. The TOC removal rates for catalysts A and B in the first run were 48.88% and 49.06%, respectively, then it dropped to 28.05% for catalyst A but remained 47.81% for catalyst B after using for nine times. This implied that the long-term performance of catalyst B would be more stable than catalyst A. Similar result were found in three-dimensional fluorescence analysis. UV254 results indicated that the removal efficiency of aromatic and unsaturated substances by catalyst B was higher than catalyst A. A possible explanation is that the active component manganese oxide formed a catalyst skeleton in catalyst B, which makes it hard to dissolve. Effect of extrusion-spheronization granulation and manganese loading on advanced oxidant treatment of petrochemical wastewater.

Lightweight and thermal insulation mullite fibers/whiskers hierarchical framework materials: Low-temperature in-situ growth method and mechanism

Mullite fibers/whiskers hierarchical structure materials (MFWs) were prepared via the three-stage method, i.e. seeds breeding, precursors introducing and whiskers growth. The mechanism of low-temperature in-situ synthesis of mullite whiskers during gas-phase reaction process has been discussed in detail. The seeds bred on mullite fibers (MFs) are the growth points and can effectively reduce the subsequent growth temperature of mullite whiskers (MWs). The precursors composed of aluminum source, silicon source and catalyst provided raw materials for whiskers growth. Under the heat treatment temperature of 800 °C, mullite seed grains were guided to in-situ transform into MWs. Moreover, MFWs fabricated via low-temperature in-situ growth mechanism on the MFs present low density (0.103–0.147 g/cm3) and ultralow thermal conductivity (0.0426–0.0514 W·m−1·K−1). Due to the lower whiskers growth temperature in this work than the ones in the most recent literatures, the three-stage method can be regarded as a viable strategy for low-temperature in-situ growth whiskers.

Co supported on Cex[Al2O3]0.5-x as an effective catalyst for low-temperature CO oxidation: Effect of calcination temperature

The low-temperature behavior of CO oxidation was investigated using 0.1 mol Ce doped Co supported on alumina catalysts prepared using co-precipitation followed by deposition precipitation method. The impact of calcination temperature on CO oxidation with kinetic aspects has been studied in detail and correlated to the characterizations. The Ce doped CoAl catalyst calcined at optimum temperature (550 ⁰C) shoed formation of more facile Co3+, Ce3+, and adsorbed species. The Co, Ce, and alumina interaction leads to the formation of optimum penta and hexa coordinated alumina. The physicochemical properties of the catalyst have been studied in detail using XRD, FTIR, Raman, TPR, XPS, and 27Al NMR and correlated to the catalytic activity.