Search results for: oxidation activity

Authors: Anushree, Chhaya Sharma, Satish Kumar

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Catalytic wet air oxidation (CWAO) is normally carried out at elevated temperature and pressure. This work investigates the potential of NiO-CeO₂ nano-catalyst in CWAO of paper industry wastewater under milder operating conditions of 90 °C and 1 atm. The NiO-CeO₂ nano-catalysts were synthesized by a simple co-precipitation method and characterized by X-ray diffraction (XRD), before and after use, in order to study any crystallographic change during experiment. The extent of metal-leaching from the catalyst was determined using the inductively coupled plasma optical emission spectrometry (ICP-OES). The catalytic activity of nano-catalysts was studied in terms of total organic carbon (TOC), adsorbable organic halides (AOX) and chlorophenolics (CHPs) removal. Interestingly, mixed oxide catalysts exhibited higher activity than the corresponding single-metal oxides. The maximum removal efficiency was achieved with Ce₄₀Ni₆₀ catalyst. The results indicate that the CWAO process is efficient in removing the priority organic pollutants from wastewater, as it exhibited up to 59% TOC, 55% AOX, and 54 % CHPs removal.

Keywords: catalysis, nano-materials, NiO-CeO2, paper mill, wastewater, wet air oxidation

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Authors: Zhanat Shomanova, Ruslan Safarov, Yuri Nosenko, Zheneta Tashmuchambetova, Alima Zharmagambetova

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An effective way of utilization of ferroalloy production wastes is preparing hydrocarbon refining catalysts from them. It is possible due to accordable transition metals containing in the wastes. In the work, we are presenting the results on elemental analysis of sludge samples from Aksu ferroalloy plant (Aksu, Kazakhstan), method of catalysts preparing, results of physical-chemical analysis of obtained catalysts (X-ray analysis, electron microscopy, the BET method etc.), results of using the catalysts in some hydrocarbons refining processes such as hydrocracking of rubber waste, cracking of gasoil, oxidation of cyclohexane. The main results of catalytic activity research are: a) In hydrocracking of rubber waste 64.9% of liquid products were fuel fractions; b) In cracking of gasoil conversion was 51% and selectivity by liquid products was 99%; c) In oxidation of cyclohexane the maximal product yield 87.9% and selectivity by cyclohexanol 93.0% were achieved.

Keywords: catalyst, cyclohexane oxidation, ferroalloy production waste, gasoil cracking

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Authors: Yu-Chen Luo, Wan-Tzu Yen, I-Ping Liu, Po-Hsuan Yeh, Yuh-Lang Lee

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The use of a Pt electrode leads to high catalytic efficiency in the ethanol electro-oxidation. However, the carbon monoxide (CO) released in the reaction will poison the Pt surfaces, lowering the electrocatalytic activity. In this study, composite electrodes are prepared to overcome the poisoning issue, and the related electro-oxidation behaviors are studied by surface-enhanced infrared absorption spectroscopy (SEIRAS) and cyclic voltammetry (CV). An electroless plating method is utilized to deposit Pt catalytic layers on the Pd film-coated FTO substrates. According to the SEIRAS spectra, the carbon dioxide signal of the Pt/Pd composite electrode is larger than that of the Pt one, whereas the CO signal of the composite electrode is relatively smaller. This result suggests that the studied Pt/Pd electrode has a better ability against CO poisoning. The CV analyses are conducted in alkaline environments, and current densities related to the ethanol oxidation in the forward scan (If) and to the CO poisoning in the backward scan (Ib) are measured. A higher ratio of If to Ib (If/Ib) usually represents a better ability against the poisoning effect. The If/Ib values are 2.53 and 2.07 for the Pt and Pt/Pd electrodes, respectively, which is possibly attributed to the increasing ability of CO adsorption of Pt electrode. Despite the lower If/Ib, the Pt/Pd composite electrode shows a higher ethanol oxidation performance in the alkaline system than the Pt does. Furthermore, its stability is also superior.

Keywords: cyclic voltammogram, electroless deposition, ethanol electro-oxidation, surface-enhanced infrared absorption spectroscopy

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Authors: Salima Tabti, Chaima Maouche, Tinhinene Louaileche, Amel Djedouani, Ismail Warad

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Novel Schiff base ligand HL has been synthesized by condensation of aromatic amine and DHA. It was characterized by UV-Vis, FT-IR, SM, NMR (1H, 13C) and also by single-crystal X-ray diffraction. The crystal structure shows that compound crystallized in a triclinic system in P-1 space group and with a two unit per cell (Z = 2).The asymmetric unit, contains one independent molecules, the conformation is determined by an intermolecular N-H…O hydrogen bond with an S(6) ring motif. The molecule have an (E) conformation about the C=N bond. The dihedral angles between the phenyl and pyran ring planes is 89.37 (1), the two plans are approximately perpendicular. The catecholase activity of is situ copper complexes of this ligand has been investigated against catechol. The progress of the oxidation reactions was closely monitored over time following the strong peak of catechol using UV-Vis. Oxidation rates were determined from the initial slope of absorbance. time plots, then analyzed by Michaelis-Menten equations. Catechol oxidation reactions were realized using different concentrations of copper acetate and ligand (L/Cu: 1/1, 1/2, 2/1). The results show that all complexes were able to catalyze the oxidation of catechol. Acetate complexes have the highest activity. Catalysis is a branch of chemical kinetics that, more generally, studies the influence of all physical or chemical factors determining reaction rates. It solves a lot of problems in the chemistry reaction process, especially for a green, economic and less polluting chemistry. For this reason, the search for new catalysts for known organic reactions, occupies a very advanced place in the themes proposed by the chemists.

Keywords: dehydroacetic acid, catechol, copper, catecholase activity, x-ray

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Authors: Yalçın Kılıç, İbrahim Kani

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In recent years, interest in the synthesis of coordination compounds has greatly increased due to various application areas (such as catalysis, gas storage, luminescence). Dicarboxylic acids are often used in the synthesis of metal complexes. Bis-thiosalicylate derivative ligands contribute to the synthesis of structures of crystal engineering interest, as they can have both rigid and flexible properties. In addition, these ligands have great potential in terms of catalytic applications with the sulfur and oxygen donor atoms in their structures. In this study, we synthesized a Cu(II) complex [Cu(tsaxyl)(phen)2]•CH3OH (where tsaxyl = 2,2'-(1,2-phylenebis(methylene))bis(sulfanedyl)dibenzoate, phen = 1,10-phenantroline) and characterized through X-ray crystallography. The catalytic activities of Cu(II) complex on oxidation of ethylbenzene, cyclohexane, diphenylmethane, p-xylene were performed in acetonitrile with t-BuOOH as the source of oxygen.

Keywords: complex, crystallography, catalysis, oxidation

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Authors: Zineb Benouahmane, Zhang Lifeng

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Experimental oxidation tests at high temperature (1300°C-1500°C) on α-SiC samples have been performed with different holding times and atmosphere (air, argon). Oxidized samples were then analyzed using X-ray photoelectron spectroscopy coupled to SEM and DAKTEK surface profiler verification. The oxidation rate and the mas gain were found to increase with temperature and holding times, corresponding to a passive oxidation regime which lead to the formation of SiO2 layer. The sessile drop method is employed in order to measure the wetting angles between Si/SiC system at high temperature (1430°C-1550°C). Contact angle can be varied between 44 °C to 85°C, by controlling the oxygen content in α-SiC. Increasing the temperature occurred the infiltration of liquid silicon and deoxidation of the coating.

Keywords: oxidation, wettability, silicon, SiC

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Authors: Krasimir Ivanov, Dimitar Dimitrov, Tatyana Tabakova, Stefka Kirkova, Anna Stoilova, Violina Angelova

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It has been suggested that nicotine, CO and tar in mainstream smoke are the most important substances and have been judged as the most harmful compounds, responsible for the health hazards of smoking. As nicotine is extremely important for smoking qualities of cigarettes and the tar yield in the tobacco smoke is significantly reduced due to the use of filters with various content and design, the main efforts of cigarettes researchers and manufacturers are related to the search of opportunities for CO content reduction. Highly active ceria supported gold catalyst was prepared by the deposition-precipitation method, and the possibilities for CO oxidation in the synthetic gaseous mixture were evaluated using continuous flow equipment with fixed bed glass reactor at atmospheric pressure. The efficiently of the catalyst in CO oxidation in the real cigarette smoke was examined by a single port, puf-by-puff smoking machine. Quality assessment of smoking using cigarette holder containing catalyst was carried out. It was established that the catalytic activity toward CO oxidation in cigarette smoke rapidly decreases from 70% for the first cigarette to nearly zero for the twentieth cigarette. The present study shows that there are two critical factors which do not permit the successful use of catalysts to reduce the CO content in the mainstream cigarette smoke: (i) significant influence of the processes of adsorption and oxidation on the main characteristics of tobacco products and (ii) rapid deactivation of the catalyst due to the covering of the catalyst’s grains with condensate.

Keywords: cigarette smoke, CO oxidation, gold catalyst, mainstream

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Authors: Krasimir Ivanov, Elitsa Kolentsova, Dimitar Dimitrov, Petya Petrova, Tatyana Tabakova

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This work studies the effect of chemical composition on the activity and selectivity of γ–alumina supported CuO/ MnO2/Cr2O3 catalysts toward deep oxidation of CO, dimethyl ether (DME) and methanol. The catalysts were prepared by impregnation of the support with an aqueous solution of copper nitrate, manganese nitrate and CrO3 under different conditions. Thermal, XRD and TPR analysis were performed. The catalytic measurements of single compounds oxidation were carried out on continuous flow equipment with a four-channel isothermal stainless steel reactor. Flow-line equipment with an adiabatic reactor for simultaneous oxidation of all compounds under the conditions that mimic closely the industrial ones was used. The reactant and product gases were analyzed by means of on-line gas chromatographs. On the basis of XRD analysis it can be concluded that the active component of the mixed Cu-Mn-Cr/γ–alumina catalysts consists of at least six compounds – CuO, Cr2O3, MnO2, Cu1.5Mn1.5O4, Cu1.5Cr1.5O4 and CuCr2O4, depending on the Cu/Mn/Cr molar ratio. Chemical composition strongly influences catalytic properties, this influence being quite variable with regards to the different processes. The rate of CO oxidation rapidly decrease with increasing of chromium content in the active component while for the DME was observed the reverse trend. It was concluded that the best compromise are the catalysts with Cu/(Mn + Cr) molar ratio 1:5 and Mn/Cr molar ratio from 1:3 to 1:4.

Keywords: Cu-Mn-Cr oxide catalysts, volatile organic compounds, deep oxidation, dimethyl ether (DME)

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Authors: Mulatu Kassie Birhanu

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Electro-oxidation of glycerol is an important process to convert the less price glycerol into other expensive (essential) and energy-rich chemicals. In this study, nickel was electro-deposited on laboratory-made carbon ceramic electrode (CCE) substrate using electrochemical techniques that is cyclic voltammetry (CV) to prepare an electro-catalyst (Ni/CCE) for electro-oxidation of glycerol. Carbon ceramic electrode was prepared from graphite and methyl tri-methoxy silane (MTMOS) through the processes called hydrolysis and condensation with methanol in acidic media (HCl) by a sol-gel technique. Physico-chemical characterization of bare CCE and modified (deposited) CCE (Ni/CCE) was measured and evaluated by Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD). Electro-oxidation of glycerol was performed in 0.1 M glycerol in alkaline media (0.5 M NaOH). High-Performance Liquid Chromatography (HPLC) technique was used to identify and determine the concentration of glycerol, reaction intermediates and oxidized products of glycerol after its electro-oxidation is performed. The conversion (%) of electro-oxidation of glycerol during 9-hour oxidation was 73% and 36% at 1.8V and 1.6V vs. RHE, respectively. Formate, oxalate, glycolate and glycerate are the main oxidation products of glycerol with selectivity (%) of 75%, 8.6%, 1.1% and 0.95 % at 1.8 V vs. RHE and 55.4%, 2.2%, 1.0% and 0.6% at 1.6 V vs. RHE respectively. The result indicates that formate is the main product in the electro-oxidation of glycerol on Ni/CCE using the indicated applied potentials.

Keywords: carbon-ceramic electrode, electrodeposition, electro-oxidation, Methyltrimethoxysilane

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Authors: Lin-Lin Liu, Song-Qi Hu, Yin Wang

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Paraffin-based fuels are regarded to be a promising fuel of hybrid rocked motor because of the high regression rate, low price, and environmental friendliness. Graphene Oxide (GO) is an attractive energetic material which is expected to be widely used in propellants, explosives, and some high energy fuels. Paraffin-based fuels with paraffin and GO as raw materials were prepared, and the oxidation process of the samples was investigated by thermogravimetric analysis differential scanning calorimetry (TG/DSC) under oxygen (O₂) and nitrous oxide (N₂O) atmospheres. The oxidation reaction kinetics of the fuels was estimated through the non-isothermal measurements and model-free isoconversional methods based on the experimental results of TGA. The results show that paraffin-based fuels are easier oxidized under O₂ rather than N₂O with atmospheres due to the lower activation energy; GO plays a catalytic role for the oxidation of paraffin-based fuels under the both atmospheres, and the activation energy of the oxidation process decreases with the increase of GO; catalytic effect of GO on the oxidation of paraffin-based fuels are more obvious under O₂ atmospheres than under N₂O atmospheres.

Keywords: graphene oxide, paraffin-based fuels, oxidation, activation energy, TGA

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Authors: Janjira Triped, Wipada Sanongraj, Wipawee Khamwichit

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The research work covered in this study includes the morphological structure and optical properties of TiO2-coated silk fibroin (SF) filters at 2.5% wt. TiO2/vol. PVA solution. SEM micrographs revealed the fibrous morphology of the TiO2-coated SF filters. An average diameter of the SF fiber was estimated to be approximately 10µm. Also, it was confirmed that TiO2 can be adhered more on SF filter surface at higher TiO2 dosages. The activity of semiconductor materials was studied by UV-VIS spectrophotometer method. The spectral data recorded shows the strong cut off at 390 nm. The calculated band-gap energy was about 3.19 eV. The photocatalytic activity of the filter was tested for gaseous formaldehyde removal in a modeling room with the total volume of 2.66 m3. The highest removal efficiency (54.72 ± 1.75%) was obtained at the initial formaldehyde concentration of about 5.00 ± 0.50ppm.

Keywords: photocatalytic oxidation process, formaldehyde (HCHO), silk fibroin (SF), titanium dioxide (TiO2)

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Authors: I. Yordanova, H. Kolev, S. Todorova, Z. Cherkezova-Zheleva

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Catalysis plays a key role in solving many environmental problems by establishing efficient catalytic systems for environmental protection and reducing emissions of greenhouse gases from industry. Volatile organic compounds are major air pollutants. There are several ways to dispose of emissions like - adsorption, condensation, absorption, bio-filtration, thermal, catalytic, plasma and ultraviolet oxidation. The catalytic oxidation has more advantages over other methods. For example - lower energy consumption; the concentration of the organic contaminant may be low or may vary within wide limits. Catalysts for complete oxidation of VOCs can be classified into three categories: noble metal, metal oxides or supported metal oxides and mixture of noble metals and metal oxides. Most of the catalysts for the complete catalytic oxidation are based on Pt, Pd, Rh or a combination thereof. The oxides of the transition metal are one of the alternatives to noble metal catalysts for these reactions. They are less active at low temperatures, but at higher - their activity is similar. The properties of the catalyst depend on the distribution of the active phase, the medium type of the pre-treatment, the interaction between the active phase and the support and the interaction between the active phase and the reaction medium. Supported mono-component Mn and bi-component Mn-Co systems are examined in present study. The samples are prepared using co-precipitation method. SiO2 (Aerosil) is used as a support. The studied samples were precipitated by NH4OH. The synthesized samples were characterized by XRD, XPS, TPR and tested in the catalytic reaction of complete oxidation of n-hexane, propane, methanol, ethanol and propanol.

Keywords: catalytic oxidation, Co-Mn oxide, oxidation of hydrocarbons and alcohols, environmental protection

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Authors: Muna K. Abbass, Laith A. Mohammed, Muntaha K. Abbas

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The oxidation of Al-Li base alloy containing small amounts of rare earth (RE) oxides such as 0.2 wt% Y2O3 and 0.2wt% Nd2O3 particles have been studied at temperatures: 400ºC, 500ºC and 550°C for 60hr in a dry air. Alloys used in this study were prepared by melting and casting in a permanent steel mould under controlled atmosphere. Identification of oxidation kinetics was carried out by using weight gain/surface area (∆W/A) measurements while scanning electron microscopy (SEM) and x-ray diffraction analysis were used for micro structural morphologies and phase identification of the oxide scales. It was observed that the oxidation kinetic for all studied alloys follows the parabolic law in most experimental tests under the different oxidation temperatures. It was also found that the alloy containing 0.2 wt %Y 2O3 particles possess the lowest oxidation rate and shows great improvements in oxidation resistance compared to the alloy containing 0.2 wt % Nd2O3 particles and Al-Li base alloy. In this work, Taguchi method is performed to estimate the optimum weight gain /area (∆W/A) parameter in oxidation process of Al-Li base alloys to obtain a minimum thickness of oxidation layer. Taguchi method is used to formulate the experimental layout, to analyses the effect of each parameter (time, temperature and alloy type) on the oxidation generation and to predict the optimal choice for each parameter and analyzed the effect of these parameters on the weight gain /area (∆W/A) parameter. The analysis shows that, the temperature significantly affects on the (∆W/A) parameter.

Keywords: Al-Li base alloy, oxidation, Taguchi method, temperature

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Authors: Hang Zhou, Limin Zhu

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This paper investigates the fabrication of microstructures on Si surfaces by using electrochemical anodic oxidation with agarose stamps. The fabricating process is based on a selective anodic oxidation reaction that occurs in the contact area between a stamp and a Si substrate. The stamp which is soaked in electrolyte previously acts as a current flow channel. After forming the oxide patterns as an etching mask, a KOH aqueous is used for the wet etching of Si. A complicated microstructure array of 1 cm2 was fabricated by the method with high accuracy.

Keywords: microstructures, anodic oxidation, silicon, agarose stamps

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Authors: Sherif Ismail

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Degradation of phenol-contaminated wastewater using Photocatalytic oxidation process was investigated in batch experiments using Fe doped TiO₂. Moreover, the effect of oxygen aeration on the performance of photocatalytic oxidation process by iron (Fe⁺²) doped titanium dioxide (TiO₂) was assessed. Photocatalytic oxidation using Fe doped TiO₂ effectively reduce the phenol concentration in wastewater with optimum condition of light intensity, pH, catalyst-dosing and initial concentration of phenol were 50 W/m2, 5.3, 600 mg/l and 10 mg/l respectively. The results obtained that removal efficiency of phenol was 88% after 180 min in case of N₂ addition. However, aeration by oxygen resulted in a 99% removal efficiency in 120 min. The results of photo-catalysis oxidation experiments fitted the pseudo-first-order kinetic equation with high correlation. Costs estimation of 30 m3/d full-scale photo-catalysis oxidation plant was assessed.

Keywords: phenol degradation, Fe-doped TiO2, AOPs, cost analysis

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Authors: Xiping Guo, Jing Li

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The microstructure of an Si-Al-Y co-deposition coating prepared on an Nb-Si based ultra high temperature alloy by pack cementation process at 1250°C for eight hours was studied. The results showed that the coating was composed of a (Nb,X)Si₂ (X represents Ti, Cr and Hf elements) outer layer, a (Ti,Nb)₅Si₄ middle layer and an Al, Cr-rich inner layer. For comparison, the oxidation behaviors of the coating at 800, 1050 and 1350°C were investigated respectively. Linear oxidation kinetics was found with the parabolic rate constants of 5.29×10⁻², 9×10⁻²and 5.81 mg² cm⁻⁴ h⁻¹, respectively. Catastrophic pesting oxidation has not been found at 800°C even for 100 h. The surface of the scale was covered by compact glassy SiO₂ film. The coating was able to effectively protect the Nb-Si based alloy from oxidation at 1350°C for at least 100 h. The formation process of the scale was testified following an epitaxial growth mechanism. The mechanism responsible for the oxidation behavior of the Si-Al-Y co-deposition coating at 800, 1050 and 1350°C was proposed.

Keywords: Nb-Si based ultra high temperature alloy, oxidation resistance, pack cementation, silicide coating, Al and Y modified

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Authors: Karla Lienau, Rafael Müller, René Moré, Debora Ressnig, Dan Cook, Richard Walton, Greta R. Patzke

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The increasing demand for renewable energy sources and storable fuels underscores the high potential of artificial photosynthesis. The four electron transfer process of water oxidation remains the bottleneck of water splitting, so that special emphasis is placed on the development of economic, stable and efficient water oxidation catalysts (WOCs). Our investigations introduced cobalt carbodiimide CoNCN and its transition metal analogues as WOC types, and further studies are focused on the interaction of different transition metals in the convenient all-nitrogen/carbon matrix. This provides further insights into the nature of the ‘true catalyst’ for cobalt centers in this non-oxide environment. Water oxidation activity is evaluated with complementary methods, namely photocatalytically using a Ru-dye sensitized standard setup as well as electrocatalytically, via immobilization of the WOCs on glassy carbon electrodes. To further explore the tuning potential of transition metal combinations, complementary investigations were carried out in oxidic spinel WOC matrices with more versatile host options than the carbodiimide framework. The influence of the preparative history on the WOC performance was evaluated with different synthetic methods (e.g. hydrothermally or microwave assisted). Moreover, the growth mechanism of nanoscale Co3O4-spinel as a benchmark WOC was investigated with in-situ PXRD techniques.

Keywords: carbodiimide, photocatalysis, spinels, water oxidation

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Authors: Mohamed H. El-Newehy, Badr M. Thamer, Nasser A. M. Barakat, Mohammad A.Abdelkareem, Salem S. Al-Deyab, Hak Y. Kim

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In this study, the influence of nitrogen doping on the electrocatalytic activity of carbon nanofibers with nickel nanoparticles toward methanol oxidation is introduced. The modified carbon nanofibers have been synthesized from calcination of electrospun nanofiber mats composed of nickel acetate tetrahydrate, poly(vinyl alcohol) and urea in argon atmosphere at 750oC. The utilized physicochemical characterizations indicated that the proposed strategy leads to form carbon nanofibers having nickel nanoparticles and doped by nitrogen. Moreover, due to the high-applied voltage during the electrospinning process, the utilized urea chemically bonds with the polymer matrix, which leads to form nitrogen-doped CNFs after the calcination process. Investigation of the electrocatalytic activity indicated that nitrogen doping NiCNFs strongly enhances the oxidation process of methanol as the current density increases from 52.5 to 198.5 mA/cm2 when the urea content in the original electrospun solution was 4 wt% urea. Moreover, the nanofibrous morphology exhibits distinct impact on the electrocatalytic activity. Also, nitrogen-doping enhanced the stability of the introduced Ni-based electrocatalyst. Overall, the present study introduces effective and simple strategy to modify the electrocatalytic activity of the nickel-based materials.

Keywords: electrospinning, methanol electrooxidation, fuel cells, nitrogen-doping, nickel

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Authors: Rayenne Djemil

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The mechanism of oxidation reaction of linoleic acid C18: 2 (9 cis12) by singlet oxygen 1O2 were theoretically investigated via using quantum chemical methods. We explored the four reaction pathways at PM3, Hartree-Fock HF and, B3LYP functional associated with the base 6-31G (d) level. The results are in favor of the first and the last reaction ways. The transition states were found by QST3 method. Thus the pathways between the transition state structures and their corresponding minima have been identified by the IRC calculations. The thermodynamic study showed that the four ways of oxidation of linoleic acid are spontaneous, exothermic and, the enthalpy values confirm that conjugate hydroperoxydes are the most favorable products.

Keywords: echanism, quantum mechanics, oxidation, linoleic acid H

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Authors: Elitsa N. Kolentsova, Dimitar Y. Dimitrov, Petya Cv. Petrova, Georgi V. Avdeev, Diana D. Nihtianova, Krasimir I. Ivanov, Tatyana T. Tabakova

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Recently, copper and manganese-containing systems are recognized as active and selective catalysts in many oxidation reactions. The main idea of this study is to obtain more information about γ-Al₂O₃ supported Cu-La catalysts and to evaluate their activity to simultaneous oxidation of CO, CH₃OH and dimethyl ether (DME). The catalysts were synthesized by impregnation of support with a mixed aqueous solution of nitrates of copper, manganese and lanthanum under different conditions. XRD, HRTEM/EDS, TPR and thermal analysis were performed to investigate catalysts’ bulk and surface properties. The texture characteristics were determined by Quantachrome Instruments NOVA 1200e specific surface area and pore analyzer. The catalytic measurements of single compounds oxidation were carried out on continuous flow equipment with a four-channel isothermal stainless steel reactor in a wide temperature range. On the basis of XRD analysis and HRTEM/EDS, it was concluded that the active component of the mixed Cu-Mn-La/γ–alumina catalysts strongly depends on the Cu/Mn molar ratio and consisted of at least four compounds – CuO, La₂O₃, MnO₂ and Cu_1.5Mn_1.5O₄. A homogeneous distribution of the active component on the carrier surface was found. The chemical composition strongly influenced catalytic properties. This influence was quite variable with regards to the different processes.

Keywords: Cu-Mn-La oxide catalysts, carbon oxide, VOCs, deep oxidation

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Authors: Mohammed Nasir Kajama, Ngozi Claribelle Nwogu, Edward Gobina

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Pt/γ-Al2O3 membrane catalysts were prepared via an evaporative-crystallization deposition method. The obtained Pt/γ-Al2O3 catalyst activity was tested after characterization (SEM-EDAX observation, BET measurement, permeability assessment) in the catalytic oxidation of selected volatile organic compound (VOC) i.e. propane, fed in mixture of oxygen. The VOC conversion (nearly 90%) obtained by varying the operating temperature showed that flow-through membrane reactor might do better in the abatement of VOCs.

Keywords: VOC combustion, flow-through membrane reactor, platinum supported alumina catalysts

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Authors: Jamshid Ghiasi Ghalehkandi, Naser Maheri Sis, Yahya Ebrahimnezhad, Shahin Hassanpour

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The objective of present study was to examine the effects of fresh garlic juice on semen malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GPx) and total antioxidant status (TAS) in male rats. Fifty-four male rats (230-250 g) were allocated into 3 treatment groups (each include 3 groups and 6 replicate). Group 1 served as water control. In group 2, rats were gavaged with 60 mg/kg garlic juice. In group 3, rats were offered 120 mg/kg garlic juice. Animals received treatments orally and ad libitum access to chow pellets and fresh water. After 4 weeks, animals were killed, testes were taken out and semen samples were used to determine MDA, SOD, GPx and TAS activity. According to the results, garlic juice (120 mg/kg) significantly declined semen MDA activity compared to control group (P<0.05). These results suggest that presumably garlic juice protects semen oxidation in rat testes.

Keywords: garlic juice, chromium chloride, semen, rat

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Authors: Erica T. R. Mendonça, Caroline M. B. de Araujo, Filho, Osvaldo Chiavone, Sobrinho, Maurício A. da Motta

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Oil and gas exploration is an essential activity for modern society, although the supply of its global demand has caused enough damage to the environment, mainly due to produced water generation, which is an effluent associated with the oil and gas produced during oil extraction. It is the aim of this study to evaluate the treatment of produced water, in order to reduce its oils and greases content (OG), by using flotation as a pre-treatment, combined with oxidation for the remaining organic load degradation. Thus, there has been tested Advanced Oxidation Process (AOP) using both Fenton and photo-Fenton reactions, as well as a chemical oxidation treatment using sodium ferrate(VI), Na₂[FeO₄], as a strong oxidant. All the studies were carried out using real samples of produced water from petroleum industry. The oxidation process using ferrate(VI) ion was studied based on factorial experimental designs. The factorial design was used in order to study how the variables pH, temperature and concentration of Na₂[FeO₄] influences the O&G levels. For the treatment using ferrate(VI) ion, the results showed that the best operating point is obtained when the temperature is 28 °C, pH 3, and a 2000 mg.L^-1 solution of Na₂[FeO₄] is used. This experiment has achieved a final O&G level of 4.7 mg.L^-1, which means 94% percentage removal efficiency of oils and greases. Comparing Fenton and photo-Fenton processes, it was observed that the Fenton reaction did not provide good reduction of O&G (around 20% only). On the other hand, a degradation of approximately 80.5% of oil and grease was obtained after a period of seven hours of treatment using photo-Fenton process, which indicates that the best process combination has occurred between the flotation and the photo-Fenton reaction using solar radiation, with an overall removal efficiency of O&G of approximately 89%.

Keywords: advanced oxidation process, ferrate (VI) ion, oils and greases removal, produced water treatment

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Authors: Seong-Ho Ha, Young-Ok Yoon, Shae K. Kim

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Oxide layer of normal Al-Mg alloy can be characterized by upper MgO and lower MgAl2O4 spinel. The formation of the MgO outmost layer occurs by the surface segregation of Mg in the initial oxidation. After then, the oxidation is proceeded with the formation of MgA12O4 spinel beneath the MgO. Growth of the oxide layer is accelerated by constant formation of MgA12O4 spinel. On the other hand, the oxidation resistance of Al-Mg alloys can be significantly improved simply by Mg+Al2Ca master alloy use as the Mg alloying element and such an improvement is attributed to the CaO/MgO mixed layer. Al-Mg alloy containing Al2Ca shows CaO as the upper layer and MgO as the lower one without MgA12O4 spinel. Such a dense oxide film acts as a protective layer. However, the CaO/MgO scale has the outmost MgO, partly, after a long time exposure to a harsh oxidation condition. The aim of this study is to investigate the inter-filling behaviour of CaO and MgO mixed layer in oxidation resistance mechanism of Al-Mg alloys containing Al2Ca. The process of outmost MgO layer formation will be clarified.

Keywords: Al-Mg alloy, Al2Ca, oxidation, MgO

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Authors: O. Çomaklı, M. Yazıcı, T. Yetim, A. F. Yetim, A. Çelik

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In this work, TiO₂ films were deposited on Cp-Ti substrates by thermal oxidation, DC plasma oxidation, and by the sol-gel method. Microstructures of uncoated and TiO₂ film coated samples were examined by X-ray diffraction and SEM. Thin oxide film consisting of anatase (A) and rutile (R) TiO₂ structures was observed on the surface of CP-Ti by under three different treatments. Also, the more intense anatase and rutile peaks appeared at samples plasma oxidized at 700˚C. The thicknesses of films were about 1.8 μm at the TiO₂ film coated samples by sol-gel and about 2.7 μm at thermal oxidated samples, while it was measured as 3.9 μm at the plasma oxidated samples. Electrochemical corrosion behaviour of uncoated and coated specimens was mainly carried out by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in simulated body fluid (SBF) solution. Results showed that at the plasma oxidated samples exhibited a better resistance property to corrosion than that of other treatments.

Keywords: TiO₂, CP-Ti, corrosion properties, thermal oxidation, plasma oxidation, sol-gel

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Authors: Natalina, Hwai Chyuan Onga, W. T. Chonga

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Oxidation stability of biodiesel is very important in fuel handling especially for remote location of biodiesel application. Variety of feedstocks and biodiesel production process resulted many variation of biodiesel oxidation stability. The current study relates to investigation of the impact of fatty acid composition that caused by natural and production process of calophyllum inophyllum palm oil methyl ester that correlated with improvement of biodiesel oxidation stability. Firstly, biodiesel was produced from crude oil of palm oil, calophyllum inophyllum and mixing of calophyllum inophyllum and palm oil. The production process of calophyllum inophyllum palm oil methyl ester (CIPOME) was divided by including washing process and without washing. Secondly, the oxidation stability was measured from the palm oil methyl ester (POME), calophyllum inophyllum methyl ester (CIME), CIPOME with washing process and CIPOME without washing process. Then, in order to find the differences of fatty acid compositions all of the biodiesels were measured by gas chromatography analysis. It was found that mixing calophyllum inophyllum into palm oil increased the oxidation stability. Washing process influenced the CIPOME fatty acid composition, and reduction of washing process during the production process gave significant oxidation stability number of CIPOME (38 h to 114 h).

Keywords: biodiesel, oxidation stability, calophyllum inophyllum, water content

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Authors: Sneha Samal, Iva Petrikova, Bohdana Marvalova

Abstract:

Influence of grain size, shape and grain boundary diffusion at high temperature oxidation of pure metal is investigated as the function of microstructure evolution in this article. The oxidized scale depends on the geometrical parameter of the metal-scale system and grain shape, size, diffusion through boundary layers and influence of the contamination. The creation of the inner layer and the morphological structure develops from the internal stress generated during the growth of the scale. The oxidation rate depends on the cation and anion mobile transport of the metal in the inward and outward direction of the diffusion layer. Oxidation rate decreases with decreasing the grain size of the pure metal, whereas zinc deviates from this principle. A strong correlation between the surface roughness evolution, grain size, crystalline properties and oxidation mechanism of the oxidized metal was established.

Keywords: high temperature oxidation, pure metals, grain size, shape and grain boundary

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Authors: P. Acosta-Santamaría, A. Ibatá-Soto, A. López-Vásquez

Abstract:

Organic compounds in wastewaters coming from textile and pharmaceutical industry generated multiple harmful effects on the environment and the human health. One of them is the methyl orange (MeO), an azoic dye considered to be a recalcitrant compound. The heterogeneous photocatalysis emerges as an alternative for treating this type of hazardous compounds, through the generation of OH radicals using radiation and a semiconductor oxide. According to the author’s knowledge, catalysts such as TiO₂ doped with metals show high efficiency in degrading MeO; however, this presents economic limitations on industrial scale. Black sand can be considered as a naturally doped catalyst because in its structure is common to find compounds such as titanium, iron and aluminum oxides, also elements such as zircon, cadmium, manganese, etc. This study reports the photocatalytic activity of the mineral black sand used as semiconductor in the discoloration of MeO by oxidation and reduction photocatalytic techniques. For this, magnetic composites from the mineral were prepared (RM, M1, M2 and NM) and their activity were tested through MeO discoloration while TiO₂ was used as reference. For the fractions, chemical, morphological and structural characterizations were performed using Scanning Electron Microscopy with Energy Dispersive X-Ray (SEM-EDX), X-Ray Diffraction (XRD) and X-Ray Fluorescence (XRF) analysis. M2 fraction showed higher MeO discoloration (93%) in oxidation conditions at pH 2 and it could be due to the presence of ferric oxides. However, the best result to reduction process was using M1 fraction (20%) at pH 2, which contains a higher titanium percentage. In the first process, hydrogen peroxide (H₂O₂) was used as electron donor agent. According to the results, black sand mineral can be used as natural semiconductor in photocatalytic process. It could be considered as a photocatalyst precursor in such processes, due to its low cost and easy access.

Keywords: black sand mineral, methyl orange, oxidation, photocatalysis, reduction

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Authors: Jin Lin, Shouxiang Lu, Kim Meow Liew

Abstract:

The requirement for the long-term mission of the submarine and spacecraft has made the removal of CO₂ and trace CO the critical technology to ensure the health and life of the crews. In this work, CuMnCe, a metal oxide catalyst, supporting K₂CO₃ sorbent was prepared by the wet-solid state impregnation method to realize the integrated CO and CO₂ removal, which might also reduce the volume/mass load of the purification units in the limited space. The as-prepared samples with different addition amount of K₂CO₃ were tested using the fixed bed reactor to reveal the CO oxidation and CO₂ absorption behavior. And the regeneration and stability experiments were also conducted. The results showed that the samples realized the catalyst and sorbent integration to capture CO and CO₂ at the same time. The addition amount of the sorbent had a weak influence on the CO oxidation performance. While the addition amount affected the CO₂ sorption efficiency and capacity significantly. Meanwhile, the presence of water vapor could reduce the CO oxidation activity of the samples similarly, whether with K2CO3 sorbent addition or not. Furtherly, regeneration and stability experiment results showed that the samples after 3-5 times regeneration exhibited almost the same performance of CO and CO₂ removal. Summarily, CuMnCe catalyst supporting K₂CO₃ sorbent could be a good attempt to control CO and CO₂ pollutants generated from the daily equipment running and staff breathing in the confined space such as submarine and spacecraft.

Keywords: CO oxidation, CO₂ absorptio, potassium carbonate, CuMnCe metal oxide, confined space

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Authors: Zoi Konsoula

Abstract:

Vegetable oils, which are rich in polyunsaturated fatty acids, are susceptible to oxidative deterioration. The lipid oxidation of oils results in the production of rancid odors and unpleasant flavors as well as the reduction of their nutritional quality and safety. Traditionally, synthetic antioxidants are employed for their retardation or prevention of oxidative deterioration of oils. However, these compounds are suspected to pose health hazards. Consequently, recently there has been a growing interest in the use of natural antioxidants of plant origin for improving the oxidative stability of vegetable oils. The genus Salvia (sage) is well known for its antioxidant activity. In the Cypriot flora Salvia fruticosa is the most distributed indigenous Salvia species. In the present study, extracts were prepared from S. fruticosa aerial parts using various solvents and their antioxidant activity was evaluated by the 1,1-diphenyl-2-picrylhydrazine (DPPH) radical scavenging and Ferric Reducing Antioxidant Power (FRAP) method. Moreover, the antioxidant efficacy of all extracts was assessed using corn oil as the oxidation substrate, which was subjected to accelerated aging (60 °C, 30 days). The progress of lipid oxidation was monitored by the determination of the peroxide, p-aniside, conjugated dienes and trienes value according to the official AOCS methods. Synthetic antioxidants (butylated hydroxytoluene-BHT and butylated hydroxyanisole-BHA) were employed at their legal limit (200 ppm) as reference. Finally, the total phenolic (TPC) and flavonoid content (TFC) of the prepared extracts was measured by the Folin-Ciocalteu and aluminum-flavonoid complex method, respectively. The results of the present study revealed that although all sage extracts prepared from S. fruticosa exhibited antioxidant activity, the highest antioxidant capacity was recorded in the methanolic extract, followed by the non-toxic, food grade ethanol. Furthermore, a positive correlation between the antioxidant potency and the TPC of extracts was observed in all cases. Interestingly, sage extracts prevented lipid oxidation in corn oil at all concentrations tested, however, the magnitude of stabilization was dose dependent. More specifically, results from the different oxidation parameters were in agreement with each other and indicated that the protection offered by the various extracts depended on their TPC. Among the extracts, the methanolic extract was more potent in inhibiting oxidative deterioration. Finally, both methanolic and ethanolic sage extracts at a concentration of 1000 ppm exerted a stabilizing effect comparable to that of the reference synthetic antioxidants. Based on the results of the present study, sage extracts could be used for minimizing or preventing lipid oxidation in oils and, thus, prolonging their shelf-life. In particular, given that the use of dietary alcohol, such as ethanol, is preferable than methanol in food applications, the ethanolic extract prepared from S. fruticosa could be used as an alternative natural antioxidant.

Keywords: antioxidant activity, corn oil, oxidative deterioration, sage

Procedia PDF Downloads 161