Activation Energy Of Oxidation Reaction Research Articles

Ultrasound-assisted extraction of cranberry seed oil: food waste valorization approach

Cranberry pomace considered as a by-product of fruit industry contains seeds which may be processed to highly nutritive oil. Conventional extraction methods may be, however, harmful to natural environment, thus alternative, ultrasound-assisted extraction method may be useful tool to reduce environmental impact. In the following study, sonication was applied to extract oil from cranberry seeds. The aim of the study was to determine the most efficient conditions of ultrasound-assisted extraction of oil and to investigate sonication influence on the properties of final product. Ultrasound amplitude and extraction time were independent variables; yield and maximum induction time of oils were responses. The most efficient conditions were amplitude of 95% and extraction time of 11.38 min. Model predicted extraction yield of 22.55 ± 0.36% (vs. actual 21.98 ± 0.08%) and induction time of 52.60 ± 0.95 min (vs. actual 61.95 ± 3.06 min). Detailed analyses of oil extracted in the most efficient conditions and the control sample were performed. Kinetic parameters of oil oxidation, fatty acid profile and distribution, melting characteristics studies were carried out. Sonication influenced activation energy of oxidation reaction, contribution of chosen fatty acids (oleic, α-linolenic and eicosenoic fatty acids) and distribution of oleic and α-linolenic fatty acids in sn-2 position of triacylglycerols. Slight changes in melting profile of oils were also recorded. Scanning electron microscopy of cranberry seeds revealed that ultrasound treatment resulted in pore enlargement and fat agglomeration damage. Additional studies of thermal properties of cranberry seeds: differential scanning calorimetry and modulated differential scanning calorimetry were performed, which confirmed that cranberry seeds may be a new source of oil with unique properties.

Researches Regarding the Reduction of Oxidation Losses in the Obtaining of Secondary Aluminium Alloys Using Metallic Scraps

The paper presents thermodynamic aspects regarding the low temperature processing of small metal waste - aluminum alloy scraps. The activation energies of oxidation reactions of aluminum and some alloying elements with water vapors, carbon dioxide and oxygen present inside the furnace are compared, at the usual and experimentally temperatures (at 580 � 620oC, near the eutectic temperature, when the melt is in the semisolid/pasty state), in the elaborating of EN AB 46100 secondary alloys. The composition of the flue gases is presented at different temperatures and during different technological stages. Using electronic microscopy and EDS analysis, the elemental composition of the impurities resulted from the melt is highlighted.

High Temperature Physical and Chemical Stability and Oxidation Reaction Kinetics of Ni–Cr Nanoparticles

We report on the high temperature oxidation behavior and stability of nickel–chromium (Ni:Cr at 80:20 wt %) alloy nanoparticles (NPs) at temperatures up to 973 K. Structural characterization of the oxidized Ni–Cr NPs provides evidence for the inhomogeneous oxide formation with the presence of NiO, NiCr2O4, and Cr2O3 phases, indicating a degradation in the oxidation resistance of Ni–Cr NPs compared to comparable bulk compositions. Chemical identification coupled with thermogravimetric analysis indicates an increase in the activation energy for oxidation reaction from 1.69 to 2.98 eV for conversion ratios of 0.1 to 0.56, respectively. The higher activation energy values compared to those reported for Ni NPs at similar conversion ratios demonstrate the superior oxidation resistance of Ni–Cr NPs compared to Ni NPs. Theoretical modeling of the experimental data suggests that the reaction kinetics were diffusion dominated and could be described by the classical Jander 3D diffusion model. The implications of the...

Oxidation Kinetics of UZr2.3 and U2Ti Alloys in Dry Air

The isothermal oxidation behavior of UZr2.3 and U2Ti alloys in dry air was studied by thermogravimetric technique in the temperature ranges of 773–848 and 548–623 K, respectively. The oxidation products were found to be U3O8 and ZrO2 for UZr2.3 and U3O8 and TiO2 for U2Ti by X-ray diffraction analysis. The oxidation kinetics were found to best fit into linear rate law for both the alloys in the temperature range of investigation and the lowest value of α (0.11 for UZr2.3 and 0.12 for U2Ti), which corresponds to the fraction of completed reaction. The linear rate constants (k) were evaluated from the oxidation data. The activation energies of oxidation reactions were calculated using the Arrhenius equation and found to be 161 kJ mol−1 for UZr2.3 and 88 kJ mol−1 for U2Ti.

Kinetic Study of Catalytic In-situ Combustion Processes in the Presence of Nanoparticles

In recent years, there has been great interest in the application of special nanoparticles on thermal oil recovery processes. In this article, based on nanotechnology, a new method for improving the performance of in-situ combustion process is presented. This work aims at studying the effect of engineered nanoparticles on the activation energy of crude oil oxidation reactions in relation to in-situ combustion processes. Similar to previous studies, three oxidation regions were observed in crude oil combustion in porous media and it was found that each particular nanoparticle has a different effect on each oxidation region. Results show a significant reduction in the activation energies of oxidation reactions, which is an indication of strong catalytic effect of nanoparticles. The catalytic efficiency of nanoparticles was found to be a function of nanoparticle type and concentration. From the results of this study, it can be pointed out that nanoparticles have the potential to be applied as an effective additive to improve in-situ combustion performance.

The surface oxidation behavior of Ni–45.16%Ti shape memory alloys at different temperatures

The isothermal oxidation behavior of Ni–45.16%Ti (composition in atomic percent) alloy was investigated by thermogravimetric analysis, and differential scanning calorimeter (DSC) methods. It was found that Ni-rich NiTi alloy exhibits a different oxidation behavior at temperatures above 400 °C in oxygen atmosphere. The alloy was exposed to oxygen atmosphere isothermally, i.e., between 400 and 800 °C, for 1 h. A gravimetric method was used to determine the oxidation kinetics and it was seen that the oxidation constant increases significantly with isothermal temperature. The activation energy of oxidation reaction for NiTi alloy was determined to be 65.47 kJ mol−1. According to DSC measurements, the transformation temperature of alloy (M s, M f, A s and A f) was increased and also R phase disappeared above 500 °C. The formal oxides were determined by means of SEM–EDX measurements and obtained oxides are TiO and TiO2 oxides.

Research on preparation optimization of nano CeB6 powder and its high temperature stability

High temperature self-propagating synthesis (SHS) process is very rapid, the reaction process becomes un-controlled after the SHS reaction is ignited. So the initial reaction conditions will have great effects on phase compositions and microstructures of reaction products. In this paper, the effects of the proportioning amount of Mg on the yield ratio and particle sizes of CeB6 were studied. The SHS reaction products and leached products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicated that the SHS products consisted of MgO, CeB6 and little Mg3B2O6. The single CeB6 phase was contained after the SHS reaction products were leached. The purity of CeB6 was higher than 99.0 mass%, and the minimum particle sizes of CeB6 were within 30–70 nm. When the proportioning amount of Mg was 25% more than the theoretic amount, the yield of CeB6 was 68.68%. The antioxidant ability of CeB6 was rather stronger, which was oxidized step by step, and the initial oxidation temperature was 750 °C, which indicated that it had good high temperature stability. The apparent activation energies of oxidation reactions of CeB6 were 200.09 and 312.10 kJ/mol, respectively, and reaction orders were 0.69 and 0.40, respectively.

Oxidation behavior of WC–Co hard metal with designed multilayer coatings by CVD

Multilayer coatings composed of TiN, TiCN, α-Al2O3 and κ-Al2O3 were designed and then deposited on WC–Co alloy by chemical vapor deposition (CVD) technique, the samples of WC–Co alloy with multilayer coatings were oxidized in the temperature range of 600°C–950°C for various times in a Muffle furnace, and weight gain was measured by electronic balance. Phase component and microstructure evolution of coating samples after oxidation were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the oxidation resistance of WC–Co alloy was improved markedly after deposition of multilayer coatings. The oxidation kinetics of multilayer coating samples obeyed linear law and diffusion-controlled parabolic law at different oxidation conditions. The oxidation product of coatings was rutile TiO2. The sample exhibited excellent oxidation resistance when the outermost layer was α-Al2O3, which was consistent to the results of apparent activation energy of oxidation reaction. The oxidation resistance of multilayer coatings was improved with the increase of thickness of κ-Al2O3 layer. The κ-Al2O3 transformed into α-Al2O3 over 900°C. The interface between TiN and TiCN disappeared in the coating sample without α-Al2O3 and κ-Al2O3 layer.

Oxidation Resistance Behave of Stainless Steel /TiC Nano Powders

Stainless steel/TiC nanocomposite powder were prepared by high-energy ball-milling method using 316 stainless steel powder, carbon and titanium powder as raw materials. Microstructure of the nanocomposite powder was investigated with XRD and TEM techniques. The results showed that the stainless steel/TiC nanocomposite powder obtained when the ball-milling time was more than 40 hours. DSC analysis method was used to study the characteristics of oxidation resistance and the oxidation reaction kinetics of the nanocomposites powder. Results show that the oxidant resistance of nanocomposite powder was improved, the activation energy of oxidation reaction increased.

Quantum chemical metabolism‐based simulation of carcinogenic potency of benzene derivatives

AbstractUsing an oxenoid model, we investigated dependences of carcinogenic potency of the benzenes C6H5‐X on a nature of substituents X. According to the model, a P450 enzyme breaks a dioxygen molecule and generates the oxens, which readily react with substrates. We suggest that a stability of the intermediate OC6H6‐X with tetrahedrally coordinated C atom relative to the molecule C6H5‐X determines a rate of substrate biotransformation. Using MO LCAO MNDO approach, we calculated the total energies of molecules C6H6‐X and arene oxides OC6H6‐X. A difference ΔEmin of these values determines activation energy of oxidation reaction. The compounds with the low ΔEmin values are noncarcinogenic. Benzene derivatives with high ΔEmin values belong to carcinogenic compounds series. The carcinogenicity of amino‐ and nitro‐substituted benzenes is also determined by N‐oxidation of amino and reduction of the nitro group. As the phenylhydroxylamines XC6H4NHOH and nitrenium ions XC6OH4NH+ are the common metabolites of the nitro‐ and amino‐substituted benzenes and nitrenium ions XC6H4NH+ are the ultimate carcinogens, we use the differences ΔEN = E(XC6H4NH+) − E(XC6H4NHOH) as the second parameter characterizing the carcinogenic activity of amino‐ and nitro‐substituted benzenes. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010

Study on the Oxidation Resistance of 316 Stainless Steel Nano-Powder Prepared by Ball-Milling Method

316 stainless steel nano-grain powders were prepared by high-energy ball-milling method. The evolutions of grain size and microstructure of the stainless steel powders with the change of ball-milling conditions were investigated by XRD, SEM. DSC method was used to analyze the oxidation resistance of the powders after ball milling. The law of the change in oxidation weight gain and DSC oxidation peak of samples at the different heating rates were analyzed. Oxidation kinetics studies showed that the oxidant resistance of 316 stainless steel nano-crystalline powder was improved, the activation energy of oxidation reaction increased.

High-Temperature Oxidation of β-NbTi Alloys

The isothermal oxidation kinetics of four different β-NbTi alloys with compositions of 85, 75, 60, and 50 at. pct titanium were studied using the thermogravimetric technique in the temperature range of 1073 to 1323 K at an interval of 50 K. Analysis of oxidation curves revealed that each alloy follows a complex paralinear oxidation reaction mechanism. X-ray diffraction analysis of oxidation products at each temperature revealed the simultaneous formation of TiO2 and TiNb2O7. Formation of the oxidation product TiO2 predominated at higher titanium concentration and that of the ternary compound TiNb2O7 predominated at higher niobium concentration in the β-NbTi alloys. However, in all cases, the formation of TiNb2O7 predominated at higher temperatures. The overall oxidation rate constants and the activation energies of oxidation reactions for each alloy composition were evaluated. It was observed that the overall oxidation rate constant initially decreases from pure titanium to Nb-85 at. pct Ti and then increases with further decrease in titanium concentration.

Effect of the mineral matrix in the reactions of shales. Part 2. Oxidation reactions of Turkish Göynük and US Western Reference oil shales

The effect of the mineral matrix of Turkish Göynük and US Green River oil shales and air diffusion on the conversion of organic material in oxidation reactions was investigated in the present study. The material washed with HCl from the original oil shales, mainly carbonates of calcium and magnesium, had a mild catalytical effect and the material washed with HF, silicate minerals, had an inhibition effect during oxidation reactions of organic material. The overall reaction orders from the kinetic analysis were found to be pseudo-first-order. The magnitude of the activation energies of oxidation reactions at equal heating rates changed as E a (HCl washed shale)> E a (original shale)> E a ( HCl+HF washed shale). The rate of reaction depends on the rate of transport of the gas into the zone of reaction by diffusion. It was observed that the diffusion of oxygen into the organic matrix was the major resistance controlling the rate of oxidation reactions.

The application of XPS to the determination of the kinetics of the co oxidation reaction over the Ir(111) surface

The coverages of adsorbed oxygen and CO on an Ir(111) surface have been determined using X-ray photoelectron spectroscopy (XPS) during the steady-state catalytic production of CO 2. Correlating the coverages of the reacting adsorbates with the rate of CO 2 production allows the kinetics of the CO oxidation reaction to be determined. The reaction is found to obey a Langmuir-Hinshelwood rate expression of the form R CO 22 = k 0 [CO][O] exp(− E a kT ) , where R CO 2 is the rate of CO 2 production, k 0 is the pre-exponential factor of the reaction rate coefficient, [CO] and [O] are the surface coverages of CO and oxygen, respectively, and E a is the activation energy for the oxidation reaction. The activation energy for this catalytic oxidation reaction is found to be approximately 9 kcal mole .