Kinetic Studies on Oxirane Cleavage of Epoxidized Soybean Oil by Methanol and Characterization of Polyols

The kinetics of the oxirane cleavage of epoxidized soybean oil (ESO) by methanol (Me) without a catalyst was studied at 50, 60, 65, 70 °C. The rate of oxirane ring opening is given by k[Ep][Me]², where [Ep] and [Me] are the concentrations of oxiranes in ESO and methanol, respectively and k is a rate constant. From the temperature dependence of the kinetics thermodynamic parameters such as enthalpy (ΔH), entropy (ΔS), free energy of activation (ΔF) and activation energy (ΔE _a) were found to be 76.08 (±1.06) kJ mol⁻¹, −118.42 (±3.12) J mol⁻¹ k⁻¹, 111.39 (±2.86) kJ mol⁻¹, and 78.56 (±1.63) kJ mol⁻¹, respectively. The methoxylated polyols formed from the oxirane cleavage reaction , were liquid at room temperature and had three low temperature melting peaks. The results of chemical analysis via titration for residual oxiranes in the reaction system showed good agreement with IR spectroscopy especially the disappearance of epoxy groups at 825, 843 cm⁻¹ and the emergence of hydroxy groups at the OH characteristic absorption peak from 3,100 to 3,800 cm⁻¹.     

Bleaching kinetics of sunflowerseed oil

The bleaching process for sunflowerseed oil follows a rate formula, log (A/A ₀)=−κ , according to absorbance measurements. The dark color of crude oil converts to a light color as the absorbance value decreases. The activation energy E _a was calculated from the Arrhenius equation as 3 kJ, and other activation thermodynamic parameters were determined as ΔS ^⊄=−4.4 J K⁻¹, ΔH ^⊄=−31.2 J mol⁻¹, and ΔG ^⊄=1.6 kJ mol⁻¹. The study showed that the bleaching process was exothermic, presented a decrease of entropy, and was a nonspontaneous process during activation.     

Kinetic parameter determination of vegetable oil oxidation under Rancimat test conditions

In this research, five different vegetable oils were oxidized at four different temperatures (373, 383, 393, and 403 K) under Rancimat test conditions. An increasing rate of oxidation could be observed as temperature increased. The natural logarithms of the kinetic rate constant (k value) varied linearly with respect to temperature, with the temperature coefficients (T_Coeff) ranging from 6.95×10^–2 to 7.40× 10^–2 K^–1 for the vegetable oils. On the basis of the Arrhenius equation and the activated complex theory, frequency factors (A), activation energies (E_a), Q₁₀ numbers, activation enthalpies (ΔH⁺⁺), and activation entropies (ΔS⁺⁺) for oxidative stability of the vegetable oils were calculated. The A, E_a, Q₁₀, ΔH⁺⁺, and ΔS⁺⁺ values for the vegetable oils ranged from 6.38×10³ to 28.03×10³ h^–1, from 86.86 to 92.42 kJ/mol, from 2.08 to 2.18, from 83.64 to 89.20 kJ/mol, and from –116.66 to –104.35 J/mol K, respectively.     

Thermodynamics of chromate replacements by various homologous transition metal oxyanions

The free energy change is calculated for the interaction of 19 different oxyanions (metalates) with iron (steel) or aluminum surfaces. The oxyanions considered here are those of the transition metals in the fourth through sixth periods of the periodic table. The oxyanions which produce more negative values of ΔG ^o (per mole of oxyanion) than that of chromate (CrO₄ ⁻²) are permanganate (MnO₄ ⁻), nickelate (NiO₄ ⁻²), ruthenate (RuO₄ ⁻ or RuO₄ ⁻²), and rhodate (RhO₄ ⁻²). The oxyanions which produce values of ΔG ^o (per mole of oxyanion) similar to CrO₄ ⁻² are osmate (OsO₄ ⁻²), and iridate (IrO₄ ⁻²).     

Transformation of propane and CO to carboxylic acid and ester by highly active CaCl2 catalyst

The functionalization reaction of propane with CO to afford carboxylic acids and an ester by CaCl₂ catalyst in the presence of K₂S₂O₈ and CF₃COOH has been studied. The reaction gave isobutyric acid as the main product and n-butyric acid and isopropyl trifluoroacetate as by-products. Atmospheric pressure of propane underwent the reaction with 30 atm of CO pressure at 80 °C for 24 h, giving about 95% total yield based on propane. The activation and thermodynamic parameters have been determined to be E_a = 130.3, 138.0 and 153.8 kJ/mol; A = 7.14 × 10¹³, 5.83 × 10¹⁴ and 5.80 × 10¹⁶ 1/s; ΔH ^‡ = 128.0, 134.7 and 150.5 kJ/mol; ΔS ^‡ = 10.3, 28.6 and 66.8 J/mol K and ΔG^‡ ₂₅₃ = 124.4, 123.9 and 126.9 kJ/mol for the products of isobutyric acid, n-butyric acid and isopropyl trifluoroacetate, respectively. This revised version was published online in July 2006 with corrections to the Cover Date.     

Pyrolysis kinetics and characteristics of the mixtures of waste ship lubricating oil and waste fishing rope

Kinetic investigations on the pyrolysis of a mixture of waste ship lubricating oil (WSLO) and waste fishing rope (WFR) were carried out using a thermogravimetric analyzer (TGA) at a heating rate of 0.5 ‡C/min, 1.0 ‡C/min and 2.0 ‡C/min. WSLO and WFR were mainly decomposed at the temperature of range of 400 ‡C to 455 ‡C and 370 ‡C to 410 ‡C, respectively. The WSLO/WFR mixture was mainly decomposed at the temperature range of 300 ‡C and 450 ‡C, which is a lower temperature than that for the WSLO or the WFR alone at each heating rate. The ranges of apparent activation energies of the WALO/WFR mixture were between 137 kJ mol^-1 and 197 kJ mol^-1 at conversions in the range of 10–95%. The mixture of WSLO and WFR was pyrolyzed in a micro-scale tubing reactor at 440 ‡C for 60 min and 80 min. The yield of pyrolyzed gases increased from 2.13 wt% to2.29 wt% with reaction time. The selectivity to C₇ hydrocarbons was shown in the pyrolyzed oil of the mixture.     

Thermal decomposition of 3,3,6,6,9,9-hexaethyl-1,2,4,5,7,8-hexaoxacyclononane in solution and its use in methyl methacrylate polymerization

The kinetics of the thermal decomposition reaction of diethylketone triperoxide (3,3,6,6,9,9-hexaethyl-1,2,4,5,7,8-hexaoxacyclononane, DEKTP) in ethylbenzene solution were studied in the temperature range of 120.0–150.0 °C and at an initial concentration range of 0.01–0.10 M. This peroxide was used as a new initiator in methyl methacrylate (MMA) polymerization process at high temperatures (110.0–140.0 °C) in ethylbenzene solution. The effects of initiator concentration and reaction temperature on the polymerization rate were investigated in detail. Thus, activation parameters of the solution polymerization process (ΔE _d* = 83.3 kJ mol⁻¹ and ΔE _p* − ΔE _t*/2 = 54.0 kJ mol⁻¹) will be obtained. DEKTP can effectively act as initiator in MMA polymerization and its performance is similar to that presented by a multifunctional initiator resulting in high-molecular weight polymethylmethacrylate with a high reaction rate.     

Effect of temperature on linolenic acid loss and 18:3 Δ9-cis, Δ12-cis, Δ15-trans formation in soybean oil

Oil was extracted from soybeans, degummed, alkalirefined and bleached. The oil was heated at 160, 180, 200, 220 and 240°C for up to 156 h. Fatty acid methyl esters were prepared by boron trifluoride-catalyzed transesterification. Gas-liquid chromatography with a cyanopropyl CPSil88 column was used to separate and quantitate fatty acid methyl esters. Fatty acids were identified by comparison of retention times with standards and were calculated as area % and mg/g oil based on 17:0 internal standard. The rates of 18:3ω3 loss and 18:3 Δ9-cis, Δ12-cis, Δ15-trans (18:3c,c,t) formation were determined, and the activation energies were calculated from Arrhenius plots. Freshly prepared soy oil had 10.1% 18:3ω3 and no detectable 18:3c,c,t. Loss of 18:3ω3 followed apparent first-order kinetics. The first-order rate constants ranged from .0018±.00014 min⁻¹ at 160°C to .083±.0033 min⁻¹ at 240°C. The formation of 18:3c,c,t did not follow simple kinetics, and initial rates were estimated. The initial rates (mg per g oil per h) of 18:3c,c,t formation ranged from 0.0031±0.0006 at 160°C to 2.4±.24 at 240°C. The Arrhenius activation energy for 18:3ω3 loss was 82.1±7.2 kJ mol⁻¹. The apparent Arrhenius activation energy for 18:3c,c,t formation was 146.0±13.0 kJ mol⁻¹. The results indicate that small differences in heating temperature can have a profound affect on 18:3c,c,t formation. Selection of appropriate deodorization conditions could limit the amount of 18:3c,c,t produced.     

Reaction between Hydrosulfide and Iron/cerium (hydr)oxide: Hydrosulfide Oxidation and Iron Dissolution Kinetics

Hydrosulfide oxidation and iron dissolution kinetics were studied at normal pressure, under inert (N₂) atmosphere, in a liquid–solid mechanically-stirred slurry reactor. The kinetic variables undergoing variations were: hydrosulfide initial concentration (0.90–3.30 mmol/L), oxide initial surface area (16–143 m²/L) and pH (8.0–11.0). The hydrosulfide consumption and products (thiosulfate and polysulfide) formation were quantified by means of capillary electrophoresis, while iron dissolution was monitored through atomic absorption spectroscopy. Most of Fe(II) produced at pH = 9.5 remained associated with the oxide surface in the time-scale of the experiments. The hydrosulfide oxidation by the iron/cerium (hydr)oxide was found to be surface-controlled, with rates (R_i) of both sulfide oxidation and Fe(II) dissolution expressed in terms of an empirical rate equation: R_i = k_i[HS⁻]_t=0^−0.5[A]_t=0[H⁺]_t=0^−0.5 , where k_i represents the apparent rate constants for the oxidation of HS⁻ (k_HS) or the dissolution of Fe(II) (k_Fe), [HS⁻]_{t = 0} is the initial hydrosulfide concentration, [A]_{t = 0} is the initial Fe/Ce (hydr)oxide surface area and [H⁺]_{t = 0} is the initial proton concentration. The rate constant, k_HS, for the oxidation of hydrosulfide at pH = 9.5 was (3.4219 ± 0.65) × 10⁻⁴ mol² L⁻¹ m⁻² min⁻¹, with the rate of hydrosulfide oxidation being ca. 10 times faster than the rate of Fe(II) dissolution (assuming a 1:2 stoichiometric ratio between HS⁻ oxidized and Fe(II) produced; k_Fe = (3.9116 ± 0.41) × 10⁻⁵ mol² L⁻¹ m⁻² min⁻¹).     

Synthesis,crystal structure and dehydration kinetics of NaB(OH)<Subscript>4</Subscript>·2H<Subscript>2</Subscript>O

Sodium metaborate tetrahydrate (NaB(OH)₄·2H₂O) was synthesized by reaction of anhydrous borax (Na₂O·2B₂O₃) with sodium hydroxide (NaOH) under conditions at 90 °C for 150 min. The structure was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscope (SEM) and Thermogravimetric (TG) analyses. Moreover, dehydration kinetics of NaB(OH)₄·2H₂O was carried out under non-isothermal conditions and the Coats-Redfern method was applied to analyze the TG data for calculation of activation energies (E _a ) and pre-exponential factors (k _o ) for different heating rates. It was determined that dehydration of sodium metaborate tetrahydrate occurred in five steps. According to the Coats-Redfern non-isothermal model, E _a and k _o were calculated as 50.89 kJ/mol and 26×10⁴ min⁻¹ for region I, 18.51 kJ/mol and 0.87×10³ min⁻¹ for region II, 15.72 kJ/mol and 0.52×10³ min⁻¹ for region III, 4.37 kJ/mol and 0.04×10³ min⁻¹ for region IV and 37.42 kJ/mol and 8.56×10³ min⁻¹ for region V, respectively.     

Cationic polymerizations at elevated temperatures by novel initiating systems having weakly coordinating counteranions 2. Isobutylene/isoprene copolymerizations

As a sequel to our studies on isobutylene (IB) homopolymerizations, we have investigated the copolymerization of IB/isoprene (IP) mixtures containing up to ∼20 mole% IP in the feed by the use of the in situ (CH₃)₃Si[B(C₆F₅)₄] initiating system in close-to-neat monomers in the temperature range from −35 to −8 (reflux)°C. The effects of temperature and IB/IP feed ratio on copolymer molecular weights were determined and compared with those produced by AlCl₃. The molecular weights of butyl rubbers obtained by the novel initiating system under a variety of conditions are invariably and significantly higher than those made with AlCl₃. High molecular weight gel-free rubbers containing up to ∼5 mol% unsaturation can be obtained at relatively high temperatures. Copolymer compositions can be controlled by the IB/IP ratio in the feed. Product molecular weights decrease with increasing IP content. To gain insight into the copolymerization mechanism, the activation enthalpy of molecular weights (ΔH^‡=−5.9 kcal/mol, −24.7 kJ/mol) and the reactivity ratios (r_IB= 1.8, r_IP= 1.5) have been determined. Received: 8 July 1998/Revised version: 16 October 1998/Accepted: 16 October 1998     

A DSC study of Z<Subscript>2</Subscript>−Z<Subscript>3</Subscript> viscosity blown soybean oil

The thermal oxidation of four commercially available neat blown soybean oil samples and a heat-bodied soybean oil sample, obtained from various manufacturers, having Gardner bubble viscosities between Z₂ and Z₃ was investigated using nonisothermal DSC under a constant oxygen flow and a heating rate (β) ranging from 3 to 20°C/min. The extrapolated onset temperatures (T _e1 and T _e2 ) and maximum temperature of heat flow (T _p2 ) at different β were determined from the DSC curves and used in conjunction with the Ozawa-Flynn-Wall method to estimate the kinetic parameters of oil thermal oxidation. At a β of 10°C/min, the calculated activation energies (E _a ) for the blown soybean oil samples investigated ranged between 57.7 and 74.3 kJ/mol for T _e1 , 37.6 and 55.3 kJ/mol for T _e2 , and 54.7 and 63.0 kJ/mol for T _p2 . For comparison, a Z ₂ −Z ₃ heat-bodied soybean oil sample had activation energies of 72.5, 39.8, and 61.9 for T _e1 , T _e2 , and T _p2 , respectively. By ¹H NMR, the amount of allylic and bis-allylic hydrogens present in the blown soybean oil samples relative to an unmodified soybean oil sample was determined to range from 40.3 to 48.2% and 14.9 to 22.4%, respectively.     

Epoxidation of karanja (Pongamia glabra) oil by H2O2

Epoxidation of karanja oil (KO), a nondrying vegetable oil, was carried out with peroxyacetic acid that was generated in situ from aqueous hydrogen peroxide and glacial acetic acid. KO contained 61.65% oleic acid and 18.52% linoleic acid, respectively, and had an iodine value of 89 g/100 g. Unsaturated bonds in the oil were converted to oxirane by epoxidation. Almost complete epoxidation of ethylenic unsaturation was achieved. For example, the iodine value of the oil could be reduced from 89 to 19 by epoxidation at 30°C. The effects of temperature, hydrogen peroxide-to-ethylenic unsaturation ratio, acetic acid-to-ethylenic unsaturation ratio, and stirring speed on the epoxidation rate and on oxirane ring stability were studied. The rate constant and activation energy for epoxidation of KO were 10⁻⁶ L·mol⁻¹·s⁻¹ and 14.9 kcal·mol⁻¹, respectively. Enthalpy, entropy, and free energy of activation were 14.2 kcal·mol⁻¹, −51.2 cal·mol⁻¹·K⁻¹, and 31.1 kcal·mol⁻¹, respectively. The present study revealed that epoxides can be developed from locally available natural renewable resources such as KO.     

Isolation and characterization of the monounsaturated long chain fatty acids ofMycobacterium tuberculosis

The positions of double bond in the monounsaturated C₁₅−C₃₂ fatty acids ofMycobacterium tuberculosis H37Ra were established by gas chromatography/mass spectrometry of the ozonized esters and their pyrrolidide derivatives. The monounsaturated C₁₅−C₂₁ fatty acids had the double bond primarily at the Δ⁹ position while the monounsaturated longer chain fatty acids (C₂₂−C₃₂) had the double bond in several positions. Many of the latter acids, especially the odd-numbered series, were very complex isomeric mixtures. Quantitation showed the most abundant even-numbered long chain fatty acid isomers to be as follow: C₂₂, Δ⁴; C₂₄, Δ⁵; C₂₆, Δ⁷ and Δ⁹; C₂₈, Δ⁹; C₃₀, Δ¹¹ and Δ¹³; C₃₂, Δ¹³ and Δ¹⁵.     

Ferrocene-Based Cationic Surfactants: Surface and Antimicrobial Properties

A novel series of ferrocenyl surfactants was synthesized by the reaction of ferrocene disulfonic acid with different primary and tertiary fatty amines to produce the corresponding ammonium salts Fc[SO₃ ^{− +}NH₃(CH₂) _n CH₃]₂, where n = 9, 11, or 15 and Fc[SO₃^{− +}NH(CH₃)₂(CH₂) _n CH₃]₂, where n = 7 or 11, respectively, and where Fc = ferrocene. Chemical structures were confirmed by microelemental analysis, FTIR, and ¹H NMR spectroscopy. The critical micelle concentration of each prepared surfactant was determined using equilibrium surface tension. Furthermore, air/water interface parameters including effectiveness (π _CMC), efficiency (Pc₂₀), maximum surface excess (Г_max), and minimum surface area (A _min) were determined at 30, 40, and 50 °C. Thermodynamic parameters (ΔG°, ΔS°, and ΔH°) for both micellization and adsorption processes were recorded. The new synthesized surfactants were screened as antimicrobial agents against different bacterial and fungal organisms.     

NH3 Decomposition Kinetics on Supported Ru Clusters: Morphology and Particle Size Effect

The supported Ru clusters with mean sizes ranging from 1.9 to 4.6 nm showed a high activity towards the NH₃ decomposition reaction. The structural properties of catalysts were characterized by N₂ adsorption/desorption, X-ray diffraction (XRD) and transmission electron micrograph (TEM). Steady-state reaction kinetics revealed that the apparent activation energy increased with a decrease in Ru particle size and ranged from 79 kJ mol⁻¹ to 122 kJ mol⁻¹. The decomposition rate over Ru nanoparticles showed a strong dependency on mean crystallite size and the optimum appeared at d _Ru = 2.2 nm. The dependencies of reaction rate on partial pressures of NH₃ and H₂ were also sensitive to the varying Ru particle size. Experimental data could be well fitted by the Temkin–Pyzhev equation, indicating that the recombinative desorption of surface nitrogen atom acts as the rate-determining step. A compensation effect between the pre-exponential factor (k ₀) and activation energy (E _a ) was quantified.     

Saturated fatty acid adsorption by acidified rice hull ash

Rice hull ash (RHA) was treated with 1.0 M HNO₃ (RHA-A1) and another batch was treated with 14.0 M HNO₃ (RHA-A14). RHA-A1 and RHA-A14 had a pH of 6.58 and 6.13, respectively. Adsorption of saturated fatty acids (C₈, C₁₀, C₁₂, C₁₄, C₁₆, and C₁₈) was carried out on RHA-A1 and RHA-A14 at 32±1°C. The adsorption data conformed to the Langmuir isotherm. The specific surface area of RHA-A1 was 183.84 m² g⁻¹ while that of RHA-A14 was 174.67 m² g⁻¹. The specific pore volume of RHA-A1 was 0.216 cm³ g⁻¹ while that of RHA-A14 was 0.234 cm³ g⁻¹. The acid-treated ash, RHA-A14 (q _m =0.43±0.03 mmol g⁻¹ where q _m is the amount of adsorbate adsorbed to form a monolayer coverage on the ash particles) showed a twofold increase in the adsorption of fatty acid per gram ash compared to RHA-A1 (q _m =0.25±0.03 mmol g⁻¹). The free energy of adsorption, ΔG° _ads, was determined to be −7.06±0.10 and −6.75±0.11 kcal mol⁻¹ for RHA-A1 and RHA-A14, respectively. The reduced ΔG° _ads values observed for RHA-A14 were attributed to the electrostatic repulsion of the hydrophobic chain of the fatty acid adsorbed on adjacent sites and brought into close proximity of each other. The ΔG° _ads values showed that the process of adsorption took place through physisorption on both RHA.     

Ozonide ions on the surface of MgO nanocrystals

The adsorption properties of oxygen radicals on the surface of polycrystalline oxides can provide relevant information about the functionality of specific surface sites in oxidation catalysis. Using electron paramagnetic resonance spectroscopy, we investigated O₂ adsorption at MgO nanocrystal surfaces which were previously enriched with O⁻ radicals i.e. trapped hole centers. On dehydroxylated particle surfaces, two ozonide radical types O ₃ ⁻ were isolated as adsorbates and the related energies for O₂ adsorption were found to be 55 ± 5 kJ mol⁻¹ and 100 ± 5 kJ mol⁻¹. The respective adsorption sites are assigned to hole centers trapped on oxygen terminated corners and cation vancancies, respectively. In addition, O ₃ ⁻ ions were also employed as probes for electron trapping sites on partially hydroxylated sample surfaces. Five types of O⁻ radicals emerge from surface colour centre bleaching with N₂O, but only two of them adsorb O₂ at room temperature. A connection between the well-characterized (H⁺)(e^-) defect – an electron trapped in close vicinity of a nearby proton [Chiesa et al. J. Phys. Chem. B 109 (2005) 7314] – and one ozonide type which exhibits significant magnetic coupling with an adjacent proton, was established on the basis of their production parameter dependence. Although the g tensor of an O₃ ⁻ species reflects the properties of the radical itself rather than the structure of the adsorption site, the related signatures are proposed to serve also as spectroscopic fingerprints for catalytically relevant surface anion environments.     

Identification of noveltrans isomers of 20∶5n−3 in liver lipids of rats fed a heated oil

Trans polyunsaturated n−3 fatty acids are formed as a result of the heat treatment of vegetable oils. It was demonstrated previously that the 18∶3 Δ9cis, 12cis, 15trans containing acis Δ9 ethylenic bond was converted to a geometrical isomer of 20∶5n−3, the 20∶5 Δ5cis, 8cis, 11cis, 14cis, 17trans. In the present study, we have identified two new isomers of eicosapentaenoic acid, the Δ11 monotrans and the Δ11, 17 ditrans isomers in liver of rats fed a heated oil. These are formed as a result of the conversion of two of the main isomers of linolenic acid which are present in refined and frying oils, the 18∶3 Δ9trans, 12cis, 15cis and the 18∶3 Δ9trans, 12cis, 15trans.     

Cadmium removal from aqueous solutions using biosorbent <Emphasis Type="Italic">Syzygium cumini</Emphasis> leaf powder: Kinetic and equilibrium studies

Syzygium cumini L. leaf powder and Cd(II) loaded samples were characterized using FTIR and SEM techniques. The biosorption of cadmium ions from aqueous solution was studied in a batch adsorption system as a function of pH, contact time, adsorbate, adsorbent, anion and cation concentrations. The biosorption capacities and rates of transfer of cadmium ions onto S. cumini L. were evaluated. The kinetics could be best described by both linear and nonlinear pseudo-second order models. The isothermic data fitted to various models in the order Freundlich>Redlich-Peterson>Langmuir>Temkin. The maximum adsorption capacity of S. cumini L. leaves at room temperature was estimated to be 34.54 mg g⁻¹. The negative values of ΔG⁰ indicated the feasibility of the adsorption process. The endothermic nature was confirmed by the positive value of the enthalpy change (ΔH⁰=3.7 kJ mol⁻¹). The positive value of entropy change (ΔS⁰=16.87 J mol⁻¹ K⁻¹) depicted internal structural changes during the adsorption process.