Kinetics of the formation of symmetrical wax esters from the corresponding alcohols with the use of hydrobromic acid and hydrogen peroxide

The primary aliphatic alcohols n-octanol, n-decanol, and n-dodecanol have been converted to their corresponding symmetrical esters by using HBr and H₂O₂ in the absence of a solvent. The reaction was carried out at 30, 40, and 50°C and at mole ratios of alcohol to HBr of 1∶0.1, 1∶0.2, 1∶0.3, and 1∶0.5. The rate of the reaction was found to increase with increase in the reaction temperature and concentration of HBr. The maximal conversion of n-octanol was 72% at 40°C and a mole ratio of n-octanol to HBr of 1∶0.5. The kinetics of the reaction have been established, and the reaction was found to be first-order with respect to alcohol and bromine concentration in the organic phase, and second-order with respect to both. The second-order rate constants for n-octanol, n-decanol, and n-dodecanol are 27.08, 32.58, and 37.42 mL mol⁻¹ min⁻¹, respectively, at 40°C. The activation energy for the esterification reaction of n-octanol was found to be 16.32 kcal mol⁻¹.     

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.     

Kinetics of the Chemical Dissolution of Vanadium Pentoxide in Acidic Bromide Solutions

A novel vanadium bromide redox flow battery employing a vanadium bromide electrolyte in both half-cells has been proposed. Preparation of the electrolyte for this redox cell requires the chemical dissolution of vanadium pentoxide powder in the acidic bromide supporting electrolyte. In this study, the kinetics of the chemical dissolution process were investigated and a second order surface controlled reaction is reported with rate equation given by: Rate = 5 × 10⁻⁴(l mol⁻¹ s⁻¹)[Br⁻]² at 25 °C and an activation energy of 37.2 kJ mol⁻¹.     

Kinetics of the catalytic esterification of castor oil with lauric acid using <Emphasis Type="Italic">n</Emphasis>-butyl benzene as a water entrainer

The esterification of castor oil with lauric acid was investigated using tetra n-butyl titanate (TBT), SnCl₂·2H₂O (stannous chloride), CoCl₂·6H₂O (cobalt chloride), and (CH₃COO)₂Zn·2H₂O (zinc acetate dihydrate) as catalysts. Effects of catalyst concentration and reaction temperature on the progress of the reaction were investigated. TBT was the best catalyst for the esterification of castor oil with lauric acid at temperatures lower than 200°C. The reaction was first order with respect to each reactant. The activation energy for the esterification reaction of castor oil with lauric acid using TBT was 26.69 kcal/mol. The rate constants obtained for the esterification of castor oil with decanoic, lauric, palmitic, and stearic acids were nearly the same (15.80, 15.44, 15.06, and 14.67 mL mol⁻¹ min⁻¹), as were the rate constants obtained for the reaction of castor oil and hydrogenated castor oil.     

Electrochemical investigation of Li–Al anodes in oligo(ethylene glycol) dimethyl ether/LiPF<Subscript>6</Subscript>

1 M LiPF₆ dissolved in oligo(ethylene glycol) dimethyl ether with a molecular weight 500 g mol⁻¹ was investigated as a new electrolyte (OEGDME500, 1 M LiPF₆) for metal deposition and battery applications. At 25 °C a conductivity of 0.48 × 10⁻³ S cm⁻¹ was obtained and at 85 °C, 3.78 × 10⁻³ S cm⁻¹. The apparent activation barrier for ionic transport was evaluated to be 30.7 kJ mol⁻¹. OEGDME500, 1 M LiPF₆ allows operating temperature above 100 °C with very attractive conductivity. The electrolyte shows excellent performance at negative and positive potentials. With this investigation, we report experimental results obtained with aluminum electrodes using this electrolyte. At low current densities lithium ion reduction and re-oxidation can be achieved on aluminum electrodes at potentials about 280 mV more positive than on lithium electrodes. In situ X-ray diffraction measurements collected during electrochemical lithium deposition on aluminum electrodes show that the shift to positive potentials is due to the negative Gibbs free energy change of the Li–Al alloy formation reaction.     

Autoxidation of methyl linoleate initiated by the ozonide of allylbenzene

Allylbenzene ozonide (ABO), a model for polyunsaturated fatty acid (PUFA) ozonides, initiates the autoxidation of methyl linoleate (18∶2 ME) at 37°C under 760 torr of oxygen. This process is inhibited by d-α-tocopherol (α-T) and 2,6-di-ert-butyl-4-methylphenol (BHT). The autoxidation was followed by the appearance of conjugated diene (CD), as well as by oxygen-uptake. The rates of autoxidation are proportional to the square root of ABO concentration, implying that the usual free radical autoxidation rate law is obeyed. Activation parameters for the thermal decomposition of ABO were determined under N₂ in the presence of radical scavengers and found to be E_a=28.2 ±0.3 kcal mol⁻¹ and log A=13.6±0.2; k_d (37°C) is calculated to be (5.1±0.3)×10⁻⁷ sec⁻¹. Autoxidation data are also reported for ozonides of 18∶2 ME and methyl oleate (18∶1 ME).     

Synthesis and Kinetic Studies on Dimer Fatty Acid/Polyethylene Glycol Polyester

Dimer fatty acid polyethylene glycol polyester, a new kind of non-ionic polymeric surfactant, was synthesized by using dimer fatty acid and polyethylene glycol (400) as materials in this paper. The optimum reaction conditions of esterification were as follows: the molar ratio of dimer fatty acid (DFA)/PEG (400) is 1 / 1.20, the preferable catalyst is stannous chloride and the amount is 0.3% (w/w) of the mass of DFA, reaction temperature is 200°C, reaction time is 6 h. The conversion ratio of polyesterification can reach 98.11%. A new kinetic model of polyesterification reaction catalyzed with stannous chloride was presented. The Genetic Algorithms and Runge–Kutta were used to estimate the parameters of the kinetic model. The results of experiments and computer operations indicated that the reaction order is 0.998 to the carboxyl and 1 order to the hydroxyl. The activation energy obtained from Arrhenius plot is 97.18 kJ mol⁻¹, and the pre-exponential frequency factor is lnA = 21.39 kg² mol⁻² min⁻¹ at temperature range of 160 ∼ 190°C.     

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.     

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.     

Kinetics of geometrical isomerization of unsaturated FA in soybean oil

Laboratory treatment of soybean oil were carried out at the following conditions: atmospheric pressure in the presence of air or nitrogen at different temperatures ranging from 160 to 250°C for 12 to 72 h. These conditions were used to study geometric isomerization of cis,cis-linoleic and cis,cis,cis-linolenic acid in the presence or in the absence of oxidative degradation reactions. Based on these experiments, a model of consecutive, parallel reactions was developed to describe the reaction steps occurring in the soybean oil during heating at constant temperature. For both cis,cis-linoleic and cis,cis,cis-linolenic acid, the reaction of formation isomers followed a first-order reaction, and the rate constant of isomerization varied according to the Arrhenius law. The isomerization rate constant for linoleic acid was 9.57×10⁻³±0.50 h⁻¹ in the presence of oxygen and 7.39×10⁻³±0.39 h⁻¹ in its absence, and the isomerization rate constant for linolenic acid was 1.18×10⁻¹±0.10 h⁻¹ in the presence of oxygen and 0.87×10⁻¹±0.07 h⁻¹ in its absence (all obtained at 250°C).     

Kinetic Parameters of a Homogeneous Transmethylation of Soybean Oil

The kinetic parameters of a truly homogeneous base-catalyzed transmethylation of soybean oil at four temperatures from 23 to 50 °C have been determined for the first time. The addition of oxolane, as well as a high methanol/oil molar ratio (27:1), was used to achieve and maintain a monophasic system throughout the reactions. Second order rate constants were determined in terms of the concentrations of the mechanistic reactants, which were the glycerides and methoxide ions (and not methanol). Doubling the methoxide concentration increased the reaction rate twofold. At 23 °C the rate constants for the conversion of triglycerides to diglycerides, diglycerides to monoglycerides, and monoglycerides to glycerol were 6.3, 15.3 and 13.0 L mol⁻¹ min⁻¹, respectively. These increased to 54.2, 136 and 139 L mol⁻¹ min⁻¹ at 50°C. These latter values (adjusted to 60 °C) were 65, 770 and 190 times larger, respectively, than values cited previously (and adjusted to the methoxide basis) for a transmethylation of Pongamia oil, which was also claimed to be homogeneous. Activation energies for all three steps were the same (63 kJ mol⁻¹). Pre-exponential factors showed that in diglycerides and triglycerides the second and third ester chains sterically hindered the attack of methoxide ions on the ester carbonyl groups.     

Redox and transport behaviors of Cu(I) ions in TMHA-Tf<Subscript>2</Subscript>N ionic liquid solution

The redox and transport behavior of monovalent copper species in an ammonium imide-type ionic liquid, trimethyl-n-hexylammonium bis((trifluoromethyl)sulfonyl)amide (TMHA-Tf₂N) were examined with a micro-disc electrode to clarify its applicability to, for example, electroplating. It was found that the diffusion coefficient of Cu(I) ions in TMHA-Tf₂N containing 12 mmol dm⁻³ Cu(I) ions was 1.2 × 10⁻⁶ cm² s⁻¹ and the redox potential of Cu(I)/Cu was in the potential range 0.1–0.2 V vs. I ⁻/I ₃⁻ at 50 °C. The diffusion coefficient was one order smaller than that of Cu(II) ions in aqueous solution due to the high viscosity of the ionic liquid. The diffusion coefficient of Cu(I) ion increased with rising temperature and was 1.0 × 10⁻⁵ cm² s⁻¹ at 112 °C, which was comparable to that of Cu(II) ions in aqueous CuSO₄ solutions at ambient temperature. This is accounted for by the drastic decrease in the viscosity of the ionic liquid solution with increasing temperature. The activation energy of diffusion was estimated to be 39 kJ mol⁻¹ in the ionic liquid solution.     

Kinetic study of the reaction between tocopheroxyl radical and unsaturated fatty acid esters in benzene

A kinetic study of the reaction between a tocopheroxyl radical and unsaturated fatty acid esters has been undertaken. The rates of allylic hydrogen abstraction from various unsaturated fatty acid esters (ethyl oleate2, ethyl linoleate3, ethyl linolenate4, and ethyl arachidonate5) by the tocopheroxyl radical (5,7-diisopropyltocopheroxyl6) in benzene have been determined spectrophotometrically. The second-order rate constants, k₃, obtained are 1.04×10⁻⁵ M⁻¹s⁻¹ for2, 1.82×10⁻² M⁻¹s⁻¹ for3, 3.84×10⁻² M⁻¹s⁻¹ for4, and 4.83×10⁻² M⁻¹s⁻¹ for5 at 25.0°C. Thus, the rate constants, k_abstr/H, given on an available hydrogen basis are k₃/4=2.60×10⁻⁶ M⁻¹s⁻¹ for2, k₃/2=9.10×10⁻³ M⁻¹s⁻¹ for3, k₃/4=9.60×10⁻³ M⁻¹s⁻¹ for4, and k₃/6=8.05×10⁻³ M⁻¹s⁻¹ for5. The k_abstr/H values obtained for the polyunsaturated fatty acid esters3,4, and5 containing H-atoms activated by two π-electron systems are similar to each other, and are about three orders of magnitude higher than that for the ethyl oleate2 containing H-atoms activated by a single π-system. From these results, it is suggested that the prooxidant effect of α-tocopherol in edible oils and fats may be induced by the above hydrogen abstraction reaction.     

Mass transport mechanism for the formation of latex-modified epoxy coatings by evaporation from aqueous dispersions

The transport mechanism for the evaporation of dispersing liquid during the solidification of an epoxy dispersion that had been stabilized to prevent crack formation with a latex dispersion was studied. Aqueous dispersions consisting of an experimentally determined ratio of epoxy resin and nitrile latex were evaporated at 35°C. When the dispersion was evaporated under controlled conditions without forced air flow, a flexible and adherent polymer material formed. The mechanism for coalescence was related to the loss in weight of dispersing liquid during an initial zero order kinetics stage. This was followed by a rate-controlled Fick’s law diffusion through the developing coating with subsequent evaporation to the atmosphere. Experimental measurements are compared with theoretical predictions. The rate constant for the zero order time frame is 0.086±0.02 hr⁻¹. In the second time frame, Ficks’s law evaporation rate constant is 0.046 ±0.017 cm·hr⁻¹ with a diffusion coefficient of 0.00092±0.00051 cm²·hr⁻¹ at 35±1°C and RH 35±7%. Applications for evaporation kinetics are discussed.     

Supported Pt and Pt–Ru catalysts prepared by potentiostatic electrodeposition for methanol electrooxidation

Methanol electrooxidation was investigated on Pt–Ru electrocatalysts supported on glassy carbon. The catalysts were prepared by electrodeposition from solutions containing chloroplatinic acid and ruthenium chloride. Bulk composition analysis of the Pt–Ru catalyst was performed using an X-ray detector for energy dispersive spectroscopy analysis (EDX). Three different compositions were analyzed in the range 0–20 at.% Ru content. Tafel plots for the oxidation of methanol in solutions containing 0.1–2 M CH₃OH, and in the temperature range 23–50 °C showed a reasonably well-defined linear region. The slope of the Tafel plots was found to depend on the ruthenium composition. The lower slope was determined for the Pt catalyst, varying between 100 and 120 mV dec⁻¹. The values calculated for the alloys were higher, ranging from 120 to 140 mV dec⁻¹. The reaction order for methanol varies from 0.5 to 0.8, increasing with the ruthenium content. The activation energy calculated from Arrhenius plots was found to change with the catalyst composition, showing a lower value around 30 kJ mol⁻¹ for the alloys, and a higher value, of 58.8 kJ mol⁻¹, for platinum. The effect of ruthenium content is explained by the bifunctional reaction mechanism.     

Crystal Structure, Thermal and Magnetic Behavior of Inorganic–Organic Hybrid [VIV 4O10 VV 2O4] (C6H14N2)·H2O Polymeric Framework

Summary The inorganic–organic hybrid [V^IV ₄O₁₀V^V ₂O₄] (C₆H₁₄N₂)·H₂O polymeric framework was prepared under mild hydrothermal conditions from a mixture of DABCO and V₂O₅ in deionized water with a 1:1:450 mole ratio, at neutral pH. The reaction was carried out at 180 °C for 3 days under autogenous pressure yielding phase pure crystals product. The crystal structure was studied using both powder and single crystal X-ray crystallography, revealing the structure to be of the ({UuDd}:T*)α′ type in the SP+T class and Z-T subclass. The presence of the organic cation was confirmed by FT-IR spectrum and chemical composition analysis. The structure was thermally stable up to over 400 °C, and showed ferromagnetic character at room temperature with the maximum molar susceptibility of 8.26 × 10⁻³ emu/mol⁻¹ at zero applied field.     

Kinetic Study on Oxirane Cleavage of Epoxidized Palm Oil

A ring-opened product (EPO-HOAc) was prepared using epoxidized palm oil (EPO) and acetic acid (HOAc). The kinetics of the oxirane cleavage of EPO were investigated at 50, 60, 70, 80, and 90 °C, respectively, in the presence of HOAc. The rate equation of oxirane cleavage was as follows: r = k[Ep][CH₃COOH]^1.6 ([Ep] is the molar concentration of oxiranes, [CH₃COOH] is the molar concentration of HOAc), and the activation energy of oxirane cleavage was 40.28 kJ mol⁻¹. The structure of EPO-HOAc was confirmed by FT-IR and ¹H NMR. The oxidative stability of EPO-HOAc was better than that of palm oil (PO), and the pour point of EPO-HOAc was lower than that of PO and EPO, which made EPO-HOAc more suitable for biodegradable lubricant materials than PO and EPO.     

Free Radical Polymerisation of Methylmethacrylate Using p-nitrobenzyltriphenyl Phosphonium Ylide as Novel Initiator

p-nitrobenzyl triphenyl phosphonium ylide initiated radical polymerisation of MMA in 1-4 dioxane at 65 ± 1°C for 2 h under a nitrogen blanket, follows ideal kinetics with bimolecular termination. The overall activation energy and average value of k _p ²/k _t are 75.7 kJ mol and 1.14 × 10² l mol⁻¹ s⁻¹. FTIR Spectroscopy confirms a band of 1,729 cm⁻¹ of the ester group. ¹H NMR and ¹³C NMR confirms methoxy protons at 3.8 δ ppm and 52 δ ppm, respectively. E.S.R studies confirm a free radical mode of polymerisation. TGDTA analysis confirms the atactic nature of polymer and its thermal stability up to 120°C. Ylide dissociates to give a phenyl radical which is responsible for polymerisation.     

Studies on the radical polymerization of N-vinyl 2-pyrrolidone initiated by diphenyl ditelluride

N-vinyl pyrrolidone (NVP) was polymerized in dioxan at 60 ± 0.1°C for 1 h using diphenyl ditelluride as radical initiator. The system follows ideal kinetics i.e. R _p α [DPDT]^0.5[NVP]. The activation energy and dissociation constant is computed as 46 kJ mol⁻¹ and 1.1 × 10⁻¹¹ s⁻¹, respectively. The polymer was characterized with the help of FTIR, ¹H-NMR, ¹³C-NMR, ESR spectroscopy. The FT-IR spectrum showed bands at 1660–1680 cm⁻¹ due to combination of >C = O and C–N stretching. The gyromagnetic constant ‘g’ has been computed as 2.2203. The main product of this reaction were poly(N-vinylpyrrolidone)s with phenyl tellanyl ends. The presence of tellurium in polymer is confirmed by ICP analysis. The DSC shows the T _g of poly(N-vinylpyrrolidone) is 168°C due to rigid pyrrolidane group. The TGA showed that polymer was stable up to 380°C.The GPC studies showed that the weight average molecular weight decreases with increase of [DPDT].     

Microwave-Assisted Synthesis and Properties of Sodium Glycol Bis-(Isooctyl)Sulfosuccinate

An anionic gemini surfactant was synthesized under microwave irradiation conditions. The optimum reaction conditions were obtained by the reaction of maleic anhydride, glycol, isooctyl alcohol and sodium sulfite. The first step esterification reaction was carried out at 90 °C and 100 W microwave power for 20 min with a ratio a n _{maleic anhydride}:n _glycol = 2.1:1, and 1.0 wt% of catalyst. The second step esterification reaction was carried out at 80 °C for 25 min and 100 W microwave power. Optimum sulfonation was carried out with n _{sodium sulfite}:n _{glycol bismaleic anhydride bisester} = 2.25:1 and 1.5% catalyst for 25 min at 60 °C. It is found that microwave-assisted synthesis is an efficient means of preparation of this anionic gemini surfactant with shorter reaction times and higher yields. The title compound structure was confirmed by IR. The critical micelle concentration of the title compound is 6.2 × 10⁻⁴ mol L⁻¹, γ_CMC is 25.7 mN m⁻¹, and benzene emulsion persistence was 2 days.