Production of tung oil epoxy resin using low frequency high power ultrasound

Epoxy resins made from vegetable oils are an alternative to synthesize epoxy resins from renewable sources. Tung oil is rich in α -eleostearic fatty acid, which contains three double bonds producing epoxy resins with up to three epoxy groups per fatty acid. This work studied the production of tung oil epoxy resin using hydrogen peroxide as an oxidizing agent and acetic and formic acid as percarboxylic acid precursors, applying low frequency high power ultrasound. This study evaluated the effects of ultrasound power density, hydrogen peroxide concentration, acetic acid concentration, and formic acid concentration on the yield into epoxy resin, selectivity, and by-products formation. Application of ultrasound was carried out using a 19 kHz probe ultrasound (horn ultrasound) with a 1.3 cm diameter titanium probe, 500 W nominal power, 2940 W L⁻¹ maximum effective power density applied to the reaction mixture. Ultrasound technology yielded up to 85% of epoxy resin in 3 h of reaction. The use of formic acid resulted in a slightly lower oil conversion than acetic acid but with a much higher selectivity towards epoxidized tung oil. However, using acetic acid resulted in the production of high-value by-products, such as 2-heptenal and 2,4-nonadienal. The ultrasound-assisted epoxidation showed to be particularly efficient when applied to oils containing conjugated double-bonds.     

活性炭负载硅钼钒杂多酸催化苯羟基化反应

以活性炭为载体,采用回流吸附法制备了负载型硅钼钒杂多酸催化剂,以冰醋酸作溶剂,过氧化氢作氧化剂,研究了由苯直接羟基化制苯酚的催化活性。结果表明,苯为2mL,冰醋酸为15mL,过氧化氢为5mL,当负载型杂多酸的用量为0.2g、反应温度70℃、反应时间60m in时,硅钼钒催化合成苯酚的收率可达7.4%,选择性达97.1%。     

乙酰水杨酸的制备

以水杨酸和乙酸酐为原料,以浓硫酸为催化剂,合成乙酰水杨酸。考察了对反应产率的影响因素,实际结果表明:水杨酸和乙酸酐物质的量比为1∶2,反应温度为80℃,反应时间为30min时,反应产率为86.65%。     

Water softening by combination of ultrasound and ion exchange

Ion exchange resin used in this work was styrene-divinylbenzene co-polymer with sulfonic acid group as a strong acid cation resin. This resin is particularly well suited for the removal of water hardness. In water treatment, commonly used softening processes are chemical precipitation and ion exchange. In this study, a combination of ultrasound and ion exchange was applied for reducing the hardness of water. The rate of exchange or kinetics of ion exchange is governed by several parameters. Therefore, important variables such as intensity of ultrasound, amount of resin, concentration of ions and contact time were investigated. The experimental data related to the removal of magnesium and calcium ions were fitted properly with Langmuir model. The kinetic of removal for both ions was pseudo-first-order. In point of mechanism, the internal porous and film diffusion were both effective in the process. The capacity of sorption and the velocity of removal were higher in the presence of ultrasound than control method and this is related to the cavitation process.     

Study of various parameters influencing the fixation of metallic ions Cu2+, Zn2+, and Ni2+ at the catalytic Amberlyst-15 resin in the presence of alcohols

The ionic exchange behavior of Zn²⁺, Ni²⁺, and Cu²⁺ metallic ions on Amberlyst-15 commercial resin was studied as a function of resin solution contact time, initial concentration of metallic ions, nature of the solvent, and the amount of resin. The metallic ions were studied in ternary mixtures using both column and batch experiments. In addition, water, methanol, ethanol, and propan-2-ol were used as solvents for dissolving metallic ions. It was found that the resin behavior depends on the solvent nature and the metallic ion concentration. The analysis of solutions by atomic absorption spectrometry revealed that the affinity of the resin for the studied metallic ions followed the sequence Cu²⁺ > Ni²⁺ > Zn²⁺ in the case of an aqueous medium. Furthermore, uptake increased with increasing amount of resin. A better uptake was observed in the case of the 75:25 % water/methanol compositions when the column technique was used. For the batch technique, we noted a better uptake using 100 % water. The uptake rate decreased with an increase in the number of carbons for the 50 % water–50 % alcohol solvents. The acid–base properties of Amberlyst-15 commercial resin were studied by 2-propanol decomposition test. Propene and acetone are the main expected products and it is believed that they are formed through dehydration or dehydrogenation reaction on acid and base sites, respectively.     

Nickel/Chromium oxide/Zirconium oxide Catalysts for Hydrogen/Deuterium Isotopic Exchange

Catalysts composed of nickel and promoted with different metal oxides proved to be suitable for H/D isotropic exchange between hydrogen and water vapour. They loss their activity due to water condensation on their surfaces. Several nickel/chromium oxide/zirconium oxide catalysts of different composition were prepared by the coprecipitation technique. The liquid phase activity of these catalysts were followed using the hydrogen peroxide decomposition on their surfaces at different temperatures. The surface characteristics of the examined catalysts were followed by applying the BET method. The results were discussed and lead to the required catalyst composition which resists the water condensation on its surface during operation and has relatively high activity in the vapour phase H/D isotopic exchange reaction between hydrogen and water.     

Determination of Cr(III) and Cr(VI) in water by wavelength‐dispersive X‐ray fluorescence spectrometry after preconcentration with an ion‐exchange resin disk

A rapid and simple method using an ion‐exchange resin disk combined with wavelength‐dispersive X‐ray fluorescence (WDXRF) spectrometry was developed for the determination of Cr(III) and Cr(VI) in water. A 100‐ml water sample was first adjusted to pH 3 with nitric acid and then passed through an anion‐exchange resin disk placed on top of a cation‐exchange resin disk at a flow rate of 1 ml min^?1 to separate Cr(III) and Cr(VI). Anionic Cr(VI) was preconcentrated on the upper anion‐exchange resin disk, whereas cationic Cr(III) was preconcentrated on the lower cation‐exchange resin disk. Each ion‐exchange resin disk was dried at 100 °C for 30 min in an electric oven and coated with a commercially available laminate film. The specimens were measured using a WDXRF spectrometer. The calibration curves of Cr(III) and Cr(VI) showed good linearity in the range 1–10 µg. The detection limits corresponding to three times the standard deviation (n = 5) of blank values were 0.17 µg for Cr(III) and 0.16 µg for Cr(VI). If a 1‐l water sample is used, these limits would be 0.17 and 0.16 µg l^?1, respectively. A spike test for 50 µg l^?1 Cr(III) and Cr(VI) in tap water and river water showed quantitative recoveries (94–114%), although this was not observed for mineral drinking water owing to the overlap of V Kβ with Cr Kα. The recovery after overlap correction was satisfactory (115%). Copyright © 2011 John Wiley & Sons, Ltd.     

黄嘌呤氧化酶-乙醛-吖啶酯化学发光分析新体系

乙醛在黄嘌呤氧化酶催化作用下,被空气氧化生成乙酸和过氧化氢,酶反应生成的过氧化氢氧化新吖啶酯试剂[10-甲基-9-(对甲酰苯基)吖啶羧酸酯氟磺酸盐]产生化学发光,化学发光强度与己醛浓度在一定范围内成线性关系.由此建立了一种化学发光分析新体系,用于测定乙醇含量.线性范围2.0×10-7～1.2×10-3mol/L,测定5.0×10-7mol/L乙醛,相对标准偏差为6.8%,检测限为1.2×10-7mol/L,测定环境水样中乙醇含量,取得满意结果,回收率为95～106%.     

Production mechanism of active species on the oxidative bromination following perhydrolase activity

Hypobromous acid and molecular bromine have been described as the active species involved in the oxidative bromination using perhydrolase, which catalyzes the reaction from acetic acid and hydrogen peroxide to peracetic acid (AcOOH). However, the brominating activity of them in a chemical model system was lower than that of the active species produced by the spontaneous reaction between AcOOH and Br^?. Consequently, acetyl hypobromite (AcOBr) was suggested as new active species on the bromination by detection of the decarboxylation in the reaction between AcOOH and Br^? and the strong brominating power with some tolerance against H₂O₂. Its production mechanism was explained as the ionic reaction involving the protonated intermediate of AcOOH by kinetic analysis. Copyright © 2015 John Wiley & Sons, Ltd.     

Wastes Treatment: Hydrothermal electrolytic oxidation of wastewater

Abstract

Electrochemical evolution of hydrogen gas, oxygen gas and chlorine at the electrodes is the usual reaction in conventional electrolysis of aqueous salt solution. However, here we demonstrate that the electrolysis governing reaction in hydrothermal solutions is different from the electrolysis performed at atmospheric pressure and temperatures up to 100°C. Experimental electrolytic reaction of aqueous salt solution carried out inside a sealed 300-mL batch autoclave showed that; accumulation of hydrogen gas, oxygen gas and chlorine is highly suppressed under hydrothermal (250°C and 7 MPa) conditions. We have also observed that, when organics are present in the aqueous salt solution being hydrothermally electrolyzed, an effective oxidation of organics is accomplished. Furthermore, for hydrothermal electrolytic oxidation (HEO) with oxygen gas added, experimentally observed TOC removal profile demonstrates apparent anodic oxidation electrical current efficiency of almost 200% for highconcentrated acetic acid solutions.     

Improvement in sonochemical degradation of 4-chlorophenol by combined use of Fenton-like reagents

Studies on the sonolysis of a wide range of organic compounds have demonstrated that ultrasonic irradiation has potential for decomposition of organic pollutants in hazardous wastewater. However, the ultrasonic irradiation alone cannot provide high enough rate of decomposition to be used practically. One of the solutions to increase the degradation efficiency is to combine the ultrasound application with other advanced chemical oxidation processes (AOPs). In this study, in order to increase the efficiency of ultrasonically assisted degradation of organic pollutants in water, we examined effects of three kinds of solid Fe-containing catalysts, namely iron powder, basic oxygen furnace (BOF) slag and mill scale on the degradation rate of 4-CP (4-chlorophenol) in aqueous solutions containing hydrogen peroxide. In the experiments, 4-CP was considered as a model organic compound. All three Fe-containing matters when react with hydrogen peroxide are involved in the Fenton-like reaction system, which is one of the promising AOPs. The results showed that both the iron powder and mill scale additions can accelerate the degradation of 4-CP, although the effect is dependent on the solution pH. All 4-CP could be decomposed for 2 min at pH=3 and for 1h at pH=5.6. On the other hand, the BOF slag had no catalysis effect on the 4-CP degradation because of higher concentration of calcium and lower concentration of iron.     

Oxidation of garbage in supercritical water

Abstract

In the present study, 17 kinds of organic materials selected from groups of vegetable, meat, fat and fish as main components of garbage were oxidized with H₂O₂, using a batch reactor system under the condition of supercritical water, in order to treat organic wastes of high water content and low calorific value. It was found that they were easily oxidized, and remarkable influence of the kind of material in each group on the TOC decomposition was not recognized, but meats, fats and fishes, especially beef suet, were more difficult to be oxidized than vegetables.

The residual intermediate product was acetic acid in reactions of one minute at 400°C for all materials. Based on this result, the rate expression for supercritical water oxidation of acetic acid was determined.     

A novel surface cleaning method for chemical removal of fouling lead layer from chromium surfaces

Most products especially metallic surfaces require cleaning treatment to remove surface contaminations that remain after processing or usage. Lead fouling is a general problem which arises from lead fouling on the chromium surfaces of bores and other interior parts of systems which have interaction with metallic lead in high temperatures and pressures. In this study, a novel chemical solution was introduced as a cleaner reagent for removing metallic lead pollution, as a fouling metal, from chromium surfaces. The cleaner aqueous solution contains hydrogen peroxide (H₂O₂) as oxidizing agent of lead layer on the chromium surface and acetic acid (CH₃COOH) as chelating agent of lead ions. The effect of some experimental parameters such as acetic acid concentration, hydrogen peroxide concentration and temperature of the cleaner solution during the operation on the efficiency of lead cleaning procedure was investigated. The results of scanning electron microscopy (SEM) showed that using this procedure, the lead pollution layer could be completely removed from real chromium surfaces without corrosion of the original surface. Finally, the optimum conditions for the complete and fast removing of lead pollution layer from chromium surfaces were proposed. The experimental results showed that at the optimum condition (acetic acid concentration 28% (V/V), hydrogen peroxide 8% (V/V) and temperature 35 °C), only 15-min time is needed for complete removal of 3 g fouling lead from a chromium surface.     

邻菲咯啉-过氧化氢-铬黑T反应体系的光谱研究及其应用

在稀醋酸介质中,痕量邻菲咯啉对过氧化氢氧化铬黑T的褪色反应有明显的阻抑作用,据此建立了阻抑动力学光度法灵敏测定痕量邻菲咯啉的新方法,并讨论了该方法的动力学参数。在最佳实验条件下,其线性范围为0.003～0.08mg·L-1;检出限为4.0μg·L-1。该方法灵敏、快速、操作简便,用于水样中邻菲咯啉含量的测定,结果令人满意。     

2017年10期电子期刊

为了增强β-NaGdF₄：Yb³⁺,Tm³⁺纳米晶的上转换发光,克服外延增长钝化壳增大尺寸的不足,利用阳离子交换法制备核壳纳米结构,研究了样品在980 nm激发下的上转换发光性质。首先,利用高温热分解法制备了直径为10 nm的β-NaGdF₄：Yb³⁺,Tm³⁺纳米晶;然后,将制备的纳米晶与Gd³⁺在油酸-十八烯混合溶液中在300℃进行交换反应。实验结果表明,随着表面Yb³⁺和Tm³⁺被Gd³⁺取代,钝化壳的形成抑制了内部Yb³⁺的表面去激发过程,增强了内部Yb³⁺（²F₅）→ Tm³⁺（³H₅,³F_2,3）的能量传递,上转换发光逐渐增强。交换30 min后,Tm³⁺的³H₄ →³H₆近红外发光增强达到最大,为对照样品的6.5倍,而尺寸基本保持不变。在生物成像方面,上转换纳米晶的尺寸必须与生物分子相匹配,同时发光强度要高,阳离子交换法既能增强近红外发光,又能保持原来小的尺寸,在生物成像领域具有很好的应用前景。     

Ultrasound assisted phase-transfer catalytic epoxidation of 1,7-octadiene - a kinetic study

An ultrasound assisted phase-transfer catalyzed epoxidation of 1,7-octadiene is greatly enhanced by using a cocatalyst of phosphotungstic acid in the presence of hydrogen peroxide in an organic solvent/aqueous solution two-phase medium. An active intermediate of the catalyst (Q3PW12(O)nO40, where Q = R4N+) produced from the reaction of phosphotungstic acid, hydrogen peroxide, and Aliquat 336. A rational mechanism of epoxidation is proposed to account for the reaction from the experimental evidence. The organic-phase reactions, including two series reactions, are the rate-controlling steps to produce two products, viz., 1,2-epoxy-7-octene and 1,2,7,8-diepoxyoctane. The kinetics of epoxidation, including the characteristics of the catalyst and the effect of the amount of cocatalyst, agitation speed, quaternary ammonium salts, amount of Aliquat 336, amount of hydrogen peroxide, amount of chloroform, pH value, organic solvents, and temperature on the conversion of 1,7-octadiene were investigated in detail. A kinetic model was built, from which a pseudo-first-order rate law is sufficient to describe the behavior of the reaction.     

Effect of titanium dioxide and 3.5% hydrogen peroxide with 405-nm diode laser irradiation on bonding of resin to pulp chamber dentin

This study was conducted to determine the effect of a 3.5% hydrogen peroxide solution containing titanium dioxide on bonding of resin to pulp chamber dentin. Extracted bovine anterior teeth were allocated to three groups of ten teeth each. The coronal labial pulp chamber dentin was exposed and bleached with 3.5% hydrogen peroxide with titanium dioxide with 405-nm diode laser irradiation for 15 min (Group 1); 30% hydrogen peroxide with halogen lamp irradiation for 15 min (Group 2); and distilled water for 15 min (Group 3). After bleaching, the pulp chamber dentin was prepared for composite resin bonding and the interface between the resin and dentin was observed by scanning electron microscopy. The microtensile bond strength (μTBS) and failure patterns were determined. The μTBS values (mean ± SD) were: 17.28 ± 5.79 MPa (n = 36), 0 MPa, and 26.50 ± 9.83 MPa (n = 36) in Groups 1, 2, and 3, respectively. The μTBS in Group 3 was significantly higher than that in Group 1 (P < 0.05). Hybrid layers and resin tags were clearly observed at the interface in Groups 1 and 3, but not in Group 2. Adhesive failure was mainly observed in Group 1, whereas dentin failure was the main failure pattern in Group 3.     

NMR analysis of diacyl peroxide decomposition in methanol in response to temperature and microwave radiation

We have studied the decomposition of benzoyl and acetyl benzoyl peroxides in methanol-d₄ in response to temperature and microwave radiation. We have shown that chemically-induced dynamic nuclear polarization (CIDNP) can be observed even when the reactions are carried out in spectrometers with high magnetic fields. In this case, spin correlation persists in geminal radical pairs involving labile acyloxyl radicals. Regardless of the method used to initiate peroxide decomposition, the same amount of products are formed. Homolysis occurs according to a chain mechanism. The contribution of induced decomposition decreases over the course of the reaction. Dissolved oxygen molecules efficiently terminate the chain, decreasing the rate of peroxide decomposition. In the case of acetyl benzoyl peroxide, the product yield depends on the initiation mechanism: for microwave irradiation, the solvent molecules are more active while dissolved oxygen is less active than in thermolysis.     

Application of Black Pearl carbon-supported WO3 nanostructures as hybrid carriers for electrocatalytic RuSex nanoparticles

RuSe_x electrocatalytic nanoparticles were deposited onto hybrid carriers composed of Black Pearl carbon-supported tungsten oxide; and the resulting system's electrochemical activity was investigated during oxygen reduction reaction. The tungsten oxide-utilizing and RuSe_x nanoparticle-containing materials were characterized using transmission electron microscopy, X-ray diffraction and electrochemical diagnostic techniques such as cyclic voltammetry and rotating ring-disk voltammetry. Application of Black Pearl carbon carriers modified with ultra-thin films of WO₃ as matrices (supports) for RuSe_x catalytic centers results during electroreduction of oxygen in 0.5 mol dm⁻³ H₂SO₄ (under rotating disk voltammetric conditions) in the potential shift of ca. 70 mV towards more positive values relative to the behavior of the analogous WO₃-free system. Also the percent formation (at ring in the rotating ring-disk voltammetry) of the undesirable hydrogen peroxide has been decreased approximately twice by utilizing WO₃-modified carbon carriers. The results are consistent with the bifunctional mechanism in which oxygen reduction is initiated at RuSe_x centers and the hydrogen peroxide intermediate is reductively decomposed at reactive WO₃-modified Black Pearl supports. The electrocatalytic activity of the system utilizing WO₃-modified Black Pearl supports has been basically unchanged upon addition of acetic acid, formic acid or methyl formate to the sulfuric acid supporting electrolyte.     

Determination of NAD(P)H by A Bioluminescent Enzyme Fiber Optic Probe

Abstract

A fiber optic probe was interfaced to a photon counting system for the determination of nicotinamide adenine dinucleotide reduced [NAD(P)H] by a bioluminescence method. The reagents employed in a bacterial luciferase/flavin mononucleotide /decanal system were optimized. Attempts were made to increase the quantum yield of the system. Dodecanal, tridecanal, and tetradecanal were evaluated as alternative aldehyde reagents for decanal, and hydrogen peroxide was added to the system. Neither attempt increased the quantum yield of the system. However, a relatively low detection limit of 1.6 × 10^?9 M for NAD(P)H was obtained with a linear dynamic range of 3.8 orders of magnitude. These results demonstrate the sensitivity of this instrumentation and assay.