Ultrasound assisted PTC catalyzed saponification of vegetable oils using aqueous alkali

A few vegetable oils were saponified using aqueous KOH and different PTCs at room temperature in the presence of ultrasound. The extent of saponification was studied using the saponification value as a reference. Optimizations of various parameters such as time, selection of PTC, quantity of PTC, quantity of KOH and quantity of water were carried out using soyabean oil as a sample oil under sonication with stirring. To study the effect of ultrasound, the saponification was also carried out at 35 +/- 2 degrees C under different conditions, namely stirring, sonication, stirring and sonication, and heating at 100 degrees C. It was found that the heterogeneous liquid-liquid phase saponification of different vegetable oils using aq. KOH/CTAB was remarkably accelerated at 35 +/- 2 degrees C in the presence of ultrasound along with stirring.     

Propargylation of indene-1,3-dione under a new phase-transfer catalyst combined with ultrasonication – A kinetic study

In the present study, kinetics of synthesis of 2,2-di(prop-2-ynyl)-1H-indene-1,3(2H)-dione was successfully carried out by propargylation of indene-1,3-dione with propargyl bromide using aqueous potassium hydroxide and catalyzed by a newly synthesized phase-transfer catalyst viz., N-benzyl-N-ethyl-N-isopropylpropan-2-ammonium bromide, PTC under ultrasonic (40 kHz, 300 W) assisted organic solvent condition. The pseudo first-order kinetic equation was applied to describe the overall reaction. Under ultrasound irradiation (40 kHz, 300 W) in a batch reactor, it shows that the overall reaction rate can be greatly enhanced with ultrasound irradiation than without ultrasound.     

Ultrasonically-promoted synthesis of mandelic acid by phase transfer catalysis in an ionic liquid

An efficient and facile process to synthesize mandelic acid through phase transfer catalysis (PTC; also phase transfer catalyst) using ultrasound in an ionic liquid has been developed. Mandelic acid was synthesized from benzaldehyde with chloroform in an 89.6% yield at 60°C for 2h by using tetrabutyl ammonium bromide (TBAB) as a phase transfer catalyst. Effects of different factors, such as frequency of ultrasound, reaction temperature, kinds of PTC and solvents had been investigated to obtain the optimum condition. It was observed that the ultrasonically promoted synthesis of mandelic acid by PTC in the ionic liquid exhibited significant enhancement in reaction yields under ambient conditions.     

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.     

Monomerization of photosensitizers by ultrasound irradiation in surfactant micellar solutions

The absorption and fluorescence properties of pheophorbide-a, Sodium salt of pheophorbide-a and its long chain (C₂₀H₃₉) ester (Pheophytine) were investigated in air-saturated micellar aqueous solutions before and after ultrasound irradiation (48 kHz, 10 min). The absorption spectra changed depending on the surfactant; cetyltrimethyl ammonium bromide (CTAB) or sodium dodecyl sulfate concentrations. The formation of different molecular species in various micellar solutions was estimated from the analysis of the absorption spectra. The absorption bands resulted from an aggregated form of the chromophore present in 50 mM phosphate buffer and in pre-micellar solutions. The specific bands of the aggregate disappeared with a simultaneous increase of the bands of monomer in normal micellar solution. The fluorescence spectra, the lifetimes and the fraction of each component (with a characteristic lifetime) of the chromophore in the micellar solutions changed significantly before and after ultrasound irradiation although the changes in absorption spectra were small. The fluorescence emission band at 710 nm due to the aggregate almost disappeared in the pre-micellar solution after ultrasound irradiation. The fraction of the short-lifetime component estimated for the aggregates decreased 55% in H₂O or 85% in 2 mM CTAB, however the long-lifetime components increased after the ultrasound treatment. From these fluorescence properties, it was concluded that the aggregated molecules were converted to a stable monomeric form by ultrasound. Extrapolation of these data to in vivo situations suggests that pretreatment of certain photosensitizers with ultrasound in micellar solutions may lead to increased efficiency of photodynamic therapy since only the monomers are photodynamically active.     

阳离子表面活性剂与酚红的显色反应及其分析应用

研究了阳离子表面活性剂（ＣＳＡＡ）溴化十六烷基三甲铵（ＣＴＡＢ）、溴化十六烷基吡啶（ＣＰＢ）在水溶液中与溴酚红（ＢＰＲ）的显色反应。发现在ＰＨ５．０～６．０范围内,ＣＳＡＡ单体与ＢＰＲ形成离子缔合物（缔合比为３：２）,可用于微是ＣＳＡＡ及ＣＳＡＡ的临界胶束浓度（ＣＭＣ）的测定。本文还研究了显色２的适宜条件、分析特征,并讨论了反应机理。     

阳离子表面活性剂三甲基溴化铵与硝酸铵相互作用的表面和热力学研究

本文系统研究了阳离子表面活性剂三甲基溴化铵和硝酸铵盐的表面现象和自聚集行为. 采用电导法和表面张力法研究在不同温度下阳离子表面活性剂三甲基溴化铵的表面性质和热力学性质. 通过表面张力测定得到临界胶束浓度、吸附自由能、胶束化的自由能、最小分子面积和表面过量浓度. 该研究表明,胶束化过程是自发放热反应. 电导测定结果确定了临界胶束浓度、电离程度和反离子结合度. 加入硝酸铵盐至表面活性剂溶液后,临界胶束浓度降低,电离程度和反离子结合度增加,更加有利于胶束化过程的自发. 该研究对进一步理解电解质和表面活性剂之间相互作用具有重要意义.     

High-power ultrasound in olive paste pretreatment. Effect on process yield and virgin olive oil characteristics

The effect of high-power ultrasound on olive paste, on laboratory thermo-mixing operations for virgin olive oil extraction, has been studied. Direct sonication by an ultrasound probe horn (105 W cm⁻² and 24 kHz) and indirect sonication with an ultrasound-cleaning bath (150 W and 25 kHz) were applied and their effects compared with the conventional thermal treatment.

A quick-heating of olive paste, from ambient (12–20 °C) to optimal temperature conditions (28–30 °C), and an oil extractability improvement were observed when applying sonication. Better extractability was obtained by direct sonication for high moisture olives (>50%) whereas indirect sonication gave greater extractability for low moisture olive fruits (<50%).

Optimal application of ultrasound was achieved with direct sonication for 4 min at the beginning of paste malaxation and with indirect sonication during the malaxation time.

Effect of high-power ultrasound on oil quality parameters and nutritional and sensory characteristics were studied. Changes in quality parameters (free acidity value, peroxide value, K270 and K232) were not found, however significant effects on the levels of bitterness, polyphenols, tocopherols (vitamin E), chlorophyll and carotenoids were observed. Oils from sonicated pastes showed lower bitterness and higher content of tocopherols, chlorophylls and carotenoids. Related to sensory characteristics, off-flavour volatiles were not detected in oils from sonication treatments. Total peak areas of volatiles and the ratio hexanal/E-2-hexenal, as determined by SPME analysis, were lower than non-sonicated reference oils; sensory evaluation by panel test showed higher intensity of positive attributes and lesser of negative characteristics than those untreated.     

Preparation of 1,3-bis(allyloxy)benzene under a new multi-site phase-transfer catalyst combined with ultrasonication – A kinetic study

In the present work, kinetics of synthesis of 1,3-bis(allyloxy)benzene was successfully carried out by O-allylation of resorcinol with allyl bromide using aqueous potassium hydroxide and catalyzed by a new multi-site phase-transfer catalyst viz., 1,3,5,7-tetrabenzylhexamethylenetetraammonium tetrachloride, MPTC under ultrasonic (40 kHz, 300 W) assisted organic solvent condition. The pseudo first-order kinetic equation was applied to describe the overall reaction. Under ultrasound irradiation (40 kHz, 300 W) in a batch reactor, it shows that the overall reaction rate can be greatly enhanced to seven fold faster with ultrasound irradiation than without ultrasound. The present study provides a method to synthesize ethers by ultrasound assisted liquid–liquid phase-transfer catalysis condition.     

Phase-transfer catalytic dichlorocyclopropanation of styrene under the influence of ultrasound conditions - A kinetic study

The kinetics for dichlorocyclopropanation of styrene with an excess of chloroform were studied under phase-transfer catalysis and ultrasound irradiation conditions using aqueous sodium hydroxide as the base and benzyltriethylammonium bromide as a catalyst. The reaction was carried out at 35°C under pseudo-first order conditions by keeping aqueous sodium hydroxide and chloroform in excess and was monitored by gas chromatography (GC). The effects of agitation speed, quaternary ammonium salts, amount of catalyst, amount of sodium hydroxide and temperature on the kinetics of the conversion were investigated.     

The effect of frequency on sonochemical reactions III: dissociation of carbon disulfide

Investigations were made of the effects of frequency, temperature, intensity and gases on the rate of sonochemical dissociation of carbon disulfide. Application of 900 kHz ultrasound did not produce any noticeable change. When carbon disulfide was irradiated with 20 kHz, the liquid formed a heterogeneous mixture of black particles in a yellow solution. The rate of dissociation decreased with increasing temperature, in agreement with most sonochemical reactions. The rate also decreased with decreasing area of the horn tip, keeping total power constant. This dependence on the horn tip area, as well as that on the frequency, is in opposition to the dependence for the formation of iodine from the sonication of aqueous potassium iodide solution [See Part II, Ultrasonics Sonochemistry 3 (1996) 19]. The X-ray spectrum of the black particles and the yellow residue obtained after evaporation showed the presence of amorphous carbon and monoclinic sulfur. The rate of sono-dissociation of carbon disulfide in the presence of different gases is in the order He > H2 > Air > Ar > O2 > CO2.     

基于高效分离不皂化物的傅里叶红外光谱结合化学计量学鉴定芝麻油

芝麻油是日常生活中常用食用油之一,掺假芝麻油会导致严重的健康问题.研究芝麻油鉴定方法是非常重要的.皂化植物油提取不皂化物是食用油鉴定的经济方法之一,现有植物油皂化方法需要较长时间,较高的温度,且不皂化物提取过程非常繁琐.采用超声技术替代常规回流加热法,提高了皂化效率,皂化时间缩短至10分钟,在此基础上采用专用固相萃取(...     

Ultrasound-assisted third-liquid phase-transfer catalyzed esterification of sodium salicylate in a continuous two-phase-flow reactor

The esterification of sodium salicylate to synthesize butyl salicylate by third-liquid phase-transfer catalysis under ultrasound irradiation was investigated in a continuous two-phase-flow reactor. The reactor was designed to keep the third-liquid phase in the middle part and to have the aqueous and organic phases flowing through it in countercurrent. Using tetra-n-butylphosphonium bromide to prepare the third-liquid phase for this esterification, the product yield in the organic outlet (toluene) at 70 °C was 49.7% in silent condition, showing the reaction promoted simply by countercurrent mixing of the aqueous and organic phases. In the conditions of space time at 168 min, stirring at 150 rpm and ultrasound irradiation (28 kHz, 300 W), the product yield was greatly enhanced to 78.2%. As prepared, above 90% of the added catalyst existed in the third-liquid phase, and after 4-h on stream for a large excess of n-butyl bromide to sodium salicylate, the fraction of catalyst retaining in the reactor was reduced to around 80%. The distributions of catalysts between phases before and after reaction were analyzed. A kinetic model was proposed to estimate the apparent rate constants, and the feasibility for third-liquid phase-transfer catalysis assisted by ultrasound irradiation in a continuous flow reactor was demonstrated.     

纺锤形β-FeOOH的形成过程研究

应用透射电镜技术观察了FeCl3 水解形成纺锤形 β FeOOH过程中颗粒的形貌变化 ,发现纺锤形β FeOOH颗粒是由针形初级粒子沿长轴聚集长大形成的 .加入表面活性剂十六烷基三甲基溴化铵 (CTAB)后 ,β FeOOH 形成机制发生改变 ,β FeOOH晶核通过扩散过程而长成纺锤形颗粒 .CTAB的存在使 β FeOOH颗粒变小而且粒径更均匀 .改变反应条件包括起始FeCl3 的浓度、陈化温度 ,得到了纺锤形和针形、不同轴比的单分散β FeOOH .     

A surface-enhanced Raman scattering study of CTAB adsorption on copper

Surface-enhanced Raman spectroscopy (SERS) has been used to study, in situ, the adsorption of cetyltrimethylammonium bromide (CTAB) on copper. The data obtained allow the determination of CTAB's adsorption rate from aqueous solution and are consistent with physisorption or weak chemisorption via the quaternary ammonium group. The use of “surface selection rules” to derive orientation information is examined.     

Ultrasound promoted reaction of Rhodamine B with sodium hypochlorite using sonochemical and dental ultrasonic instruments

The sonochemical acceleration of bleaching of Rhodamine B by sodium hypochlorite has been studied using ultrasound intensities in the range 0-7 W cm(-2). Using a 20 kHz ultrasonic horn, it was shown that ultrasound could significantly shorten the treatment time and/or the concentration of hypochlorite required for the reaction. A number of intermediate species formed during the reaction have been identified. It was demonstrated that the same sonochemical reactions occur during the use of dental ultrasound instruments of the type used in endodontics where hypochlorite solutions act as disinfectants. Results showed pseudo-first order degradation kinetics for the degradation of Rhodamine B for both types of source. Both the distribution of cavitation and the resulting bleaching reactions were dependent on the design of the tips. The bleaching reaction can therefore be used to characterise the behaviour of dental instruments and aid in the optimisation of their performance.     

Improved optical performance of CdO films prepared with CTAB as surfactant

The influence of surfactant cetyl trimethyl ammonium bromide (CTAB) on structural, morphological and optical properties of CdO films has been investigated. Five series of CdO films were successfully prepared by successive ionic layer adsorption and reaction method with the assistance of CTAB. These CdO films were characterized by X-ray diffraction, scanning electron microscopy and UV–vis spectroscopy. The CTAB caused in a decrease in crystallite size but an increase in the optical band gap of CdO films. From the optical investigations, it was observed that the transmittance of the pure film was about 2% and it increased dramatically to 37% for 2?M% CTAB added CdO films at the wavelength of 1100?nm. The results show that the amount of CTAB played an important role in determining the physical properties of the CdO nanostructures.     

Emulsification by ultrasound: drop size distribution and stability

The aim of this work is to compare the oil-in-water emulsions produced by mechanical agitation (Ultra-Turrax, 10,000 rpm, P = 170 W) or power ultrasound (ultrasound horn, 20 kHz, 130 W) using the same model system: water/kerosene/polyethoxylated (20 EO) sorbitan monostearate. The following parameters were varied: emulsification time, surfactant concentration, consumed power and volume fraction of oil. With ultrasound, the drop size (Sauter diameter, d32) is much smaller than that given by mechanical agitation under the same conditions, which makes insonated emulsions more stable. For a given drop size (d32), less surfactant is required.     

Effects of ultrasonic waves on the interfacial forces between oil and water

The effect of ultrasound on flow through a capillary using the pendant drop method was investigated. Water was injected into a 0.1 mm Hastelloy C-276 capillary tube submersed into several mineral oils with different viscosity, and kerosene. The average drop rate per minute was measured at several ultrasonic intensities. We observed that there exists a peak drop rate at a characteristic intensity, which strongly depends on oil viscosity and the interfacial tension between water and the oil. The semi-quantitative results reveal that the remarkable change in the interfacial forces between oil and water could be the explanation to the enhancement of oil recovery when the ultrasonic waves are applied.     

液体材料超声处理过程中声场和流场的分布规律研究

针对合金熔体等液体材料的超声处理过程,选取水作为透明模型材料,采用数值模拟计算和示踪粒子实验方法,研究了20和490 kHz两种频率超声作用下水中的声场和流场分布.结果表明,增大变幅杆半径能够提高水中声压水平,扩大空化效应的发生区域.当超声频率为20 kHz时,水中声压最大值出现在超声变幅杆下端面处,且声压沿传播距离的增大而显著减小.如果超声频率增加至490 kHz,水中的声压级相比于20 kHz时明显提高,且声压沿着超声传播方向呈现出周期性振荡特征.两种频率超声作用下水中的流场呈现相似的分布特征,且平均流速均随着变幅杆半径增大表现出先升高后降低的趋势.变幅杆半径相同时,20 kHz频率超声作用下水中的平均流速高于490 kHz频率超声.采用示踪粒子图像测速技术实时观察和测定了水中的流速分布,发现其与计算结果基本一致.