Rapid crystallization and morphological adjustment of zeolite ZSM-5 in nonionic emulsions

Zeolite ZSM-5 was synthesized for the first time in a nonionic emulsion composed of polyoxyethylated alkylphenol, butanol, cyclohexane and tetraethylammonium hydroxide (TEAOH)-containing zeolite synthesis mixture. The crystallization kinetics in the emulsion was investigated and the ZSM-5 product was characterized in detail by XRD, SEM, FT-IR, TG, N₂ adsorption and CHN analysis techniques. Compared with the conventionally hydrothermal synthesis with the same structure directing agent TEAOH, the emulsion system allows rapid crystallization of ZSM-5. The ZSM-5 product exhibits unusual agglomerated structure and possesses larger specific surface area. The FT-IR, TG results plus CHN analysis show the encapsulation of a trace of emulsion components in the emulsion ZSM-5. Control experiments show the emulsion system exerts the crystallization induction and morphological adjustment effects mainly during the aging period. The effects are tentatively attributed to the confined space domains, surfactant-water interaction as well as surfactant-growing crystals interaction existing in the emulsion.     

界面膜引发的乳化燃油燃烧中的振荡反应

有关小分子醇、H。和CO等易燃气体在铂催化下的高温燃烧的温度振荡及以表面活性剂为关键组分的液膜扩散振荡已有报道"－'－．但由界面膜作用而产生的乳化燃油燃烧中的振荡反应尚无其它可操作的原始研究文献,只是在前文［'j中提及过出现该现象．为了解乳化燃油燃烧过程中界面变化及其对燃烧的作用,通过静态燃烧实验配方的调节及变换以改变燃烧界面的情况．实验发现,在乳化燃油中加入一般的食用豆油,并使之水解出长链竣酸盐,则富集在燃烧界面上的长链竣酸盐所形成的界面膜对燃烧的自阻抑作用便会产生明显的振荡反应,形成火焰温度与高…     

水性环氧复合乳化剂的合成及性能

以环氧树脂E-44、2-氨基-5-磺酸基苯甲酸、乙二醇丁醚和正丁醇为原料,合成一种新型阴离子环氧乳化剂EP-D;同时,E-44和聚乙二醇(PEG6000)以摩尔比2∶1反应,合成端环氧基非离子环氧乳化剂EP-PEG;将EP-D与EP-PEG按不同质量比复配获得不同配比的EP-D/EP-PEG水性环氧复合乳化剂。 分别研究了EP-D/EP-PEG及EP-PEG在环氧树脂中加入质量分数为6%~12%时的乳化性能及形成乳液的表面张力、电导率和胶粒的Zeta电位、粒径。 结果表明,当EP-D和EP-PEG以质量比3∶5复配,总加入质量分数为9%时,制备的环氧乳液性能最佳。 与EP-PEG形成的环氧乳液相比,复配环氧乳化剂用量少,乳液铺展性好、稳定性高,且乳液在相反转时的固含量提高了10%以上。 复配环氧树脂乳液中胶粒的Zeta电位为-41.9 mV、粒径为342 nm、表面张力为25.5 mN/m、粘度为14 mPa·s。 这表明利用乳化剂EP-D与EP-PEG复配新合成的EP-D/EP-PEG水性环氧复合乳化剂可制备稳定性好,固含量高的乳液。     

Influence of environmental stresses on stability of oil-in-water emulsions containing droplets stabilized by beta-lactoglobulin-iota-carrageenan membranes

An oil-in-water emulsion (5 wt% corn oil, 0.5 wt% beta-lactoglobulin (beta-Lg), 0.1 wt% iota-carrageenan, 5 mM phosphate buffer, pH 6.0) containing anionic droplets stabilized by interfacial membranes comprising of beta-lactoglobulin and iota-carrageenan was produced using a two-stage process. A primary emulsion containing anionic beta-Lg coated droplets was prepared by homogenizing oil and emulsifier solution together using a high-pressure valve homogenizer. A secondary emulsion containing beta-Lg-iota-carrageenan coated droplets was formed by mixing the primary emulsion with an aqueous iota-carrageenan solution. The stability of primary and secondary emulsions to sodium chloride (0-500 mM), calcium chloride (0-12 mM), and thermal processing (30-90 degrees C) were analyzed using zeta-potential, particle size and creaming stability measurements. The secondary emulsion had better stability to droplet aggregation than the primary emulsion at NaCl 相似文献   

增感染料与卤化银微晶之间的作用及其聚集态的研究

本文研究了光谱增感染料的结构对立方体卤化银乳剂的感光性能的影响,并利用反射光谱和彩色分析荧光电镜研究了染料在卤化银微晶上的聚集态和Ｊ 聚集体的相对尺寸,通过测定乳剂离子电导率研究了染料的结构对乳剂离子电导率的影响．实验结果表明：本文中所用的九个染料不管是增感还是减感染料都能在立方体卤化银乳剂上形成Ｊ 聚集态;对噻碳菁染料而言,其５位上无论是吸电子基团还是推电子基团的染料形成的Ｊ 聚集体的平均尺寸皆较未取代染料的大,其增感效果也较好;苯环５位上吸电子基取代或平面性好的噻碳菁染料可提高立方体ＡｇＢｒＩ乳剂的离子电导率,证明它们的增感效果也好;６位硝基取代的吲哚碳菁染料是典型的减感染料,其在立方体乳剂上所形成的Ｊ 聚集体较小,但是对乳剂的离子电导无影响．此外,本文还试图对不对称插烯菁染料Ｄｙｅ９使立方体ＡｇＢｒＩ乳剂减感的作用进行了解释     

Anionic emulsion-directed synthesis of zeolite ZSM-5 with tunable morphology and Si/Al ratio

Zeolite ZSM-5 was synthesized for the first time in an anionic emulsion system composed of sodium dodecylbenzene sulfonate, pentanol, cyclohexane and zeolite synthesis mixture, and subsequently characterized by XRD, SEM, FTIR, TG and N₂ adsorption techniques. It is found that altering emulsion composition and adding electrolyte can effectively change the morphologies and/or Si/Al ratios of the ZSM-5 samples. Besides the commonly seen coffin morphology, ZSM-5 particles with rare elliptic cylinder, column and ellipsoid morphologies are also obtained. Depending on the weight ratios of anionic surfactant and zeolite reaction mixture, the framework Si/Al ratios of ZSM-5 samples vary slightly. Investigations on the crystallization process further show the emulsion system can induce rapid crystallization by virtue of shortening the induction time. The ways that the emulsion system affects zeolite crystallization, framework Si/Al ratio and particle morphology are tentatively discussed.     

Analyzing the Stability of the Water-in-Diesel Fuel Emulsion

The diesel engine exhaust gas consists of many hazardous components that need to be reduced. Incorporation of water in fuel restricts the emission of such toxic gases and helps to reduce pollution. The aim of this research work is to develop a water-in-diesel fuel emulsion having maximum stability. Initially, the most suitable surfactant/blend of surfactants has been investigated, which gives the maximum stability to the Water-in-Diesel (W/D) emulsion. It is found that a blend of Span 80 and Tween 80 gives an effective result. The W/D emulsion was prepared by using a high-speed mixing homogenizer and adding a small amount of water into the diesel containing blend of Span 80 and Tween 80. The results show that 10% W/D emulsion having 5% surfactant concentration gives the most desirable emulsion stability. Beyond 10% water concentration, the properties of the W/D emulsion get lowered.     

天然蚕丝丝素蛋白的乳化活性

采用不同油相制备了系列丝素蛋白乳液, 研究了丝素蛋白浓度、 油相体积分数和油相极性对丝素蛋白的乳化活性指数、 丝素蛋白乳液的稳定性和类型及乳液液滴的微观形态、 粒径与zeta电位的影响, 探讨了丝素蛋白的乳化活性和乳液稳定机制. 结果表明, 丝素蛋白具有两亲性和表面活性, 可在油水界面富集并形成稳定的黏弹性保护膜; 丝素蛋白的乳化活性随其浓度的增大而减小, 随油相体积分数的增大而增大; 丝素蛋白浓度和油相体积分数的增加可提高稳定乳液体积分数.     

Nondestructive Monitoring of Sucrose Diffusion in Oil-in-Water Emulsions by Ultrasonic Velocity Profiling

The diffusion of sucrose through an optically opaque oil-in-water emulsion was monitored nondestructively by measuring the ultrasonic velocity as a function of height. Initially, a corn oil-in-water emulsion (0, 5, 10, 15, or 20 wt% oil) stabilized by Tween 20 (1 wt%) and xanthan (1 wt%) was placed in a measurement cell at 30°C. A 20 wt% sucrose solution containing the same concentration of Tween 20 and xanthan as the aqueous phase in the emulsion was placed on top of the emulsion. The ultrasonic velocity of this two-layer system was measured as a function of sample height and time and then converted into sucrose and oil concentration–distance profiles using empirical calibration curves. The translational diffusion coefficient of the sucrose in the upper and lower layers was determined by fitting the experimental data to a Fickian diffusion model. The measured diffusion coefficients of the sucrose molecules decreased as the droplet concentration in the emulsion increased, indicating retardation of the sugar molecule movement. Ultrasonic profiling was also used to monitor the compression of the emulsion due to movement of water molecules into the upper layer.     

The Role of Internal Droplet Size on Emulsion Stability and the Extraction Performance of Kraft Lignin Removal from Pulping Wastewater in Emulsion Liquid Membrane Process

It has been discovered that the size of internal droplets in primary emulsion determines emulsion dispersion and stability in emulsion liquid membrane (ELM) process for removal of lignin from pulping wastewater. Generally, primary emulsion contains kerosene, Aliquat 336, sodium bicarbonate, as well as Span 80 as diluent, carrier, internal phase, and surfactant, respectively. Hence, this study had looked into the parameters, including concentration of surfactant, carrier, and stripping agent; emulsification speed and time; as well as agitation speed and time. As a result, the diameter of the smallest droplets (1.4 µm) was formed with maximum lignin extraction (95%), minimum swelling (5%) at 3% (w/v) surfactant concentration, 12,000 rpm of emulsification within 5 minutes, 0.01 M of Aliquat 336, 0.1 M of NaHCO_3, and 250 rpm of extraction within 10 minutes.     

Water-in-oil emulsion containing oxine for the collection of traces of copper(II) in water

An oil type emulsion containing tiny encapsulated droplets of hydrochloric acid has been used for the concentration of traces of copper(II) ions in water. Milligram quantities of oxine and a non-ionic surfactant (Span-80) were dissolved in 5-10 ml of chloroform and mixed vigorously with 3 ml of 1 mol/l hydrochloric acid by ultrasonic irradiation. The resulting water-in-oil type emulsion was gradually added to 50-500 ml of water sample and dispersed by stirring as numerous small globules (0.1 to 0.5 mm in diameter). The copper diffused through the chloroform layer into the small droplets of hydrochloric acid, which occurred quantitatively in the sample of pH 3-10. After separating the emulsion by sedimentation, it was demulsified by heating to segregate the aqueous and organic phases. The copper in the aqueous phase was successfully determined by GFAAS. The emulsion method allows to perform both extraction and back-extraction more easily and rapidly than the conventional liquid-liquid extraction method.     

Cellulose gel dispersions: fascinating green particles for the stabilization of oil/water Pickering emulsion

A facile approach for the preparation of cellulose gel dispersions with particle size less than 5 μm has been developed. The particles were obtained by dissolving cellulose in NaOH/urea solvent, followed by regeneration in ethanol/H₂O mixed solution with homogenizer shearing. The characteristics of the cellulose gel dispersions were evaluated in terms of particle dimensions and crystalline structure, size distribution and rheology behavior. The cellulose gel dispersions had low crystallinity, and the concentration of the cellulose solution had little influence on the particle size of the gel dispersions. Furthermore, the cellulose gel dispersions could be well dispersed in deionized water, and they could be used to stabilize oil/water emulsion without addition of any surfactant. The formed Pickering emulsion had typical shear-thinning behavior and higher storage modulus. The concentration of cellulose gel dispersions had a significant influence on the emulsion stability. The Pickering emulsion stabilized by the cellulose gel dispersions would open opportunities for the development of food emulsion systems or environmentally friendly functional materials.     

Multivariate Screening Analysis of Water-in-Oil Emulsions in High External Electric Fields as Studied by Means of Dielectric Time Domain Spectroscopy

The effect of crude oil resins with various polar characters on the stability of w/o model emulsions containing asphaltenes is investigated using a mixture design. The resins were extracted using an adsorption-desorption technique. One asphaltene fraction and four different resin fractions from one European crude oil were used. The stabilities are measured using time-domain dielectric spectroscopy in high external electric field. It is found that resins with different polar character have different effects on the emulsion stability. At asphaltene/resin ratios of 1 and 5 : 3 the resins in some cases lead to an emulsion stability higher than that of a similar emulsion stabilized by asphaltenes only, while at low asphaltene/resin ratios ( approximately 1 : 3) the emulsion stability is reduced by the resins. The effect on emulsion stability of combining two different resin fractions depended on the resin types combined as well as the relative amount of resins and asphaltenes. Also, an increase in the stability of some of the emulsions containing resins and asphaltenes for a period of 50-300 min after the emulsification was observed. This time-dependence of emulsion stability is attributed to the mobility of resins at the oil-water interface and the slow buildup of a stabilizing interfacial film consisting of resins and asphaltenes. Copyright 2000 Academic Press.     

Esterification of Octanoic Acid with Octanol in Microemulsion and Emulsion System

The esterification of octanoic acid with octanol in microemulsion and emulsion system is studied. In the presence of 5–10% dodecylbenzene-sulfonic acid (DBSA), which is a surfactant-type catalyst, high conversion of esterification can be given both in microemulsion and in emulsion system. Compared with emulsion system, single-phase microemulsion is a more effective reaction system for esterification, with the advantages of comparatively little influence by the amount of water, no need of hard stirring, and stable state when laid long. The esterification of other fatty acids and alcohols in this reaction system were also accomplished in favorable conversion.     

改性明胶沉降剂的研制

沉降法在浓缩乳剂的制备中起着很重要的作用,改性明胶沉降剂的应用越来越被人们重视。本文研究了多种改性明胶的合成、取代度的测定、物理性能、沉降条件、沉降过程中明胶及卤化银的回收率和改性明胶卤化银乳剂的感光性能等。研究结果表明:改性明胶沉降剂具有以下的优点:取代度高、沉降诱发期短,沉降的pH范围较窄(一般0.6pH单位),卤化银的回收率高,而改性明胶沉降乳剂的性能比传统的水洗乳剂的性能优异:表现在灰雾小,最大密度高,分辨率好,感光度高和自然保存性能好。文章对造成上述现象的原因也进行了初步的分析和讨论。     

Physical stability of oil-in-water emulsions in the presence of gamma irradiated gum tragacanth

Gum tragacanth (GT) exuding from an Iranian Astragalus species was γ-irradiated at 0, 0.75, 1.5, 3, 5, 7, and 10?kGy and used to stabilize a model oil-in-water emulsion system. Stability and physicochemical properties of emulsion samples were investigated with respect to the effect of irradiation treatment on functional properties of gum tragacanth. Particle size distribution, interfacial tension, zeta potential, steady shear, and oscillatory rheological measurements were used to characterize and evaluate the emulsion samples and obtain more information about the possible stability mechanism. Emulsions were prepared by homogenizing 10% w/w sun flower oil with 90% w/w aqueous gum dispersions and stored quiescently at 25°C for 120 days. The results indicated that using 1.5?kGy irradiated GT was more effective in providing optimum values of apparent viscosity, number mean diameter, electrosteric repulsion, and structure strength for getting the maximum emulsion stability. GT significantly reduced the interfacial tension of the oil and water system, but no significant differences were observed among all irradiation treated and non-irradiated samples. This study revealed that GT acts as a bifunctional emulsifier and irradiation treatment has a great positive influence on its ability to reduce droplets’ collision frequency and stabilize the oil-in-water emulsion.     

Emulsion copolymerization of styrene and methyl methacrylate

Chain transfer constants to monomer have been measured by an emulsion copolymerization technique at 44°C. The monomer transfer constant (ratio of transfer to propagation rate constants) is 1.9 × 10^?5 for styrene polymerization and 0.4 × 10^?5 for the methyl methacrylate reaction. Cross-transfer reactions are important in this system; the sum of the cross-transfer constants is 5.8 × 10^?5. Reactivity ratios measured in emulsion were r₁ (styrene) = 0.44, r₂ = 0.46. Those in bulk polymerizations were r₁ = 0.45, r₂ = 0.48. These sets of values are not significantly different. Monomer feed compcsition in the polymerizing particles is the same as in the monomer droplets in emulsion copolymerization, despite the higher water solubility of methyl methacrylate. The equilibrium monomer concentration in the particles in interval-2 emulsion polymerization was constant and independent of monomer feed composition for feeds containing 0.25–1.0 mole fraction styrene. Radical concentration is estimated to go through a minimum with increasing methyl methacrylate content in the feed. Rates of copolymerization can be calculated a priori when the concentrations of monomers in the polymer particles are known.     

Preparation of monodisperse crosslinked polymelamine microcapsules by phase separation method

Monodisperse polymelamine microcapsules were prepared by phase separation method. Control of microcapsule diameter was investigated using the uniform-sized oil-in-water emulsion droplets as the capsule core. The monodisperse emulsion droplets were prepared using the Shirasu porous glass (SPG) membrane emulsification technique. The effects of the diameter of the oil droplet and concentration of sodium dodecyl sulfate (SDS), which is a typical emulsifier in SPG membrane emulsification, on microencapsulation were investigated. The microcapsules were aggregated when oil droplets with small size were microencapsulated at high SDS concentration. To reduce the SDS concentration, the creamed emulsion was used. The monodisperse polymelamine microcapsules were successfully prepared by using the creamed emulsion. The microcapsule diameter was almost similar to the diameter of the encapsulated oil droplet. The coefficient of variation values was about 10% for all microcapsules prepared in this study. Control of microcapsule diameter was achieved in the range of 5–60 μm.     

Development of an ab initio emulsion atom transfer radical polymerization: from microemulsion to emulsion

Atom transfer radical polymerization (ATRP) has been successfully extended to an ab initio emulsion system using a "two-step" procedure, in which the final emulsion polymerization system was formed by adding monomer to an ongoing microemulsion ATRP. The newly developed AGET (activators generated by electron transfer) initiation technique was employed in the first stage of this ab initio ATRP. It allows using oxidatively stable Cu(II) species that is reduced in situ by ascorbic acid. The surfactant concentration in the final emulsion system was efficiently decreased to approximately 2 wt % (approximately 10 wt % vs monomer) by decreasing the catalyst concentration and changing the ratio of the monomer added at the microemulsion stage to the monomer added during the second stage. This two-step procedure avoids the necessity of transporting catalysts through the aqueous media during polymerization, resulting in a controlled emulsion polymerization, as evidenced by a linear first-order kinetic plot and formation of a polymer with a relatively narrow molecular weight distribution (Mw/Mn = 1.2-1.4). The polymerization typically reached 70-90% monomer conversion in 5-6 h. The resulting polymer had high chain-end functionality and was successfully chain extended to form in situ block copolymers by adding the second monomer to an ongoing emulsion polymerization. The stable latex from the ab initio emulsion ATRP had a particle size approximately 120 +/- 10 nm.     

几种光谱增感染料吸附在AgBr晶体上的光电导效应

使用AgBr晶体作为AgBr乳剂的模型,利用光电导法研究光谱增感的机理及染料的增感性能。采用“蚶埚下降法”重复地制备出了透明度相当好的AgBr晶体,还研究了晶体片的抛光与化学处理过程,这对于光电导实验都是重要的。对几种实用的光谱增感染料进行了光电导实验,实验结果与照相乳剂的光谱响应一致。而且观察到四氯咪碳菁与其它染料相比,光敏化电流有显著的不同。同时还进行了不同电荷染料的组合实验,由实验看到,由于染料吸附的先后次序不同,光电导曲线上峰电流的位置和大小发生了明显地变化,这对于照相乳剂的配制将具有一定的实际指导意义。