碱性季胺聚砜膜制备及其催化酯交换反应的研究

以聚砜(PSf)为原材料,通过氯烷基化和季胺化后浇铸成膜,进一步进行碱化处理制备碱性聚砜膜.采用红外光谱表征聚砜膜的化学结构,并将此碱性季胺聚砜膜用于催化大豆油酯交换反应制备生物柴油.考察并优化了原料油中含水率、共溶剂种类、共溶剂添加量以及醇油质量比对酯交换反应转化率的影响.研究结果表明,在醇油摩尔比9∶1,碱性聚砜膜用量为油重的2%,反应时间1h,正己烷添加量为油重的50%,反应温度65℃,大豆油转化率达到最大值95.2%.当原料油中的含水率≤5%时,碱性季胺聚砜膜可以吸收原料油中的水分,原料油中的水分对酯交换反应影响较小.碱性季胺聚砜膜重复使用5次后,酯交换反应转化率没有明显下降.     

PBT/PC 体系熔融共混期间的酯交换反应

用特性粘度测量、溶解度分离、红外光谱分析和选择降解等方法,对由国产原料组成的 PBT/PC 熔融共混物进行了研究,证明在熔融共混期间 PBT 和 PC 之间发生了酯交换反应,并考察了酯交换反应催化剂的量和共混时间对交换反应速度和程度的影响,得到了半定量的结果。     

超声辐照促进声化学产额的研究及应用

针对多频超声促进声化学产额的研究热点问题,简述了单频、双频、三频超声辐照的声化学反映规律及其研究进展,分析了多频辐射能显著提高声化学产额的原因。指出了多频超声在医药方面的应用,尤其是在中药复方提取中更显示出其优越性,可以达到很好的提取率,多频辐射有很好的开发前景。     

多频超声辐照的声化学产额研究进展

声化学是一门新兴的交叉学科，具有很多用途，广泛地应用于医药，生物，海洋，航空，轻工，食品，化学，化工等诸多领域，打基础这年来对声化学的研究十分活跃，多频超声对声化学产额的影响是其中研究的热点之一。声化学反应的主动力是声空化，声化学产额与超声辐照频率有一定的关系。双频，三频正交超声辐照能显著地提高声化学产额，具有明显的增强效应。文章综述了这方面的研究进展情况，阐述了声化学产额的影响因素。提出了目前所存在的问题并进行展望。     

可见光辐照下碘释放现象超声效应的实验研究

1引言 超声波辐照水溶液时,空化泡在声波的作用下形成、振荡、生长、收缩至崩溃.空化泡崩溃时在空化泡周围的极小空间内可以产生5000K以上的高温和高达5×107pa的高压等极端物理条件,同时可以产生氧化电位很高、化学性质十分活泼的羟基自由基(·OH)[1].利用声空化发生时产生的物理化学条件,通过进行超声预处理,可产生一系列声化学效应如超声诱导效应等,提高反应的产率和速率[2,3].本文研究了碘化钾溶液在可见光辐照下碘释放现象的超声效应.实验结果表明:超声的预辐照可以大大增加碘释放量.我们采用临界模型对该现象进行了初步分析.     

PET/PEN扩链反应共混的研究 Ⅰ.共混条件对酯交换及链结构的影响

用1H-NMR方法对PET/PEN在少量扩链剂存在下的反应性共混条件对酯交换反应及序列结构的影响作了系统研究.结果表明,混合时间、温度对酯交换反应有显著的影响.随着时间的增加和温度的提高酯交换程度增加,而导致共聚酯的数均序列长度变短.共混物的组成及少量扩链剂的存在,在某些条件下对酯交换反应及序列结构也显现出较明显的影响.     

超声技术在提取工艺和有机合成中的应用

超声波技术在化学实验及化工生产工艺研究和应用等方面都可发挥重要作用,可应用于有机合成、药物化学、环境化学、食品化工等许多领域。如运用超声提取法提取分离出中草药的有效成分,具有耗时短、提取率高、溶媒用量小等优点;超声技术在有机合成中的应用研究发展很快,应用广泛,超声波可以使许多有机合成在较温和的条件下进行,能够加速反应速率、提高产率、降低反应条件、缩短反应时间、改变反应历程等,能够显著降低成本,提高效益。     

PBT/PET共聚酯的合成

PBT/PET共聚酯是兼有PET和PBT优良特性的新材料。本文研究了共聚酯的合成条件。结果表明催化剂和反应温度对EG/BD与DMT的酯交换和共聚合反应有明显的影响,混合催化剂比单一催化剂效果好,Zn-Co-Ti催化体系对酯交换有较高的催化活性,缩聚催化荆以Sb-Ti体系为佳。共聚酯的色泽与反应温度、时间、催化剂种类及EG/BD的比例有关。在合适条件下,得到特性粘度为0.9以上的无着色的共聚酯。     

我国功率超声技术近况与应用进展

文章综述了我国功率超声技术近10年发展状况,介绍了功率超声的超声空化机理、超声换能器、超声发生器等基础研究以及在超声清洗、超声焊接、超声处理、环保、声化学、超声治疗、超声马达等方面的新应用及其发展重点.     

化学气相沉积反应研究的量子化学方法及应用

量子化学方法在研究化学气相沉积反应体系的反应机理、动力学计算方面有很大的潜力.本文分析了化学气相沉积过程的特点,并对量子化学计算的主要方法进行介绍.在此基础上,针对气相和表面基元过程的量子化学研究现状进行总结和评述.     

用碘释放法研究低频超声的声化学产额

本文用碘释放法研究了２８ｋＨｚ超声的声化学产额随扬强和辐照时间的变化。表明声化学产额随声强呈非线性变化，而随辐照时间近似呈线性变化。进而研究了由２８ｋＨｚ与１．０６ＭＨｚ组成的正交辐照系统的声化学产额。     

点聚焦超声辐照下液体中的声场和声化学场分布

通过数值模拟和实验分别研究了点聚焦超声换能器在液体中直接辐照和间接辐照时产生的声场和声化学场分布。研究结果表明,在直接辐照时,数值模拟得到的液体中声压较大位置与声化学反应场位置相一致:在聚焦超声焦点处及液体表面附近。当使用间接辐照时,焦点处声压减小,在试管底与超声换能器之间形成驻波。为了增加间接辐照时容器内的声压,实验使用底端贴有薄膜的双通试管,通过计算机模拟和实验证明在该情况下,容器内声压,特别是容器焦点处声压和声化学反应场有所增强。     

Rapid sonochemical preparation of shape-selective lead iodide

Lead iodide (PbI₂) films/crystals with various nano/micro morphologies (e.g., Nanoflake, block and microrod) were rapidly synthesized by taking advantage of a simple sonochemical method. The PbI₂ crystals with uniform nanoflake structures could be fabricated directly on lead foils with the irradiation time as short as 36 s via interfacial reaction between lead foils and elemental iodine in ethanol at ambient temperature. It was found experimentally that the morphologies of the resulting thin films/crystals could be well controlled by the adjustment of several parameters including irradiation time, reaction solvents, iodine concentration, ultrasonic power, and reaction temperature. Most importantly, the resultant PbI₂ films are stable enough to resist rolling under the drastic ultrasound irradiation in a liquid media. This method is believed to be the fastest way for in situ fabrication of morphology-controlled semiconductor films on various metal substrates for subsequent applications related to the other metal iodide or metal sulfide semiconductor films.     

Sonochemical reaction engineering

Ultrasound has been widely used by chemists to enhance yields as well as rates of homogeneous as well as heterogeneous chemical reactions. The effect of ultrasound on the course of chemical reactions is mediated through cavitation bubbles it generates. High temperatures and pressures are attained inside the cavitating bubbles when they collapse. The extreme conditions so generated lead to the formation of reactive intermediates, e.g., free radiacls, inside the bubbles, which cause chemical reactions to occur when they enter the surrounding liquid. This is the mechanism through which ultrasound influences the path of homogeneous reactions. The cavitation bubbles collapse asymmetrically in the vicinity of solids, e.g., catalyst particles. Asymmetric collapse lead to formation of high speed microjets. The microjets can enhance transport rates, the increase surface area through pitting as well as particle fragmentation through collisions. Both can alter the rates of heterogeneous reaction rates. It however appears that these effects do not exhaust the scope of the influence of ultrasound on heterogeneous reactions. Modelling and quantitative prediction of the effect of ultrasound on chemical reactions is however at a stage of infancy as the phenomena are complex. Only a few examples of modelling exist in literature. Apart from this, reactor design and scaleup pose significant problems. Thus sonochemical reaction engineering offers large scope for research and development efforts.     

Degradation of polycyclic aromatic hydrocarbons in aqueous solutions by ultrasonic irradiation

The effect of various operating conditions (initial concentration, liquid phase temperature, applied power, ultrasound frequency) and of the presence of matrix components (1-butanol, NaCl and FeSO(4)) on the sonochemical degradation of naphthalene, acenaphthylene and phenanthrene in water has been studied. A horn-type sonicator was used to deliver the ultrasound energy, while immersion sampling solid-phase microextraction (SPME) coupled with GC-MS was employed to follow concentration-time profiles of the chosen PAHs. At the operating conditions in question (initial concentrations of 150, 300 and 450 microg/l, temperatures of 20 and 40 degrees C, applied power of 45, 75 and 150 W and ultrasound frequencies of 24 and 80 kHz), all PAHs were susceptible to sonochemical treatment and, in most cases, complete degradation could be achieved in up to 120 min of treatment. Conversion was found to decrease with increasing initial concentration and temperature and decreasing power and frequency as well as in the presence of an excess of dissolved salts. Addition of 1-butanol, a known hydroxyl radical scavenger, substantially suppressed degradation throughout the course of the reaction, thus highlighting the role of oxidation reactions in PAHs degradation. In contrast, addition of Fe(2+) ions at a low concentration enhanced degradation through a Fenton-like reaction.     

Synthesis of monodisperse Fe3O4 nanoparticles by optimized sonochemical method using mono(ethylene glycol) (MEG)

In this study, we successfully synthesized monodisperse magnetite nanoparticles (NPs) (Fe3O4) by sonochemical method using mono (ethylene glycol) (MEG) as a modifier of the reaction environment and found that MEG could be a good candidate to prevent oxidation and toxicity in sonochemical synthesis. The microstructure and size distribution of the Fe3O4 NPs were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) respectively. It revealed that the NPs prepared by MEG assisted sonochemical method show a smaller average size and better monodispersity compared to conventional sonochemical method. Due the the reduced average size and uniform size distribution nature of the NPs, it also showed good superparamagnetic properties with very low coercivity less than 0.5 Oe.     

Controllable synthesis of hierarchical micro/nano structured FePO4 particles under synergistic effects of ultrasound irradiation and impinging stream

Hierarchical micro/nano-structured FePO₄ (FP) particles were environmental-friendly and controllable synthesized through synergistic intensification of ultrasound and impinging streams. Nano-scale FP seeds were firstly synthesized via ultrasound irradiation intensified impinging stream reaction (UISR), where the enhanced turbulent micromixing in the impinging streams benefits the nucleation process while the application of ultrasound to the impinging streams further intensifies such micromixing. The ultrasound frequency and power applied were 20 kHz and 600 W. The hierarchical micro/nano-structured FP particles are obtained when taking sufficient reaction time and stirring FP nano-seeds in a continuous stirring tank reactor (CSTR). Effects of the sonochemical pre-treatment, mean residence time and rotation speed on the physical-chemical properties of FP were investigated systematically. The characterization revealed that under the optimum operating condition, the FP particles presented near-spherical hierarchical micro/nano-structure, consisting of nanoscale primary grains. The mechano-chemical effects on the synthesized FP particles during different synthesis process were also studied.     

声化学法制备均匀分散的ZnO纳米晶(英文)

采用超声化学方法制备ZnO纳米颗粒,透射电子显微镜(TEM)测试结果显示,合成出的ZnO纳米颗粒尺寸均匀,形状规则。而X-射线衍射(XRD)结果表明,提高反应温度可以促进ZnO的生长。因而,对于合成单一分散的ZnO纳米晶而言,声化学方法是一种非常简便的方法。