Copolymerization of ethylene and 1-butene using a Cr—silica catalyst in a slurry reactor

A novel slurry reactor was used to investigate the copolymerization behavior of ethylene and 1-butene in the presence of 1 wt % Cr on Davison silica (Phillips-type) catalyst over the temperature range of 0–50°C, space velocity of about 0.0051 [m³ (STP)]/(g of catalyst) h, and a fixed ethylene to 1-butene feed mole ratio of 95 : 5. The effect of varying the ethylene to 1-butene feed ratios, 100 : 0, 96.5 : 3.5, 95 : 5, 93 : 7, 90 : 10, 80 : 20, and 0 : 100 mol/mol at 50°C was also studied. The addition of 1-butene to ethylene typically increased both copolymerization rates and yields relative to ethylene homopolymerization with the same catalyst, reaching a maximum yield for an ethylene: 1-butene feed ratio of 95 : 5 at 50°C. The incorporation of 1-butene within the copolymer in all cases was less than 5 mol %. The average activation energy for the apparent reaction rate constant, k_a, based on total comonomer mole fraction in the slurry liquid for the ethylene to 1-butene feed mole ratio of 95 : 5 in the temperature range of 50–30°C measured 54.2 kJ/mol. The behavior for temperatures between 30 to 0°C differed with an activation energy of 98.2 kJ/mol; thus, some diffusion limitation likely influences the copolymerization rates at temperatures above 30°C. A kinetics analysis of the experimental data at 50°C for different ethylene to 1-butene feed ratios gave the values of the reactivity ratios, r₁ = 27.3 ± 3.6 and r₂ ≅ 0, for ethylene and 1-butene, respectively. © 1996 John Wiley & Sons, Inc.     

Robust Amino-Functionalized Mesoporous Silica Hollow Spheres Templated by CO2 Bubbles

Hollow-structured mesoporous silica has wide applications in catalysis and drug delivery due to its high surface area, large hollow space, and short diffusion mesochannels. However, the synthesis of hollow structures usually requires sacrificial templates, leading to increased production costs and environmental problems. Here, for the first time, amino-functionalized mesoporous silica hollow spheres were synthesized by using CO₂ gaseous bubbles as templates. The assembly of anionic surfactants, co-structure directing agents, and inorganic silica precursors around CO₂ bubbles formed the mesoporous silica shells. The hollow silica spheres, 200–400 nm in size with 20–30 nm spherical shell thickness, had abundant amine groups on the surface of the mesopores, indicating excellent applications for CO₂ capture, Knoevenagel condensation reaction, and the controlled release of Drugs.     

利用Triton X-100合成介孔二氧化硅及其形貌研究

以非离子型表面活性剂Triton X-100为模板剂,正硅酸乙酯为硅源,合成了介孔二氧化硅分子筛.利用XRD、N2吸附—脱附、SEM、以及TG-DTA对样品进行了表征,结果表明合成的材料具有有序介孔结构、高比表面积及高孔容。同时比较了不同条件下所得产物的形貌结构,并分析了它们的形成机理。     

掩埋式多模干涉型分束器的反射性能

通过束传播方法(BPM)模拟了SiO2基掩埋式波导结构多模干涉(MMI)型分束器的反射性能,模拟结果表明,MMI工作在分束模式时存在最优的多模干涉长度实现最大输出和最小反射,而在合束模式下实现最大输出时反射也达到最大,这是由自映象原理决定的。SiO2基掩埋式波导结构MMI分束器对反射具有良好的抑制作用,其最大反射功率为-60dB。分析表明,多模干涉区末端的界面反射率决定了器件的反射强弱,SiO2基掩埋式波导的界面反射率非常低,这是其低反射的原因。     

Fluorogenic Detection of Human Serum Albumin Using Curcumin-Capped Mesoporous Silica Nanoparticles

Mesoporous silica nanoparticles loaded with rhodamine B and capped with curcumin are used for the selective and sensitive fluorogenic detection of human serum albumin (HSA). The sensing mesoporous silica nanoparticles are loaded with rhodamine B, decorated with aminopropyl moieties and capped with curcumin. The nanoparticles selectively release the rhodamine B cargo in the presence of HSA. A limit of detection for HSA of 0.1 mg/mL in PBS (pH 7.4)-acetonitrile 95:5 v/v was found, and the sensing nanoparticles were used to detect HSA in spiked synthetic urine samples.     

Cu/SiO2催化剂上苯胺和正丙醇高效合成N-丙基苯胺

采用等体积浸渍法经程序升温焙烧制备了Cu/SiO2催化剂,考察了该催化剂对苯胺和正丙醇气相合成N-丙基苯胺的催化活性和选择性.常压下,当反应温度为260℃时,Cu/SiO2上正丙醇转化率达到100%,N-丙基苯胺选择性超过92%.X射线衍射分析表明,该催化剂具有较好的铜结晶度.     

基于二氧化硅胶体晶体薄膜和反射干涉光谱的蛋白冠监测方法

生物分子与纳米材料作用形成的"蛋白冠"影响纳米材料的物理和化学性质,目前缺少有效的原位实时技术监测蛋白冠的形成过程.本研究基于二氧化硅胶体晶体薄膜和反射干涉光谱法,研究了三种代表性血液蛋白质在二氧化硅纳米粒子表面的蛋白冠形成过程,结果表明这三种蛋白具有不同的蛋白冠形成过程及参数;研究了人血清白蛋白在三种表面曲率的二氧化...     

酰胺功能化修饰琼脂糖/硅胶复合材料的制备及吸附性能研究

采用溶胶-凝胶法,以氧化琼脂糖和四甲氧基硅烷为前驱体,通过水解、缩聚反应制得琼脂糖/硅胶复合材料,进一步利用开环、"巯-烯"点击和酰胺化反应对复合材料实现酰胺基团功能化修饰.借助红外光谱(FT-IR)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)对所制备复合材料进行结构、组成和微观形貌表征.以制备的酰胺功能化修饰琼脂糖/硅胶复合材料为吸附剂,探讨其对莱克多巴胺的吸附过程,实验考察了溶剂、吸附时间、莱克多巴胺的初始浓度等对吸附的影响.结果表明:经过修饰反应酰胺基团成功接枝到琼脂糖/硅胶复合材料,该材料颗粒呈球形,粒径在2～3μm之间;复合材料对莱克多巴胺表现出良好的吸附性能,吸附过程50 min达到平衡,适合准二级动力学特征,属化学吸附,吸附等温线符合Freundlich模型;复合材料经过6次吸附解析,再生后对莱克多巴胺的吸附率仅有小幅下降,表明具有较好的循环再生吸附能力.     

P2O5/SiO2 as an Efficient Reagent for the Preparation of Z -Aldoximes Under Solvent-Free Conditions

Abstract

A facile and efficient method for the preparation of Z-aldoximes is improved by means of P₂O₅/SiO₂ reagent in solvent-free media. Advantages of this method are the use of inexpensive and selective reagent, with high yields in simple operation, and short reaction time under solvent-free conditions.     

Performance evaluation of functionalized ordered mesoporous silica for VOCs adsorption by molecular dynamics simulation

Volatile organic compounds (VOCs) are growing pollutants now that cause the serious environmental pollution and threaten human health. The functionalized ordered mesoporous silica (FOMS) has attracted considerable attention in adsorbing VOCs. In this paper, the molecular dynamics simulation was used to simulate the adsorption performance of FOMS on VOCs (acetone, ethyl acetate and toluene). After simulating different pore sizes (2 nm, 3 nm and 4 nm) adsorption performances of ordered mesoporous silica (OMS) on VOCs, OMS with a pore size of 4 nm was selected to further study the influence of functional groups (vinyl, methyl, and phenyl). The following law was obtained: the saturated adsorption capacities of vinyl-functionalized OMS (V-FOMS) to acetone, ethyl acetate and toluene were 3.045 mmol.g^?1, 2.568 mmol.g^?1 and 1.976 mmol.g^?1 respectively; the saturated adsorption capacities of methyl-functionalized OMS (M-FOMS) to acetone, ethyl acetate and toluene were 2.798 mmol.g^?1, 2.312 mmol.g^?1 and 1.698 mmol.g^?1 respectively; the saturated adsorption capacities of phenyl-functionalized OMS (P-FOMS) to acetone, ethyl acetate and toluene were 2.124 mmol.g^?1, 1.941 mmol.g^?1 and 1.539 mmol.g^?1 respectively. These results show that the adsorption ability of FOMS for different adsorbates follows the sequence of acetone > ethyl acetate > toluene. Furthermore, the interaction between functional groups (vinyl, methyl and phenyl) in FOMS and VOCs was explored. It is found that the interaction between different functional groups and adsorbates is different (interaction energy effect). This interaction energy effect promotes FOMS to better adsorb VOCs. This work would provide fundamental understanding and guidance for the development of novel adsorption materials for the adsorption of VOCs.