富马酸二乙酯制备工艺的改进

以顺酐和乙醇为原料,硫酸氢钠和氯化铝为催化剂合成富马酸二乙酯。考察了影响收率的因素,确定量佳工艺条件为：顺酐0．1mol,乙醇0．3mol,硫酸氢钠0．5g,氯化铝0．6g,反应时间4h,油浴温度110-120℃,收率可达90％以上。     

采前喷施胺鲜酯对采后龙眼果实贮藏期间果皮膜脂代谢的影响

为研究采前喷施胺鲜酯（diethyl aminoethyl hexanoate,DA-6）对采后龙眼果实贮藏期间果皮膜脂代谢的影响,以‘福眼’龙眼为实验材料,在龙眼盛花期后70、90、110 d用10 mg/kg DA-6溶液各喷施龙眼果实1 次,以蒸馏水喷施为对照。龙眼果实在盛花期后120 d采收,采后龙眼果实经过挑选、清洗和晾干后用厚度为0.015 mm的聚乙烯薄膜袋密封包装（每组50 袋,每袋50 个）,在（28±1）℃、相对湿度85%条件下贮藏。结果表明：采前喷施DA-6可延缓采后龙眼果实贮藏期间果皮细胞膜透性的增加,降低果皮脂氧合酶、脂酶和磷脂酶D等膜脂降解酶活力,延缓果皮膜磷脂（磷脂酰胆碱（phosphatidylcholine,PC）、磷脂酰肌醇（phosphatidylinositol,PI））和不饱和脂肪酸（油酸（C18:1）、亚油酸（C18:2）、亚麻酸（C18:3））的降解,保持较高的PC和PI含量及脂肪酸不饱和指数、脂肪酸不饱和度,保持较低的磷脂酸含量,维持正常细胞膜区室化功能和结构。因此,采前喷施DA-6增强采后龙眼果实耐贮性与采前喷施DA-6能有效降低采后龙眼果实贮藏期间果皮膜脂代谢有关。     

马来酸二乙酯熔融接枝聚丙烯蜡的研究(Ⅰ)

用马来酸二乙酯接枝改性聚内烯蜡,在烃链上导入极性基团,目的是以此做为第三组分用于改进聚丙烯与含极性基团聚合物,如聚酰胺、聚氯乙烯等的相容性。通过对引发剂用量、单体用量、反应温度和反应时间等条件的研究,制得接枝率为17％的接枝改性聚丙烯蜡。     

活性炭负载磷钨酸催化合成丙二酸二乙酯的研究

以丙二酸和乙醇为原料，采用活性炭负载磷钨酸作催化剂合成丙二酸二乙酯。考察了催化剂用量、酸醇物质的量比、带水剂用量以及反应时间等因素对收率的影响。确定最佳酯化反应条件：n(丙二酸n(乙醇）∶n(催化剂）＝1∶3∶0.007，带水剂甲苯15 mL，反应时间90 min。收率可达96.25%。     

己二酸废料乙醇酯化反应动力学研究

以对甲苯磺酸为催化剂,甲苯为带水剂,过量的乙醇和生产环己酮的副产混合二元酸为原料进行酯化反应合成以己二酸二乙酯为主的产物。通过反应动力学实验,建立了分水条件下酯化合成反应的动力学模型。结果表明此条件下表现为二级不可逆反应,测出了反应的表观活化能Ea=38.63 kJ/mol,指前因子k0=1.277×10-4L·mol-1·min-1,为反应器设计提供了基础数据。     

Linux下以太网网络监听技术研究

随着网络技术的飞速发展,自由操作系统Linux的普及越来越迅速,Linux下的网络管理迫在眉睫,网络监听是网络管理的重要技术手段之一。本文介绍以太网环境中Linux系统下网络监听技术的原理、检测网络侦听的方法和网络监听技术在网络测试中的应用,重点介绍网络监听程序的设计。     

碳酸二甲酯和乙醇酯交换合成碳酸二乙酯工艺研究

碳酸二乙酯分子结构中含有活性基团乙氧基和羰基,化学性质活泼,是一种重要的有机合成中间体、溶剂和性能优良的燃料添加剂,在化工领域具有很高的应用价值。以碳酸二甲酯和乙醇为原料,甲醇钠为催化剂,通过酯交换反应合成碳酸二乙酯。气相色谱分析表明,在酯与醇物质的量比1∶20、催化剂用量为碳酸二甲酯质量的1.0%、反应温度78 ℃和反应时间1 h条件下,碳酸二甲酯转化率达99%,碳酸二乙酯和碳酸甲乙酯选择性分别为86%和14%。     

Synthesis of diethyl carbonate from ethanol through different routes: A thermodynamic and comparative analysis

In this study, thermodynamic analysis of various possible synthesis routes of diethyl carbonates (DEC), a benign organic carbonate, was carried out and a comparative analysis was performed. Chemical equilibrium constants at standard conditions were calculated using Gibbs free energy of the system. The Benson group contribution method was used to estimate standard heat of formation and standard entropy change of some raw materials/components like dimethyl carbonate. Variation of heat capacity (C_p) with temperature was estimated for different components from the Rozicka‐Domalski model. Variation of chemical equilibrium constants with temperature and pressure was studied for various routes. Synthesis of DEC from ethylene carbonate (EC) was also found to be better considering equilibrium constants at room temperature. The CO₂ route was found to be the most unfavourable route for DEC synthesis due to stability of CO₂ molecules. Moreover, DEC synthesis through the urea route was found to be best at high temperatures since the equilibrium constants were found to increase exponentially. Experiments were conducted for DEC synthesis using the EC route at two temperatures. Activity coefficients were calculated using the UNIFAC model. Experimentally and theoretically determined chemical equilibrium constant values were found to be similar. PRO/II was also used to minimize Gibbs free energy of the system and estimate the equilibrium constants and the results were comparable with those obtained by the equilibrium constant method and the trend was found to be the same for both the methods.     

丙二酸二乙酯在Cu/SiO_2催化剂上的加氢过程

在连续流动固定床反应器上,研究了Cu/SiO_2催化丙二酸二乙酯(DEM)加氢制备1,3-丙二醇(1,3-PDO)的反应。采用H_2-TPR、XRD、SEM、N_2吸附-脱附等方法对催化剂进行表征。进一步优化了原料液含量、氢酯摩尔比、液态空速、反应温度、反应压力等因素对反应结果的影响。表征结果显示,不同还原条件会影响Cu/SiO_2还原后活性铜的量及其分散状态;于300℃下还原4 h时,Cu/SiO_2催化剂的活性中心较多且分散均匀。实验结果表明,采用于300℃下还原4 h的Cu/SiO_2催化剂,在原料液含量7.5%(w)、氢酯摩尔比330、液态空速1.8 h-1、反应温度200℃、反应压力2.0 MPa的反应条件下,DEM的转化率为85.2%,产物1,3-PDO的收率为41.0%,副产物3-羟基丙酸乙酯的收率为32.9%。     

宽带接入网技术的应用

文中介绍了宽带接入技术的几种方式以及特征，分析了最新接入技术VDSL的特点和应用。