Prediction of Experimental Methanol Decomposition Rates on Platinum from First Principles

A microkinetic model for methanol decomposition on platinum is presented. The model incorporates competitive decomposition pathways, beginning with both O–H and C–H bond scission in methanol, and uses results from density functional theory (DFT) calculations [Greeley and Mavrikakis, J. Am. Chem. Soc. 124 (2002) 7193, Greeley and Mavrikakis, J. Am. Chem. Soc. 126 (2004) 3910]. Results from reaction kinetics experiments show that the rate of H₂ production increases with increasing temperature and methanol concentration in the feed and is only nominally affected by the presence of CO or H₂ with methanol. The model, based on the values of binding energies, pre-exponential factors and activation energy barriers derived from first principles calculations, accurately predicts experimental reaction rates and orders. The model also gives insight into the most favorable reaction pathway, the rate-limiting step, the apparent activation energy, coverages, and the effects of pressure. It is found that the pathway beginning with the C–H bond scission (CH₃OH→H₂COH→HCOH→CO) is dominant compared with the path beginning with O–H bond scission. The cleavage of the first C–H bond in methanol is the rate-controlling step. The surface is highly poisoned by CO, whereas COH appears to be a spectator species.     

Anionic synthesis of poly(epichlorohydrin-g-styrene) and chemical modification of polyepichlorohydrin

Poly(epichlorohydrin-g-styrene) copolymers, P(ECH-g-S)s, have been prepared in solution by two different methods of coupling polyepichlorohydrin, PECH, with polystyrene, PS, containing a functional end group. In the first method, polystyryl carboxylic acid, PSCOOH, prepared from living polystyrene, was converted to the corresponding potassium salt which was coupled with PECH in dimethyl formamide solution usually at 60°C. In the second method, polystyryl potassium, PS^?K⁺, in tetrahydrofuran solution was end-capped with propylene sulphide to form PSCH₂CH(CH₃)S^?K⁺ which was coupled directly with PECH in tetrahydrofuran at 40°C. Grafting by the first reaction was relatively slow but occurred without significant adverse side reactions. The grafting by the second reaction was relatively fast, but side reactions occurred resulting in a cleavage of the graft copolymer. The graft copolymers were purified by fractional precipitation and extraction procedures and were characterized by infra-red and ultra-violet spectroscopy, microanalysis, gel permeation chromatography, differential scanning calorimetry, solution viscometry, dynamic mechanical testing, and electron microscopy. Solution properties of the graft copolymers in benzene-carbon tetrachloride and toluene-cyclohexane mixtures were studied. There was evidence of micelle formation in dilute solutions of the mixed solvents and microphase separation of components in the solid state. Nucleophilic substitution of chlorine atoms in PECH by phenyl acetate (C₆H₅ CH₂COO-) and thiophenoxide (C₆H₅S-) groups was performed.     

胺烷基化聚羟基酸酰胺类超分散剂的研制及应用

对胺烷基化聚羟基酸酰胺的合成方法进行研究，确立了反应条件与制得的聚羟基酸酯特征之间的一些相互关系。并为获得适当长度的聚酯链选择了最佳合成条件。同时扼要论述了这类超分散剂的结构特性，以及对于颜料粒子表面吸附作用、分散体系的稳定作用以及对涂料、油墨生产的重要意义。     

表面改性活性炭对饮用水中THMs吸附性能研究

通过对活性炭的表面改性，并对氯化消毒后的高色度水进行吸附处理，可使其三氯甲烷（THMs)的含量降低到44μg/dm^3，达到国家生活饮用水质标准。     

纤维素科学与技术研究进展

本文综述纤维素科学与技术的研究进展。阐述了纤维素结构、纤维素的合成、纤维素液晶、功能纤维素、纤维素溶剂、纤维素裂解和纤维素的废物利用等的最新动态。     

Different support effect of M/ZrO2 and M/CeO2 (M = Pd and Pt) catalysts on CO adsorption: A periodic density functional study

CO adsorption over Pd₄ and Pt₄ cluster supported by c-ZrO₂(1 1 1) and CeO₂(1 1 1) catalyst systems was investigated using periodic density functional method in order to clarify the support effect on CO activation. We found that the support increases the CO activation for bridge and three-fold sites but decreases for the atop site. Moreover, it was found that the support changes the site preference for the CO adsorption. Bridge site on both the Pt₄/c-ZrO₂ and Pt₄/CeO₂ show larger CO adsorption energies than those on the other sites while the atop site is energetically preferable on isolated Pt₄ cluster. c-ZrO₂ supported Pd shows the largest CO activation with large charge transfer from the catalyst to the CO molecule. This reveals that ZrO₂ supported Pd can be a good catalyst for CO activation because of its higher probability to the three-fold site CO adsorption. We also found that positively charged M₄ clusters on the support keep their strong electron-donating properties and have enough charge density to contribute to the activation of an adsorbed CO molecule by a charge transfer.     

基于十二烷基衣康酸甘油酯的光电双响应传感器

该文制备了一种利用结构色水凝胶作为导电电极的光电双响应传感器。以十二烷基衣康酸甘油酯(DGI)、丙烯酰胺、十二烷基硫酸钠(SDS)、氯化钠等为原料,通过双分子层自组装的方法,制备了结构色水凝胶。将这种结构色水凝胶与传统电容型传感器相结合,得到了光电双响应传感器。采用SEM、LCR数字电桥、拉力试验机、光纤光谱仪等对器件进行了结构、光学、电学及机械性能的表征。结果表明:传感器在拉伸状态(0～100%)和压缩状态(0～60.9k Pa)下,传感器的电容分别变化了31%和44%,其自身颜色在可见光光谱内可以动态可逆地从红色变化到紫色。经历15000次循环拉伸后,传感器性能依旧保持稳定。利用传感器颜色的刺激响应性,传感器在发生形变时,其表面可以清楚地显示出应变源的位置和形状,这样传感器在检测时就可以实现可视化效果。     

基于国家电网的财务管理系统的开发与研究

随着社会生产力的不断发展,越来越多的企业认识到了财务工作的重要性。企业要利用现代高效的运作方式来开发和管理组织中最重要、最昂贵的资源,实现财务管理的精细化、自动化,提高财务资源的利用率,促进企业的发展。     

液晶材料取代联苯硼酸化合物的研究

以液晶材料取代联苯硼酸化合物异构体混合物为原料,在相转移催化剂正十六烷基三甲基溴化胺的作用下,于碱性条件下,105~115℃反应3~8 h,得到液晶材料取代联苯化合物,它是生产相应的液晶材料取代联苯硼酸化合物的初始原料。并对其结构进行了质谱确认。     

基于QEMU的外部总线仿真技术

综合嵌入式系统通过外部总线实现各个子系统之间的通信连接。为解决综合嵌入式系统的接口测试问题,采用系统虚拟机仿真综合嵌入式系统的连接方式,通过在虚拟机中创建外部总线仿真模块,配置仿真模块的连接,从而实现虚拟机之间的通信。提出一种基于以太网通信的外部总线仿真结构,以CAN总线仿真为例,在全系统虚拟机QEMU的内部总线上配置与注册外部总线设备,为读写总线设备数据的接口建立共享内存,组织总线协议报文。实验结果表明,通过网络收发报文,可实现总线仿真节点模块之间的数据交换,从而达到仿真总线的数据通信功能。