KINETIC AND TRACER STUDIES ON METHANOL CONVERSION OVER SUPPORTED PLATINUM CATALYSTS

Hydrogen-deuterium exchange in methanol over Al₂,O₃, platinum black and alumina supported platinum catalysts have been investigated by means of mass spectrometry. The hydrogen-deuterium exchange proceeds faster over Pt/Al₂O₃ than either platinum black or alumina, and the rate (as well as the rate of dimethyl ether formation) increases with platinum dispersion. From the reactions CH₃OH + D₂, CD₃OH + H₂ and CD₃OH + D₂ the different exchange rates of the CH₃ and OH groups (R₁, and R₂, respectively) were determined. For all catalysts studied the exchange in the OH group was two or three orders of magnitude faster than CH₃ group. Exchange in the methyl group needs higher activation energy: R₁/R₂ ratio increases with temperature. Catalyst pretreatment has an important effect: higher activation temperature results in a higher R₁/R₂ ratio.

A methematical method is suggested for the evaluation of exchange rates of a molecule with two different types of hydrogen and a model is given for the interpretation of measured data: methanol is activated mainly on Al₂,O₃, forming surface methoxide groups on the Lewis acidic sites. This methoxide can react with deuterium atoms having been activated over platinum sites. With increasing dispersion the metal-support interface is enhanced which leads to higher rate of exchange.     

聚乙烯转光棚膜的加工及应用研究

本文对聚乙烯转光棚膜的加工和光转换剂的作用、配比关系及物理性能进行了讨论。     

Conversion measurement in polyethylene/peroxide coupling system under steady shear flow

The coupling reaction of melt linear low density polyethylene (LLDPE) initiated by dicumyl peroxide (DCP) in steady shear flow field was investigated. The conversion of DCP was measured by electron spin resonance (ESR) and chemical titration. An absolute method was proposed to calculate the actual conversion of DCP from rheological data. The coupling efficiency of DCP was obtained from those analyses, which was shown to increase at first, reach a maximum and then decrease in the end stage. A linear relationship between the coupling efficiency of DCP and the concentration of macroradicals was also found in the experiments.     

双氧水生产装置应用变频调速的节能改造技术

本文简述了在双氧水生产装置上应用变频调速技术对物料输送系统改造，实现有效节省能耗，降低生产成本，提高生产效率。     

民间陶瓷的现实意义

中国民间陶瓷流传远久,传递着中华大地自然的禀赋与历史的繁荣,不论造型结构、式样,或是装饰题材、内容,都是现代陶瓷艺术可借鉴的经验与成果,将民间陶瓷文化的视觉信息符号或元素融入现代陶瓷艺术之中,使民间的陶瓷语言转换为现代陶瓷艺术的话语应是当下陶艺创作的思考方向。     

空气钻转为泥浆钻的技术分析与探讨

对空气钻转为泥浆钻的气液转化技术进行优化配方,为提高上部地层钻进速度找到了一条切实可行的成功之路。实践表明:(1)气液转化技术应从化学因素和钻井工艺因素入手,除选择高效钻井液体系、合理的钻井液密度外,还应采用封堵固壁技术,封固地层微裂隙,提高地层整体强度,达到稳定井壁的目的,并且稳定井壁必须采取多专业多学科共同治理才有成效。(2)建南地区巴东组以上地层相对稳定,适合空气钻井作业,如果配合使用空气锤,速度提高幅度会更大(在普光106井的气体钻井由于使用了空气锤,机械钻速达到10m/h以上)。     

浅谈债务转为资本存在的问题及解决对策

债务转为资本是债务重组的方式之一,是指债务人将债务转为资本,同时债权人将债权转为股权的债务重组方式。本文将分析这一重组方式在重组运作过程中存在的问题,并提出一系列的解决对策。     

海洋温差能发电冷水管涡激振动性能

以海洋温差能发电（Ocean Thermal Energy Conversion,OTEC）平台的冷水管为研究对象,根据结构方程和尾流振子方程建立冷水管流固耦合模型,采用有限元方法和 法对冷水管涡激振动（Vortex-Induced Vibration,VIV）进行时域分析,并在MATLAB软件中开发相应的求解程序。针对冷水管所面临的复杂工况,分别研究外部流场、内部流场、长径比和压载质量等因素对VIV产生的影响。结果表明：随着外流流速和长径比的增大,冷水管横流向VIV模态和振动幅值也发生相应改变,振动强度呈现波动上升;在不发生动态失稳的情况下,内流流速的增加可有效减小冷水管横流向振动幅值,压载质量可大幅减小冷水管自由端的振动位移。     

The characterization and corrosion resistance of cerium chemical conversion coatings for 304 stainless steel

A golden yellow-colored cerium conversion coating was obtained on 304 stainless steel surface by immersing the steel into a solution containing cerium (III), KMnO₄ and sulfuric acid. The corrosion resistance of the coatings was evaluated by electrochemical methods, potentiodynamic polarization experiments and electrochemical impedance spectrum. The experimental results indicated that the corrosion resistance for the conversion coated 304SS in 3.5% NaCl solution increased markedly. The corrosion potential of the treated steel increased to a more noble level, the pitting corrosion potential increased also, the passive potential range was enlarged markedly and the passive current density decreased about one order compared to that of the untreated steel. The cathodic and anodic reaction were both inhibited to some extent. The chemical state of the elements in the coatings was investigated by XPS. The cerium element was in the form of tetravalent state. And AES depth profile analysis suggested that the thickness of the conversion coatings was less than 66 nm. The mechanisms of coatings formation and corrosion resistance are discussed.     

Investigations on composition and morphology of electrochemical conversion layer/titanium dioxide deposit on stainless steel

In this study, the formation and characterization of conversion coatings modified by a sol-gel TiO₂ deposit were investigated as a way to develop a new photocatalyst for water and air depollution. The conversion coating, characterised by strong interfacial adhesion, high roughness and high surface area facilitates the sol-gel deposition of titania and enhances its adhesion to the substrate. The conversion treatment is carried out in an acid solution. Observation by Scanning Electron Microscopy (SEM) reveals a rough surface with pores and cavities. According to SIMS measurements, the thickness of the initial conversion layer is evaluated at about 1.5 μm. On this pre-functionalised support, the titanium dioxide was deposited by the sol-gel method. The roughness measurements coupled with SIMS analysis allowed a precise evaluation of the surface state of the final layers. The coating consists of two layers: a TiO₂ outer layer and an inner layer containing iron chromium oxides. Characterization by X-ray diffraction (XRD) showed the existence of the TiO₂ anatase structure as the main compound.