Pathways of liquefied petroleum gas pyrolysis in hydrogen plasma:A density functional theory study

A density functional theory(DFT) study has been conducted in this work to investigate the pyrolysis pathways of propane and n-butane,which are the main components of liquefied petroleum gas(LPG),for better understanding the pyrolysis behavior of LPG in hydrogen thermal plasma. Over 60 possible reactions are considered.The reaction enthalpies and activation energies of these reactions are calculated and analyzed with a Gaussian method of B3LYP and basic set of 6-31G(d,p).A most possible reaction pathway is brought up.According to this reaction pathway, the main products of LPG pyrolysis are acetylene,ethylene,methane,ethane and extra hydrogen.Acetylene mainly comes from the pyrolysis of propylene and ethylene,and hydrogen ion reactions are the main source of extra hydrogen gas.Active H·radicals are found to play a very important role in many reactions,and they can remarkably lower the energies needed for reactions.     

X80管线钢钝化膜内点缺陷扩散系数的计算

X80管线钢;扩散系数;点缺陷模型;钝化膜;电容测试法     

Plasma Decomposition and Reduction in Supported Metal Catalyst Preparation

Supported metal catalysts are of importance in chemical engineering. But some disadvantage exists in the conventional method for their preparation. In this review, we summarized our recent works about plasma treatment of catalyst and clarified the phenomena of plasma decomposition and reduction. According to the present research, a criterion is proposed whether the catalyst can be reduced by plasma or not. The plasma reduction has great potential in catalyst preparation.     

22Cr双相不锈钢钝化膜组成及其半导体性能研究

借助于Mott-Schottky方程分析了成膜电位、成膜时间、成膜温度以及氯离子等因素对22Cr双相不锈钢在碳酸氢钠/碳酸钠缓冲溶液中所成钝化膜半导体性能的影响, 同时借助于X射线光电子能谱(XPS)技术分析了所成钝化膜的组成. 结果表明: 22Cr双相不锈钢在碳酸氢钠/碳酸钠缓冲溶液中所成钝化膜呈n-p型半导体结构, 钝化膜内施主/受主密度随成膜电位增加、成膜时间延长、成膜温度降低、以及介质中氯离子浓度的降低而减小, 同时膜对基体保护作用随这些因素变化而增强. 钝化膜的XPS分析表明, 钝化膜呈现双层结构, 外层膜主要由三价铁的氧化物(Fe2O3)组成, 内层膜主要由三价铬氧化物(Cr2O3)以及少量二价铁氧化物(FeO)组成.     

N80油套管钢钝化膜的光电化学性能

采用电容测试法研究了N80油套管钢在浓度为0.5 mol/L NaHCO3溶液中形成钝化膜的半导体性能,结合Mott-Schottky方程分析了测试频率,成膜电位和C l-浓度对钝化膜半导体性能的影响。电容测试结果表明,钝化膜呈n型半导体特性,Mott-Schottky曲线的斜率随着测试频率的增加、成膜电位的正移和溶液中氯离子浓度的增加而增加,相应地膜内的施主密度减小。光电化学实验结果表明,光电流强度随成膜电位的正移及成膜时间的延长而增加,这主要归功于高电位和长时间下所成的钝化膜具有比较均匀的组成,光激发所成的空位或电子在膜内的迁移率的增加。     

温度对铅阳极膜电化学性能的影响

利用线性电位扫描法、交流伏安法、电化学阻抗谱(EIS)及Mott-Schottky方程, 研究了温度对纯铅在4.5 mol/L H₂SO₄溶液中形成的阳极腐蚀膜电性能的影响. 结果表明: 温度对膜电化学性能具有显著的影响, 随着温度的升高, 膜的电阻增加, 孔隙率增加, 传递电阻减小. EIS结果表明膜的生长遵循固相机理, Mott-Schottky曲线显示腐蚀膜呈现n型半导体特性, 随着溶液温度升高, 膜内的施主密度减小.     

铅铈和铅钙锡合金阳极腐蚀膜的性能研究

利用叠加交流伏安法、线性电位扫描法、交流阻抗技术和XPS研究了铅铈合金和铅钙锡合金在阳极1.28 V, 4.5 mol/L的硫酸溶液中所形成的阳极腐蚀膜. 结果表明: 稀土铈能抑制阳极膜中高阻抗的Pb(II)化合物的生长, 降低腐蚀膜的阻抗, 并增加膜的孔隙率. 同时可以提高合金的析氢过电位, 有利于电池免维护性能的提高.     

修饰晶种法合成MFI型分子筛膜包覆的活性炭颗粒

由于分子筛膜的分离和催化作用, 分子筛膜包覆的传统催化剂颗粒可以实现高效的催化过程. 活性炭颗粒作为一种常用的催化剂载体, 由于其表面的憎水性和不平整, 在不规则活性炭颗粒表面直接水热合成包覆一层分子筛膜非常困难. 为了克服上述缺点, 本文采用一种勃姆石凝胶修饰的晶种法在活性炭颗粒表面合成连续的分子筛膜. 以勃姆石溶胶为前驱体, 在活性炭颗粒表面通过喷涂预先形成一层相对平整的勃姆石凝胶层以改善活性炭表面. 在随后的晶种涂覆过程中, 晶种分散液加入部分勃姆石溶胶为胶粘剂, 所得的晶种层覆盖载体完全, 与载体结合牢固, 无需焙烧处理. 将晶种涂覆后颗粒在旋转动态水热175℃处理6 h, 得到分子筛膜包覆的活性炭颗粒, 所得材料分别用X射线衍射和扫描电镜进行表征. 包覆的分子筛膜为MFI 结构, 厚度约为5μm. 对比实验表明, 没有勃姆石溶胶修饰的活性炭颗粒上不能成膜. 这种勃姆石凝胶修饰晶种法为在各种惰性载体上合成分子筛膜提供了便捷的方法.     

Highly efficient Pt/TiO2 photocatalyst prepared by plasma-enhanced impregnation method

Highly efficient Pt/TiO₂ photocatalyst has been prepared using plasma-enhanced impregnation method. Impregnated 0.5 wt%Pt/TiO₂ was treated by plasma followed with thermal calcinations and hydrogen reduction. The catalyst characterizations show that Pt is highly dispersed with a size of 3–5 nm. UV–Vis reflection spectrum suggests it a high photosensitivity in near UV region. Such plasma prepared catalyst exhibits a much higher activity and better metal stability for hydrogen generation from methanol/water mixture, compared to the catalyst prepared conventionally. This highly efficient photocatalyst should have extensive applications in photocatalytic processes.