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通过具体实例说明对于气相反应,使用基于压力的速率方程解题比使用基于浓度的速率方程更直接﹑更简便。总结了具有简单级数的反应的基于压力的速率方程及其特征。 相似文献
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以直线交叉法为依据,根据最小二乘原理,采用Matlab GUI工具设计了一款用于计算二元共聚合反应竞聚率的图形用户程序。与传统的求解竞聚率方法相比,该图形用户程序具有设计原理简单、计算快捷的特点;同时程序提供界面简洁、交互友好的数据输入平台,实用性强。实际应用表明:采用该款图形用户程序所测得的数据与微机动态搜索法、Tidwell-Mortimer法相近,而比采用斜率截距法计算竞聚率的最小差方和更小,并且也避免了采用斜率截距法由于所用方程的非对称性造成的计算结果的不一致性。 相似文献
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众所周知,物理力学性能是照相明胶的一种很重要的属性。在各种彩色及黑白胶片都面向高温快速加工发展的今天,这种属性就显得更为重要。提高胶片的物理力学性能,一方面要从提高明胶本身的胶冻强度着手,例如减少明胶中溶胶组份(分子量小、冷水中溶解度高),提高明胶中的α和β组份的相对含量,减少分子量过大的组份等等。 相似文献
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体毛的化学和头发的保护 总被引:1,自引:0,他引:1
本文介绍了体毛结构和功能的一般化学基础,讨论了毛发的化学特征如氨基酸及微量元素的组成和应用依据,研究了护发的化学方法。作为皮肤附属器官的体毛,特别是头发,除一般的美容化妆外,近10多年来还由于人体微量元素研究的进展而引起人们的重视。曾多次召开过国际人发研究学术讨论会[1],国际原子能研究机构(IAEA)还在全球范围内收集了人发数据,并发布了人发标样(IAEA-HH-1),我国也研制了类似的标准物。在各种病因诊断、法医学研究中,头发分析是重要项目。而在日常消费新潮中,青年人也常把相当多的精力和金钱投放在发型的美化上。因此体毛的化学和头发的保护问题,日益成为化学与生活联系的重要渠道,其社会意义已不容忽视。本文尝试就毛发的结构、功能、组成及可能的病交的化学基础和有关化妆的化学信息作一简介。 相似文献
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在地球的低层地幔下 ,可能存在着比现在的海洋还要多 4倍的水 ,这是日本工业大学的M .Murakami和他的同事们最近估测出来的。日本地球科学家们利用了一种多功能钻探仪 ,通过对 3种据信包含低层地幔中在高温高压下生成的主要矿物组成的分析后 ,得到了这个结论。这 3种矿物是 :Mg perovskite ,Ca perovskite和Magnesiow櫣stite。再利用SIMS对矿物中溶解的氢的含量进行测量 ,矿物学家认为氢是水的标记。发现这3种矿物的含水量都相当可观 ,大约在 0 .2 %至 0 .4 %(重量比率 )之间。用红外… 相似文献
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Fe K‐Edge X‐ray Absorption Fine Structure Determination of γ‐Al2O3‐Supported Iron‐Oxide Species 下载免费PDF全文
Dr. Atsuko Tomita Dr. Takeshi Miki Takeru Tango Tatsuro Murakami Hideyuki Nakagawa Dr. Yutaka Tai 《Chemphyschem》2015,16(9):2015-2020
The structure of FeOx species supported on γ‐Al2O3 was investigated by using Fe K‐edge X‐ray absorption fine structure (XAFS) and X‐ray diffraction (XRD) measurements. The samples were prepared through the impregnation of iron nitrate on Al2O3 and co‐gelation of aluminum and iron sulfates. The dependence of the XRD patterns on Fe loading revealed the formation of α‐Fe2O3 particles at an Fe loading of above 10 wt %, whereas the formation of iron‐oxide crystals was not observed at Fe loadings of less than 9.0 wt %. The Fe K‐edge XAFS was characterized by a clear pre‐edge peak, which indicated that the Fe?O coordination structure deviates from central symmetry and that the degree of Fe?O?Fe bond formation is significantly lower than that in bulk samples at low Fe loading (<9.0 wt %). Fe K‐edge extended XAFS oscillations of the samples with low Fe loadings were explained by assuming an isolated iron‐oxide monomer on the γ‐Al2O3 surface. 相似文献
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Cu-Co bi-metal catalysts derived from CuO/LaCoO3 perovskite structure were prepared by one-step citrate complexing method, and the structure evolution reaction from CuO/LaCoO3 to Cu-Co2C/La202CO3 under 1-12 pretreatment was investigated by techniques of XRD, TPR and TEM. The results suggest that a much higher dispersion of copper significantly enhanced the reduction of cobalt, and a stronger interaction between copper and cobalt ions in LaCoO3 particles led to the formation of bi-metallic Cu-Co particles in the reduced catalysts and the enrichment of Co on the surface of bimetallic particles. The prepared catalysts were highly active and selective for the alcohol synthesis from syngas due to the presence of copper-modified C02C species. 相似文献
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Catalytic properties of Cu-Co catalysts supported on HNO3-pretreated CNTs for higher-alcohol synthesis 下载免费PDF全文
Limin Shi Wei Chu Siyu Deng . School of Materials Chemical Engineering Xi’an Technological University Xi’an Shanxi China . School of Chemical Engineering Sichuan University Chengdu Sichuan China 《天然气化学杂志》2011,20(1):48-52
HNO 3 -pretreated CNTs were employed as supports, and a special ultrasound-assisted impregnation method was designed to prepare supported Cu-Co catalysts for higher-alcohol synthesis from syngas. The catalysts used in this work were characterized by N 2 adsorption-desorption, TEM, XRD, H 2 -TPR, CO-TPD techniques. It was found that the pre-treatment procedure of CNTs remarkably promoted the catalytic properties of the Cu-Co/CNTs catalysts. For the Cu-Co catalyst supported on CNTs pre-treated by 68 wt% HNO 3 , some active components were introduced into the CNTs channels, their dispersions and the amount of strongly adsorbed CO-species were improved. The CO conversion and alcohol yield on the HNO 3 -pretreated Cu-Co/CNTs catalyst were increased by ~21% and ~69%, respectively, compared with those on the normal Cu-Co/CNTs catalyst. 相似文献
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采用连续共沉淀和喷雾干燥相结合的方法制备了微球形 Fe 基催化剂, 采用 N2 吸附-脱附、X 射线衍射和穆斯堡尔谱等手段, 考察了催化剂在不同还原条件下铁物相的转变, 并在浆态床反应器中评价了催化剂的费-托合成 (FTS) 反应性能. 结果表明, Fe 基催化剂在合成气气氛下首先从α-Fe2O3 转变为 Fe3O4, 然后转变为铁碳化物 (FexC); 还原压力的增大有利于 α-Fe2O3 向 Fe3O4 的转变, 而抑制 Fe3O4 向 FexC 的转变; 还原空速的增加则促进 Fe3O4 转变为 FexC. 催化剂的 FTS 反应活性随着催化剂中 Fe3O4 含量的增加而逐渐下降, 而随着 FexC 含量的增加而逐渐上升. 相似文献
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用共沉淀法制备了一系列不同硅含量的铁基催化剂,采用N2吸附和原位X射线衍射对催化剂进行了表征,在固定床反应器中考察了催化剂的费-托合成反应活性、选择性和稳定性.结果表明,含硅的催化剂具有较大的比表面积和较小的平均孔径,在CO还原及费-托合成反应中生成的碳化铁物种的稳定性比不含硅的催化剂高.在费-托合成反应中,不含硅的催化剂具有较高的初始活性,但易失活;含硅的催化剂具有较低的初始活性,但稳定性较高.Fe7C3是活性最高的碳化铁物种.随着硅含量的增加,催化剂的费-托合成反应更易生成低碳数产物. 相似文献
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MgFe2O4纳米粉体的水热合成及其表征(英) 总被引:3,自引:0,他引:3
MgFe2O4 nanoparticles were hydrothermally synthesized at 150 ℃ using iron nitrate [Fe(NO3)3·9H2O], magnesium nitrate [Mg(NO3)2·6H2O] and sodium hydroxide (NaOH) as starting materials by carefully controlling the reaction conditions. The influences of several factors such as presence or absence of Na+, molar ratio of Fe3+ / Mg2+, concentration of mental ions, temperature and reaction time on resultant products were investigated in the hydrothermal process. The sample was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), and its magnetic properties were measured using vibrating sample magnetometer (VSM). 相似文献
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Ju Li SHEN Hua Zhang LIU Xiao Nian LI Weng Feng HAN Yi Fan ZHENG 《中国化学快报》2005,16(10):1393-1396
The effect of the precursor composition of fused iron catalyst on the performance of Fischer-Tropsch synthesis was investigated. XRD, BET and CO2 adsorption experiments were carried out to provide better insight into the relationship therein. The results showed that the selectivity of C5+ hydrocarbon products was dependent on the mole ratio of Fe^2+/Fe^3+, which was represented by a hump-shaped curve. Catalysts with precursors containing Fe3O4 phase favored the magnetite spinal formation during F-T reaction, while Fe(1-x)O-based catalysts were more likely to favor the formation and growth of the iron carbide crystals. 相似文献