整体式Pd/La_2O_3-Al_2O_3和Pd/CeO_2-ZrO_2-Y_2O_3催化剂上汽油车尾气净化性能的比较

采用共沉淀法制备了耐高温高比表面积的La2O3-Al2O3(LA)材料和CeO2-ZrO2-Y2O3(CZY)储氧材料,并用浸渍法制备了整体式Pd/LA和Pd/CZY汽油车尾气净化三效催化剂,考察了它们的三效催化性能和空燃比性能,并单独通过水煤气变换和CO氧化反应性能的考察,探讨了两种催化剂空燃比窗口扩大的原因.结果表明,Pd/CZY催化剂三效窗口明显较宽,且催化氧化CO的性能明显更优;对于CO+NO反应,Pd/CZY催化剂的活性较高.当反应中逐步通入O2后,抑制了该反应的进行,但CO氧化的转化率升高,而NO转化率降低,直至CO+NO反应完全被抑制,表明CO氧化反应对于抑制催化剂在NO贫燃方向的窗口具有一定的作用.另外,Pd/CZY催化剂上对于水煤气变换反应性能明显优于Pd/LA催化剂,在一定温度下逐步通入O2后,不会抑制水煤气变换反应的发生;当逐步通入NO时,可以促进水煤气变换反应的进行,表明Pd/CZY催化剂在富燃时对扩展CO转化窗口的性能明显优于Pd/LA催化剂.     

富氧条件下贵金属催化剂上丙烯选择性还原NO研究

用溶胶-凝胶(Sol-gel)法制备了以γ-Al₂O₃为载体,以Pt,Pd和Rh等为活性组分的单组分及双组分催化剂,在稀燃汽油机条件下评价了丙烯对NO的选择性催化还原活性.结果表明,在单组分催化剂中,催化剂的活性及顺序为Rh(73%)>Pt(65%)>Pd(47%),最高活性对应的温度分别为Pt(225℃),Pd(275℃)和Rh(375℃),N₂选择性顺序为Rh,Pd(>80%)>Pt(48%),氧化性顺序为Pt>Rh>Pd.Sol-gel制备的双组分催化剂中的不同贵金属活性位具有一定的协同效应,可明显拓宽活性温度范围,其中以Pt-Rh组合活性最好.Rh/Al₂O₃和Pt/Al₂O₃两种催化剂分层有序填装时,可提高C₃H₆的利用率,在200～450℃范围内,可有效地催化净化NO.     

添加贵金属的Ni/α-Al2O3催化剂甲烷部分氧化制合成气的研究

甲烷部分氧化制合成气因其高空速、高转化率、低H2/CO比而引起人们的重视[1～5].本文研究了在Ni/α-Al2O3催化剂中添加的Rh、Ru、Pt和Pd等贵金属在甲烷部分氧化制合成气反应中的催化作用,重点研究了添加Pt对Ni/α-Al2O3催化剂反应性能的影响.     

Pt/HM、Pd/HM催化剂上CO氧化反应活性和动力学研究

研究了Pt/HM、Pd/HM催化剂上CO氧化反应的活性,求出了各种催化剂的CO氧化反应动力学方程。考察了不同气氛下CO氧化活性的演变规律和V⁴⁺、Co²⁺离子对Pt、Pd的助催化作用,并用催化剂集团结构适应模型对以上结果作出了解释。     

柴油尾气DOC催化剂Pt-Pd/CeO2的活性和抗硫性

采用浸渍法制备了不同Pt、Pd比例的Pt-Pd/CeO₂催化剂,考察了其催化氧化模拟柴油车尾气的活性,并测试了抗硫性。活性测试结果表明,Pt、Pd协同降低了催化剂的起燃温度,其比例对催化剂性能影响很大,其中,Pt_0.2Pd_0.8/CeO₂催化剂在模拟柴油车尾气(丙烯(C₃H₆)、一氧化碳(CO)和一氧化氮(NO))中的催化活性最高;C₃H₆的t₅₀降到170℃,CO的t₅₀降到了150℃,显示了良好的Pt、Pd协同效应;H₂-TPR表征和抗硫性结果分析表明,高比例Pt/Pd催化剂具有更多的表面活性氧,其相对数值与催化剂抗硫性能的关联度高,在催化剂硫酸盐中毒的条件下,更有利于催化反应的进行。     

钯基三效催化剂在实际排气体系中的应用性研究

将实验室制备的钯基三效催化剂在工厂实际条件下放大,制备了钯基三元催化净化器.分别考察了其在实验室配气条件下催化活性,及按照国家催化转化器认定技术条件进行的发动机老化及工况法排放性能.所制备的净化器具有等同于传统Pt/Pd/Rh或Pt/Rh催化剂的催化性能.     

催化型DPF对车用柴油机气态污染物的影响研究

基于催化器小样评价测试仪对催化型颗粒捕集器CDPF小样进行活性评价,再结合柴油机台架性能测试,采用AVL(Systemforemissionsamplingandmeasurement,SESAM)FT-IR傅里叶变换红外光谱仪对全尺寸CDPF进行柴油机气态污染物影响研究,综合分析不同催化剂的CDPF对柴油机排放(二次气溶胶)气态前体物的影响。结果表明,随贵金属含量的增加,CDPF小样对CO、C3H8的起燃温度t50依次降低。相同物种起燃温度因相同比例贵金属的剂量不同而异。在高温时,催化剂中贵金属含量、价态以及混合气组分协同作用对C3H8转换效率影响明显;在柴油机台架性能实验中,全尺寸CDPF对CO、THC具有更低的起燃温度。在适度反应温度范围内,增加Pt负载量会促进NO氧化,Pd多以氧化态PdO存在促进NO的氧化,并且PdO还原成的Pd会促进催化剂热稳定性。NO氧化生成NO2的过程受到NO2浓度的抑制,同时也受柴油机排气中氧浓度的影响。在Pt、Pd和Rh同在的催化剂中,Pd含量较低的CDPF对SO2的吸附量较大,但随温度升高,助剂中CeO2促进SO2脱附,使CDPF具有一定的抗硫性。     

铑、镧对贵金属尾气净化催化剂性能的影响

研究了Rh对Pt-Pd/Al2O3汽车尾气净化催化剂的三效性能及其对CO, O2和C3H6的吸附性能的影响.研究了镧对Pt-Pd-Rh/Al2O3尾气净化催化剂的活性、耐热性能的影响.结果表明,在没有助剂的情况下, Rh是Pt-Pd-Rh/Al2O3三效催化剂中一个必不可少的组元,它在贵金属催化剂中主要是调整金属键的d百分数.镧是Pt-Pd-Rh贵金属催化剂的一种性能良好的助剂.     

Pd/γ-Al2O3三效催化剂中CeO2助剂的作用

 研究了以浸渍法制备的以氧化铈为助剂的Pd／CeO2－Al2O3催化剂,对丙烯和一氧化碳氧化及一氧化氮还原反应的三效催化活性．主要考察了钯及CeO2助剂含量对催化剂三效转化活性的影响,并对部分催化剂进行了X射线光电子能谱（XPS）及氧饱和吸附后NO吸附的程序升温脱附－质谱（TPD－MS）表征．结果表明,在Pd含量（不大于1．0％）较低时,增加Pd含量可明显提高催化剂的活性．适量的CeO2能使Pd催化剂具有较好的热稳定性及富氧条件下的转化活性,过量的CeO2会降低催化剂的热稳定性．CeO2助剂使Pd／CeO2－Al2O3催化剂中的Pd2＋较易被还原为Pd0,并促进Pd上NO的解离吸附．     

负载金属助催化剂MgAl-LDO/TiO2的光催化还原CO2性能

通过原位光沉积将不同贵金属Cu、Ag、Au、Pt、Rh、Pd和Cu-Pt、Cu-Pd、Pt-Pd、Au-Ag作为助催化剂负载在MgAl层状双金属氧化物(MgAl-LDO)/TiO_2催化剂表面,研究了助催化剂种类对MgAl-LDO/TiO_2的光催化还原CO_2性能的影响.结果表明:沉积Cu、Ag、Au、Rh和Ag-Au时,还原反应倾向于生成CO,而沉积Pt、Pd、Cu-Pt、Cu-Pd和Pt-Pd时,反应倾向于生成CH_4.在所选择的助催化剂体系中,Au是最佳的单一金属助催化剂,Cu-Pt则是最佳的双金属助催化剂体系.     

Dichroism of absorption and polarization of phosphorescence of molecules of the closed form of nitrobenzospirothiopyran

The spectral-polarization characteristics of absorption and phosphorescence of molecules of the initial form of nitro-substituted indolinospirobenzothiopyran were studied in oriented polyethylene films and in solutions with different polarity. An oscillator model of the electron transitions responsible for the formation of absorption and luminescence spectra was suggested. It was established that the principal differences in the spectral and photophysical properties of the compound studied and its oxygen-containing analog are associated with the fact that the electronegativity of the S atom is lower than that of the O atom. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1143–1146, June, 1997.     

Synthesis of phenolic components of Grains of Paradise

Two vanilloids, (5E)-8-(4-hydroxy-3-methoxyphenyl)oct-5-en-4-one (1) and 4-[3-hydroxydecyl]-2-methoxyphenol (2), isolated from the dried seeds of Grains of Paradise (Aframomum melegueta), were synthesized; the latter compound was made as the S-enantiomer and the material derived from the seeds was found to be a 1:1.7 mixture of the R and S isomers. The synthetic route used should allow the preparation of analogs having extended alkyl chains and consequently different lipophilicity, and 3, a homolog of 2, was also prepared.     

非那雄胺合成工艺改进

非那雄胺能抑制5α-还原酶的活性,明显降低二氢睾酮水平,是一种治疗良性前列腺增生的有效药品。该合成工艺以甾烯酮酸为原料,将其与氯化亚砜反应,无须分离即与叔丁胺反应得17β-酰胺化合物,再氧化开环,环合,氢化,脱氢合成了非那雄胺。经元素分析、IR、1HNMR、13CNMR、MS分析表征了其结构。该法无须使用昂贵的2,2-二吡啶二硫化物和剧毒药品苯亚硒酸酐,且以乙酸铵代替氨气,降低了对设备的要求和腐蚀,更适用于工业生产。     

Study of hydration of two cements of different strengths

Main hydration products of two cement pastes, i.e. CSH-gel, portlandite (P) (and specific surface S) were studied by static heating, and by SEM, TEM and XRD, as a function of cement strength (C-33 and C-43) hydration time (th) and subsequent hydration in water vapour.Total change in mass on hydration and air drying, M_o, increased with strength of cement paste and with hydration time. Content of water escaping at 110 to 220°C, defined as water bound with low energy, mainly interlayer and hydrate water, was independent on cement strength but its content increased with (th). Content of chemically bound (zeolitic) water in CSH-gel, escaping at 220-400°C, was slightly dependent on strength and increased with (th). It was possibly derived from the dehydroxylation of CSH-gel and AFm phase. Portlandite water, escaping at 400-500°C, was independent on cement strength and was higher on longer hydration. Large P crystals were formed in the weaker cement paste C-33. Smaller crystals were formed in C-43 but they increased with (th). Carbonate formated on contact with air (calcite, vaterite and aragonite), decomposed in cement at 600-700^oC. It was high in pastes C-33(1 month) and C-43(1 month), i.e. 5.7 and 3.3%, respectively; it was less than 1% after 6 hydration months (low sensitivity to carbonation) in agreement with the XRD study showing carbonates in the air dry paste (1month), and its absence on prolonged hydration (6 months) and on acetone treatment. Water vapour treatment of (6 months) pastes or wetting-drying increased this sensitivity.Nanosized P-crystals, detected by TEM, could contribute to the cement strength; carbonate was observed on the rims of gel clusters.This revised version was published online in November 2005 with corrections to the Cover Date.     

Determination of heats of detonation and influence of components of composite explosives on heats of detonation of high explosives

The heats of detonation of 20 simple high explosives and explosive mixtures were determined by means of an adiabatic detonation calorimeter designed by the authors. The results indicated that the performance of the instrument was reliable and the experimental data were very accurate. For explosive mixtures, there was a linear accumulative relationship between the heats of detonation of the explosive mixture and its components. Accordingly, the heats of detonation of explosive mixtures could be calculated directly from the heats of detonation of simple explosives and the characteristic heats of other components. The experiments showed that the gold or brass shell of the cylindrical charge could be substituted by a thick-walled porcelain shell, which had the advantage of cheapness.

     

Investigation of Kinetics of Solid-Phase Synthesis of Lithium Orthosilicate

The kinetics of the interaction between lithium carbonate and silica with various degrees of dispersion was investigated by TG and DTA methods. It was found that the utilization of pyrogenic silica with a specific surface area of about 300 m²g^-1 instead of aerosil with one of 175 m²g^-1 leads to an increase of the reaction rate between lithium carbonate and silica, which depends on the formation and growth of lithium orthosilicate crystals in the first stage, and is conditioned by the diffusion of lithium and oxygen ions through the lithium orthosilicate layer formed at temperatures above 800 K. This supposition is supported by the kinetic analysis results obtained with the use of the different models. The optimal regime of heating is recommended. This revised version was published online in July 2006 with corrections to the Cover Date.     

小环化合物中饱和碳质子化学位移的计算

小环化合物由于其张力、构型、构象和各向异性效应等原因,环碳上质子化学位移缺乏规律性,难以预测,对此作者曾提出一种近似算法。本文根据303种小环化合物中饱和碳质子的化学位移实验数据,将适于计算这类质子化学位移的公式表述为:     

恶臭嗅辨实验室建设探讨

针对恶臭测试的环境影响问题,提出了解决的实例方案,并对方案的要点及优缺点进行讨论,此方案在实际操作中具有较好的效果。     

结合实际发展电化学科学─—武汉大学电化学研究室工作简介

结合实际发展电化学科学─—武汉大学电化学研究室工作简介查全性,陆君涛（武汉大学化学系电化学研究室,武汉４３００７２）在物理化学的众多分支学科中,电化学长期保持良好的发展势头。除了电化学所研究的体系（溶液、电极／溶液界面等）具有广泛的基础意义外,促使电...