正庚烷在超稳Y沸石(USY)负载超强酸催化剂上加氢异构化

The Pt-bearing SO₄^2-/ZrO₂ superacid catalysts supported on ultra stable Y (USY) zeolite were prepared by impregnation and characterized by X-ray diffraction, nitrogen adsorption and Hammett indicators. Their catalytic activities were evaluated in the hydroisomerization of n-heptane with an atmospheric fixed-bed reactor. The catalysts possessed a high surface area, superacidity and well maintained pore structure of USY support. The supported catalysts with a suitable SO₄^2-/ZrO₂ loading exhibited a higher catalytic activity and selectivity than the unsupported SO₄^2-/ZrO₂ catalyst or the Pt supported on USY catalyst without superacid. At the reaction temperature of 220 ℃, over the catalyst with a Pt loading of 0.8wt% and ZrO₂ loading of 10wt%, the conversion of n-heptane could be as high as 35.2% with a selectivity of 87.9% for isomerization products.     

分叉碳纳米管的催化生长

Branching carbon nanotubes were synthesized by pyrolysis of acetylene at 700℃ over oxygen-free copper and γ-Al₂O₃-supported Cu unitary or Cu/Fe binary catalysts. The morphologies of the as-grown products were charac-terized by transmission electron microscopy. The results indicated that the branching structures were closely related to the Cu component of the catalysts. We proposed that the special electronic structure (3d¹⁰4s¹) of Cu play the crucial role in the formation of the heptagon defects related to the branching structures.     

Cr/CeO2体系及其对乙烷脱氢反应催化性能的研究

The dehydrogenation reaction of ethane over Cr/CeO₂ catalysts in presence of CO₂ was studied with fixed-bed micro-reactor. The Cr/CeO₂ catalysts of different Cr loading have been synthesized using impregnation techniques. The Cr/CeO₂ system has already been found to be active and selective in the reaction at around 740 ℃. The function of carbon dioxide is to remove coke and hydrogen to accelerate dehydrogenation of ethane. The results of catalysts characterizations indicated that Cr³⁺ and Cr⁶⁺ occurred on the surface of the catalysts. The 1.2 mmol Cr/100m₂ CeO₂ catalyst sample with a monolayer dispersion of Cr on CeO₂ support showed a stronger surface acidity and a maximum yield of ethylene of about 35.5% at 36.6% conversion of ethane.     

Carbon Nanotubes Supported Pt-Ru-Ni as Methanol Electro-Oxidation Catalyst for Direct Methanol Fuel Cells

Carbon nanotubes (CNTs) supported Pt-Ru and Pt-Ru-Ni catalysts were prepared by chemical reduction of metal precursors with sodium borohydride at room temperature. The crystallographic properties and composition of the catalysts were characterized by X-ray diffraction (XRD) and energy dispersive X-ray (EDX) analysis, and the catalytic activity and stability for methanol electro-oxidation were measured by electrochemical impedance spectroscopy (EIS), linear sweep voltammetries (LSV), and chronoamperometry (CA). The results show that the catalysts exhibit face-centered cubic (fcc) structure. The particle size of Pt-Ru-Ni/CNTs catalyst is about 4.8 nm. The catalytic activity and stability of the Pt-Ru-Ni/CNTs catalyst are higher than those of Pt-Ru/CNTs catalyst.     

Effect of rare earths on selective hydrogenation of p-chloronitrobenzene over PtMOx/CNTs catalysts

The effect of rare earths(Sm,Pr,Ce,Nd and La)on the hydrogenation properties of p-chloronitrobenzene(CNB)over Pt/CNTs catalyst was studied in ethanol at 303 K and normal pressure.The results exhibited that the hydrogenation of p-CNB could be carded out over PtMOx/CNTs catalysts.Both catalytic activities and yields of p-chloroaniline(CAN)were all improved.PtCeOx/ CNTs catalyst exhibited the best catalytic activity(TOF was 0.47 s~(-1))and the highest yield of p-CAN(97.5 mol%).PtCeOx/CNTs (1.0 wt%)catalyst ...     

溶剂化金属原子浸渍法制备Pd-Cu/γ-Al2O3低温CO氧化催化剂

Nano-particle Pd/γ-Al₂O₃ monometallic and Pd-Cu/γ-Al₂O₃ bimetallic catalysts were prepared by solvated metal atom impregnation (SMAI) method. The results of XRD measurement indicated that Pd- Cu alloy was formed in the bimetallic catalysts and the crystalline particle size of the alloy increased as Cu contents increased with av-erage diameters < 6.0nm for all the samples. XPS and Auger spectra showed that Pd was in zero- valent state, Cu existed mainly in zero- valent state and partially in monovalent state Cu⁺. The Pd/γ-Al₂O₃ and Pd-Cu/γ-Al₂O₃ catalysts exhibited higher activity for CO oxidation at low temperature. The activity of Pd-Cu/γ-Al₂O₃ bimetallic catalyst was higher than that of Pd/γ-Al₂O₃ monometallic catalyst. The Pd-Cu/γ-Al₂O₃ catalyst with Pd/Cu atomic ratio of 1∶1 showed the highest activity.     

水热改性对NiMo/γ-Al2O3加氢脱氮催化剂结构及性能的影响

The influence of hydrothermal modification on the structure and hydrodenitrogenation (HDN) activity of NiMo/γ-Al₂O₃catalyst was studied in the range 140～180 ℃. The experimental results indicated that the hydrodenitrogenation reaction rate of pyridine was accelerated using the NiMo/γ-Al₂O₃catalyst synthesized via hydrothermal route due to the change of the structure, the increase of the amount of Mo and Ni and the rise of the specific surface area. The change of the structure of catalysts was enhanced at higher hydrothermal temperature, producing NiMo/γ-Al₂O₃catalyst with better HDN activity.     

New Rh—ZnO／Carbon Nanotubes Catalyst for Methanol Synthesis

A new catalyst for methanol synthesis,ZnO-promoted rhodium supported on carbon nanotubes,was developed.It was found that the Rh-ZnO/CNTs catalyst had high activity of 411.4mg CH3OH/g/cat/h and selectivity of 96.7% for methanol at 1 MPa and 523 K.The activity of this catalyst is much higher than that of NC 207 catalyst at the same reaction conditions.It was suggested that the multi-walled strueture CNTs favored both the couple transfer of the proton and clectron over the surface of the catalyst and the uptake of hydrogen which was favorable to methanol synthesis.     

MWPCVD低温合成纳米碳管的生长机理

The synthesis of carbon nanotubes (CNTs) at low temperature has received a great deal of attention and be-comes a challenging issue. But few model which accounts for the growth of CNTs is suited for the synthesis of CNTs by microwave plasma chemical vapor deposition (MWPCVD) at low temperature because most researchers conclude that the growth mechanism is determined by the catalyst-supporter interaction while ignored the diffusion of carbon in the catalyst. In this paper, under the catalytic effect of cobalt supported by SiO₂ and Al₂O₃, CNTs are synthe-sized by MWPCVD at about 500℃, and tip-growth, the model which accounts for the catalytic growth of CNTs is outlined. It is the temperature difference between the upper and bottom of the catalytic particle that results in the diffusion of carbon atoms from upper to the bottom, and precipitation of saturated carbon on the bottom surface to form CNTs.     

碳纳米管负载的Fe2O3催化剂制备

Carbon nanotubes were modified by FeSO₄-H₂O₂ system, iron hydroxides were adsorbed on the wall of carbon nanotubes simultaneously. These precursors were treated at 723K for 2 h under hydrogen, nitrogen and air atmosphere to prepare carbon nanotubes supported γ-Fe₂O₃catalyst, γ-Fe₂O₃and α-Fe₂O₃compound catalyst and amorphous Fe₂O₃catalyst, respectively. This is green method to prepare high Fe₂O₃loading (≥50 %) catalyst without adding other cation. The different structures Fe₂O₃catalysts can be synthesized by controlling the condition of thermal treatment to content active phase requirements for different catalytic reactions. The paper presents a new method to prepare carbon nanotubes supported catalysts.     

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。     

氯氧化镁生成热的研究

用氧化镁氯化镁水溶液制备了8水合氯氧化镁[nMg(OH)2·MgCl2·8H2O], 并测定了其在盐酸中的溶解热, 实验结果表明, 氯氧化镁溶解热与n值呈线性关系, 根据溶解热求出5Mg(OH)2·MgCl2·8H2O和3Mg(OH)2·MgCl2·8H2O的生成热分别为-7727.1和5888.1kJ·mol^1^-。