Insoluble polystyrene-bound quaternary onium salt catalysts for the synthesis of cyclic carbonates by the reaction of oxiranes with carbon dioxide

The addition reaction of oxiranes ( 26a—e ) with carbon dioxide (CO₂) was performed using insoluble polystyrene beads containing pendant quaternary ammonium or phosphonium salts as catalysts under atmospheric pressure. The reaction of 26a—e with CO₂ proceeded smoothly catalyzed by 1–2 mol % of the polymer-supported quaternary onium salts to give the corresponding cyclic carbonates ( 27a—e ) in high yields at 80–90°C. In this reaction system, the catalytic activity of the polymer-supported quaternary onium salts was strongly affected by the following factors: degree of ring substitution (DRS) of the onium salt residues to the polymer, degree of crosslinking (DC) of the polystyrene beads, chain length of the alkylene spacer between the polymer back-bone and the onium salt, hydrophobicity of the alkyl group on the onium salts, and kind of onium salts. That is, the polymer-supported quaternary phosphonium salts with low DRS and DC and with long alkylene spacer chain were found to have higher catalytic activity than low molecualr weight quaternary onium salts. The above polymer-supported catalysts can easily be separated at the end of a reaction by filtration and can be reused for at least seven runs. It was also found that the rate of reaction was proportional to the products of catalyst concentration and oxirane concentration. © 1993 John Wiley & Sons, Inc.     

Density of supercritical CO_2-tetrahydrofuran binary mixture and the partial molar volume of the cosolvent

The densities of supercritical CO2-tetrahydrofuran (cosolvent) binary mixture weremeasured at temperatures in range of 308.15 to 323.15 K and at pressure up to 16.5 MPa.The concentrations of tetrahydrofuran were from 0 to 0.57 mol/L.The partial molar volume of tetrahydrofuran was calculated based on the relationship between the density of the mixture and the concentration of the cosolvent.It is observed that the partial molar volume of the cosolvent is negative and the absolute value decreases with increasing pressure and the concentration of the cosolvent.     

Determination of Diffusion Coefficients for Binary Nonelectrolyte Mixtures. A Free-Volume Predictive Approach

A diaphragm cell has been used to measure mutual diffusion coefficients at 25°C for four binary nonelectrolyte mixtures: ethylbenzene + n-hexane, carbon tetrachloride + ethylbenzene, cyclohexane + p-xylene, and 1,2-dichloroethane + cyclohexane. A free-volume predictive approach for binary mutual diffusion coefficients was developed and tested. Only infinite dilution diffusion coefficients, some readily available pure substance data, and UNIFAC group contribution parameters are used in the model. No binary equilibrium thermodynamic information is required. For 73 binary systems with an overall average absolute deviation of 5.2%, it has been shown that the developed method is better than two commonly available reference methods for the prediction of liquid diffusion coefficients.     

Carbon dioxide reduction under visible light: a comparison of cadmium sulfide and titania photocatalysts

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互通多孔碳/二氧化锰纳米复合材料的原位水热合成及电化学性能

以互通多孔碳（IPC）为载体，水热条件下在碳表面原位反应生成纳米结构的二氧化锰（MnO₂），制备互通多孔碳/二氧化锰纳米（IPC/MnO₂）复合电极材料. 采用扫描电镜（SEM），透射电镜（TEM），X射线衍射（XRD），热重分析（TGA）对其结构进行表征；采用循环伏安法、恒流充放电和交流阻抗对其电化学性能进行研究. 结果表明：生成的MnO₂均匀地负载在碳的表面，形成多层次结构，并且随着温度的升高IPC表面负载的MnO₂由纳米颗粒变为纳米片状结构；MnO₂纳米片具有典型的K-Birnessite 型晶体结构；复合物中MnO₂的含量约为34%（w）. 在100 ℃制备的IPC/MnO₂复合材料在三电极系统中最高比电容达到了411 F·g^-1；随着反应温度的升高,比容量先增长后基本保持不变. 以IPC/MnO₂为正极，活性炭（AC）为负极，1 mol·L^-1 Na₂SO₄溶液为电解液组装成IPC/MnO₂//AC 混合超级电容器，发现IPC/MnO₂电极的电容器其电位窗口从1 V扩展到1.8 V，容量可达86F·g^-1，且表现出良好的电容特性和大电流放电性能.     

缓慢炭化部分氧化对制备煤质活性炭的影响

研究了炭化升温速度、炭化低温区引入空气部分氧化对活性炭制备过程中炭化阶段、炭化物结构、活性炭性能等的影响。结果表明，炭化时低温部分氧化可提高炭化物得率，使炭化物微晶的ｄ００２值升高和Ｌｃ值减小；而较慢的炭化升温速度有利于制备优质活性炭。缓慢炭化、部分氧化可以在一定程度上控制炭化路径，使炭化向生成取向性差、难石墨化、各向同性、呒定形炭多的炭化物的方向进行；并讨论了它们控制炭化的作用机理。以此为指导，     

Electrochemical instability of bis(trifluoromethylsulfonyl)imide based ionic liquids as solvents in high voltage electrolytes for potassium ion batteries

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A hybrid nonaqueous electrochemical supercapacitor using nano-sized iron oxyhydroxide and activated carbon

A beta-iron oxyhydroxide (FeOOH) was synthesized via a hydrolyzing route and investigated as a lithium intercalation host. It delivers a capacity of about 170 mAh/g and exhibits good cycling performance when charged/discharged in the voltage range from 1.6 V to 3.3 V. For the first time we have confirmed that FeOOH is suitable for using it as a negative electrode for hybrid electrochemical supercapacitor assembled with an activated carbon positive electrode in 1.0 M LiPF₆ ethylene carbonate/dimethyl carbonate (EC/DMC, 1:2 in volume) solution. The cell reveals a slightly sloping voltage profile from 0 V to 2.8 V and gives an estimated specific energy of 45 Wh/kg based on the total weight of two electrode materials, approximately two times of carbon/carbon electrochemical double layer capacitors. The hybrid supercapacitor shows a good cycling performance, it remains approximately 96% of initial capacity after 800 cycles at a charge/discharge rate of 4 C. The capacitor also shows a desirable rate capability, even at 10 C discharge rate, it holds 80% of capacity compared with that at 1 C discharge rate.     

Catalytic oxidation of CO,hydrocarbons, and ethyl acetate over perovskite-type complex oxides

The catalytic activity of M^IM^IIO₃] perovskite-type complex oxides (M^I = La, Y, Nd, Yb; M^II = Co, Mn, Ni) in the oxidation of CO, propylene, benzene, ethylbenzene,o-xylene, and ethyl acetate was investigated. The Co-containing catalysts were shown to be more active in the oxidation than the Mn-containing catalysts. A relationship between the catalytic and adsorption properties was established.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 602–605, April, 1994.     

Mechanistic Aspects of Carbon Nanotube Nucleation and Growth

The discovery, synthesis, characterization, and applicability of carbon nanotubes have produced tremendous excitement and interest among scientists and engineers. In particular, the use of these unique tubular nanostructures for new strong lightweight materials, nanoelectronics, fuel storage and cells, electron emitters and bio, scanning probe microscopy, and chemical sensing devices has created an intense effort to advance the synthesis so as to mass produce carbon nanotubes with control over diameter and helicity. The massive and controlled synthesis of this heralded nanostructure has been a great challenge. Although significant progress has advanced the preparation, more synthetic development is required. The syntheses have so far involved three main approaches: arc discharge vaporization, laser vaporization, and catalytic chemical vapor deposition. The synthetic trend has progressed to a point where further advancement with these techniques will require a better understanding of the mechanism of nucleation and growth. The mechanics of carbon nanotube nucleation and growth involve very complex and diverse phenomena occurring under extreme conditions and on the mesoscopic scale. As yet the detail mechanism is unknown. Difficulties with experimental probing and computational simulation have increased the mystery of this mechanism. This review presents an account of research on the synthesis of carbon nanotubes and the mechanism of formation. This overview includes all three mentioned synthetic approaches and hybrids thereof. On the basis of this broad account a comprehensive mechanism for carbon nanotube nucleation and growth naturally arises. This mechanism is qualitative and it hopes to inspire more quantitative exploration and synthetic advancement.