Routes to polymer-based photonics

The advances in polymer materials and technologies for telecom applications are reported. The polymers include new highly halogenated acrylates, which possess absorption losses less than 0.25 dB/cm and refractive indices ranging from 1.3 to 1.5 in the 1.5 μm wavelength region. The halogenated liquid monomers are highly intermixable, photocurable under UV exposure and exhibit high contrast in polymerization. The polymer technologies developed at the Institute on Laser and Information Technologies of the Russian Academy of Sciences (ILIT RAS) include:

分子结构分区处理方法用于单取代烷烃热容的预测

将单取代烷烃RX(X=OH,NH_2,SH,Cl,Br,I,NO_2,CN)分子结构分为2个区域R和X去提取分子结构参数,从3方面的影响因素:烷基R、取代基X、R与X相互作用,去定量关联RX气相热容。以烷基部分碳原子个数N_C,取代基X对单取代烷烃RX的热容贡献△C_P,以及极化效应指数与取代基电负性的乘积PEI*X_P3参数为变量,建立定量结构-保留相关模型。     

Environmental high resolution electron microscopy of gas‐catalyst reactions

Environmental electron microscopy has become an important scientific method for fundamental studies of dynamic chemical reaction processes in heterogeneous catalysis and of catalytic growth of carbon nanotubes. Outstanding contributions are resulting from the ability to observe gas‐catalyst surface reactions in situ, on the atomic scale. A great deal of structural and chemical information including lattice modification of working catalysts is possible. This is key to understanding novel reaction processes, including release mechanism of structural oxygen in oxide catalysts in selective oxidation of hydrocarbons and to designing improved catalysts. This brief survey of the recent spectacular developments in environmental high resolution electron microscopy shows that new opportunities are being opened up in catalysis. This revised version was published online in August 2006 with corrections to the Cover Date.     

Electrochemical cells as reactors for selective oxygenation of hydrocarbons at low temperature

New oxidation methods for the partial oxidation of alkenes at low temperatures (<373 K) using gaseous alkene–O₂ fuel cell systems and for hydroxylation of alkanes and aromatics applying H₂–O₂ fuel cell reactions are shown. Catalytic oxidation systems can be converted into electrochemical cells which control the reaction rate and selectivity by a variable resister or potentiostat in the outer circuit, as shown for the Wacker type and π-allyl type oxidations. The hydroxylation of benzene to phenol and of light alkanes could be realized at room temperature by applying H₂–O₂ fuel systems. The reverse H₂–O₂ cell reaction enables the epoxidation of propylene into porpylene oxides. It is also possible to combine the two reactions for the cogeneration of phenol and epoxide. Some problems to develop these processes on a commercial scale are also discussed.     

Electrophilic Aromatic Nitration Using a Mixed Catalyst of Lithium,Molybdenum, Ytterbium on Silica Gel

A novel mixed catalyst of LiClO₄ (15% w/w), Yb(OPf)₃ (15% w/w, Pf=perfluorooctanesulfonyl), MoO₃ (15% w/w) on silica gel for electrophilic aromatic nitration reaction has been explored. The nitration reactions were accomplished by this mixed catalyst and nitric acid under solvent‐free conditions. Moreover, the mixed catalyst can be easily recovered from the aqueous layer by heating in an oven and reused for the next nitration reaction.     

Extraction of Lanthanides(III) from HClO4 Solutions with Bis(diphenylphosphorylmethylcarbamoyl)alkanes

Abstract

Novel polyfunctional neutral organophosphorus compounds, namely bis(diphenylphosphoryl-methylcarbamoyl)alkanes of general formula [Ph₂P(O)CH₂C(O)NH]₂(CH₂)_n (I-III; n = 3, 5, 8), were synthesized and studied as extractants for La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y from perchloric acid solutions. The influence of both of HClO₄ concentration in the aqueous phase and that of the extractant in the organic phase on the extraction of metal ions is considered. The stoichiometry of the extracted complexes has been determined. Bis(diphenylphosphorylmethylcarbamoyl)alkanes II and III possess a higher extraction efficiency towards Ln(III) than their monoanalogue Ph₂P(O)CH₂C(O)NHC₉H₁₉. The potentialities of polymeric resin impregnated with bis(diphenylphosphorylmethylcarbamoyl)pentane II for the preconcentration of lanthanides(III) from perchloric acid solutions are demonstrated.     

High-temperature adsorption of n-alkanes on ZSM-5 zeolites: influence of the Si/Al ratio and the synthesis method on the low-coverage adsorption properties

The influence of the composition and synthesis method on the low-coverage adsorption properties of C₅–C₉ n-alkanes on ZSM-5 zeolites was studied using the pulse chromatographic technique at temperatures between 200 and 400 °C. Experiments were performed with materials having Si/Al ratios between 12 and 400, synthesized with and without an organic template. For all ZSM-5 samples, the Henry adsorption constants increase exponentially with the carbon number, while zero-coverage adsorption enthalpies increase in a linear way. With decreasing Al content, the Henry constants and adsorption enthalpies decrease. An increase in adsorption enthalpy of 10.1 kJ/mol per added –CH₂– group is observed for an Si/Al ratio of 400, while an increase of 12.1 kJ/mol is found for an Si/Al ratio of 15. The contribution to the adsorption entropy per carbon atom depends on the ZSM-5 composition and varies between 11.2 and 14.4 J/(mol K). A significant effect of the synthesis method on the Henry constants, adsorption enthalpies and entropies is observed. All ZSM-5 samples synthesized using organic templates show the same unique relationship between adsorption enthalpy and entropy, different from that of zeolites synthesized without organic template.     

纤维状BPO4/SiO2催化剂的制备及其丙烷氧化脱氢性能

通过静电纺丝法制备了一种高温焙烧后具有纤维状结构的磷酸硼/二氧化硅（BPO₄/SiO₂）催化剂,并考察了BPO₄负载量和焙烧温度对该催化剂的结构和催化丙烷氧化脱氢性能的影响。研究发现焙烧过程使纤维直径减小。随着BPO₄负载量的增加,丙烷氧化脱氢活性增高。当BPO₄负载量为7%（质量分数）,焙烧温度为600℃时,BPO₄/SiO₂催化剂具有最佳的催化性能;在反应温度为480℃下,丙烷转化率和丙烯产率分别达到17.0%和13.0%,且催化剂稳定性良好。当焙烧温度较低时（550℃）,催化剂中的有机物分子未被除尽,导致烯烃的选择性偏低;当焙烧温度较高时（700℃）,SiO₂结构收缩紧密,抑制了活性相的暴露。由于纤维结构可暴露更多活性位点,该催化剂较相同条件下粉末状BPO₄催化剂有着更高的催化活性。     

Bifunctional N-Oxides of Alkyldiamidoamines

A homologous series of new surface-active 1,1-bis{[3-(N,N-dimethylamino)ethyl]-amido}alkane-di-N-oxides were synthesized in the reaction of an appropriate diethyl 2-alkylmalonate with N,N-dimethylethylenediamine followed by oxidation with an aqueous solution of hydrogen peroxide. The adsorption isotherms of their aqueous solutions were measured and evaluated to obtain adsorption parameters: critical micelle concentration (CMC), surface excess concentration (Γ_CMC), equilibrium surface tension at the CMC (γ _CMC), cross-sectional area of the adsorbed surfactant molecule (A _CMC), standard free energies of adsorption and micellization