Densities,Viscosities, and Refractive Indices of Mixtures of Hexane with Cyclohexane,Decane, Hexadecane,and Squalane at 298.15 K

Densities, ρ, viscosities, η, and refractive indices, n_D, have been measured as a function of composition for binary mixtures of cyclohexane, decane, hexadecane, and squalane with hexane at 298.15 K and atmospheric pressure. From these measurements the excess molar volumes, V_m^E, viscosity deviations, δη, and the change in refractive indices on mixing, Δn_D, were calculated. These results were fitted to Redlick–Kister polynomial equations to estimate the binary coefficients and standard errors. The effects of size and shape of the components on excess properties have been discussed.     

Chemical polymorphism of the cuticular lipids of the cabbage white Pieris rapae

The epicuticular composition of different body parts of the Cabbage White, Pieris rapae L., was investigated using GC and GC/MS. The major group of components, hydrocarbons, occurs in two distinct classes, which show different distributions on the cuticle of the insects. Unbranched shorter chain compounds (C₂₁ to C₃₁, linear group) dominate on body, head and wings, while longer chain, polymethyl-branched compounds (C₃₅ to C₃₉, branched group) are predominantly found on the antennae. Several other components like 1,3-pentacosadiene and oxygenated aliphatic compounds occur in minor amounts on the cuticle. The reason for this polymorphism is discussed.     

A neural network (CSA-LSSVM) model for the estimation of surface tension of branched alkanes

The current study highlights the application of a model based on least square support vector machine (LSSVM) for prediction of surface tension of branched alkanes. An optimization algorithm, namely, coupled simulated annealing (CSA) was applied to the model. Surface tensions of alkanes show a specific interaction between adjacent molecules of the branched alkanes which affects the anisotropic dispersion force component of the surface energy. In this paper, surface tension of branched alkanes was studied in temperature range of 283.15 and 448.15 K. To evaluate the performance and accuracy of this model, statistical and graphical error analyses have been used simultaneously. By applying CSA-LSSVM on 600 data points and finding optimum parameters, the estimated values of surface tension of branched alkanes were compared with experimental data which showed a reasonable agreement with the experimental results. Results demonstrate that the model is precise and viable for prediction of solubility data. The model shows an overall R² and AARD% estimations of 0.9921 and 0.89%, respectively.     

Occurrences and distributions of normal alkanes and biological markers to detections of origin,environments, and maturation of crude oils in El Hamed oilfield,Gulf of Suez,Egypt

The gas chromatography (GC) and gas chromatography–mass spectrometry (GC-MS) analyses for crude oils from Kareem reservoir in the wells El Hamed-1, 3, and 5 are used to provide information on source organic matters input, depositional environment, and maturation level. Data include normal alkane and acyclic isoprenoids distribution, terpane, and sterane aliphatic biomarkers. Pristine/phytane (Pr/Ph), Pr/nC17, and Ph/nC18 ratios indicated mixed organic sources of organic matters (kerogen type II, III) dominantly (kerogen type III) with a less effect of biodegradation and mature stage of occurrence. The diasteranes/steranes ratio showed generally low ratios as in most marine carbonate sources, while algal-bacterial organic matter contribution for the oil samples suggested dependence on the predominance of C23 tricyclic terpane relative to the C19 tricyclic terpane, and the C25 tricyclic terpane greater than C24 tricyclic terpane. The gammacerane index indicated that a low-salinity environment of deposition for the initial organic matters existed in the analyzed samples.     

单体正构烷烃及其混合物的热性能比较

使用差示扫描量热法从吸热温度范围及吸热量大小两个方面研究了单体正构烷烃及其混合物的热性能 ,实验结果表明 ,单体正构烷烃与正构烷烃混合物的热性能明显不同 ,正构烷烃中碳原子数的数目及其分布 ,对相变材料用石蜡的吸热温度范围及吸热量大小影响很大 ,石蜡中正构烷烃种类越少 ,正构烷烃含量越高 ,其热性能越好     

Progress of vanadium phosphorous oxide catalyst for n-butane selective oxidation

The utilization of lighter alkanes into useful chemical products is essential for modern chemistry and reducing the CO₂ emission. Particularly, n-butane has gained special attention across the globe due to the abundant production of maleic anhydride (MA). Vanadium phosphorous oxide (VPO) is the most effective catalyst for selective oxidation of n-butane to MA so far. Interestingly, the VPO complex exists in more or less fifteen different structures, each one having distinct phase composition and exclusive surface morphology and physiochemical properties such as valence state, lattice oxygen, acidity etc., which relies on precursor preparation method and the activation conditions of catalysts. The catalytic performance of VPO catalyst is improved by adding different promoters or co-catalyst such as various metals dopants, or either introducing template or structural-directing agents. Meanwhile, new preparation strategies such as electrospinning, ball milling, hydrothermal, barothermal, ultrasound, microwave irradiation, calcination, sol–gel method and solvothermal synthesis are also employed for introducing improvement in catalytic performance. Research in above-mentioned different aspects will be ascribed in current review in addition to summarizing overall catalysis activity and final yield. To analyze the performance of the catalytic precursor, the reaction mechanism and reaction kinetics both are discussed in this review to help clarify the key issues such as strong exothermic reaction, phosphorus supplement, water supplement, deactivation, and air/n-butane pretreatment etc. related to the various industrial applications of VPO.     

Hydrocarbon Oxidations with Hydrogen Peroxide Catalyzed by a Soluble Polymer‐Bound Manganese(IV) Complex with 1,4,7‐Triazacyclononane

Soluble manganese(IV) complexes with polymer‐bound 1,4,7‐triazacyclononanes as ligands (compound 2 ) catalyze the oxidation of alkanes by hydrogen peroxide in acetonitrile at room and lower temperatures. The corresponding alkyl hydroperoxides are the main products. The presence of a relatively small amount of acetic acid is obligatory for this reaction. The oxidation of alkanes and olefins exhibits some features (kinetic isotope effect, bond selectivities) that distinguish this system from an analogous one based on the dinuclear Mn(IV) complex 1 .     

Utilizing Terminal Oxidants to Achieve P450‐Catalyzed Oxidation of Methane

Terminal oxidant‐supported P450 reactions alleviate the need for substrate binding to initiate catalysis by chemically generating “compound I.” This allows investigation of the innate substrate range of the enzyme active site. Using iodosylbenzene as the oxidant, CYP153A6, a medium‐chain terminal alkane hydroxylase, exhibits methanol formation in the presence of methane demonstrating that P450‐mediated methane hydroxylation is possible.     

介孔Pt/SAPO-11的制备工艺优化及其催化油酸脱羧制备航空煤油性能评价北大核心CSCD

为提高SAPO-11分子筛在催化油酸脱羧制备航空煤油主要成分C8~C17烷烃的催化反应效果,以聚环氧乙烷-聚环氧丙烷-聚环氧乙烷三嵌段共聚物(P123)和十二烷基三甲基溴化铵(DTAB)为介孔双模板剂,采用原位合成法制备了介孔Pt/SAPO-11分子筛催化剂,探究不同晶化温度、晶化时间和煅烧温度对介孔Pt/SAPO-11结晶度、孔结构、形貌特征的影响,并考察其催化油酸脱羧制备C8~C17烷烃效果。结果表明:在晶化温度190℃、晶化时间36 h、煅烧温度650℃、煅烧时间5 h时,合成的介孔Pt/SAPO-11具有较大的比表面积、较高结晶度、较合适孔径和较好的形貌特征;在油酸脱羧制备C8~C17烷烃的反应中,在反应温度340℃、剂油比1∶10、反应时间6 h时,C8~C17烷烃收率可达78.3%。     

“Magic Numbers” in Self-Faceting of Alcohol-Doped Emulsion Droplets

Oil-in-water emulsion droplets spontaneously adopt, below some temperature T_d, counterintuitive faceted and complex non-spherical shapes while remaining liquid. This transition is driven by a crystalline monolayer formed at the droplets' surface. Here, we show that ppm-level doping of the droplet's bulk by long-chain alcohols allows tuning T_d by >50 °C, implying formation of drastically different interfacial structures. Furthermore, “magic” alcohol chain lengths maximize T_d. This we show to arise from self-assembly of mixed alcohol:alkane interfacial structures of stacked alkane layers, co-crystallized with hydrogen-bonded alcohol dimers. These structures are accounted for theoretically and resolved by direct cryogenic transmission electron microscopy (cryoTEM), confirming the proposed structures. The discovered tunability of key properties of commonly-used emulsions by minute concentrations of specific bulk additives should benefit these emulsions' technological applicability.