Kinetics of heat release during the reaction ofn-decane with nitrogen dioxide in the liquid phase

The rates of heat release in the nitrogen dioxide—n-decane system at a molar ratio of nitrogen oxides ton-decane (β) from 2.4·10⁻³ to 3.1 and gaseous volumes per mole ofn-decane (V(g)) equal to 0.05–4.5 were studied in the 55.2–92.8 °C temperature range. The initial rate of the process is determined by the interaction of NO₂ withn-decane. The equilibrium constants of dissociation of N₂O₄ inn-decane and Henry's constants of NO₂ and N₂O₄ in ann-decane solution were determined by complex analysis of the thermodynamic equilibrium in the NO₂—n-decane system and dependences of the initial rates onV(g) and β. The experimentally observed self-acceleration of the process in the region of high β and lowT values was suggested to be due to the reaction of N₂O₄ with intermediate oxidation products. The rate constants of the reaction of NO₂ withn-decane were compared with analogous values determined in its mixtures with HNO₃ solutions. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1789–1794, October, 1997.     

Effects of the Operating Conditions on Coke Deactivation of 5A Molecular Sieve in N-Decane Adsorption/Desorption

The influence of operating conditions (time-on-stream, temperature, pressure and paraffin feed concentration) on the deactivation of a 5A molecular sieve during the adsorption/desorption of n-decane has been studied using a cyclic operating procedure. After 10 adsorption/desorption cycles, the 5A molecular sieve used in this study showed the same deactivation level as an used industrial molecular sieve provided that the deactivation of the zeolite was due to coke deposition by site coverage and pore blockage. The temperature effect was studied in the range of 373–523 K, obtaining a minimum deactivation at 448 K. The pressure does not influence adsorption parameters in the range of 1–3 MPa, but it does affect the nature of the coke deposited on the zeolite. The influence of paraffin concentration can be considered negligible.     

Importance of Size and Distribution of Ni Nanoparticles for the Hydrodeoxygenation of Microalgae Oil

Improved synthetic approaches for preparing small‐sized Ni nanoparticles (d=3 nm) supported on HBEA zeolite have been explored and compared with the traditional impregnation method. The formation of surface nickel silicate/aluminate involved in the two precipitation processes are inferred to lead to the stronger interaction between the metal and the support. The lower Brønsted acid concentrations of these two Ni/HBEA catalysts compared with the parent zeolite caused by the partial exchange of Brønsted acid sites by Ni²⁺ cations do not influence the hydrodeoxygenation rates, but alter the product selectivity. Higher initial rates and higher stability have been achieved with these optimized catalysts for the hydrodeoxygenation of stearic acid and microalgae oil. Small metal particles facilitate high initial catalytic activity in the fresh sample and size uniformity ensures high catalyst stability.     

Facile synthesis of 5A zeolite from attapulgite clay for adsorption of <Emphasis Type="Italic">n</Emphasis>-paraffins

5A zeolites were facilely synthesized from attapulgite clay and sodium aluminate precursors. The optimum synthesis condition for 4A zeolite (Na-form) were H₂O/attapulgite ratio of 40:1 volume/mass, NaOH/attapulgite mass ratio of 2.35:1, the crystallization time was 4 h at 80–85 °C. The 4A zeolite was converted to related 5A zeolite (Ca-form) through ionic exchanges using calcium chloride solution with the Si/Al mole ratio of 1.3. SEM images demonstrated that as-synthesized 5A zeolites are ordered cubic crystals, average crystals length dimension is 1–2 μm. And the zeolites product had a specific surface area of 482 m² g^?1 and total pore volume of 0.274 cm³ g^?1. The static adsorption experiments showed that the equilibrium adsorption capacities of n-decane and n-pentadecane on produced 5A zeolite were 0.253 and 0.510 g g^?1, respectively. And the adsorption equilibrium time of n-decane and n-pentadecane on 5A zeolite were 45 and 60 min, respectively. The experimental adsorption data of n-decane and n-pentadecane on three zeolites could be properly fitted by the Langmuir–Freundlich isotherm model.     

Analysis of Excess Molar Volumes of the Ternary Systems Containing a Propyl Alkanoate and Two Alkanes with Some Predictive Methods

Abstract

Excess molar volumes at 298.15 K of the ternary mixtures (propyl ethanoate + n-heptane + n-decane), (propyl propanoate + n-heptane + n-decane) and (propyl butanoate + n-heptane + n-decane) were determined using a DMA 60/602 Anton Paar densimeter. All the experimental values were compared with the results obtained with empirical expressions for estimating ternary properties from binary data and with the Nitta-Chao group-contribution model. For these ternary mixtures the same behaviour that had been observed in ester + n-alkane binary systems was found: excess volumes decrease when the ester length increases.     

Excess Enthalpies of Ternary Mixtures: (2-Methyltetrahydrofuran or Di-n-Butyl ether) + 3-Methylpentane + n-Decane at 25°C

Measurements of excess molar enthalpies at 25°C in a flow microcalorimeter are reported for the two ternary mixtures 2-methyltetrahydrofuran + 3-methylpentane + n-decane and di-n-butyl ether + 3-methylpentane + n-decane. Smooth representations of the results are described and used to construct constant-enthalpy contours on Roozeboom diagrams. It is shown that useful estimates of the ternary enthalpies can be obtained from the Liebermann–Fried model using only the physical properties of the components and their binary mixtures.     

Study of Self-Diffusion ofn-Decane in NaX Zeolite by the Pulsed Magnetic-Field Gradient NMR Method

Translational mobility of n-decane molecules in a porous space of NaX zeolite was studied within the wide ranges of diffusion times and temperatures. The dependence of the effective self-diffusion coefficient on diffusion time was established. Confined mobility of diffusant molecules inside the crystallite was observed both for complete and partial filling of NaX pores with a liquid, when the adsorption barrier was absent at the interface between intra- and intercrystallite regions. It was suggested that obstacles are present at the surface of NaX crystallites complicating the transfer of liquid molecules from crystallite channels to intercrystallite space. True value of self-diffusion coefficient ofn-decane in the itracrystallite space of NaX was determined and its dependence on the concentration of liquid molecules in zeolite channels was considered. A special attention was paid to the study of molecular exchange between intra- and intercrystallite-confined liquids.     

Einfluß aliphatischer Kohlenwasserstoffe auf die Kompressionseigenschaften monomolekularer Fettsäurefilme

Zusammenfassung Das Kompressionsverhalten folgender binärer Systeme wurde beiT=298 K auf 0,01 M HCl mittels Filmwaage untersucht: Stearinsäure/n-Dekan,n-Docosan,n-Octacosan Myristinsäure/n-Dekan,n-Docosan,n-Octacosan. Die Analyse derF/A-Isothermen der gespreiteten Mischungen ergibt, daß bei sämtlichen 6 Systemen der Filmtyp der Mischungen vom Filmtyp der Fettsäuren bestimmt wird. Die festgestellten Flächenaufweitungen sind erklärbar durch die Anwesenheit der Kohlenwasserstoffe in der Monoschicht und durch Linsen aus reinen Kohlenwasserstoffen, die durch Entmischungsvorgänge gebildet wurden.

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The compression behaviour of the following systems was studied by use of a film balance atT=298 K on 0,01 M HCl substrate: stearic acid/n-decane,n-docosane,n-octacosane, myristic acid/n-decane,n-docosane,n-octacosane. From the analysis of theF/A-Isotherms of spread mixtures follows, that in all of the six systems the fatty acid determins the film type of mixtures. Area expansion of the fatty acid monolayers are thought to be due to the presence of the hydrocarbons within the monolayers and to the hydrocarbon lenses formed by demixing processes.

     

The viscosity of the methanol-<Emphasis Type="Italic">n</Emphasis>-decane system in the region of low <Emphasis Type="Italic">n</Emphasis>-decane concentrations

The kinematic viscosity and density of the methanol-n-decane system were measured at various temperatures at low n-decane concentrations (over the miscibility range). The theory of free volume with taking into account molecular association was used to calculate the dynamic viscosity of this system at 298.15 K. The results substantiated the presence of an anomaly in this system (positive Δlnη values).     

Effect of NaOH and NaCl on the disodiumn-decane phosphonate micellar aggregation number

The diffusion coefficient of disodiumn-decane phosphonate micelles was studied by polarography at 25°C in NaCl and in NaOH solutions, and the size and aggregation number of the micelles was computed as a function of Na⁺ concentration. All other conditions being equal, the addition of NaCl produces micelles with an aggregation number one order of magnitude larger than the NaOH addition. This is due to the increase of the effective charge per micellized head group produced by the reaction of OH- with the hydrolized head groups which are mainly present as-PO₃H- in the micellar Stern layer.     

高岭土原位无溶剂法合成小粒径ZSM-5分子筛

结合原位水热法和无溶剂法的优点,在不添加有机模板剂和溶剂的基础上,以高岭土为原料通过晶种诱导绿色高效地合成出ZSM-5分子筛。运用X射线衍射、N2吸附-脱附、扫描电镜、透射电镜和NH3程序升温脱附(TPD-NH3)等技术对ZSM-5分子筛进行表征。表征结果与原位水热法合成的ZSM-5分子筛相比,原位无溶剂法合成ZSM-5分子筛的结晶度较高、晶体粒径较小、酸强度略高、孔结构相似。     

Paramagnetic complexes of 9,10-anthraquinone on zeolite surfaces and their thermal transformations

The concentration of one-electron transfer sites on the surface of H-ZSM-5, H-Y, H-mordenite, and H-β zeolites was measured by EPR using 9,10-antrhraquinone as a probe. It has been found that the hyperfine structure from four protons typical for one-centered complexes of anthraquinone with one acidic site was observed in the EPR spectra after anthraquinone interaction with a zeolite surface in the temperature range of 373 to 423 K. It has been established that an elevated temperature of 473 K promoted the decomposition of the adsorbed anthraquinone and the disappearance of the hyperfine structure. It has been shown that the thermal instability of anthraquinone adsorbed on zeolites changed in the series H-β > H-Y > H-ZSM-5 ～ H-mordenite; the coke-forming ability of zeolites with regard to n-decane at 443 K changed in a similar manner. It has been established that the presence of air promoted coke-forming processes upon interaction between n-decane and zeolites.     

Excess Enthalpies of 2-Methyltetrahydrofuran + 2,2,4-Trimethylpentane + (Decane or Dodecane) at 25°C

Measurements of excess molar enthalpies at 25°C in a flow microcalorimeter, are reported for the two ternary mixtures 2-methyltetrahydrofuran + 2,2,4-trimethylpentane + n-decane and 2-methyltetrahydrofuran + 2,2,4-trimethylpentane + n-dodecane. Smooth representations of the results are described and used to construct constant-enthalpy contours on Roozeboom diagrams. It is shown that useful estimates of the ternary enthalpies can be obtained from the Liebermann–Fried model using only the physical properties of the components and their binary mixtures.     

异相晶种诱导快速合成低硅菱沸石分子筛

在不含有机模板剂体系(OSDAs)中,利用异相晶种(T型分子筛)诱导快速合成出纯相的低硅菱沸石分子筛。采用XRD、SEM、TEM、27Al MAS NMR和紫外拉曼等手段表征分子筛的结构属性和形貌特点。详细研究了菱沸石分子筛的晶化过程以及晶种添加量、nAl2O3/nSi O2、nH2O/nSiO2和碱度对菱沸石分子筛晶化的影响,并探讨T型分子筛晶种诱导合成菱沸石分子筛的晶化机理。原位合成体系中仅形成L型分子筛晶相,而一定量T型分子筛异相晶种的加入诱导溶胶快速制备出纯相的菱沸石分子筛。T型分子筛晶体在一定的水热条件下不断溶解而释放的六元环(6R)和四元环(4R)迅速形成菱沸石分子筛特征笼(CHA笼),抑制了L型分子筛特征单元和特征笼(不含四元环的CAN笼)的形成。     

Isomerization of n-Hexane Over Platinum Ion-Exchanged Zeolite Beta

Zeolite Beta was synthesized from appropriate gels and crystallized under the controlled temperature and pressurized conditions. For isomerization of n-hexane, platinum ion-exchanged zeolite Beta exhibited high activity and selectivity for 2,2-dimethylbutane (2,2-DMB), 2,3-dimethylbutane (2,3-DMB), 2-methylpentane (2-MP) and 3-methylpentane (3-MP). As high as 72% of n-hexane conversion and 98% of product selectivity were obtained at 250°C, 1600 h^–1 for 20 min on stream. The influences of reaction temperature and space velocity were also studied. Pt/H-Beta zeolite was recommended as one of the promising catalyst for n-hexane isomerization due to its high activity and stability. The combined effect of the stronger acidity possessed by H-Beta and the dehydrogenation role played by Pt was believed to be responsible for the good catalytic performance of Pt/H-Beta.     

Solubility and State of Elemental Selenium in Hydrocarbons

The solubility of metallic and amorphous selenium in n-heptane, n-octane, n-nonane, n-decane, n-undecane, and n-dodecane was determined in the range 298-493 K. The effect of temperature and alkane nature is considered. The average composition of selenium molecules in alkanes was determined from ebullioscopic data.     

Growth kinetics for AgI nanoparticles in AOT reverse micelles: effect of molecular length of hydrocarbon solvents

The growth kinetics for AgI nanoparticles formed in the solutions of water/AOT reverse micelles in n-hexane, n-octane, n-decane, and n-dodecane were investigated. In small micelles, the rate of nanoparticles growth was found to be independent of the type of solvent, while in large micelles the growth rate grew with increasing length of solvent molecules. The effect was explained by a different amount of free water in the micelle pools of the same size.     

Catalytic Activity of Polymetalorganosiloxanes Supported on Silica in the Metathesis of a C–Cl Bond

The catalytic activity of structurally different Cu- and Ni-containing polymetalorganosiloxanes supported on silica was studied using the reaction of C–Cl bond metathesis in the carbon tetrachloride–saturated hydrocarbon (n-decane) system as an example. Catalysts with low metal contents were found to exhibit the highest activity; an increase in the metal content resulted in a decrease in both conversion and specific activity. At the initial portions of kinetic curves, the reaction was described by first-order rate equations with respect to n-decane; the reaction was of fraction order with respect to CCl₄and catalyst. The activation energy of the process in the n-decane–carbon tetrachloride system on a copper-containing network catalyst was 23 ± 2 kcal/mol. The mechanism of catalysis on immobilized catalysts from the above class is discussed.     

Photo-controlled extraction and active transport of amino acids by functional reversed micelles containing spiropyran derivatives

In a reversed micellarn-decane solution, a spiropyran derivative 3,3-dimethyl-1-octadecyl-6-nitrospiro(2H-benzopyran-2,2-indoline) (PC18) showed normal photochromism, and the reversed micelles provided polar microenvironment increasing stability of a zwitterionic merocyanine (MC) form of PC18. Though the reversed micelles of tetraethyleneglycol dodecylether (TEGDE) alone inn-decane had relatively low ability to extract amino acid from aqueous solutions, the PC18-incorporated TEGDE reversed micelles inn-decane showed good photo-controlled extraction of zwitterionic amino acid under UV-irradiation and release under VIS-irradiation. Extent of the extracted amino acid was higher for tryptophane (Trp) bearing hydrophobic side chain than alanine (Ala), showing amino acid selectivity. Photo-driven active transport of amino acid across a liquid membrane was attained by the PC18-incorporated TEGDE reversed micellar carrier in a water/n-decane/water three-phase system, where one side of an aqueous/organic interface was irradiated by the UV-light and the other side by the VIS-light. When Trp and Ala were present in the aqueous solution, Trp was selectively transported.     

The effect of adamantane on the hydroconversion ofn-heptane over pure and platinum-containing H-Y and H-mordenite zeolites

The effect of adamantane (Ad) has been studied on the activity and selectivity of the H- and Pt/H-forms of zeolite Y and mordenite (MOR) in the hydroisomerization and cracking ofn-heptane at 443 K.Ad was found to induce pronounced increase in the isomerization activity and selectivity of the H-Y zeolite, while the activity of the Pt/H-Y and MOR was only moderately influenced. Findings suggest thatAd acts as a hydride transfer cocatalyst, but, its activity is controlled by the limited accessibility of the active sites within the zeolitic channels.