Phase composition of asphaltenes

The phase composition of asphaltenes taken from oils of Romashskino field (Russia) was studied with calorimetry. It was found that in asphaltenes there are ordered amorphous phases which break in the temperature ranges 70–130 and 130–170 °C. Polarization microscopy data show that the liquid crystal phase appears at temperatures from 180 to 190 °C. Moreover, it is shown that in asphaltenes the crystal phases of co-precipitated paraffinic hydrocarbons and salts can be present.     

桦甸油页岩热解过程中热沥青的组成变化规律

将桦甸油页岩分别在300、350、400、450、500和550℃热解得到半焦,对半焦进行逐级抽提和酸洗,得到自由沥青、碳酸盐束缚沥青和硅酸盐束缚沥青,采用柱层析、FT-IR和GC-MS表征不同沥青的化学组成和结构特征,探讨沥青的化学组成变化及与矿物质的相互作用。结果表明,沥青总产率先增大后减小并在400℃取得最大值4.63%,400-450℃大量沥青分解生成页岩油,使沥青产率降至0.98%。350-450℃自由沥青主要发生羧酸脱羧、酯基分解和长链烷烃裂解反应,使羧酸和酯类化合物含量降低、烷烃碳链长度缩短。干酪根分解生成的羧酸与碳酸盐反应生成羧酸盐,使400℃碳酸盐束缚沥青中羧酸含量达78.82%;含氧化合物可与黏土矿物结合,且烷烃可进入蒙脱石层间,使400℃硅酸盐束缚沥青中含氧化合物和烷烃各占80.79%和19.21%。     

Effects of experimental conditions on the molecular composition of maltenes and asphaltenes derived from oilsands bitumen: Characterized by negative-ion ESI FT-ICR MS

A vacuum topped Canadian oilsands bitumen (VTB) was subjected to solvent precipitation and subsequently characterized by elemental analysis, gel permeation chromatograph (GPC), 1 H-NMR spectroscopy and negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Effects of experimental conditions such as solvent types (n-C5 , n-C6 , and n-C7 ), solvent purity, and solvent washing time on asphaltenes yields, bulk composition, and molecular composition of detectable heteroatom compounds in ESI source were determined. Elemental nitrogen and sulfur were enriched in asphaltenes while elemental oxygen had comparable content in maltenes and asphaltenes. Molecular composition of asphaltenes varies with separation conditions. The N1 and O1 species identified by ESI FT-ICR MS were enriched in maltenes. The O2 species exhibited two different double bond equivalents (DBE) distributions and solubility in normal paraffin solvents, indicating two types of molecular structures. Multi oxygen atom containing compounds mainly detected in asphaltenes. Compound class distributions are similar for maltenes derived from n-C5 , n-C6 , and n-C7 , as well as for asphaltenes. The cyclic paraffin impurities in normal paraffin solvents had a significant influence on asphaltenes yields and heteroatom molecular composition. A portion of neutral N1 species and acidic O2 species adsorbed on asphaltenes could be dissolved by increasing washing time. Cautions should be exercised when interpreting the properties and composition of asphaltenes obtained with different experimental conditions.     

Depletion mechanism of antioxidants in MDPE-clay nanocomposites under thermal aging

The depletion behavior of two types of hindered phenolic antioxidants (AO), Irganox^® 1010 (I-1010) and Irganox^®1076 (I-1076), in medium density polyethylene (MDPE)/nanoclay composite was evaluated by incubating samples in a forced air oven at 85 °C. The presence of 4 wt% nanoclay accelerated the depletion of both types of AO, particularly at the surface region of the sample. However, the depletion mechanism in the interior of sample was governed by the AO molecular structure. For samples containing the bulky Irganox®1010, OIT decreased exponentially with aging time consistent with a first order reaction. In contrast, an increase of OIT was detected in first 60 days of heat aging for sample containing I-1076 and afterward the OIT decreased slowly with aging time. The hypothesis for the initial increase of OIT is that the relatively small and linear structure of I-1076 may enable it to be trapped inside the nanoclay galleries and then subsequently released into the polymer matrix during heat aging.     

Alterations in the peptidergic regulation of energy balance in the course of aging

With advancing age most aspects of the peptidergic regulation of energy balance are altered. The alteration involves both the peripheral peptides derived from the adipose tissue or the gastrointestinal tract and the peptides of the central nervous system (brainstem and hypothalamus). In general, the expression of orexigenic peptides and their receptors decreases with age, while that of the anorexic ones rather increases, but not simultaneously and not in a linear fashion. Apart from such quantitative changes, the efficacy of the related peptides may also change with age. These changes are not necessarily linear, either: instead of continuous decline or increase of its effects, the effects of a peptide may become less pronounced in some phases of aging and much enhanced in other ones. Comparing the individual peptides, the phasic alterations in their anabolic or catabolic roles in the regulation of energy balance may exhibit dissimilar time-patterns. In addition, within the overall anabolic or catabolic effects, the feeding and metabolic actions of certain peptides may not change simultaneously. Altogether, as compared with young adults, in middle-aged animals or individuals the anabolic processes (increased food intake with decreased energy expenditure) seem to prevail, which processes may contribute to the explanation of age-related obesity, while in the old ones the catabolic processes (anorexia with enhanced metabolic rate) dominate, which possibly explain the aging anorexia, frailty and sarcopenia.     

Oxidation of Sn(II) in methanesulfonate electrolytes in presence of antioxidants

The influence of copper(II) ions and some aromatic organic compounds on the oxidation of Sn²⁺ ions in the methanesulfonate electrolyte was studied.     

Synthesis of polyolefin composition in the presence of supported catalysts

Polyolefins are basic materials in the plastics. Their application is limited by their low thermostability, adhesion, hardness and other physico-mechanical properties. The following treatments are known to improve and modify polyolefin properties: the incorporation of inorganic or organic fillers with a greater hardness and rigidity into the polyolefin matrix, the grafting of functional groups to polyolefins, and crosslinking with the formation of a network structure in the polyolefin matrix. In the case of polymers and inorganic materials, the activation of their surface by the functionalizing and fixing of transition metals allows one to perform polymerization of monomers on a surface to obtain a polymer–polymer composites and a highly filled polymer–inorganic composites.     

Improving the aging resistance of styrene-butadiene-styrene tri-block copolymer modified asphalt by addition of antioxidants

The aging properties of base asphalt and styrene-butadiene-styrene tri-block copolymer (SBS) modified asphalts (PMA) are evaluated using Fourier Transform Infrared (FTIR) spectroscopy. An aging cell fitted to the FTIR microscope was used to continually and directly study the oxidation of the PMA. In particular, Attenuated Total Reflectance, ATR, with a zinc selenide prism was used to quantify the changes in the spectra of the PMA before and after thin film oven test (TFOT). The effect of a small amount (1 wt%) of some modifiers, zinc dialkyldithiophosphate (ZDDP), zinc dibutyl dithiocarbamate (ZDBC) or naphthenoid oil, on the chemical and physical properties of the PMA was studied. The modification extent of the modifiers increases in the order: oil, ZDBC, ZDDP. With the aging of the PMA, carbonyl groups formed and the intensity of the absorption peak at 965 cm⁻¹ (the characteristic peak of SBS) decreased. Antioxidants, ZDDP or ZDBC modified PMA are resistant to the formation of carbonyl to some extent, indicating the improvement of aging resistance of the PMA by the addition of the antioxidants. ZDDP and ZDBC as antioxidants can retard the oxidation of the PMA through the inhibition of peroxides and radical scavenging. Furthermore, ZDDP in a liquid state at room temperature acts as plasticiser, giving rise to a good aging resistance of PMA.     

Variation of the isotopic composition of xenon in the solar system

Re-examination of a vast amount of existing xenon isotope data, which have been accumulated in the literature since the 1960's, reveals that the variation of the isotopic composition of xenon in the solar system can be attributed to a combined effect of (a) mass-fractionation, (b) spallation and (c) stellar-temperature neutron-capture reactions plus the addition of (d) the beta-decay product of ¹²⁹I and of (e) the spontaneous fission products of ²⁴⁴Pu. The effect of each of the above-mentioned processes can be extremely large, due, primarily to the fact that these processes occurred in the interior of a supernova, which exploded about 5.1 billion years ago.     

Kinetics of ethylbenzene oxy-chemiluminescence in the presence of antioxidants from tissues of the marine invertebrate Eupentacta fraudatrix: Estimating the concentration and reactivity of the natural antioxidants

Extracts from tissues of the holothuria Eupentacta fraudatrix suppress the oxy-chemiluminescence of ethylbenzene in chlorobenzene initiated by azobisisobutyronitrile thermolysis and enhanced by energy transfer to 9,10-dibromoanthracene. The decrease of the chemiexcitation rate in the reaction between peroxyl radicals is caused by radical interception by the antioxidants contained in the extracts. The concentrations of the antioxidants in the extracts and the rate constants of their reactions with peroxyl radicals have been estimated from chemiluminescence kinetics.     

废轮胎热解油重质馏分制备的道路沥青老化性能研究

针对废轮胎热解油重质馏分(＞350℃)组成上具有蜡含量低,芳香分、胶质和沥青质含量高的特点,研究了废轮胎热解油重质馏分采用蒸馏法生产道路沥青的可行性。结果表明,废轮胎热解油中＞420℃、＞430℃、＞440℃三种渣油的性质可以满足不同牌号道路石油沥青老化实验前的技术指标,特别是延展性能优异,但是抗老化性能较差。渣油老化前后的族组成、官能团、氢分布及分子量分布变化表明,渣油在老化过程中存在氧化反应以及脱氢缩合反应,使渣油的化学组成发生变化,即芳香分、胶质含量减少,沥青质含量明显增加,使得沥青胶体体系中分散相明显增多而分散介质相对减少,造成热解油的渣油抗老化性能较差。     

Variation of the elemental composition of plants and soils

INAA with thermal and epithermal irradiation has been applied for determination of 40 chemical elements in soils and different organs of plants. The time and spatial variations of elemental composition of plants and soils are studied.     

Kinetics of the reaction between nitroxide and thiyl radicals: nitroxides as antioxidants in the presence of thiols

Cyclic nitroxides effectively protect cells, tissues, isolated organs, and laboratory animals from radical-induced damage. The present study focuses on the kinetics and mechanisms of the reactions of piperidine and pyrrolidine nitroxides with thiyl radicals, which are involved in free radical "repair" equilibria, but being strong oxidants can also produce cell damage. Thiyl radicals derived from glutathione, cysteine, and penicillamine were generated in water by pulse radiolysis, and the rate constants of their reactions with 2,2,6,6-tetramethylpiperidine-1-oxyl (TPO), 4-OH-TPO, and 3-carbamoyl-proxyl were determined to be (5-7) x 10 (8) M (-1) s (-1) at pH 5-7, independent of the structure of the nitroxide and the thiyl radical. It is suggested that the reaction of nitroxide (>NO (*)) with thiyl radical (RS (*)) yields an unstable adduct (>NOSR). The deprotonated form of this adduct decomposes via heterolysis of the N-O bond, yielding the respective amine (>NH) and sulfinic acid (RS(O)OH). The protonated form of the adduct decomposes via homolysis of the N-O bond, forming the aminium radical (>NH (*+)) and sulfinyl radical (RSO (*)), which by subsequent reactions involving thiol and nitroxide produce the respective amine and sulfonic acid (RS(O) 2OH). Nitroxides that are oxidized to the respective oxoammonium cations (>N (+)O) are recovered in the presence of NADH but not in the presence of thiols. This suggests that the reaction of >N (+)O with thiols yields the respective amine. Two alternative mechanisms are suggested, where >N (+)O reacts with thiolate (RS (-)) directly generating the adduct >NOSR or indirectly forming >NO (*) and RS (*), which subsequently together yield the adduct >NOSR. Under physiological conditions the adduct is mainly deprotonated, and therefore nitroxides can detoxify thiyl radicals. The proposed mechanism can account for the protective effect of nitroxides against reactive oxygen- and nitrogen-derived species in the presence of thiols.     

Variation of the reactivity of flax fiber cellulose in the course of flax ripening

Carboxymethyl cellulose ethers were prepared from flax fibers of various degrees of ripeness. The influence exerted by the degree of ripeness of flax fibers on their reactivity in carboxymethylation was examined. The rheological properties of aqueous solutions of the synthesized carboxymethyl cellulose were studied.     

Variation in enthalpy of the systemn-tetracosane-n-hexacosane as functions of temperature and composition

Differential enthalpy analyses were performed on the binaryn-alkane systemn-C₂₄H₅₀-n-C₂₆H₅₄ with a Setaram DSC111 calorimeter of Tian Calvet type. The measurements provided enthalpy data from 260 to 260 K onn-tetracosane,n-hexacosane and 19 binary mixtures. An analytical expression, derived from the Einstein model, is proposed for every pure phase in its temperature domain, to represent the variation in the enthalpy with temperature. A general expression for the enthalpy as a function of temperature and composition is also given.     

Comparison of antioxidants for combined radiation and thermal aging and superposition of radiation and thermal aging for EPR and XLPE

Thermal and combined thermal and radiation aging of low voltage EPR and XLPE cable insulation with Agerite MA antioxidant and with the ZMTI/Aminox antioxidant system was examined to compare the relative effectiveness of the antioxidant and polymer systems. All provided significant stability with no clear choice of any particular combination being superior to the others. A comparison of degradation from thermal and radiation aging with degradation from combined thermal/radiation aging showed that the damage from the individual aging effects was superposable. This indicates that synergistic effects have little importance for the EPRs and XLPEs tested under the aging conditions observed.     

Thermal plasma composition in the presence of easily and noneasily ionized components

The influence of easily and noneasily ionized components on equilibrium particle density ratios in thermal plasmas has been investigated. Particular emphasis is given to the modeling of metal halide discharges with iodine as a halide. The calculations were done for standard air with lithium or iodine, standard argon with aluminum, and with a mixture of aluminum and iodine. The system setup is in agreement with spectroscopic results for an open-chamber gas-stabilized d.c. arc, with a pressure of 1×10⁵ Pa and temperatures corresponding to the radial distribution of temperature for this type of discharge. It is shown that the behavior of the plasma core is dominated by the easily ionized component (Li or Al) while the periphery is characterized by the noneasily ionized component (iodine).     

Predicting adsorption isotherms of asphaltenes in porous materials

In this paper we present a molecular thermodynamics approach for the modeling of adsorption isotherms of asphaltenes adsorbed on Berea sandstone, Bedford limestone and dolomite rock, using a model for bulk asphaltenes precipitation and a quasi-two-dimensional approach for confined fluids [E. Buenrostro-González, C. Lira-Galeana, A. Gil-Villegas, J. Wu, AIChE J., 50 (2004) 2552–2570; A. Martínez, M. Castro, C. McCabe A. Gil-Villegas, J. Chem. Phys. 126 (2007) 074707, respectively], both based on the Statistical Associating Fluid Theory for Potentials of Variable Range [A. Gil-Villegas, A. Galindo, P.J. Whitehead, S.J. Mills, G. Jackson, A.N. Burgess, J. Chem. Phys. 106 (1997) 4168–4186]. The theory is applied to model adsorption isotherms from experimental data of asphaltenes extracted from a dead sample of heavy crude oil from a Mexican reservoir. The theoretical results give the right Langmuir Type II adsorption isotherms observed experimentally. The model requires the determination of ten molecular parameters related to the size of the particles and the square-well potentials used to describe the particle–surface and particle–particle interactions at the bulk and adsorbed phases. Nine parameters are taken from previous published results about the behavior of asphaltenes in bulk phases and the adsorption of several molecular fluids onto activated carbon and graphite surfaces. The remaining parameter, the energy strength of the particle–surface interaction, is adjusted to reproduce the experimental data, obtaining values that are consistent with Molecular Mechanics calculations for asphaltenes adsorbed on different surfaces and solutions. Although the agreement between theory and experiments shows some deviations at low bulk concentrations, the model reproduces adsorption data at high concentrations where other semi-empirical approaches fail.