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The Butadiene is a raw material used in the petrochemical industry. The use of Butadiene has risen with petrochemical market growth. The Global market is forecasting a demand growth for butadiene applications, especially for rubber materials. The estimated synthetic rubber market is $19.1 billion in 2021 and forecasted to reach $23.2 billion in five years. The dynamic growth in butadiene applications will introduce new products used in many things from the food industry to sports and goods. Also, the rubber materials have different applications in the automotive industry, oil and gas, medical products, and plastics. Companies’ strategic planning to increase the production of synthetic rubber for the global market. The demand increased as new applications were introduced to the market. The stability of oil prices will have the rubber market steady which always leads to optimal pricing. The diver for Butadiene rubber applications is to maximize production by having different kind of materials that applied for several products. The global business development indicated the ability to increases the synthetic rubber market rubber and capacities, which will enhance the chemical process techniques, new technology design, and efficiency that will maximize production and minimize product cost. Looking into the price difference between synthetic and natural rubber, many fluctuation variables were introduced in the price of each type. For example, synthetic rubber price is high, depending on crude oil, natural gasoline and naphtha prices, since those feedstocks are fed to the cracking units, as C4 is one of the cracking products. Therefore, any change in the oil prices will influence the butadiene price, which is the feed for most rubber plants. In addition, the utilities required for those plants to operate have a major impact on overall price. On the other hand, Natural rubber is an agricultural product and dependent on soil type and weather.

There is a growing interest in the production of biobutadiene from bioethanol, but it is not possible to conclude from the literature which conversion process, either by one or two reaction steps, is preferred since there is a lack of works comparing their economic and environmental performances. The aim of this work is to perform that comparison so it can serve as a guide for decision making by future investors as well as set future research needs that can improve the technology. Assuming production in Brazil from sugarcane ethanol, technoeconomic and lifecycle assessments were performed from process simulations, and the reliability of the results was studied with uncertainty analyses. The comparison reveals that the one-step process should be preferred because of its better economic and environmental performance. Biobutadiene from ethanol is not cost competitive against naphtha-derived butadiene (probability of positive net present value is 11–17% for one-step process scenarios and 5% for the two-step process scenarios) but producing biobutadiene from ethanol in Brazil leads to significant reductions in emissions of CO2 compared to naphtha-derived butadiene (102–103% and 7.6–52.4% for one- and two-step process scenarios, respectively). A critical issue for the cost competitiveness of biobutadiene is that the CO2 saved can be sold in an international carbon emission trading market. In that case, the one-step processes would be much more favored. Future research is needed concerning the development of highly selective two-step catalysts operating in less energy-demanding conditions so that two-step processes can compete with one-step processes.

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Theoretical consideration about the impact of methyl groups on the structure and vibrational properties of β-carotenoids, using medium size molecules of trans-butadiene and trans-isoprene, are reported. Density functional theory (DFT) calculations with correlation-consistent and polarization-consistent basis sets were applied to trans-1,3-butadiene and trans-isoprene as the smallest building bricks of β-carotenoids. Their structure and harmonic vibrations were estimated in the complete basis set limit (CBS) using the non-linear least square fit. Optimized geometries and harmonic frequencies, obtained with B3LYP and BLYP density functionals and large basis sets, were favorably reproduced by a significantly faster approach, using a recently modified STO(1M)-3G Slater-type basis set. Selected density functionals with STO(1M)-3G and 6-311++G** basis sets were also successful in predicting β-carotene structures and harmonic vibrations. This work demonstrates the potential applicability of the proposed level of theory for larger molecules, including β-carotenoids, present in numerous natural food sources. The proposed scheme of molecular modeling, applied to biologically active compounds in food, could provide a deeper insight into their function in vivo, which is directly related to their structure and spectroscopic properties. It could also support the experimental qualitative analysis, based on peak assignment of β-carotenoids in various food sources.

We report the use of the ionic liquid tetrabutylphosphonium bromide as a solvent and catalyst for dehydration of diols to conjugated dienes. This system combines stability, high reaction rates and easy product separation. A reaction mechanism for the model compound 1,2-hexanediol is proposed and experimentally corroborated. This particular mechanism allows for the selective formation of conjugated dienes, in contrast with purely acidic catalysis. Next, the reaction is also performed on various other diols. As a first application, we assessed the bio-based production of 1,3-butadiene. Starting from 1,4-butanediol, a 94% yield of butadiene was reached at 100% conversion. ispartof: ACS Catalysis vol:7 issue:9 pages:5802-5809 status: published

RASSCF calculations of vertical excitation energies were carried out on a benchmark set of 19 organic molecules studied by Thiel and co-workers [J. Chem. Phys.2008, 128, 13411018397056]. The best results, in comparison with the MS-CASPT2 results of Thiel, were obtained using a RASSCF space that contains at most one hole and one particle in the RAS1 and RAS3 spaces, respectively, which we denote as RAS[1,1]. This subset of configurations recovers mainly the effect of polarization and semi-internal electronic correlation that is only included in CASSCF in an averaged way. Adding all-external correlation by allowing double excitations from RAS1 and RAS2 into RAS3 did not improve the results, and indeed, they were slightly worse. The accuracy of the first-order RASSCF computations is demonstrated to be a function of whether the state of interest can be classified as covalent or ionic in the space of configurations built from orbitals localized onto atomic sites. For covalent states, polarization and semi-internal correlation effects are negligible (RAS[1,1]), while for ionic states, these effects are large (because of inherent diffusiveness of these states compared to the covalent states) and, thus, an acceptable agreement with MS-CASPT2 can be obtained using first-order RASSCF with the extra basis set involving 3p orbitals in most cases. However, for those ionic states that are quasi-degenerate with a Rydberg state or for nonlocal nπ* states, there remains a significant error resulting from all external correlation effects.

A critical challenge for the bioenergy research community has been producing drop-in hydrocarbon fuels and chemicals at yields sufficient to compete with their petroleum-derived counterparts. Biological production of highly reduced compounds poses fundamental challenges. Conversely, glucose, xylose, and sucrose can be fermented to ethanol at near-theoretical yields. Just as olefin crackers are often considered a gateway for petrochemical complexes that produce an array of downstream products, catalytic ethanol upgrading can potentially enable an entire biorefining complex able to produce renewable, low-carbon fuels and chemicals. By doping the Ta2O5/SiO2 catalyst with different transition metals, we show that Ostromyslensky catalysts can be utilized for direct conversion of ethanol to varying ratios of 1,3-butadiene (1,3-BD), dietheylether (DEE), and ethylene. These results are integrated into the first comprehensive analysis of ethanol conversion to 1,3-BD, DEE, and ethylene that incorporates empirical data with chemical process modeling and life-cycle greenhouse gas (GHG) assessment. We find that the suite of products can replace conventional rubber, plastics, and diesel, achieving as much as a 150% reduction in GHG-intensity relative to fossil pathways (net carbon sequestration). Selecting the route with the greatest ethylene and DEE output can maximize total potential emission reductions.

Продолжено рассмотрение вопроса гелеобразования в процессе растворной полимеризации бутадиена (или бутадиена со стиролом) на анионных каталитических системах в каскаде реакторов и с учётом реакций передачи цепи на полимер (ПЦП). Показано, что характер влияния ПЦП на строение макромолекул, образующихся в периодическом и непрерывных процессах, имеет существенные различия. В периодическом процессе одновременное влияние реакций ПЦР и ПЦП вызывает резкое повышение коэффициента полидисперсности (К). Определена Uкр — критическая конверсия, при которой начинается гелеобразование. Предложена принципиальная технологическая схема для анализа и оптимизации на различных каталитических системах., The consideration of the issue of gel formation in the process of solution polymerization of butadiene (or butadiene with styrene) on anionic catalytic systems in a cascade of reactors taking into account chain transfer to polymer reactions is continued. It is shown that the nature of the influence of chain transfer to polymer on the structure of macromolecules formed in batch and continuous processes has significant differences. In a batch process, the simultaneous effect of reactions of chain transfer to solvent and chain transfer to polymer causes a sharp increase in the polydispersity index (K). Ucr is defined as a critical conversion at which gel formation begins. A process flow scheme for analysis and optimization on various catalytic systems is proposed.

Рассмотрены элементарные стадии анионной полимеризации бутадиена со стиролом, в том числе реакции передачи цепи на растворитель (ПЦР) и передачи цепи на полимер (ПЦП). Рассмотрены механизмы образования высокомолекулярных фракций (ВМФ) и нерастворимого полимера (НРП), а также механизм зарастания внутренних конструкций полимеризаторов НРП или гелем. По мнению авторов, основной причиной образования ВМФ и НРП является передача цепи на полимер. При этом эта реакция оказывает разное влияние в периодическом способе безобрывной анионной полимеризации и в непрерывном, осуществляемом в каскаде реакторов. Предложено при разработке технологических схем использовать разработанный ранее А.А. АрестЯкубовичем и Г.И. Литвиненко метод математического моделирования рассматриваемых процессов (для их анализа и оптимизации)., Elementary stages of anionic polymerization of butadiene with styrene, including the reaction of chain transfer to solvent and chain transfer to polymer are considered. Mechanisms of the formation of high molecular weight fractions and insoluble polymer, as well as the mechanism of overgrowth of internal structures of polymerizers by insoluble polymer or gel are considered. According to the authors, the main reason of the formation of high molecular weight fraction and insoluble polymer is the transfer of the chain to the polymer. In this case, this reaction has a different effect in the periodic method of non-explosive anionic polymerization and in the continuous reactor cascade. It was proposed to use the developed earlier method (A.A. Arest-Yakubovich and T.I. Litvinenko) of mathematical modeling of the processes under consideration (for their analysis and optimization).

© 2017 Elsevier B.V. 1,3-Butadiene is a carcinogenic compound that can be emitted to the atmosphere from several sources, such as the combustion of organic matter or traffic. However, petrochemical industry is one of the main origins of this compound. Several campaigns (2013-2017) were conducted in twelve Catalan urban areas to determine 1,3-butadiene concentrations in outdoor air, five of which were close to Tarragona petrochemical region. 1,3-Butadiene was dynamically sampled in multi-sorbent bed tubes (Carbotrap, Carbopack X and Carboxen 569) using portable pump equipment. The analysis was performed by automatic thermal desorption coupled with capillary gas chromatography/mass spectrometry detector. El Morell, Perafort and Puigdelfi´, located near petrochemical facilities, were the most impacted locations, with average concentrations up to 15±33, 33±41 and 27±39µgm-3, respectively. Maximum 24h concentrations of 125µgm-3 were observed in Puigdelfi´. However, 1,3-butadiene average and maximum concentrations in the Tarragona petrochemical region diminished significantly (p =0.05) in a drastic way (40-80%) since the first monitoring program in 2013. On the other hand, average concentrations in the rest of studied Catalan urban areas generally presented average values below 1µgm-3, ranging from 0.07-1.1µgm-3. Spain does have neither a monitoring strategy nor standard regulations related to 1,3-butadiene. Taking into account that relevant values can be found in locations near petrochemical facilities, a regulation should be implemented as soon as possible, at least in this specific areas.

Supported gold nanoparticles are highly selective catalysts for a range of both liquid-phase and gas-phase hydrogenation reactions. However, little is known about their stability during gas-phase catalysis and the influence of the support thereon. We report on the activity, selectivity, and stability of 2–4 nm Au nanoparticulate catalysts, supported on either TiO2 or SiO2, for the hydrogenation of 0.3% butadiene in the presence of 30% propene. Direct comparison of the stability of the Au catalysts was possible as they were prepared via the same method but on different supports. At full conversion of butadiene, only 0.1% of the propene was converted for both supported catalysts, demonstrating their high selectivity. The TiO2-supported catalysts showed a steady loss of activity, which was recovered by heating in air. We demonstrated that the deactivation was not caused by significant metal particle growth or strong metal–support interaction, but rather, it is related to the deposition of carbonaceous species under reaction conditions. In contrast, all the SiO2-supported catalysts were highly stable, with very limited formation of carbonaceous deposits. It shows that SiO2-supported catalysts, despite their 2–3 times lower initial activities, clearly outperform TiO2-supported catalysts within a day of run time.

Dehydrogenation or oxidative dehydrogenation (ODH) of alkanes to produce alkenes directly from natural gas/shale gas is gaining in importance. Ti3AlC2, a MAX phase, which hitherto had not been used in catalysis, efficiently catalyzes the ODH of n‐butane to butenes and butadiene, which are important intermediates for the synthesis of polymers and other compounds. The catalyst, which combines both metallic and ceramic properties, is stable for at least 30 h on stream, even at low O2:butane ratios, without suffering from coking. This material has neither lattice oxygens nor noble metals, yet a unique combination of numerous defects and a thin surface Ti1−yAlyO2−y/2 layer that is rich in oxygen vacancies makes it an active catalyst. Given the large number of compositions available, MAX phases may find applications in several heterogeneously catalyzed reactions.

The primary objective of this work is to characterize and compare the dynamic mechanical behavior of asphalt concrete mixes with styrene butadiene styrene (SBS) polymer and crumb rubber modified asphalt binders with the behavior of mixes with unmodified viscosity grade asphalt binders. Asphalt binders are characterized for their physical and rheological properties. Simple performance tests like dynamic modulus, dynamic and static creep tests are carried out at varying temperatures and time. Dynamic modulus master curves constructed using numerical optimization technique is used to explain the time and temperature dependency of modified and unmodified asphalt binder mixes. Creep parameters estimated through regression analysis explained the permanent deformation characteristics of asphalt concrete mixes. From the dynamic mechanical characterization studies, it is found that asphalt concrete mixes with SBS polymer modified asphalt binder showed significantly higher values of dynamic modulus and reduced rate of deformation at higher temperatures when compared to asphalt concrete mixes with crumb rubber and unmodified asphalt binders. From the concept of energy dissipation, it is found that SBS polymer modification substantially reduces the energy loss at higher temperatures. Multi-factorial analysis of variance carried out using generalized liner model showed that temperature, frequency and asphalt binder type significant influences the mechanical response of asphalt concrete mixes. The mechanical response of SBS polymer modified asphalt binders are significantly correlated with the rutting resistance of asphalt concrete mixes. � 2011 Elsevier B.V.

In the present work, statistical analysis (16 processing conditions and 2 virgin unmodified samples) is performed to study the influence of antioxidants (AOs) during acrylonitrile-butadiene-styrene terpolymer (ABS) melt-blending (220 &deg, C) on the degradation of the polybutadiene (PB) rich phase, the oxidation onset temperature (OOT), the oxidation peak temperature (OP), and the yellowing index (YI). Predictive equations are constructed, with a focus on three commercial AOs (two primary: Irganox 1076 and 245, and one secondary: Irgafos 168) and two commercial ABS types (mass- and emulsion-polymerized). Fourier transform infrared spectroscopy (FTIR) results indicate that the nitrile absorption peak at 2237 cm&minus, 1 is recommended as reference peak to identify chemical changes in the PB content. The melt processing of unmodified ABSs promotes a reduction in OOT and OP, and promotes an increase in the YI. ABS obtained by mass polymerization shows a higher thermal-oxidative stability. The addition of a primary AO increases the thermal-oxidative stability, whereas the secondary AO only increases OP. The addition of the two primary AOs has a synergetic effect resulting in higher OOT and OP values. Statistical analysis shows that OP data are influenced by all three AO types, but 0.2 m% of Irganox 1076 displays high potential in an industrial context.

The new bis(bidentate) tetraphosphane cis,trans,cis1,2,3,4-tetrakis(diphenylphosphanyl)buta-1,3-diene (dppbd) (7) was obtained by applying a photochemical synthetic protocol. The key step of the photochemical reaction consisted of an intramolecular [2+2] cycloaddition involving a C-C double and triple bond of the Pt-dimer species of the formula [Pt2Cl4(dppa)(trans-dppen)] (2) {dppa = 1,2-bis(diphenylphosphanyl)acetylene and dppen = 1,2-bis(diphenylphosphanyl)- ethene} leading to [Pt2Cl4(dppbd)] (5). The asymmetrically bridged precursor complex 2 was obtained by combinatorial chemistry. Single crystal X-ray structure analyses of 2 and 5 proved that the intramolecular photochemical reaction occurred. Cyanolysis of 5 gave 7, which was oxidized to dppbdO4 (8). Compounds 7, 8, and the PdII dimer complex [Pd2Cl4- (dppbd)] (9) were characterized in the solid state by a singlecrystal X-ray structure analysis. Interesting photophysial properties emerged from the UV/Vis spectra acquired for 7 and the dimer Os complexes meso-?,?/?,?-[Os2(bpy)4(dppbd)](PF6)4 (10) and rac-?,?/?,?-[Os2(bpy)4(dppbd)](PF6)4 (11).

Trialkylamines were used as additives in the decarbonylation–elimination reaction catalysed by the combination of palladium(II) chloride and DPE-Phos. Aliphatic carboxylic acids were transformed at relatively low temperature into terminal alkenes in high yield and high selectivity, without the need for distillation, thereby avoiding isomerisation.

Two-photon absorption in systems with parity permits access to states that cannot be prepared by one-photon absorption. Here we present the first time-resolved photoelectron spectroscopy study using this technique, applied to 1,3-butadiene, in which we investigated the dynamics of its dark valence, Rydberg, and superexcited states. The dark valence state dynamics are accessed via the Rydberg manifold, excited by two photons of 400 nm. We find that the 'dark' 2(1)Ag state populated in this manner has a much longer lifetime than when accesses via the 1(1)Bu 'bright' valence state when populated by one photon of 200 nm. In addition, we compared the dynamics of the 3sπ- and 3dπ-Rydberg states. These Rydberg states relax to the valence manifold on a subpicosecond time scale, with the 3sπ-Rydberg state decay rate being larger due to a stronger valence-Rydberg mixing. Finally, we investigated superexcited valence states that fragment or autoionize within 200 fs, likely without involving Rydberg states.

The combination of strong few-cycle laser pulses with a reaction microscope, a spectrometer capable of detecting the momentum-vectors of all charged particles that emerge from ionization or dissociation processes in coincidence, enables precise and detailed investigations of strong field processes that occur in atoms and small molecules. However, to avoid false coincidences, experiments with a reaction microscope rely on a low ratio between event rate and laser rate. Common repetition rates of strong few cycle laser systems are on the order of a few kHz leading to long measurement duration up to several days to get reliable information e.g. on angular and energy resolved data. If, in addition, laser parameters such as pump probe delay or polarization have to be scanned, the duration for such experimental runs can extend even beyond this time scale. For such long time periods it is very difficult to maintain stable experimental conditions. Hence, the possibility to scan through large parameter sets is very limited. To overcome this limitation, we combined a reaction microscope with a 400 kHz high repetition rate NOPA-system delivering strong few-cycle laser pulses to study multi-electron dynamics in strong field ionization experiments. First measurements on strong field ionization of argon were performed to characterize the setup. In these experiments unexpected sharp structures have been observed in the electron momentum distributions. With the help of TDSE (Time Dependent Schrödinger Equation) calculations, it was found that these sharp structures originate from the temporal shape of the laser pulses which contains weak post pulses. In this 'unwanted' pump probe scheme, the strong main pulse not only ionizes the argon atom but also populates Rydberg states in the neutral atom. A weaker post pulse ionizes the Rydberg states. This leads to interferences between the direct and the indirect created photo electrons and thus to sharp structures in the electron spectra. The TDSE calculation has shown that the relative population and initial phases of Rydberg states populated by the strong field interaction can be extracted when studying the time dependence of these interferences in a pump probe experiment., Die Kombination starker kurzer Laserimpulse von wenigen Zyklen mit einem Reaktionsmikroskops, welches die Impulsvektoren aller geladenen Teilchen, die aus einem Ionisations- oder Dissoziationsprozess stammen, koinzident detektieren kann, ermöglicht eine genaue und detaillierte Untersuchung von atomaren und molekularen Starkfeldprozessen. Experimente mit Reaktionsmikroskopen bedürfen jedoch eines niedrigen Verhältnisses zwischen Ereignisrate und Laserrate, um falsche Koinzidenzen zu vermeiden. Gewöhnliche Wiederholraten von Lasersystemen, die starke Laserimpulse mit wenigen Zyklen erzeugen, sind in der Größenordnung weniger kHz. Dies führt zur Messdauern von bis zu einigen Tagen für verlässliche Informationen über z.B. winkel- und energieaufgelöste Daten. Falls zusätzlich noch Laserparameter wie Polarisation oder der zeitliche Abstande zweier Laserimpulse variiert werden soll, kann die Dauer eines solchen Experimentes sogar noch größere Zeitskalen erreichen. Es ist sehr schwierig Experimente auf diesen Zeitskalen stabil zu halten. Deshalb sind die Möglichkeiten große Parameterräume zu durchsuchen stark eingeschränkt. Wir haben ein Reaktionsmikroskop mit einem NOPA-System kombiniert, das starke, kurze Laserimpulse von wenigen Zyklen mit einer Wiederholrate von 400 kHz erzeugt, um diese Einschränkung zu überwinden und Mehrelektronendynamiken in Starkfeldexperimenten zu untersuchen. Es wurden erste Experimente mit Starkfeldionisation an Argon durchgeführt, um den experimentellen Aufbau zu charakterisieren. Die Impulsverteilungen der Elektronen aus diesen Experimenten zeigten unerwartet scharfe Strukturen. TDSE (Time Dependent Schrödinger Equation) Berechnungen zeigten, dass diese Strukturen durch die zeitliche Form des Laserimpulses, der schwache Satellitenimpulse enthält, verursacht wurden. In diesem ungewollten pump-probe Schema ionisiert der starke Hauptimpuls nicht nur das Argonatom, sondern er bevölkert auch gleichzeitig Rydbergzustände des neutralen Atoms. Die Rydbergzustände werden durch einen späteren schwächeren Impuls ionisiert. Dies führt zu Interferenzen zwischen den direkt und indirekt erzeugten Photoelektronen sichtbar als scharfe Strukturen in den Elektronenspektren. Zusätzlich zeigte die TDSE-Berechnung, dass die relative Population und die initialen Phasen der Rydbergzustände, die durch die Starkfeldinteraktion bevölkert werden, aus den Photoelektronenspektren extrahiert werden können, wenn die Zeitabhängigkeit dieser Interferenzen durch ein Pump-Probe-Experiment untersucht wird. In einem anderen Starkfeldexperiment an mehratomigen Molekülen wie Butadien und n-Butan untersuchten wir deren Fragmentation. Es wurden winkelaufgelösten Photoelektronenspektren für unterschiedliche Fragmentationskanäle aufgenommen. Diese Messungen zeigten, dass unterschiedliche ionische Zustände während einer Starkfeldionisation bevölkert werden. Dies deutet daraufhin, dass in mehratomigen Molekülen nicht nur das am schwächsten gebundene Elektron in Starkfeldionisationsprozessen teilnimmt.

Computations find that o-phenylene(halo)carbenonitrenes 2-XN, X = F, Cl, Br, have quinoidal singlet biradical ground states such as the parent o-phenylenecarbenonitrene (2-HN). Compared to the parent 2-HN, halogen substitution stabilizes the A″ states relative to the A′ ones. Halogen substitution also affects the barrier and exothermicity of the ring-opening reaction (to form unsaturated nitriles 4-XN, X = F, Cl, Br), but it has a smaller effect on the ring-closing reaction (to form benzo(aza) cyclobutadiene 3-XN, X = F, Cl, Br). Attempts to generate and observe the o-phenylene(halo)carbenonitrenes 2-XN, X = F, Cl, Br, using matrix isolation spectroscopy under conditions similar to those of the successful observation of 2-HN failed. Instead, the observed photoproducts were a mixture of 3-XN and 4-XN. In each case, the major product of the mixture appears to be the thermodynamically more stable one. In the case of X = Br, the observed mixture contains an additional component that is postulated to be Z-6-BrN. o-Phenylenechlorocarbenocarbene is also computed to have a quinoidal singlet biradical ground state and relatively stabilized A″ excited states. Attempts to generate the biscarbene under matrix isolation conditions led to the detection of benzochlorocyclobutadiene (3-ClC), small amounts of the ring-open product (dienediyne 4-ClC), and cycloalkyne 5-ClC. Computations suggest that the formation of 5-ClC implies the generation of Z-6-ClC, which is analogous to the formation of Z-6-BrN from 2-BrN. © 2005 American Chemical Society. 70 19 7744 7754 Cited By :9

In strong-field ionization (SFI) of polyatomic molecules, the participation of multiple electronic ionization channels is emerging as a key aspect. In the molecular frame, each channel is expected to show a characteristic dependence of the SFI yield on the polarization direction of the ionizing field. We apply a new angle- and channel-resolved SFI technique to the polyatomic molecule 1,3-butadiene and compare these molecular-frame measurements with two leading theoretical models. © 2013 American Physical Society.

Reaction of (CO) 6 Fe 2 (μ-Se) 2 with HCCCCR (R  Sime 3 or Sn n Bu 3 ) at room temperature in methanol containing sodium acetate yielded the unexpected product {(CO) 6 Fe 2 Se 2 } 2 (μ-s- trans -C 4 H 2 ) in which a 1,3-butadiene ligand is coordinated to Fe 2 Se 2 core in a trans conformation as determined by a single-crystal X-ray diffraction studies. The complex was also obtained with a low yield by reaction of (CO) 6 Fe 2 (μ-Se) 2 with HCCCCH under similar conditions.

Blends of nitrile butadiene rubber (NBR) with polyvinyl chloride (PVC) are widely used in products such as hoses and seals. As part of a project that uses NBR/PVC blends for manufacturing forest fire hoses, blends of NBR/PVC with various inorganic fillers, such as Mg(OH)2, china clay (organic modified kaolin) and nano clay (organic modified bentonite) were studied by TG-MS. No significant changes were observed to the type of the polymers' decomposition products, compared to that of NBR/PVC blend without additives. The most remarkable change was the absence of HCl from decomposition products in the presence of the Mg(OH)2 additive. © 2011 Elsevier B.V. All rights reserved. 92 1 106 110 Cited By :10

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International audience; The health effects of human exposure to 1,3-butadiene (BD) have been extensively studied using both epidemiological and animal toxicology approaches. However, various data and knowledge gaps remain, one of which is an understanding of the human heterogeneity in BD dosimetry. The objective of our study was to better understand the role of individual variability in delivered tissue dose. We designed a study of laboratory exposures of a relatively large group of healthy human subjects. Subjects were then exposed to 2.0 ppm BD through a face mask for 20 min, followed by 40 min of breathing clean air. Exhaled breath concentrations of BD were measured at ten time points during and after exposure, and a three-compartment physiologically based pharmacokinetic (PBPK) model was used to quantify the kinetic behavior of BD. We implemented a Markov chain Monte Carlo procedure to fit the model to the experimental data, and used global sensitivity analysis techniques to examine the sensitivity of exhaled breath concentrations to PBPK model parameters. Uptake during exposure was strongly influenced by rebreathing of exhaled BD during exposure; inclusion of rebreathing in the model simulations resulted in a 21% increase in the amount of BD retained in the body. We found that uptake ranged from 38% to 77% across individuals. We measured considerable intra-individual variability from 11 subjects who underwent the testing twice. Most of this variation stemmed from phase I metabolism of BD, which varied by as much as a factor of 2.6 within individuals. Overall, we have sought to quantify the sources of inter- and intra-individual variabilities in the pharmacokinetic behavior of BD. The results of our research may impact the current framework for biomarker and pharmacokinetic studies by improving our understanding of the sources of heterogeneity in response to chemical exposures.

Mechanical spectroscopy has been used to qualify possible improvements of the mechanical properties of acrylonitrile-butadiene-styrene-carbon nanotubes (ABS-CNTs) composites. The properties of ABS matrix are first investigated. Two relaxations that mark the glass transition of the polybutadiene and the styrene-acrylonitrile (SAN) phases of the polymer are identified. Composite samples with ABS matrix and CNT reinforcement were processed by blending and injection molding. The carbon nanotube additions are 3 wt%, 7 wt% and 15 wt%. The SAN glass transition evidenced by a mechanical loss peak is broadened by the presence of CNT and it is slightly shifted towards higher temperatures. Carbon nanotubes contribute to delay the modulus drop that characterizes the SAN phase glass transition. (C) 2009 Elsevier B.V. All rights reserved.