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Silica-supported phosphoric acid and metal phosphate catalyzed 1,3-butadiene (BDE) production from 2,3-butanediol (2,3-BDO) was studied using experimental and computational techniques. The catalyst was initially tested in a continuous flow reactor using commercially available 2,3-BDO, leading to maximum BDE yields of 63C%. Quantum chemical mechanistic studies revealed 1,2-epoxybutane is a kinetically viable and thermodynamically stable intermediate, supported by experimental demonstration that this epoxide can be converted to BDE under standard reaction conditions. Newly proposed E2 and SN2′ elementary steps were studied to rationalize the formation of BDE and all detected side-products. Additionally, using quantum mechanics/molecular mechanics (QM/MM) calculations, we modeled silica-supported phosphate catalysts to study the effect of the alkali metal center. Natural population analysis showed that phosphate oxygen atoms are more negatively charged in CsH2PO4/SiO2 than in H3PO4/SiO2. In combination with temperature-programmed desorption experiments using CO2, the results of this study suggest that the improved selectivity achieved when adding the metal center is related to an increase in the basicity of the catalyst.

Gas-phase solvation of halides by 1,3-butadiene has been studied via a combination of photoelectron spectroscopy and density functional theory. Photoelectron spectra for X−⋯(C4H6)n (X=Cl, Br, I where n=1-3, 1–3 and 1–7 respectively) are presented. For all complexes, the calculated structures indicate that butadiene is bound in a bidentate fashion through hydrogen-bonding, with the chloride complex showing the greatest degree of stabilisation of the internal C−C rotation of cis-butadiene. In both Cl− and Br− complexes, the first solvation shell is shown to be at least n = 4 from the vertical detachment energies (VDEs), however for I−, increases in the VDE may suggest a metastable, partially filled, first solvation shell for n = 4 and a complete shell at n = 6. These results have implications for gas-phase clustering in atmospheric and extraterrestrial environments.

Structure-sensitive catalyzed reactions can be influenced by a number of parameters. So far, it has been established that the formation of Pd-C species is responsible for the behavior of Pd nanoparticles employed as catalysts in a butadiene partial hydrogenation reaction. In this study, we introduce some experimental evidence indicating that subsurface Pd hydride species are governing the reactivity of this reaction. In particular, we detect that the extent of formation/decomposition of PdHx species is very sensitive to the Pd nanoparticle aggregate dimensions, and this finally controls the selectivity in this process. The main and direct methodology applied to determine this reaction mechanism step is time-resolved high-energy X-ray diffraction (HEXRD).

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.

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.

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.

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.

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.

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.

Fundamental studies in catalysis rely on well-defined catalyst materials and reactions. In this thesis we focused on the synthesis, characterization and performance of carbon-supported Cu-based materials in hydrogenation catalysis. The main aim was to investigate the effects of the Cu nanoparticle size, support interactions and metal oxide promotion, on the catalytic performance in three industrially-relevant gas-phase hydrogenation reactions, namely methanol synthesis by hydrogenation of CO and CO2, selective hydrogenation of butadiene in excess of propene, and hydrogenation of ethyl acetate to ethanol, a new reaction in our research group. In summary, the physicochemical phenomena involved in catalyst assembly were investigated on the nanometer scale for a series of carbon-supported Cu catalysts, which allowed us to prepare model catalysts with tailored structures. The work presented in this thesis showed that disentangling the effects of Cu particle size, supports and promoters, facilitated the establishment of structure-performance relationships in three important hydrogenation reactions. The advanced understanding of these relationships may assist in developing more active, selective and stable Cu-based hydrogenation catalysts, which may ultimately contribute to more efficient use of energy and materials resources.

A process to produce 1,3-butadiene (1,3-BD) from ethanol in a one-step reaction with a Hf-Zn catalyst was designed using experimental data from the catalyst performance under industrial conditions, taking into account the presence of water and other byproducts in recycled ethanol. The techno-economic and life cycle assessments of the process were performed and compared to the naphtha-cracking route. In these assessments two scenarios were defined to evaluate the impact of catalyst selectivity to 1,3-BD (58 and 69%). For the assessment of the environmental sustainability, three further cases were defined to determine the influence of the geographical location of the production plant considering the world's major ethanol suppliers: The United States, Brazil, and Europe. The results of the economic evaluation show that for a plant with a production capacity of 200 ktonne/year of 1,3-BD, and considering an average market price of azeotropic ethanol (450 €/m3), the minimum butadiene selling price for a 10% rate of return on investment ranges 1.13-1.26 times the average butadiene market price (1529 €/tonne). The process can be profitable for favorable combinations of market prices of ethanol and 1,3-butadiene, but the profitability of the process ultimately relies on the development of higher selective catalysts to reduce the consumption of ethanol per tonne of 1,3-butadiene since ethanol dominates the production costs. The LCA shows that switching from naphtha-derived butadiene to biobutadiene can lead to substantial reductions in CO2 emissions (GWP100) (8-26%) but, in turn, to a significant increase in water consumption (62 to 137-fold) and cumulative energy demand (50-250%). Being that ethanol is the major contributor to all impact categories (65-98% of the impacts), the location of the plant and catalyst selectivity significantly affects the environmental sustainability of the process. Considering the three impact categories and the uncertainty analysis of the LCA res

The stereoselective polymerization of the linear terpenes P-myrcene and P-ocimene and their binary copolymerizations with styrene and butadiene promoted by titanium complexes dichloro{l,4-dithiabutanediyl-2,2' -bis( 4,6-di-tert-butyl-phenyl)}titanium (1) or dichloro{l,4- dithiabutanediyl-2,2' -bis[ 4,6-bis(2-phenyl-2-propyl)phenoxy]}titanium (2) activated by methylaluminoxane (MAO) is reported. In the homopolymerization of P-myrcene, complex 1 and 2 led obtaining a polymer with a mainly 1,4-trans microstructure (92% and 60% of stereoselectivity, respectively). In the case of P-ocimene, both catalysts produce a polymer with l,4-trans structure (70%) at 70 °C while at a lower temperature (0 °C) an isotactic poly-1,2-ocimene (selectivity up to 99%) is obtained. Copolymerizations of P-myrcene and P-ocimene with styrene or butadiene, catalyzed by complexes 1 or 2 were also carried on, giving the corresponding binary copolymers in a wide range of compositions through judicious control of the alimentation feed, The stereoselective polymerization of the linear terpenes P-myrcene and P-ocimene and their binary copolymerizations with styrene and butadiene promoted by titanium complexes dichloro{l,4-dithiabutanediyl-2,2' -bis( 4,6-di-tert-butyl-phenyl)}titanium (1) or dichloro{l,4- dithiabutanediyl-2,2' -bis[ 4,6-bis(2-phenyl-2-propyl)phenoxy]}titanium (2) activated by methylaluminoxane (MAO) is reported. In the homopolymerization of P-myrcene, complex 1 and 2 led obtaining a polymer with a mainly 1,4-trans microstructure (92% and 60% of stereoselectivity, respectively). In the case of P-ocimene, both catalysts produce a polymer with l,4-trans structure (70%) at 70 °C while at a lower temperature (0 °C) an isotactic poly-1,2-ocimene (selectivity up to 99%) is obtained. Copolymerizations of P-myrcene and P-ocimene with styrene or butadiene, catalyzed by complexes 1 or 2 were also carried on, giving the corresponding binary copolymers in a wide range of compositions through judicious control of the alimentation feed

Построена математическая модель синтеза бутадиенового каучука в реакторе непрерывного действия под действием неодимсодержащей каталитической системы. Идентифицирован механизм процесса. Математическая модель представляет собой систему обыкновенных дифференциальных уравнений, размерность которой стремится к бесконечности, ввиду бесконечного числа реакционных компонентов. Применяя метод статистических моментов, бесконечная система дифференциальных уравнений сводится к системе с конечным числом уравнений и становится разрешимой. Численное решение конечной системы позволяет определить усредненные молекулярные характеристики процесса. A mathematical model for the synthesis of butadiene rubber in a continuous reactor under the action of a neodymium-containing catalyst system is constructed. The mechanism of the process is identified. The mathematical model is a system of ordinary differential equations, whose dimension tends to infinity, in view of the infinite number of reaction components. Applying the method of statistical moments, an infinite system of differential equations reduces to a system with a finite number of equations and becomes solvable. The numerical solution of the finite system allows us to determine the average molecular characteristics of the process.

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.

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.

A comparison was made between the relative performance of active and passive sampling methods for the analysis of 1,3-butadiene in outdoor air. Active and passive sampling was conducted using multi-sorbent bed tubes (Carbotrap, Carbopack X, Carboxen 569) and RAD141 Radiello® diffusive samplers (filled with Carbopack X), respectively. Daily duplicate samples of multi-sorbent bed tubes were taken over a period of 14 days (9 + 5 days) at El Morell (Tarragona, Spain), near the petrochemical area. As 1,3-butadiene is a reactive pollutant and can be rapidly oxidized, half of the samplers were equipped with ozone scrubbers. Samples consisted in two tubes connected in series (front and back) to allow determination of breakthrough. Quadruplicate samples of Radiello® tubes were taken over a period of 14 days (9days and 5 days), too. During those days, ozone concentration was measured using RAD172 Radiello® samplers. In addition to this, daily duplicate samples of multi-sorbent bed tubes were taken in the city of Barcelona over a period of 8 days. Simultaneously, 4 samples of Radiello® tubes were exposed to outdoor air. Sampling was done throughout June and July 2017. Analysis was performed by thermal desorption coupled with gas chromatography/mass spectrometry. Analytical performance of the two sampling methods was evaluated by describing several quality assurance parameters, with results showing that performances are quite similar. They display low detection limits, good precision, linearity and desorption efficiency, low levels of blank values, and low breakthrough for multi-sorbent bed tubes. However, Radiello® samplers were not able to uptake episodic 1,3-butadiene high concentrations, leading to underestimation of real values. Hence, we can conclude that Radiello® samplers can be used for baseline 1,3-butadiene levels whereas multi-sorbent bed tubes would be advisable when relevant episodes are expected., Peer Reviewed, Postprint (author's final draft)

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 specie...

© 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., Peer Reviewed, Postprint (author's final draft)

This thesis presents studies on dissociation of two model molecules: Butadiene and Cyclopropane. Tunable synchrotron radiation was used to ionize or excite the molecules in the gas phase, and the momentum correlation of the resulting fragment ions were measured using a 3D momenta coincident ion spectroscopy. The experimental results were interpreted with the aid of ab-initio quantum calculation. This allows us to gain insight into the fundamental processes behind the molecular dissociation, that how correlated electronic and nuclear dynamics drive molecular dissociation.Tunable XUV-radiation was used to doubly ionize molecules to different states.By Comparing experimental and theoretical values for appearance energy and kinetic energy released of the dissociation channels, electronic gateway state of each dissociation channels were identified. By analysing the momentum vector of ion pairs as a function of photon energy and internal energy sharing in the dissociative double ionization channels, mechanisms of double ionization (direct or indirect) processes were investigated. The studies shed light on the electron-electron and electron-nuclear correlation effects in the molecules.Tunable X-rays were used to selectively excite a localized core electron to different valence orbitals, and the subsequent autoionization and dissociation processes were studied by analysing the correlated momentum of ionic fragments. In butadiene, the dependence of molecular dissociation on the initial site of core-hole was studied for the chemically shifted terminal and central carbon core-electrons excitation.In cyclopropane the dependence of molecular dissociation on the changing of the molecular bonding character was studied for different core-to-valence excitation.The studies indicated the importance of the ultra-fast nuclear dynamics initiatedwithin a few femtosecond core-hole lifetime changing the picture of electron-electron correlation in autoionization processes and leading to spec

Kuraray has developed a series of liquid rubber products with molecular weights ranging from a few thousands to a hundred thousand. These polymers, which consist of isoprene, butadiene, styrene and a new, bio-based monomer “Farnesene”, can be used by rubber manufacturers to achieve improvements in processing and physical properties. The most valuable physical property enhancement liquid butadiene rubber offers is a performance improvement in wet and ice grip, as well as plasticizing effect. Moreover, liquid Farnesene rubber contributes to advantaged vehicle fuel economy through reduction in tire rolling resistance. The application of each liquid rubber product in tire formulations is explained., Kuraray has developed a series of liquid rubber products with molecular weights ranging from a few thousands to a hundred thousand. These polymers, which consist of isoprene, butadiene, styrene and a new, bio-based monomer “Farnesene”, can be used by rubber manufacturers to achieve improvements in processing and physical properties. The most valuable physical property enhancement liquid butadiene rubber offers is a performance improvement in wet and ice grip, as well as plasticizing effect. Moreover, liquid Farnesene rubber contributes to advantaged vehicle fuel economy through reduction in tire rolling resistance. The application of each liquid rubber product in tire formulations is explained.

Iron complexes with nitrogen-based tridentate ligands promote polymerization of 1,3-butadiene in the presence of organoaluminum cocatalyst. The produced polybutadienes have relatively high cis-1,4-selectivity (up to 81%). The polymerization in the presence of organoaluminum chloride proceeds via chain transfer to the organoaluminum., Iron complexes with nitrogen-based tridentate ligands promote polymerization of 1,3-butadiene in the presence of organoaluminum cocatalyst. The produced polybutadienes have relatively high cis-1,4-selectivity (up to 81%). The polymerization in the presence of organoaluminum chloride proceeds via chain transfer to the organoaluminum.

Stereoregular elastomers represented by natural rubber are known to show strain-induced crystallization. Alternating copolymer of butadiene and propylene (PBR) is also shows this character. PBR made by coordination polymerization with a vanadium catalyst consists mainly of alternating sequence of trans-1, 4-butadiene and propylene unit. However, PBR shows the low crystallinity compared with natural rubber because of low stereoregurality of propylene unit in alternating chain. In this study, we report the synthesis of new crystalline PBR using a new vanadium catalyst with chiral center., Stereoregular elastomers represented by natural rubber are known to show strain-induced crystallization. Alternating copolymer of butadiene and propylene (PBR) is also shows this character. PBR made by coordination polymerization with a vanadium catalyst consists mainly of alternating sequence of trans-1, 4-butadiene and propylene unit. However, PBR shows the low crystallinity compared with natural rubber because of low stereoregurality of propylene unit in alternating chain. In this study, we report the synthesis of new crystalline PBR using a new vanadium catalyst with chiral center.

Dehydrogenation promoters greatly enhance the performance of SiO2-MgO catalysts in the Lebedev process. Here, the effect of preparation method and order of addition of Cu on the structure and performance of Cu-promoted SiO2-MgO materials is detailed. Addition of Cu to MgO via incipient wetness impregnation (IWI) or coprecipitation (CP) prior to wet-kneading with SiO2 gave similar butadiene yields (similar to 40%) as when Cu was added to the already wet-kneaded catalyst. In contrast, the catalyst prepared by impregnation of Cu on SiO2 first proved to be the worst catalyst of the series. TEM, XRD, and XPS analyses suggested that, for all catalyst materials, Cu2+ forms a solid solution with MgO. This was confirmed by UV-vis, XANES, and EXAFS data, with Cu being found in a distorted octahedral geometry. As a result, the acid base properties, as determined by Pyridine- and CDCl3-IR as well as NH3-TPD, are modified, contributing to the improved performance. Operando XANES and EXAFS studies of the evolution of the copper species showed that Cu2+, the only species initially present, is extensively reduced to a mixture of Cu-0 and Cu+, leaving only a limited amount of unreduced Cu2+. This formation of Cu-0 is the result of the reducing environment of the Lebedev process and is thought to be mainly responsible for the improved performance of the Cu-promoted catalysts.

The work presented in this PhD Thesis provides new insights into the underlying reasons that make SiO2-MgO materials excellent catalysts for the ethanol-to-butadiene Lebedev process. In particular, the preparation technique of choice affects the structural properties of the resulting SiO2-MgO materials considerably and therefore the distribution, i.e. nature and amount, of acidic-basic sites. Given the complex cascade of elementary steps required, striking a precise balance in the latter is key to obtaining a high butadiene yield and performance in general. Moreover, the adsorption of atmospheric CO2 on the active sites of these solid materials can also affect their acid-base properties, forming a number of carbonate species whose nature and thermal stability depend on the preparation method used for the SiO2-MgO samples. During the wet-kneading preparation method used for the SiO2-MgO materials significant chemical changes occur in the primary components. Moreover, a number of preparation parameters (e.g., size of SiO2 and MgO and relative amounts of those) affect the extent of those structural changes. Indeed, the different parameters employed for catalyst preparation affect the amount of MgO and magnesium silicates in the resulting materials. The formation of such magnesium silicates has been previously reported, but their function in catalysis is still unclear. In this PhD work, the magnesium silicates are proposed to improve butadiene yield by facilitating the aldol condensation step. It is well known that dehydrogenation promoters enhance the performance of SiO2-MgO catalyst materials for the ethanol-to-butadiene conversion. In this PhD work, Cu-promoted SiO2-MgO catalysts gave superior butadiene yield. Structurally such systems are very complex due to the presence of three distinct metal oxides and, additionally, of compounds resulting from the interaction of those. Nevertheless, the characterization techniques used showed that a large port

Different copolymers of styrene-butadiene-styrene (SBS) and hydrogenated SBS, styrene-ethylene/butylene-styrene (SEBS) were processed by electrospinning with micrometers fiber diameters. The effect of butadiene/styrene ratio, linear or radial block structure, hydrogenation, and carbon nanotube (CNT) loading on the overall material properties is reported. SEBS has higher initial modulus and mechanical hysteresis when compared to SBS. The mechanical hysteresis decreases with the number of applied cycles. The inclusion of CNTs increases the nanocomposites mechanical hysteresis and electrical conductivity independently on the copolymer matrix. The amount of styrene monomer within the samples is within the range allowed for food packaging applications. Finally, SBS and SEBS pristine samples and SEBS composites do not show cytotoxicity.

Different copolymers of styrene-butadiene-styrene (SBS) and hydrogenated SBS, styrene-ethylene/butylene-styrene (SEBS) were processed by electrospinning with micrometers fiber diameters. The effect of butadiene/styrene ratio, linear or radial block structure, hydrogenation, and carbon nanotube (CNT) loading on the overall material properties is reported. SEBS has higher initial modulus and mechanical hysteresis when compared to SBS. The mechanical hysteresis decreases with the number of applied cycles. The inclusion of CNTs increases the nanocomposites mechanical hysteresis and electrical conductivity independently on the copolymer matrix. The amount of styrene monomer within the samples is within the range allowed for food packaging applications. Finally, SBS and SEBS pristine samples and SEBS composites do not show cytotoxicity.

Different copolymers of styrene-butadiene-styrene (SBS) and hydrogenated SBS, styrene-ethylene/butylene-styrene (SEBS) were processed by electrospinning with micrometers fiber diameters. The effect of butadiene/styrene ratio, linear or radial block structure, hydrogenation, and carbon nanotube (CNT) loading on the overall material properties is reported. SEBS has higher initial modulus and mechanical hysteresis when compared to SBS. The mechanical hysteresis decreases with the number of applied cycles. The inclusion of CNTs increases the nanocomposites mechanical hysteresis and electrical conductivity independently on the copolymer matrix. The amount of styrene monomer within the samples is within the range allowed for food packaging applications. Finally, SBS and SEBS pristine samples and SEBS composites do not show cytotoxicity.

Different copolymers of styrene-butadiene-styrene (SBS) and hydrogenated SBS, styrene-ethylene/butylene-styrene (SEBS) were processed by electrospinning with micrometers fiber diameters. The effect of butadiene/styrene ratio, linear or radial block structure, hydrogenation, and carbon nanotube (CNT) loading on the overall material properties is reported. SEBS has higher initial modulus and mechanical hysteresis when compared to SBS. The mechanical hysteresis decreases with the number of applied cycles. The inclusion of CNTs increases the nanocomposites mechanical hysteresis and electrical conductivity independently on the copolymer matrix. The amount of styrene monomer within the samples is within the range allowed for food packaging applications. Finally, SBS and SEBS pristine samples and SEBS composites do not show cytotoxicity.

A highly selective photo-induced nitrile imine mediated tetrazole-ene coupling (NITEC) of chain-end-functionalized nitrile-butadiene rubber (NBR) is reported, providing nitrile rubbers with molar masses of up to 48 000 g·mol-1. NBR was obtained via the reversible addition-fragmentation chain transfer (RAFT) mediated copolymerization of acrylonitrile and 1,3-butadiene employing a novel photoreactive tetrazole-functionalized trithiocarbonate. The herein reported tetrazole-functionalized trithiocarbonate represents - to the best of our knowledge - the first ever reported photoreactive RAFT agent capable of undergoing light-induced ligations with enes. Molar masses of the tetrazole-functionalized NBRs were in the range of 1000 to 38 000 g·mol-1 with dispersities between 1.1 to 1.6. By an appropriate choice of the tetrazole substituents, a reaction of the in situ formed enophile with the double bonds or the nitrile moieties of the incorporated monomer units within the polymer backbone - present in high excess relative to the dipolarophile linker molecule - was not observed. Underpinned by DFT calculations, the selectivity was identified to originate from a reduced LUMO energy level of the maleimide linker compared to the nonactivated backbone olefins when employing a nitrile-imine of moderate reactivity. © 2013 American Chemical Society.

An in-depth mechanistic study into the solution based initiator-free UV-induced radical copolymerization of 1,3-butadiene with acrylonitrile is reported. The light induced constant radical flux leads to moderate monomer conversions within 4 to 24 h. The number-average molecular weights of the prepared nitrile butadiene rubber (NBR) range from 2500 to 50 000 g mol -1 (1.7 ≤ PDI ≤ 2.4), while the achievable monomer conversion ranged from close to 7 up to 31% depending on the polymerization temperature, reaction time and UV light intensity. The rate coefficient for the generation of primary radicals, determined as the coupled parameter k1 *k3, showed a dependence on the UV light intensity with values between 6.0 s-2 and 34.6 s-2 deduced for the UV light intensity range of 280 to 700 W. The estimated values of the lower limit average termination rate coefficient displayed no dependence on the UV light intensity, with lower limit values between 2.6 × 108 L mol-1 s-1 and 6.3 × 108 L mol -1 s-1 for the UV light intensity range of 280 to 700 W. The deduced values for the average termination rate coefficient were above the expected values for comparable average termination rate coefficients. © 2013 American Chemical Society.

An efficient approach for the synthesis of block copolymers of poly(acrylonitrile-co-butadiene) (NBR) and poly(styrene-co-acrylonitrile) (SAN) is described. Conjugation of preformed polymer building blocks is achieved via a hetero-Diels-Alder (HDA) mechanism employing cyclopentadiene-capped NBRs with dienophile SAN copolymers, both synthesized via reversible addition- fragmentation chain transfer (RAFT) polymerization. The protocol is further extended toward the synthesis of 4-miktoarm star polymers, consisting of two NBR and two SAN arms. Molar masses of the obtained complex macromolecular architectures range from below 10 000 g·mol-1 up to 110 000 g·mol-1 with dispersities below 1.5. Molecular verification of the coupling moieties is provided via NMR spectroscopy as well as ESI mass spectrometry. Size exclusion chromatography (SEC) traces of the obtained block copolymers and miktoarm star polymers were analyzed via deconvolution techniques, revealing the presence of 9.9-12.6 wt % (block copolymers) and 20 wt % (stars) of polymer chains not participating in the HDA conjugation, respectively. The residual polymers were analyzed toward their origin from either the loss of functionality during RAFT polymerization or incomplete conversion during the conjugation process. The comprehensive analysis of the macromolecular material was underpinned by kinetic simulations to estimate the fractions of nonfunctional polymer chains generated during the NBR and SAN polymerizations. The simulations evidenced that NBR-b-SAN samples cannot contain more than 94.4 wt % (Mn 13 000 g·mol-1), 93.6 wt % (Mn 57 000 g·mol-1), or 93.9 wt % (Mn 110 000 g·mol-1) of polymer chains actually possessing the targeted block copolymer structures when assuming an ideal RAFT process. These results unambiguously reveal that nonfunctionalized polymer chains formed during RAFT polymerization cause the incomplete conjugation of polymer building blocks, evidencing the limitations of end-group control in con

Thermoplastic elastomer/carbon nanotube composites are studied for sensor applications due to their excellent mechanical and electrical properties. Piezoresisitive properties of tri-block copolymer styrene-butadiene-styrene (SBS)/carbon nanotubes (CNT) prepared by solution casting have been investigated. The initial elastic modulus of the SBS/CNT composites increases with increasing the CNT filler content present in the samples, without losing the high deformation capability of the polymer matrix (∼1500%). Furthermore, above the percolation threshold these materials are unique for the development of large deformation sensors due to the strong piezoresistive response. Piezoresistive properties evaluated by uniaxial stretching in tensile mode and 4-point bending showed gauge factors up to 120. The linearity obtained between strain and electrical resistance makes these composites interesting for large strain piezoresistive sensors applications.

We have employed hybrid DFT and SCS-MP2 calculations at the SMD-PCM–6-311++G(2d,2p)//6-31+G(d) level to investigate the relationship between three possible channels for forming a Diels–Alder adduct from a highly nucleophilic diene and moderately to highly electrophilic dienophiles. We discuss geometries optimized using the B3LYP and M06-2X functionals with the 6-31+(d) basis set. The transition states and intermediates are characterized on the basis of geometric and electronic properties, and we also address the possibility of predicting detectability of a zwitterionic intermediate based on its relative stability. Our results show that a conventional Diels–Alder transition state conformation yields intermediates in all four investigated cases, but that these are too short-lived to be detected experimentally for the less activated reactants. The stepwise trans pathway, beginning with a conjugate addition-like transition state, becomes increasingly competitive with more activated reactants and is indeed favored for the most electrophilic dienophiles. Addition of a trans diene leads to a dead-end as the trans intermediates have insurmountable rotation barriers that prohibit formation of the second bond, unless another, heterocyclic intermediate is formed. We also show that introduction of a hydrogen bond donating catalyst favors a stepwise pathway even for less activated dienophiles., QC 20120903

1,3-Dienyl-2-silanols with a wide range of substitution patterns are readily obtained by palladium-catalyzed silaboration of 1,3-enynes followed by Suzuki-Miyaura cross coupling with aryl bromides. Subsequent Hiyama-Denmark cross coupling with aryl iodides provides either 1,3- or 1,2-dienes in high yields. The site selectivity can be fully controlled by the choice of activator used in the coupling reaction. In the presence of strong bases such as NaOt-Bu, KOt-Bu, and NaH, clean formation of 1,2-dienes takes place via allylic rearrangement. In contrast, stereo- and site-selective formation of tetra- and trisubstituted 1,3-dienes results from use of Ag 2O and Bu 4NF·3H 2O, respectively, as activators. Under microwave heating at 100 °C the base-mediated cross couplings are largely accelerated and are completed within one hour or less. The ratio of diastereomeric allenes varies depending on the substitution pattern of the silanol and ranges from >99:1 to 52:48., QC 20121120

The synthesis of acrylonitrile-butadiene rubbers (NBRs) via trithiocarbonate-mediated reversible addition fragmentation chain transfer (RAFT) polymerization of acrylonitrile (ACN) and 1,3-butadiene (BD) in solution under azeotropic conditions (38/62) was investigated for a broad range of common solvents: N,N-dimethylacetamide (DMAc), chlorobenzene, 1,4-dioxane, tert-butanol, isobutyronitrile, toluene, trimethylacetonitrile, dimethyl carbonate, acetonitrile, methyl acetate, acetone, and tert-butyl methyl ether. The gravimetrically determined conversions for the free radical polymerizations of ACN/BD after 22 h at 100 °C were in the range of 15% for methyl acetate to 35% for DMAc. The origin of the differences in conversion is attributed to the unequal decomposition behavior of the employed azo initiator 2,2′-azobis(N-butyl-2-methylpropionamide) (1) in the solvents under investigation, as determined by ultraviolet-visible (UV-vis) spectroscopy. Relative decomposition of 1 in solution (0.1 mol L-1) at 100 °C was calculated from the UV-vis spectra for selected solvents. 90% of 1 in DMAc was decomposed after 22 h, 83% in tert-butanol, 57% in 1,4-dioxane, 53% in isobutyronitrile, 45% in chlorobenzene, and 21% in toluene. The evolution of molecular weight with conversion using the initiator 1 was in accordance with the theoretically expected values, regardless of the solvent studied. Moreover, the RAFT-mediated copolymerization of ACN/BD in DMAc with azo initiators 1, 1-[(1-cyano-1-methylethyl)azo]formamide (2) and 1,1′- azobis(cyclohexanecarbonitrile) (3) was investigated. A strong deviation from the linear evolution of molecular weight due to a fast decomposition of these initiators - congruent with high primary radical delivery rates - at the selected temperature was observed when using 2 and 3. The deviation was not observed when using 1. © 2011 Wiley Periodicals, Inc.

"Nanocavitation was detected for the first time in carbon black filled styrene-butadiene rubber (CB-SBR) under uniaxial loading by real time small-angle X-ray scattering (SAXS) using synchrotron X-ray radiation. A three phase model was developed to calculate the void volume fraction from the scattering invariant Q determined from the observed SAXS patterns. The normalized scattering invariant Q/Q(0), where Q(0) is the invariant before deformation, greatly increased above a critical extension ratio lambda(onset) which we attribute to the formation of nanovoids. Analysis of the 2D scattering patterns show that voids formed are 20-40 nm in size and elongated along the tensile direction. Cavities formed beyond lambda(onset) are smaller as lambda increases. Results from the scattering experiments are strongly supported by macroscopic volume change measurements on the samples under similar uniaxial strain. A nearly constant nanocavitation stress sigma(onset) (25 MPa) was observed when the filler volume fraction phi(CB) was larger than 14%. This value is much higher than that predicted based on the elastic instability of small voids in an unfilled elastomer and shows only a weak dependence on the cross-linking density v(C) in heavily cross-linked samples. An energy based cavitation criterion stressing the importance of confined domains between particles or clusters of particles was adopted and found to be consistent with the observed results. The nanocavities are thought to alter the local stress state and promote local shear motion of filler particles."

"Nanocavitation was detected for the first time in carbon black filled styrene-butadiene rubber (CB-SBR) under uniaxial loading by real time small-angle X-ray scattering (SAXS) using synchrotron X-ray radiation. A three phase model was developed to calculate the void volume fraction from the scattering invariant Q determined from the observed SAXS patterns. The normalized scattering invariant Q/Q(0), where Q(0) is the invariant before deformation, greatly increased above a critical extension ratio lambda(onset) which we attribute to the formation of nanovoids. Analysis of the 2D scattering patterns show that voids formed are 20-40 nm in size and elongated along the tensile direction. Cavities formed beyond lambda(onset) are smaller as lambda increases. Results from the scattering experiments are strongly supported by macroscopic volume change measurements on the samples under similar uniaxial strain. A nearly constant nanocavitation stress sigma(onset) (25 MPa) was observed when the filler volume fraction phi(CB) was larger than 14%. This value is much higher than that predicted based on the elastic instability of small voids in an unfilled elastomer and shows only a weak dependence on the cross-linking density v(C) in heavily cross-linked samples. An energy based cavitation criterion stressing the importance of confined domains between particles or clusters of particles was adopted and found to be consistent with the observed results. The nanocavities are thought to alter the local stress state and promote local shear motion of filler particles."

Since the discovery of the topochemical 1,4-polymerization of 3,4-bis(methylene)hexanedioic acid (BMHA), the first reported polymerization of an internally substituted butadiene, an objective of our research group has been to characterize the chemical and structural changes undergone by the crystalline monomer during polymerization. Here, we report a method for the kinetic study of topochemical reactions. BMHA exhibits first order kinetics with a rate constant, k, of 0.215 min-1. Compared to the polymerization of (Z,Z)-2,4-hexadienedioate (EMU), discovered by Matsumoto et al., which also has first order kinetics with a rate constant, k, of 0.394 min-1, BMHA reacts slightly slower than EMU. In addition to kinetic data, structural changes in the polymerization of BMHA were assessed by X-ray powder diffraction. The reaction of BMHA is heterogeneous with polymerization beginning at defect sites in the crystal which serve to nucleate polymer growth in distinct domains that propagate through the monomer lattice. Further, differential thermal analysis demonstrates the polymerization of BMHA by heating (Tp = 165 °C). By comparing the heat of polymerization of BMHA to the heats of polymerization of liquid butadiene analogues, the energy of the lattice strain overcome during the crystal structure transformation can be approximated at 43.3 kJ/mol. The information reported in this work serves to characterize the topochemical polymerization of 3,4-bis(methylene)hexanedioic acid.

In the current work we present results on the controlled/living radical copolymerization of acrylonitrile (AN) and 1,3-butadiene (BD) via reversible addition fragmentation chain transfer (RAFT) polymerization techniques. For the first time, a solution polymerization process for the synthesis of nitrile butadiene rubber (NBR) via the use of dithioacetate and trithiocarbonate RAFT agents is described. It is demonstrated that the number average molar mass, M̄n, of the NBR can be varied between a few thousand and 60 000 g mol-1 with polydispersities between 1.2 and 2.0 (depending on the monomer to polymer conversion). Excellent agreement between the experimentally observed and the theoretically expected molar masses is found. Detailed information on the structure of the synthesized polymers is obtained by variable analytical techniques such as infrared spectroscopy (IR), nuclear magnetic resonance (NMR) spectroscopy, differential scanning calorimetry, and electrospray ionization-mass spectrometry (ESI-MS). © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Activating Notch1 mutations have been reported in human T-lineage acute lymphoblastic leukemia (T-ALL) and lymphomas from genetically modified mice. We report that Notch1 is a prevalent and major mutational target in chemically induced mouse lymphoma. The regions of the gene that are frequently mutated are the hterodimerization domain and the N-terminal ligand-binding region, important for protein stability, and (he polypeptide rich in proline, glutamate, serine and threonine WEST) domains, which is critical for protein degradation. Another gene, CDC4, is also involved in Notch1 degradation and shows frequent mutations. Mutations in the heterodimerization and the ligand-binding regions may cause ligand-independent signaling. whereas mutations preventing protein degradation result in accumulation of intracellular Notch1. We analyzed 103 chemical-induced mouse lymphomas for mutations in the Notch1 gene using single strand conformation analysis (SSCA) and DNA sequencing. Genetic alterations resulting in premature truncation of Notch I were identified in 28 tumors, whereas 8 revealed alterations in the heterodimerization and 16 harbored deletions in the ligand-binding region. Dideoxycytidine-induced lymphomas displayed the highest frequency of Notch1 mutations (49%). whereas in butadiene- and phenolphthalein-indced tumors showed lower frequencies (26 10%, respectively). In total, 26 novel and 3 previously reported mutations were detected. This report shows that Notch1 is a prevalent and major mtational target for 2,3-dideoxycytidine and butadiene-induced lymphoma..

Hydroxy-terminated polybutadiene/isophorone diisocyanate (HTPB-IPDI) polyurethane rubber that was aged in air at elevated temperatures has been studied by infrared microspectroscopy. Spectra were collected in transmission mode on microtomed samples. Analysis of sets of spectra taken across the sectioned material showed that most of the degradation was occurring in the polybutadiene part of the polymer and that the urethane linkage was essentially unchanged. The trans isomer of the polybutadiene appears to be preferentially degraded compared with the vinyl isomer. The IR technique does not provide significant information about the cis isomer. The IR spectra indicated that likely degradation products included acids, esters, alcohols, and small amounts of other products containing a carbonyl functional group. Band area ratios, supported by a principal components analysis, were used to derive degradation profiles for the material. These profiles were steep-sided indicating an oxygen diffusion limited process.

The equilibrium solubility of gases in a star-branched SB block copolymer can be reliably estimated from a volume fraction weighted average of the homopolymer solubilities; the value of heat of solution of gas in SB block copolymer lies between the two values associated with the constituent homopolymers. Diffusion coefficients for gases in SB block copolymers are bracketed by the homopolymer values over the range of temperature employed, but the activation energies for diffusion in SB are higher than either of the homopolymer values. The anomalous temperature dependence and the inability of a computer stimulation to reproduce experimental diffusion coefficient values for SB supported the concept of a temperature dependent restriction on chain mobility in the polybutadiene regions of the SB block copolymer. This Beta factor has values of about 2-3 at room temperature but decreases to unity when the polystyrene chains become mobile at the polystyrene Tg.

The thermo-oxidation of unfilled styrene-butadiene rubber (SBR) was examined by Fourier transform infrared spectroscopy and differential scanning examined by Fourier transform infrared spectroscopy and differential scanning calorimetry (DSC). The process was found to follow an auto-oxidative reaction sequence, where formation of alkyl and peroxy radicals is the initial step. It was also determined that only the butadiene portion of the copolymer was oxidized, no oxidation of the styrene portion could be detected. The DSC results yielded enthalpies in the range of 90 to 180 J/g with an activation energy of 35.0 kcal/mole.