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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).

The ammonia evaporation method, originally applied for the preparation of highly dispersed silica-supported copper catalysts, was used to synthesize magnesia-silica for the one-step conversion of ethanol to 1,3-butadiene. The MgO-SiO2 catalysts obtained by this method contained a high fraction of magnesium silicate hydrates, which are associated with enhanced butadiene selectivity. These catalysts were benchmarked against those prepared by a conventional wet-kneading method. A Mg/Si molar ratio of 4 was optimal, forming butadiene with 37% yield, which is far superior to the 15% yield obtained with MgO-SiO2 formed by wet-kneading. At 475 °C and a WHSV of 3.2 h−1, a productivity of 0.612 gBD gcat−1 h−1 was measured without the catalyst suffering from deactivation, even after 52 h TOS. The catalysts were characterized by spectroscopic and thermal techniques to elucidate their physicochemical properties and explain the differences in the catalytic performance. The presence of magnesium silicate hydrates gave a balance of surface acidity and basicity, which greatly improved butadiene formation. The open morphology of MgO-SiO2 with vertically arranged platelets and the presence of large pores are proposed to contribute to the stability of the catalyst.

Production of butadiene from biomass-based tetrahydrofuran (THF) is explored as an alternative to the existing petroleum-based processes. Metal oxide catalysts have been shown to exhibit varying product selectivities when reacted with THF. Among those oxides, ZrO2 showed the highest selectivity for butadiene. In contrast, Al2O3 showed the highest selectivity for the competing retro-Prins products, C3H6 and HCHO. The reasons behind the varying selectivity across oxides are unclear. In this work, we employ periodic density functional theory and mean-field microkinetic modeling to investigate the mechanism of the reaction of THF to butadiene and retro-Prins products on t-ZrO2 (101) (dry and hydrous) and on γ-Al2O3 (110). Our simulations reproduce the experimental selectivity trends. High selectivity for butadiene is promoted by the presence of neighboring Lewis acid metal sites that facilitate E1cB hydroxyl elimination from a 3-butenoxide intermediate; on hydrous Al2O3; where such neighboring Lewis acid centers are not available, the butenoxide undergoes E2 elimination and retro-Prins products ensue. The THF ring opening is rate-determining on ZrO2, whereas the γ-proton elimination that yields the 3-butenoxide intermediate is rate controlling on hydroxylated Al2O3. We conclude that the local topology around the active site greatly influences the mechanism and selectivity.

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.

During the polymerization of mono-olefins to prepare polymers, impurities such as alkynes and diolefins can poison the polymerization catalyst. Fossil energy driven thermocatalytic selective hydrogenation is the main impurity removal in the industry, which is a high energy consumption and high pollution process. The development of novel green and low-energy reaction pathways is one of the urgent problems in the current industry. Based on the plasmon resonance effect of metal nanoparticles, converting light energy into thermal energy to drive industrial catalytic hydrogenation is a very promising option. In this study, graphene oxide loaded gold(Au) catalysts(Au/GO) were prepared by cationic adsorption method, and the Au loading(mass fraction 0.2%—2%) was adjusted to achieve controllable preparation of Au in the particle size of 10—21 nm. The efficiency of photo-thermal conversion of Au/GO was as high as 88%. Using the selective catalytic hydrogenation of butadiene as a probe reaction, it was found that under 0.2 W/cm2 illumination conditions, the conversion of butadiene increased and then decreased with increasing loading, and the butene selectivity was above 90%. Particularly, Au/GO-0.5 exhibited high butadiene conversion (99%) and butene selectivity(90%) at a gold loading of 0.5%(particle size ca. 15 nm) and a photothermal conversion temperature of 100 ℃. More importantly, the catalyst showed no deactivation trend after 144 h stability test. In addition, the photo-thermal driven catalytic activity developed in this work was improved by a factor of 5 compared to the thermal catalytic reaction under the same conditions. The analysis by in situ X-ray photoelectron spectroscopy (XPS) tests showed that this improvement in catalytic performance was mainly derived from the large number of Auδ+ active sites generated on the excited nanogold surface during the plasma photo-transfer thermal process. This study provides a green and efficient reaction pathway for the selective catalytic hydrogenation of industrial unsaturated olefins.

Bioethanol to butadiene is currently the most promising non-oil-based butadiene production route. Here, copper is introduced into the conventional bimetallic zeolite catalyst to partially substitute for zinc; the isolated tetracoordinated Cu(II) species are formed, with weak and strong basic sites transformed into medium acid sites in trimetallic CuZnY/SiBEA catalyst. A partial substitution of zinc by copper increases the dispersion of metal, reduces the formation of ZnO clusters, decreases the pore blockage, and enhances the total pore volume of catalyst. The Cu1Zn2Y5/SiBEA catalyst with an appropriate 0.33 Cu/(Cu + Zn) mass ratio, a highest medium acid sites/(weak + strong) basic sites value of 6.17, and largest total pore volume of 0.251 cm3/g in all samples presents excellent catalytic performance in the ethanol to butadiene reaction: 99.01% ethanol conversion and 73.36% butadiene selectivity, higher than most reported ethanol to butadiene catalysts. The isolated tetracoordinated Cu(II) structure is stable, which is beneficial to the stability of trimetallic catalyst; when the reaction time is 60 h, the butadiene selectivity is 45.95%, 14% higher than corresponding bimetallic catalyst. The butadiene productivity of Cu1Zn2Y5/SiBEA catalyst reaches up to 1.68 gBD·gcat−1·h−1 at WHSV = 6 h−1 and time-on-stream = 8 h. Increasing reaction temperature could linearly increase the ethanol conversion, while the butadiene selectivity increases first and then decreases, the suitable temperature is 375 ℃ for the highest butadiene yield.

Isoprene is a small lipophilic molecule synthesized in plastids and abundantly released into the atmosphere. Isoprene-emitting plants are better protected against abiotic stresses, but the mechanism of action of isoprene is still under debate. In this study, we compared the physiological responses and proteomic profiles of Arabidopsis which express the isoprene synthase (ISPS) gene and emit isoprene with those of non-emitting plants under both drought-stress (DS) and well-watered (WW) conditions. We aimed to investigate whether isoprene-emitting plants displayed a different proteomic profile that is consistent with the metabolic changes already reported. Only ISPS DS plants were able to maintain the same photosynthesis and fresh weight of WW plants. LC–MS/MS-based proteomic analysis revealed changes in protein abundance that were dependent on the capacity for emitting isoprene in addition to those caused by the DS. The majority of the proteins changed in response to the interaction between DS and isoprene emission. These include proteins that are associated with the activation of secondary metabolisms leading to ABA, trehalose, and proline accumulations. Overall, our proteomic data suggest that isoprene exerts its protective mechanism at different levels: under drought stress, isoprene affects the abundance of chloroplast proteins, confirming a strong direct or indirect antioxidant action and also modulates signaling and hormone pathways, especially those controlling ABA synthesis. Unexpectedly, isoprene also alters membrane trafficking.

International audience; Being N-substituted unsaturated species, azabutadienes are molecules of potential relevance in astrochemistry, ranging from the interstellar medium to Titan’s atmosphere. 2-Azabutadiene and butadiene share a similar conjugated π system, thus allowing investigation of the effects of heteroatom substitution. More interestingly, 2-azabutadiene can be used to proxy the abundance of interstellar butadiene. To enable future astronomical searches, the rotational spectrum of 2-azabutadiene has been investigated up to 330 GHz. The experimental work has been supported and guided by accurate computational characterization of the molecular structure, energetics, and spectroscopic properties of the two possible forms, trans and gauche. The trans species, more stable by about 7 kJ/mol than gauche-2-azabutadiene, has been experimentally observed, and its rotational and centrifugal distortion constants have been obtained with remarkable accuracy, while theoretical estimates of the spectroscopic parameters are reported for gauche-2-azabutadiene.

1,3-Butadiene (BD) is a petrochemical manufactured in high volumes. It is a human carcinogen and can induce lymphohematopoietic cancers, particularly leukemia, in occupationally-exposed workers. BD is an air pollutant with the major environmental sources being automobile exhaust and tobacco smoke. It is one of the major constituents and is considered the most carcinogenic compound in cigarette smoke. The BD concentrations in urban areas usually vary between 0.01 and 3.3 μg/m3 but can be significantly higher in some microenvironments. For BD exposure of the general population, microenvironments, particularly indoor microenvironments, are the primary determinant and environmental tobacco smoke is the main contributor. BD has high cancer risk and has been ranked the second or the third in the environmental pollutants monitored in most urban areas, with the cancer risks exceeding 10-5. Mutagenicity/carcinogenicity of BD is mediated by its genotoxic metabolites but the specific metabolite(s) responsible for the effects in humans have not been determined. BD can be bioactivated to yield three mutagenic epoxide metabolites by cytochrome P450 enzymes, or potentially be biotransformed into a mutagenic chlorohydrin by myeloperoxidase, a peroxidase almost specifically present in neutrophils and monocytes. Several urinary BD biomarkers have been developed, among which N-acetyl-S-(4-hydroxy-2-buten-1-yl)-L-cysteine is the most sensitive and is suitable for biomonitoring BD exposure in the general population. Exposure to BD has been associated with leukemia, cardiovascular disease, and possibly reproductive effects, and may be associated with several cancers, autism, and asthma in children. Collectively, BD is a ubiquitous pollutant that has been associated with a range of adverse health effects and diseases with children being a subpopulation with potentially greater susceptibility. Its adverse effects on human health may have been underestimated and more studies are needed.

Arundo donax has been recognized as a promising crop for biomass production on marginal lands due to its superior productivity and stress tolerance. However, salt stress negatively impacts A. donax growth and photosynthesis. In this study, we tested whether the tolerance of A. donax to salinity stress can be enhanced by the addition of 5-aminolevulinic acid (ALA), a known promoter of plant growth and abiotic stress tolerance. Our results indicated that root exposure to ALA increased the ALA levels in leaves along the A. donax plant profile. ALA enhanced Na+ accumulation in the roots of salt-stressed plants and, at the same time, lowered Na+ concentration in leaves, while a reduced callose amount was found in the root tissue. ALA also improved the photosynthetic performance of salt-stressed apical leaves by stimulating stomatal opening and preventing an increase in the ratio between abscisic acid (ABA) and indol-3-acetic acid (IAA), without affecting leaf methanol emission and plant growth. Supply of ALA to the roots reduced isoprene fluxes from leaves of non-stressed plants, while it sustained isoprene fluxes along the profile of salt-stressed A. donax. Thus, ALA likely interacted with the methylerythritol 4-phosphate (MEP) pathway and modulate the synthesis of either ABA or isoprene under stressful conditions. Overall, our study highlights the effectiveness of ALA supply through soil fertirrigation in preserving the young apical developing leaves from the detrimental effects of salt stress, thus helping of A. donax to cope with salinity and favoring the recovery of the whole plant once the stress is removed.

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.

Some novel cobalt diphenylphosphine complexes were synthesized by reacting cobalt(II) chloride with (2-methoxyethyl)diphenylphosphine, (2-methoxyphenyl)diphenylphosphine, and 2-(1,1-dimethylpropyl)-6-(diphenylphosphino)pyridine. Single crystals suitable for X-ray diffraction studies were obtained for the first two complexes, and their crystal structure was determined. The novel compounds were then used in association with methylaluminoxane (MAO) for the polymerization of 1,3-butadiene, and their behavior was compared with that exhibited in the polymerization of the same monomer by the systems CoCl2(PnPrPh2)2/MAO and CoCl2(PPh3)2/MAO. Some significant differences were observed depending on the MAO/Co ratio used, and a plausible interpretation for such a different behavior is proposed.

O foco deste estudo foi realizar a síntese e dopagem do Óxido de Zinco (ZnO) e do Dióxido de Titânio (TiO2) com a Prata (Ag), visando a ação biocida de sua inserção na blenda de Polipropileno com Alta Resistência do Fundido (HMSPP) obtido por meio do processo de irradiação gama (γ) e o elastômero termoplástico Estireno-Butadieno/Etileno-Estireno (SEBS). As concentrações escolhidas para estudo foram de 0,3% e 1% de cada partícula na blenda HMSPP/SEBS. Para a realização dos testes foram obtidos filmes finos (aprox. 0,07 mm de espessura) utilizando-se o processamento no estado fundido no equipamento extrusora mono-rosca com acessório de filme. As amostras foram caracterizadas por: Microscopia Eletrônica de Varredura (MEV), Microscopia Eletrônica de Transmissão (MET), Espalhamento de Luz Dinâmico (DLS) e testes biocidas com as bactérias Escherichia coli ATCC 8739 e Staphylococcus aureus ATCC 6538 e com os fungos Candida albicans ATCC 10231 e Aspergillus niger ATCC6275, seguindo a norma JIZ 2801 e a norma INCQS 65.3210.006. Na micrografia de TEM constatou-se a presença de nanopartículas menores que 30 nm. Na superfície do filme também foi constatado a presença de aglomerados. Estes aglomerados são formados pelas nanopartículas com tamanho médio de 150 nm. Nos resultados de DRX constatou-se que os filmes de PP/SEBS/ nanopartículas retiveram as nanopartículas em função de sua concentração e corroboraram com os resultados de EDS. As nanopartículas atuaram como agente nucleante modificando a cristalinidade dos filmes conforme evidenciado por DSC. As micrografias de MEV demonstraram que as partículas de TiO2 e TiO2/Ag; ZnO e ZnO/Ag estão localizadas próximas à superfície, melhorando assim a sua possível interação com o meio microbiano. A atividade biocida avaliada nos filmes apresentou um resultado positivo , portanto satisfatório, principalmente dos filmes que possuem partículas dopadas com prata ZnO/Ag e TiO2/Ag. Identificou-se um aumento da atividade biocida dentre as concentrações estudadas, após o processo de esterilização realizado por irradiação gama. Isso pode explicar-se em razão da formação de grupos hidroxila na superfície dos filmes, a ocorrência de radiólise devido a umidade do óleo e do polímero, alteração da band-gap dos óxidos metálicos devido a incorporação da prata. The focus of this study was the synthesis and doping of Zinc Oxide (ZnO) and Titanium Dioxide (TiO2) with silver (Ag) for biocide activity on the blend of High Melt Strength Polypropylene (HMSPP) obtained by Gamma Irradiation Process (γ) and the thermoplastic elastomer Styrene-Ethylene/ButadieneStyrene (SEBS). The selected concentrations for this study were 0.3 wt% and 1 wt% for each particle on the blend of HMSPP/SEBS. For the tests were obtained thin films (~ 0.07 mm of thickness) utilizing the melting processing on the equipment of single-screw extruder with film accessory. The samples was characterized by: Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Dynamic Light Scattering (DLS) and Biocide Tests with the bacteria of Escherichia coli ATCC 8739 and Staphylococcus aureus ATCC 6538 and with the funghi of Candida albicans ATCC 10231 e Aspergillus niger ATCC6275, following the norm of JIZ 2801 and INCQS 65.3210.006. On TEM micrograph was found the presence of nanoparticles smaller than 30nm . On the film surface was also found clusters. The clusters are formed by nanoparticles with average size of 150nm. In the results of DRX were found the HMSPP/SEBS/nanoparticles retained the nanoparticles in function of the concentration and corroborate the EDS results. The nanoparticles acts as nucleant agent modifying the crystallinity of the films according to DSC. The SEM micrograph demonstrate the TiO2 TiO2/Ag; ZnO e ZnO/Ag particles were localized near of the surface, improving thus the possible interaction with microbial medium. On the tests of biocide activity realized on the films were obtained a satisfactory result in reference of biocide tests, mainly on the films with nanoparticles doped with silver ZnO/Ag and TiO2/Ag and also an increase of biocide activity in some studied concentrations, after the sterilization process by gamma irradiation. This fact can explain on the formation of the hydroxyl groups on the surface of the films, the radiolysis occurrence due the moisture from the oil and the polymer, band-gap alteration due the silver incorporation on the metallic oxides.

The Lebedev process, in which ethanol is catalytically converted into 1,3-butadiene, is an alternative process for the production of this commodity chemical. Silica–magnesia (SiO2–MgO) is a benchmark catalyst for the Lebedev process. Among the different preparation methods, the SiO2–MgO catalysts prepared by wet-kneading typically perform best owing to the surface magnesium silicates formed during wet-kneading. Although the thermal treatment is of pivotal importance as a last step in the catalyst preparation, the effect of the calcination temperature of the wet-kneaded SiO2–MgO on the Lebedev process has not been clarified yet. Here, we prepared and characterized in detail a series of wet-kneaded SiO2–MgO catalysts using varying calcination temperatures. We find that the thermal treatment largely influences the type of magnesium silicates, which have different catalytic properties. Our results suggest that the structurally ill-defined amorphous magnesium silicates and lizardite are responsible for the production of ethylene. Further, we argue that forsterite, which has been conventionally considered detrimental for the formation of ethylene, favors the formation of butadiene, especially when combined with stevensite., Nanomaterials, 11 (3), ISSN:2079-4991

Bioethanol is nowadays produced almost exclusively from biomass by fermentation. However, nowadays technologies for the direct trasnformation of lignocellulosic biomass to ethanol present unsatisfactory performances for industrial applications.. So far, synthesis of chemicals from bioethanol have been put into practice only in regions where the cost of sugars is low, such as in Brazil. Several chemicals can be sythesized strating from bioethanol. In this chaoter, we shall deal with the upgrading and homologation of ethanol into butadiene, by means of the Lebedev and Ostromisslensky routes.

Some novel monoalkyl-N-aryl-substituted iminopyridine iron chloride complexes, differing in the nature of the substituent at the iminic carbon and at the ortho position of the aryl ring, were synthesized and characterized. For one of them, single crystals were obtained, which allowed for the determination of its crystalline structure, in which the iron center is coordinated to the chlorides and to the two nitrogen atoms of the ligand. The coordination around iron is distorted tetrahedral, a coordination mode rarely identified for FeCl2 adducts with bidentate nitrogen ligands. All the complexes were used, in combination with methylaluminoxane, for the polymerization of 1,3-butadiene and isoprene, providing syndiotactic 1,2 poly(1,3-butadiene)s and poly(isoprene)s with a predominantly cis-1,4/3,4 alternating structure, in which short cis-1,4 sequences of three or five units, whose length depends on the nature of the ligand on the iron atom, are present. A detailed NMR characterization (1H-, 13C-, and 2D experiments) of the resultant poly(isoprene)s is reported, and a tentative scheme for the formation of the novel isoprene polymers is proposed.

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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.

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.

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.

Although carbon black has been the dominant filler material for rubber composites for over a century, it is a finite, fossil fuel-based product that is sensitive to geopolitical issues and economics. Renewable sources of carbon need to be developed to replace carbon black in order to reduce dependence on petroleum. Biochar is the solid material left over after the anaerobic treatment of biomass at high temperature. In this work, two biochars made from coppiced hardwoods, Paulownia elongata and Populus tremuloides were used to partially replace carbon black in rubber composites using a 50/50 blend of butadiene rubber and natural rubber. Rubber composite samples using these biochars were able to replace 30% of the carbon black with virtually no loss in tensile strength, and improved elongation and toughness compared to the reference sample containing 100% carbon black.

The oxidative dehydrogenation (ODH) of butene has been recently developed as a viable alternative for the synthesis of 1,3-butadiene due to its advantages over other conventional methods. Various catalytic reactors for this process have been previously studied, albeit with a focus on lab-scale design. In this study, a multi-tubular reactor model for the butadiene synthesis via ODH of butene was developed using computational fluid dynamics (CFD). For this, the 3D multi-tubular model, which combines complex reaction kinetics with a shell-side coolant fluid over a series of individual reactor tubes, was generated using OpenFOAM&reg, Then, the developed model was validated and analyzed with the experimental results, which gave a maximum error of 7.5%. Finally, parametric studies were conducted to evaluate the effect of thermodynamic conditions (isothermal, non-isothermal and adiabatic), feed temperature, and gas velocity on reactor performance. The results showed the formation of a hotspot at the reactor exit, which necessitates an efficient temperature control at that section of the reactor. It was also found that as the temperature increased, the conversion and yield increased whilst the selectivity decreased. The converse was found for increasing velocities.

A kinetic study of HTPB synthesis by radical polymerization of butadiene with hydrogen peroxide initiator was conducted using infrared spectroscopy. HTPB conversion was determined based on the conjunction termination rate constant, and all polymerization kinetics were evaluated to identify the constant. All polymerization steps (decomposition, initiation, propagation, conjunction, and proportional termination) can be evaluated based on polymer conversion and functionality from data provided by infrared spectroscopy. The investigation variables included the initial molar ratio of initiator to monomer (H 2 O 2 /butadiene) and the reaction temperature. These steps were assumed as the first-order reactions, giving constant reaction rates of k d , k a , k p , k t , k tc, and k td . The reaction rates obtained for these constants were 4.2 × 10 –5 sec –1 , 8.9 × 10 –4 , 7.7 × 10 3 , 8.5 × 10 7 , 3.2 × 10 7 and 5.3 × 10 7 L mol –1 sec –1 , respectively, with activation energy of 7608, 14188, 2247, 105, 87 and 135 kJ mol –1 , respectively. The determining step of the reaction rate was identified as the initiation reaction. HTPB conversion can be measured if all polymerization kinetics constants have been evaluated.

Replacing noble metal (Pd, Pt, Au) catalysts with inexpensive, environmentally harmless, active, selective, and stable substitutes is a big challenge for the chemical industry. Several aluminium-based complex intermetallic compounds have shown promises for alkynes and alkenes hydrogenation reactions, which are of interest in the chemical industry. It is the case for Al5Co2, Al13Co4 and Al13Fe4 quasicrystalline approximants. The study of their catalytic properties demands different approaches, both theoretical and experimental, in order to determine first their surface structures under ultra-high vacuum or reaction conditions, then their catalytic properties. The combination of surface science experiments (scanning tunneling microscopy, surface X-ray diffraction) and theoretical chemistry calculations (surface energies, adsorption energies and reaction pathways) allows for a better understanding of the key parameters behind the promising catalytic properties of these materials., Remplacer les catalyseurs à base de métaux nobles (Pd, Pt, Au) par des substituts peu coûteux, stables, sélectifs et actifs est un grand défi pour l’industrie chimique. Plusieurs intermétalliques complexes à base d’aluminium se sont révélés prometteurs pour les réactions d’hydrogénation d’alcynes et d’alcènes, importantes dans l’industrie des polymères. C’est le cas des approximants quasicristallins Al5Co2, Al13Co4 et Al13Fe4. L’étude des propriétés catalytiques de ces derniers nécessite plusieurs approches, théoriques et expérimentales, afin de déterminer les structures de surface hors et sous conditions de réaction, première étape avant la détermination des propriétés d’adsorption et des mécanismes de réaction. La combinaison d’expériences de sciences de surface (microscopie à effet tunnel, diffraction de surface des rayons X) et de calculs de chimie théorique (énergies de surface, énergies d’adsorption, chemins de réaction) a permis d’établir des modèles de surface détaillés, leurs propriétés d’adsorption et de mieux comprendre les facteurs clés à l’origine des propriétés catalytiques prometteuses de ces matériaux.

Portland cement is extensively used as a binder in concrete production. However, with Portland cement production, 5% of the natural resources used in this production are consumed, constituting 5–7% of the total CO2 emission. In order to mitigate the environmental problems associated with cement production, styrene-butadiene rubber latex was used as cement replacement up to 20%. In this study, compressive strength, flexural strength, unit weight, water absorption, open porosity, water sorptivity and the chloride ion permeability of Portland cement mortar mixtures modified by styrene-butadiene rubber (SBR) polymeric latex were investigated. For this purpose, the sand/cement ratio and the water/cement ratio were kept constant as 3/1 and 0.5, respectively. In addition to the control mixture containing no polymer, 1, 2, 3, 5, 10 and 20 wt.% of cement was replaced with SBR. In this way, seven mortar mixtures were prepared. Mixed curing (wet cure and dry cure) method was applied to the mortar specimens. Results showed that up to a 5% replacement level, it is possible to improve the mechanical properties of cement mortars with SBR latex addition. However, at a 10% and 20% replacement level, SBR had a significant detrimental effect on the mechanical properties of polymer modified mortars. However, the transport properties decreased with the incorporation rate of SBR latex and the detrimental effect of SBR replacement was more pronounced in 20% SBR mortar mixtures.

Relevant safety issues are associated with hazardous materials transportation, especially when transport routes cross populated areas. On March 6th, 2015, a passenger train collided with the last rail car of a freight train in Tilburg, the Netherlands. The last car contained 50 t of liquefied 1,3-butadiene. As a result of the collision, the last car showed deformation; a small leakage occurred but fortunately with no relevant consequences. However, extremely severe consequences could have happened, such as in the rail accident that occurred in Viareggio, Italy in 2009. In this work, the case of Tilburg was firstly outlined and explored by qualitative methods, in order to identify possible realistic final scenarios that could have happened. Second, the potential consequences of the identified scenarios were estimated through conventional integral model for physical effects evaluation. Comparison with the Viareggio case was also shown in order to support the discussion of the results obtained. Finally, lessons learned after the incident, policy making considerations, and indications for the risk mitigation of hazardous materials transportation are given.

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.

H. F. G. and W.Z. thank the EPSRC for a Capital Equipment Grant EP/L017008/1. Light alkenes are important raw materials for the synthesis of polymers and other chemical products. Traditionally they are obtained mainly from steam cracking and catalytic cracking units. However, dehydrogenation or oxidative dehydrogenation (ODH) of alkanes is gaining more importance to produce alkenes directly from natural gas/shale gas. Here we report that Ti3AlC2, a MAX phase, which hitherto had not used in catalysis, efficiently catalyses the ODH of n-butane to butenes and butadiene, 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. Publisher PDF

This study assesses the techno-economic performance of production lines for obtaining 1,3-butadiene and ε-caprolactam from C6 sugars. Process models were developed to assess their technical performance and to derive inputs for economic analysis. The economic assessment was carried out using net present value (NPV) and production costs as indicators. Sensitivity analyses were carried out to account for the effects of variations in inputs, such as processing capacity, valorization of humins, and prices, on the economic outputs. Results indicate that both production lines perform similarly from an energy intensity point of view (34–50 MJ/kg of main product). However, in terms of yield (kg of product per kg C6 sugar), caprolactam shows higher values by a factor of 1.6–3.6 in comparison to that of butadiene. The butadiene production line is not economically attractive, showing a negative NPV (−647 to −642 M€) and production costs 3–5 times higher than the reference market price (Case I 4369 €/tonne, Case II 3406 €/tonne). The caprolactam production line seems to be unfeasible with negative NPV (−229 M€) and production costs 30% higher than the reference price (Case III 2595 €/tonne, Case IV 1875 €/tonne). However, if the production yield is increased, the caprolactam production line becomes economically attractive with production costs 6% lower than its reference market price. The production costs of caprolactam can be further decreased if the process capacity is increased, reflecting the benefits of the economies of scale, as well as including heat and power produced from humins. Overall, the caprolactam production line shows higher economic potential.

In this study, trans-3-butadiene monomer derivatives with different carbon nanoparticles of the same mass (mass mass) under different temperature conditions were studied using density functional theory. For this purpose, the materials were first geometric optimized, then the thermodynamic parameters were calculated for all of them. Then, the process of changing the energy-dependent parameters such as specific heat capacity, enthalpy, entropy and Gibbs free energy relative to molecular mass, molecular volume and measured level in this study at a given temperature, were evaluated against each other.

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

International audience; Copolymers of ethylene and butadiene were prepared using the ansa-bisfluorenyl Me2Si(C13H8)2NdR complex in combination with dialkylmagnesium as a chain transfer agent. Thorough kinetic studies and computational mechanistic investigations of this copolymerization reaction were performed. Combined with detailed analyses of the polymer microstructure and chain-ends, these studies demonstrate that the entitled copolymerization operates according to a living coordinative chain transfer copol-ymerization of ethylene and butadiene. Besides, in addition to the formation of the previously described 1,2-cyclohexane inner chain cyclic motif, the presence of bicyclic 1,5-decalin units via the formation of transient vinylcyclohexyl-methyl chain-end is discussed in the present communication. The non-accumulation of the vinylcyclohexane motif within the chains is explained by the reversibility of its formation, as interpreted with the help of DFT calculations, or by its rapid conversion into decalin motif after one ethylene insertion. Finally, this study also illustrates the ability of the fluorenyl ligand to adjust its binding mode on demand in order to avoid inhibition of catalyst.

We present a quantum embedding theory called dynamical configuration interaction (DCI) that combines wave function and Green's function theories. DCI captures static correlation in a correlated subspace with configuration interaction and couples to high-energy, dynamic correlation outside the subspace with many-body perturbation theory based on Green's functions. DCI takes the strengths of both theories to balance static and dynamic correlation in a single, fully ab initio embedding concept. The theory adds dynamic correlation around a fixed active space of orbitals with efficient O(N-5) scaling, while maintaining a multireference treatment of the active space. We show that treating high-energy correlation up to the GW and Bethe-Salpeter equation level is sufficient even for challenging multireference problems. Our theory treats ground and excited states on equal footing, and we compute the dissociation curve of N-2, the vertical excitation energies of small molecules, and the ionization spectrum of benzene in excellent agreement with high-level quantum chemistry methods and experiment.

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 styrene–butadiene–styrene tri-block copolymer (SBS) with a high cis -1,4 unit content (greater than 97%) was synthesized by a novel synthetic strategy based on changing the catalytic active centres using n -butyllithium and a nickel-based catalyst. Firstly, styrene was polymerized via anionic polymerization using butyllithium as the initiator (Li, activity centre Li) at 50°C. The obtained alkylated macroinitiator (PSLi) was aged with nickel naphthenate (Ni) and boron trifluoride etherate (B) to prepare a second reactive centre (Ni-F), which was used to initiate the polymerization of butadiene (Bd). Finally, triphenyl phosphine (PPh 3 ) was added to adjust the electron density of the third active centre (P-Ni-F), and styrene monomer was added again to synthesize the second polystyrene block to obtain SBS. The polymerization technique presented here is simple and has an efficient initiation effect due to the high initiation activities for the different monomers. It also exhibits excellent control over the stereo-structure of the butadiene segments in the prepared copolymers, and the SBS polymers with high cis -1,4 unit content were easily achieved.

Пояснювальна записка складається із вступу, 8 розділів, висновків, переліку посилань із 27 найменувань. Загальний обсяг роботи становить 103 с. основного тексту, 20 рисунків, 4 таблиць і 4 додатків. Метою проекту є модернізація кожухотрубного теплообмінника з плаваючою головкою для виробництва бутадієну, що дозволяє підвищити ефективність роботи теплообмінника за допомогою удосконалення конструкції шляхом встановлення в міжтрубний простір кільцевих та дискових перегородок та дискову перегородку з циліндричним фрагментом. Поставлена задача досягається аналітичним визначення основних розмірів апарата, виконанням параметричного, конструктивного, гідравлічного розрахунків та розрахунків на міцність основних вузлів та деталей конструкції, розробкою рекомендації до монтажу та експлуатації теплообмінника, здійсненням оцінки рівня стандартизації та уніфікації розробки, економічним обґрунтуванням модернізації апарата та оцінюванням його ефективності, проведенням аналізу відповідності апарату до вимог охорони праці. Виконано аналіз результатів та зроблено висновки. Наведено список використаної літератури. Графічна частина дипломного проекту включає три креслення формату А1 та два креслення формату А2, що містить: технологічну схему виробництва бутадієну, складальне креслення теплообмінника, креслення корпусу, креслення розподільчої камери, креслення кришки. The explanatory note consists of an introduction, 8 chapters, a conclusion, a list of references of 27 titles. The total amount of work is 103 pages. a main text: 20 figures, 4 tables and 4 addendums. The objective of the study is the modernization of the shell and tube heat exchanger with a floating head for butadiene production, which allows to improve the efficiency of the heat exchanger by improving the design, by installing in circular and disk partitions and a disk partition with a cylindrical fragment in the interstitial space. This object is achieved by the analytical determination of the main dimensions of the unit, the parametric analysis, the constructive calculations, the hydraulic calculations and calculations of the strength of the basic units and parts of the design, the development of recommendations for mounting of installation and operation of the plate heat exchanger, the implementation of assessment of the level of standardization and harmonization of the development, the modernization of the system and justification of the assessment of its effectiveness; the analysis of correspondence of the requirements of the labor protections was conducted; the basic safety apparatus operation was outlined. The analysis of the results and conclusions was done. A list of references is given. The graphical part of the Diploma project consists of three drawings A1 and two drawings A2 format, comprising: the technological scheme of the butadiene production, the assembling drawing of a heat exchanger, the drawing of a case, the drawing of a distribution chamber, the drawing of a cover. Пояснительная записка состоит из введения, 8 глав, заключения, списка ссылок с 27 наименований. Общий объем работы составляет 103 с. основного текста, 20 рисунков, 4 таблиц и 4 приложений. Целью проекта является модернизация кожухотрубного теплообменника с плавающей головкой для производства бутадиена, что позволяет повысить эффективность работы теплообменника с помощью усовершенствования конструкции путем установления в межтрубное пространство кольцевых и дисковых перегородок и дисковую перегородку с цилиндрическим фрагментом. Поставленная задача достигается аналитическим определением основных размеров аппарата, выполнением параметрического, гидравлического расчетов и расчетов на прочность основных узлов и деталей конструкции, разработкой рекомендации к монтажу и эксплуатации теплообменника, осуществлением оценки уровня стандартизации и унификации разработки, экономическим обоснованием модернизации аппарата и оценкой его эффективности, проведением анализа соответствия аппарата с требованиями охраны труда. Выполнен анализ результатов и сделаны выводы. Приведен список использованной литературы. Графическая часть дипломного проекта включает три чертежи формата А1 и два чертежа формата А2, содержащую: технологическую схему производства бутадиена, сборочный чертеж теплообменника, чертеж корпуса, чертеж распределительной камеры, чертеж крышки.

Complex intermetallic compounds such as transition metal (TM) aluminides are promising alternatives to expensive Pd-based catalysts, in particular for the semi-hydrogenation of alkynes or alkadienes. Here, we compare the gas-phase butadiene hydrogenation performances of o-Al13Co4(100), m-Al13Fe4(010) and m-Al13Ru4(010) surfaces, whose bulk terminated structural models exhibit similar cluster-like arrangements. Moreover, the effect of the surface orientation is assessed through a comparison between o-Al13Co4(100) and o-Al13Co4(010). As a result, the following room-temperature activity order is determined: Al13Co4(100) < Al13Co4(010) < Al13Ru4(010) < Al13Fe4(010). Moreover, Al13Co4(010) is found to be the most active surface at 110°C, and even more selective to butene (100%) than previously investigated Al13Fe4(010). DFT calculations show that the activity and selectivity results can be rationalized through the determination of butadiene and butene adsorption energies; in contrast, hydrogen adsorption energies do not scale with the catalytic activities. Moreover, the calculation of projected densities of states provides an insight into the Al13TM4 surface electronic structure. Isolating the TM active centers within the Al matrix induces a narrowing of the TM d-band, which leads to the high catalytic performances of Al13TM4 compounds., Graphical abstract

Submitted by Sandra Pereira (srpereira@ufrrj.br) on 2021-11-22T20:11:01Z No. of bitstreams: 1 2019 - La?s Petra Machado.pdf: 5652073 bytes, checksum: 0f839bd7c93f2f562cf36d61e3c091b1 (MD5) Made available in DSpace on 2021-11-22T20:11:01Z (GMT). No. of bitstreams: 1 2019 - La?s Petra Machado.pdf: 5652073 bytes, checksum: 0f839bd7c93f2f562cf36d61e3c091b1 (MD5) Previous issue date: 2019-03-13 CAPES - Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior The interaction of light with matter is really important in several processes of nature. Photons are employed by natural systems as energy donors or as information elements. The energy from photons, for example, is used in the Z-E isomerization of the C = C bond of the butadiene molecule. Isomerization consists of a photochemical process widely explored and it is the fundamental step of many photobiological processes, such as vision, light-induced ion bomb and phototaxis. This work aims to obtain stationary points from the surface of the potential energy of the butadiene molecules substituted with the Cl group, butadiene substituted with carbonyl (CHO), butadiene substituted with the amine group (NH2) and butadiene. The surface description provides a model for understanding the influence of the groups on the geometry and the photoisomerization process. As a starting point for the investigations in the excited state, the configurations of the molecules corresponding to minima in the potential energy surface of the ground state have been mapped with the CASSCF method. For the carbonyl substituted butadiene molecule, an active space of six orbitals and six electrons was chosen, while, for the chlorinated substituted butadienes, amine substituted butadiene and butadiene, an active space of four orbitals and four electrons was chosen. In addition to the minima in the excited state, four minima have been found at the conic intersection (CI) for chlorobutadiene, three minima at CI for butadiene, three minima at CI for pentadienal and four minima at CI for the amine-butadiene molecule. When comparing the results of the global minimum at the CI of the substituted butadiene molecules with the results for the butadiene molecule, it is realized that the substituents do not significantly alter the geometry of the intersection of the butadiene. However, a CI has been found which is possibly associated with the chlorine dissociation process.Furthermore, two CI's for the amine substituted butadiene are possibly associated with the photoisomerization control, as only the double bond next to the substituent seems to be isomerized. A intera??o da luz com a mat?ria se faz presente em diversos processos importantes da natureza. F?tons s?o empregados por sistemas naturais como doadores de energia ou como elementos de informa??o. A partir da energia proveniente dos f?tons a isomeriza??o Z-E da liga??o C=C pode ser induzida como, por exemplo, na mol?cula do butadieno. A isomeriza??o consiste em um processo fotoqu?mico largamente explorado e forma a etapa fundamental em muitos processos fotobiol?gicos como, por exemplo, vis?o, bomba de ?ons induzida pela luz e fototaxia. O projeto tem como objetivo obter pontos estacion?rios da superf?cie da energia potencial para as mol?culas de butadieno substitu?do com grupo Cl, butadieno substitu?dos com carbonila (CHO), butadieno substitu?do com o grupo amina (NH2) e butadieno. A descri??o da superf?cie gera um modelo para a compreens?o da influ?ncia dos grupos na geometria e no processo de fotoisomeriza??o. Como ponto de partida para as investiga??es no estado excitado, foram mapeadas as configura??es das mol?culas que correspondem aos estados de energia m?nima no estado fundamental atrav?s do m?todo Hartree Fock (HF). Todas as mol?culas foram otimizadas (S0) no m?todo CASSCF, no qual escolhemos, para as mol?culas de butadieno substitu?das com carbonila seis orbitais e seis el?trons, para os butadienos substitu?dos com cloro, para o butadieno substitu?do com amina e para o butadieno foram escolhidos quatro orbitais e quatro el?trons. Al?m dos m?nimos no estado excitado, encontrou-se quatro m?nimos na interse??o c?nica (IC) para o cloro-butadieno, tr?s m?nimos na IC para o butadieno, tr?s m?nimos da IC para o pentadienal e quatro m?nimos da IC para a mol?cula amina-butadieno. Ao comparar os resultados dos m?nimos da IC das mol?culas de butadieno substitu?do com os resultados encontrados no trabalho para a mol?cula de butadieno percebe-se que os substituintes n?o alteram significativamente a geometria da interse??o do butadieno sem substituinte. Entretanto, encontrou-se tamb?m uma IC que, possivelmente, est? associada ao processo de dissocia??o do cloro e tamb?m duas IC que possivelmente est?o associadas ao controle da fotoisomeriza??o, visto que com a amina como substituinte apenas a dupla pr?xima ao substituinte isomerizou, enquanto a outra dupla se manteve.

A series of titanium(IV) complexes of general formula TiCl3[N,N-(pyridin-2-ylalkyl)anilido, TiCl3L, 8–13, were prepared by reactions of TiCl4 with substituted (pyridin-2-ylalkyl)anilines, LH, and characterized by analytical and spectroscopic methods. Compound 10 was obtained by using TiI4 as titanium precursor. In the case of LH = 2,6-diisopropyl(pyridin-2-ylmethyl)aniline, 1, and 2,6-diisopropyl(pyridin-2-ylethyl)aniline, 2, the intermediate formation of TiCl4LH, 6–7, was detected, undergoing HCl elimination on heating to finally give 8 and 9. The products are not stable in coordinating solvents (thf, CH3CN). Ligand dissociation was observed from TiCl3(N,N-2,6-diisopropyl(pyridin-2-ylmethyl)anilido, 8, resulting in the formation of Ti2OCl6(CH3CN)4 and 2-(2,6-diisopropyl-phenylaminomethyl)pyridinium hexachlorotitanate. By reaction of TiCl3(thf)3 or TiI3 with 1 and 2 at ca 100 °C, the air sensitive derivatives TiCl2L, 14, and TiI2L, 15, were afforded. All titanium complexes were evaluated as catalysts for the polymerization of 1,3-butadiene and isoprene, in association with methylaluminoxane (MAO). The results indicate that the catalytic activity is strictly dependent on the nature of the ligands and the oxidation state of the metal, while the nature of the titanium complex has negligible influence on the selectivity.

At high temperatures, isoprene-emitting plants display a higher photosynthetic rate and a lower nonphotochemical quenching (NPQ) compared with nonemitting plants. The mechanism of this phenomenon, which may be very important under current climate warming, is still elusive. - NPQ was dissected into its components, and chlorophyll fluorescence lifetime imaging microscopy (FLIM) was used to analyse the dynamics of excited chlorophyll relaxation in isoprene-emitting and nonemitting plants. Thylakoid membrane stiffness was also measured using atomic force microscope (AFM) to identify a possible mode of action of isoprene in improving photochemical efficiency and photosynthetic stability. - We show that, when compared with nonemitters, isoprene-emitting tobacco plants exposed at high temperatures display a reduced increase of the NPQ energy-dependent component (qE) and stable (1) chlorophyll fluorescence lifetime; (2) amplitude of the fluorescence decay components; and (3) thylakoid membrane stiffness. - Our study shows for the first time that isoprene maintains PSII stability at high temperatures by preventing the modifications of the surrounding environment, namely providing a more steady and homogeneous distribution of the light-absorbing centres and a stable thylakoid membrane stiffness. Isoprene photoprotects leaves with a mechanism alternative to NPQ, enabling plants to maintain a high photosynthetic rate at rising temperatures

cited By 0; The influence of the chemical microstructure on the secondary mechanical relaxations of PB and SBR has been studied by varying the content of vinyl, cis, trans butadiene and styrene groups. Two relaxational mechanisms are involved in their β mechanical relaxations with two distinct activation energies. The fitting by the summation of two Havriliak Negami functions of the experimental isochronal and isothermal curves prove that the vinyl groups are responsible for the contribution of the High Temperature part of the β-relaxation, whereas the butadiene 1,4 groups, cis and trans are at the origin of the low temperature part of this relaxation. Moreover, the intensity of the relaxation associated to each monomer appears to be proportional to their volume (and molar) fraction. Given the random characteristics of the studied copolymer, this suggests that the involved mechanisms are localized at the level of only one monomer unit. © 2019 Elsevier Ltd

In the paper the algorithm of modeling of continuous low-temperature free-radical butadiene-styrene copolymerization process in emulsion based on the Monte-Carlo method is offered. This process is the cornerstone of industrial production butadiene – styrene synthetic rubber which is the most widespread large-capacity rubber of general purpose. Imitation of growth of each macromolecule of the formed copolymer and tracking of the processes happening to it is the basis of algorithm of modeling. Modeling is carried out taking into account residence-time distribution of particles in system that gives the chance to research the process proceeding in the battery of consistently connected polymerization reactors. At the same time each polymerization reactor represents the continuous stirred tank reactor. Since the process is continuous, it is considered continuous addition of portions to the reaction mixture in the first reactor of battery. The constructed model allows to research molecular-weight and viscous characteristics of the formed copolymerization product, to predict the mass content of butadiene and styrene in copolymer, to carry out calculation of molecular-weight distribution of the received product at any moment of conducting process. According to the results of computational experiments analyzed the influence of mode of the process of the regulator introduced during the maintaining on change of characteristics of the formed butadiene-styrene copolymer. As the considered process takes place with participation of monomers of two types, besides listed the model allows to research compositional heterogeneity of the received product that is to carry out calculation of composite distribution and distribution of macromolecules for the size and structure. On the basis of the proposed algorithm created the software tool that allows you to keep track of changes in the characteristics of the resulting product in the dynamics.

In the recent years on-purpose synthesis of butadiene using bioethanol has gained unprecedented attention owing to rise in interest for bio-based feedstock along with the steeply increasing demand for butadiene (BD). In this regard a relevant process is the Ostromyslensky’s two-step process, involving dehydrogenation of ethanol to acetaldehyde in a separate step, followed by butadiene production in the second stage by co-feeding ethanol and acetaldehyde. Although the economic viability and feasibility of this ethanol to butadiene (ETB) process is well established, there is a room for better catalytic performances and selectivity. In this endeavour our aim was to develop a family of well-defined Ta-based silica-supported catalysts through Surface Organometallic Chemistry (SOMC) and test them in the conversion of EtOH/AA to BD. The first set of pre-catalysts was synthesized by treating the previously known [(=SiO)2TaHx] with N2O as mild oxidant. The second family of catalysts was prepared by calcination of the tantalum alkyl species at 500°C. The pre-catalysts were characterized by FTIR, SS NMR, UV-vis-DRS, XRD, EXAFS and HR-STEM. The N2O oxidized SOMC pre-catalysts were found to have mostly isolated [(=SiO)2Ta(OH)x] species populating the surface whereas the family of pre-catalysts synthesized via calcination evidenced a mixture of surface species, including string-like aggregations.Catalytic tests over these catalysts generated promising results exhibiting superior catalysis in the transformation of EtOH/AA to BD in terms of both BD selectivity and yield compared to the state of the art. In addition to the excellent selectivity a narrow range of product distribution and negligible coke formation was observed. Isolated TaOx species on the N2O oxidized pre-catalyst showed markedly better activity and were found to be the active sites in this conversion compared to the string-like aggregation of tantalum centres on the calcined material. Based on this and in-situ DRIFT studies over the catalysts a preliminary mechanism for this conversion was proposed; Au cours des dernières années, la synthèse ciblée du butadiène en utilisant le bioéthanol a suscité une attention sans précédent en raison de l'intérêt croissant aux matières premières biosourcées ainsi que de la demande croissante en butadiène.Un processus pertinent dans ce contexte est le processus d'Ostromyslensky, qui s’effectue en deux étapes, comprenant la déshydrogénation de l'éthanol en acétaldéhyde en une étape séparée , suivie de la production de butadiène dans la deuxième étape par réaction d'acétaldéhyde avec de l'éthanol supplémentaire. Bien que la viabilité économique et la faisabilité de ce procédé d’éthanol en butadiène (ETB) soient bien établies, il reste de la place pour de meilleures performances catalytiques et une meilleure sélectivité. Dans cet effort, notre objectif était de développer une famille de catalyseurs sur silice à base de silice bien définis, basés sur la chimie organométallique de surface (SOMC) et de les tester lors de la conversion d'EtOH / AA en BD. Le premier ensemble de pré-catalyseurs a été synthétisé en traitant le [(=SiO)2TaHx] précédemment connu avec du N2O en tant qu'oxydant doux. La deuxième famille de catalyseurs a été préparée par calcination de l'espèce alkyl de tantale à 500°C. Les pré-catalyseurs ont été caractérisés par FTIR, RMN SS, UV-vis-DRS, DRX, EXAFS et HR-STEM. On a découvert que les pré-catalyseurs SOMC oxydés au N2O avaient principalement isolé des espèces [(SiO)2Ta (OH)x] peuplant la surface, tandis que la famille des pré-catalyseurs synthétisés par calcination mettait en évidence un mélange d’espèces de surface, y compris des agrégations de type cordes. Les tests catalytiques sur ces catalyseurs ont donné des résultats prometteurs, présentant une catalyse supérieure dans la transformation d'EtOH / AA en BD en termes de sélectivité en BD et de rendement par rapport à l'état de la technique. Outre l'excellente sélectivité, une gamme étroite de distribution du produit et une formation négligeable de coke ont été observées. Les espèces de TaOx isolées sur le pré-catalyseur oxydé au N2O ont montré une activité nettement meilleure et se sont révélées être les sites actifs de cette conversion par rapport à l'agrégation en chaîne de centres de tantale sur le matériau calciné. Sur la base de ces études DRIFT et in situ sur les catalyseurs, un mécanisme préliminaire pour cette conversion a été proposé

Background Butadiene is a platform chemical used as an industrial feedstock for the manufacture of automobile tires, synthetic resins, latex and engineering plastics. Currently, butadiene is predominantly synthesized as a byproduct of ethylene production from non-renewable petroleum resources. Although the idea of biological synthesis of butadiene from sugars has been discussed in the literature, success for that goal has so far not been reported. As a model system for methanol assimilation, Methylobacterium extorquens AM1 can produce several unique metabolic intermediates for the production of value-added chemicals, including crotonyl-CoA as a potential precursor for butadiene synthesis. Results In this work, we focused on constructing a metabolic pathway to convert crotonyl-CoA into crotyl diphosphate, a direct precursor of butadiene. The engineered pathway consists of three identified enzymes, a hydroxyethylthiazole kinase (THK) from Escherichia coli, an isopentenyl phosphate kinase (IPK) from Methanothermobacter thermautotrophicus and an aldehyde/alcohol dehydrogenase (ADHE2) from Clostridium acetobutylicum. The Km and kcat of THK, IPK and ADHE2 were determined as 8.35 mM and 1.24 s−1, 1.28 mM and 153.14 s−1, and 2.34 mM and 1.15 s−1 towards crotonol, crotyl monophosphate and crotonyl-CoA, respectively. Then, the activity of one of rate-limiting enzymes, THK, was optimized by random mutagenesis coupled with a developed high-throughput screening colorimetric assay. The resulting variant (THKM82V) isolated from over 3000 colonies showed 8.6-fold higher activity than wild-type, which helped increase the titer of crotyl diphosphate to 0.76 mM, corresponding to a 7.6% conversion from crotonol in the one-pot in vitro reaction. Overexpression of native ADHE2, IPK with THKM82V under a strong promoter mxaF in M. extorquens AM1 did not produce crotyl diphosphate from crotonyl-CoA, but the engineered strain did generate 0.60 μg/mL of intracellular crotyl diphosphate from exogenously supplied crotonol at mid-exponential phase. Conclusions These results represent the first step in producing a butadiene precursor in recombinant M. extorquens AM1. It not only demonstrates the feasibility of converting crotonol to key intermediates for butadiene biosynthesis, it also suggests future directions for improving catalytic efficiency of aldehyde/alcohol dehydrogenase to produce butadiene precursor from methanol. Electronic supplementary material The online version of this article (10.1186/s12934-018-1042-4) contains supplementary material, which is available to authorized users.

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.

This study assesses the techno-economic performance of production lines for obtaining 1,3-butadiene and ε-caprolactam from C6 sugars. Process models were developed to assess their technical performance and to derive inputs for economic analysis. The economic assessment was carried out using net present value (NPV) and production costs as indicators. Sensitivity analyses were carried out to account for the effects of variations in inputs, such as processing capacity, valorization of humins, and prices, on the economic outputs. Results indicate that both production lines perform similarly from an energy intensity point of view (34-50 MJ/kg of main product). However, in terms of yield (kg of product per kg C6 sugar), caprolactam shows higher values by a factor of 1.6-3.6 in comparison to that of butadiene. The butadiene production line is not economically attractive, showing a negative NPV (-647 to -642 M€) and production costs 3-5 times higher than the reference market price (Case I 4369 €/tonne, Case II 3406 €/tonne). The caprolactam production line seems to be unfeasible with negative NPV (-229 M€) and production costs 30% higher than the reference price (Case III 2595 €/tonne, Case IV 1875 €/tonne). However, if the production yield is increased, the caprolactam production line becomes economically attractive with production costs 6% lower than its reference market price. The production costs of caprolactam can be further decreased if the process capacity is increased, reflecting the benefits of the economies of scale, as well as including heat and power produced from humins. Overall, the caprolactam production line shows higher economic potential.

Pd nanoparticles supported on SiO2, Si3N4 and Al2O3 were studied to examine the effect of particle size and support type on the hydrogenation of 1,3-butadiene. Pd nanoparticles were produced using a reverse micelle method resulting in particles with a remarkably small particle size distribution (σ

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.