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Sambiagio, Carlo, Stephen P. Marsden, A. John Blacker e Patrick C. McGowan. "Copper catalysed Ullmann type chemistry: from mechanistic aspects to modern development". Chem. Soc. Rev. 43, n.º 10 (2014): 3525–50. http://dx.doi.org/10.1039/c3cs60289c.
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Copper-catalysed arylations represent valid and complementary alternatives to Pd catalysis. This review discusses the different mechanisms suggested for these reactions, and summarises some of their latest applications in synthesis.
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Mao, Zhenjun, Haorui Gu e Xufeng Lin. "Recent Advances of Pd/C-Catalyzed Reactions". Catalysts 11, n.º 9 (7 de setembro de 2021): 1078. http://dx.doi.org/10.3390/catal11091078.
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The Pd/C-catalyzed reactions, including reduction reactions and cross-coupling reactions, play an irreplaceable role in modern organic synthesis. Compared to the homogeneous palladium catalyst system, the heterogeneous Pd/C catalyst system offers an alternative protocol that has particular advantages and applications. Herein, a review on Pd/C-catalyzed reactions is presented. Both the advances in Pd/C-catalyzed methodologies and the application of Pd/C-catalysis in total synthesis are covered in this review.
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Costentin, Cyrille, Jean-Michel Savéant e Cédric Tard. "Ligand “noninnocence” in coordination complexes vs. kinetic, mechanistic, and selectivity issues in electrochemical catalysis". Proceedings of the National Academy of Sciences 115, n.º 37 (24 de agosto de 2018): 9104–9. http://dx.doi.org/10.1073/pnas.1810255115.
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The world of coordination complexes is currently stimulated by the quest for efficient catalysts for the electrochemical reactions underlying modern energy and environmental challenges. Even in the case of a multielectron−multistep process, catalysis starts with uptake or removal of one electron from the resting state of the catalyst. If this first step is an outer-sphere electron transfer (triggering a “redox catalysis” process), the electron distribution over the metal and the ligand is of minor importance. This is no longer the case with “chemical catalysis,” in which the active catalyst reacts with the substrate in an inner-sphere manner, often involving the transient formation of a catalyst−substrate adduct. The fact that, in most cases, the ligand is “noninnocent,” in the sense that the electron density and charge gained (or removed) from the resting state of the catalyst are shared between the metal and the ligand, has become common-place knowledge over the last half-century. Insistent focus on a large degree of noninnocence of the ligand in the resting state of the catalyst, even robustly validated by spectroscopic techniques, may lead to undermining the essential role of the metal when such essential issues as kinetics, mechanisms, and product selectivity are dealt with. These points are general in scope, but their discussion is eased by adequately documented examples. This is the case for reactions involving metalloporphyrins as well as vitamin B12 derivatives and similar cobalt complexes for which a wealth of experimental data is available.
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Li, Yongfei, Shu Zhang, Ying Wang, Guobin Qi, Tao Yu, Xin Xin, Bin Zhao e Gang Chen. "Oil-Soluble Exogenous Catalysts and Reservoir Minerals Synergistically Catalyze the Aquathermolysis of Heavy Oil". Molecules 28, n.º 19 (22 de setembro de 2023): 6766. http://dx.doi.org/10.3390/molecules28196766.
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Oil is the “blood” and economic lifeblood of modern industry, but traditional light crude oil has been over-consumed, and it has been difficult to meet human demand for energy, so the exploitation of heavy oil is particularly important. In this paper, an oil-soluble catalyst was synthesized to catalyze the pyrolysis reaction of heavy oil in collaboration with reservoir minerals, so as to achieve efficient viscosity reduction of heavy oil and reduce production costs. The experimental results showed that Zn(II)O + K had the best synergistic viscosity reduction effect after the aquathermolysis of No. 1 oil sample under the reaction conditions of 180 °C, 4 h, 30% of water, and 0.2% of catalyst, respectively, and the viscosity reduction rate was 61.74%. Under the catalysis of the isopropanol system, the viscosity reduction rate was increased to 91.22%. A series of characterizations such as freezing point, thermogravimetric analysis, DSC analysis, component analysis, gas chromatography, wax crystal morphology analysis, and GC-MS analysis of aqueous organic matter were carried out on heavy oil after reaction by different reaction systems, and it could be verified that the viscosity of heavy oil was reduced. Finally, through the study of the reaction mechanism of the model compound, combined with the aqueous phase analysis, it can be clearly found that the depolymerization between macromolecules, the breaking of heteroatom chains, hydrogenation, ring opening, and other effects mainly occur during the reaction, thereby weakening the van der Waals force and hydrogen bond of the recombinant interval, inhibiting the formation of grid structure in heavy oil and effectively reducing the viscosity of heavy oil.
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Wetchasat, Piraya, Saros Salakhum, Thidarat Imyen, Duangkamon Suttipat, Wannaruedee Wannapakdee, Marisa Ketkaew, Anittha Prasertsab, Pinit Kidkhunthod, Thongthai Witoon e Chularat Wattanakit. "One-Pot Synthesis of Ultra-Small Pt Dispersed on Hierarchical Zeolite Nanosheet Surfaces for Mild Hydrodeoxygenation of 4-Propylphenol". Catalysts 11, n.º 3 (5 de março de 2021): 333. http://dx.doi.org/10.3390/catal11030333.
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The rational design of ultra-small metal clusters dispersed on a solid is of crucial importance in modern nanotechnology and catalysis. In this contribution, the concept of catalyst fabrication with a very ultra-small size of platinum nanoparticles supported on a hierarchical zeolite surface via a one-pot hydrothermal system was demonstrated. Combining the zeolite gel with ethylenediaminetetraacetic acid (EDTA) as a ligand precursor during the crystallization process, it allows significant improvement of the metal dispersion on a zeolite support. To illustrate the beneficial effect of ultra-small metal nanoparticles on a hierarchical zeolite surface as a bifunctional catalyst, a very high catalytic performance of almost 100% of cycloalkane product yield can be achieved in the consecutive mild hydrodeoxygenation of 4-propylphenol, which is a lignin-derived model molecule. This instance opens up perspectives to improve the efficiency of a catalyst for the sustainable conversion of biomass-derived compounds to fuels.
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Khairulin, Sergei, Mikhail Kerzhentsev, Anton Salnikov e Zinfer R. Ismagilov. "Direct Selective Oxidation of Hydrogen Sulfide: Laboratory, Pilot and Industrial Tests". Catalysts 11, n.º 9 (15 de setembro de 2021): 1109. http://dx.doi.org/10.3390/catal11091109.
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This article is devoted to scientific and technical aspects of the direct catalytic oxidation of hydrogen sulfide for the production of elemental sulfur. It includes a detailed description of the Claus process as the main reference technology for hydrogen sulfide processing methods. An overview of modern catalytic systems for direct catalytic oxidation technology and known processes is presented. Descriptions of the scientific results of the Institute of Catalysis of the SB RAS in a study of the physical and chemical foundations of the process and the creation of a catalyst for it are included. The Boreskov Institute of Catalysis SB RAS technologies based on fundamental studies and their pilot and industrial testing results are described.
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Latos, Piotr, Anna Wolny e Anna Chrobok. "Supported Ionic Liquid Phase Catalysts Dedicated for Continuous Flow Synthesis". Materials 16, n.º 5 (5 de março de 2023): 2106. http://dx.doi.org/10.3390/ma16052106.
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Heterogeneous catalysis, although known for over a century, is constantly improved and plays a key role in solving the present problems in chemical technology. Thanks to the development of modern materials engineering, solid supports for catalytic phases having a highly developed surface are available. Recently, continuous-flow synthesis started to be a key technology in the synthesis of high added value chemicals. These processes are more efficient, sustainable, safer and cheaper to operate. The most promising is the use of heterogeneous catalyst with column-type fixed-bed reactors. The advantages of the use of heterogeneous catalyst in continuous flow reactors are the physical separation of product and catalyst, as well as the reduction in inactivation and loss of the catalyst. However, the state-of-the-art use of heterogeneous catalysts in flow systems compared to homogenous ones remains still open. The lifetime of heterogeneous catalysts remains a significant hurdle to realise sustainable flow synthesis. The goal of this review article was to present a state of knowledge concerning the application of Supported Ionic Liquid Phase (SILP) catalysts dedicated for continuous flow synthesis.
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Kaur, Navjeet, Neha Ahlawat, Pooja Grewal, Pranshu Bhardwaj e Yamini Verma. "Organo or Metal Complex Catalyzed Synthesis of Five-membered Oxygen Heterocycles". Current Organic Chemistry 23, n.º 25 (14 de janeiro de 2020): 2822–47. http://dx.doi.org/10.2174/1385272823666191122111351.
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: The reactions involving the formation of C-O bond using metal as a catalyst have emerged to be one of the most influential reactions for the synthesis of heterocycles in modern organic chemistry. Catalysis by metals offers diverse opportunities to invent new organic reactions with a promising range of selectivities such as chemoselectivity, regioselectivity, diastereoselectivity, and enantioselectivity. The methodologies used earlier for synthesis were less approachable to the organic chemist because of their high cost, highly specified instrumentation and inconvenient methods. For both stereoselective and regioselective formation of five-membered O-containing heterocycles, cyclic reactions that are metal and non-metal-catalyzed have known to be very efficient. The present review article covers the applications of metal and non-metal as a catalyst for the synthesis of five-membered O-containing heterocycles.
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Fiore, Michele, e René Buchet. "Symmetry Breaking of Phospholipids". Symmetry 12, n.º 9 (10 de setembro de 2020): 1488. http://dx.doi.org/10.3390/sym12091488.
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Either stereo reactants or stereo catalysis from achiral or chiral molecules are a prerequisite to obtain pure enantiomeric lipid derivatives. We reviewed a few plausibly organic syntheses of phospholipids under prebiotic conditions with special attention paid to the starting materials as pro-chiral dihydroxyacetone and dihydroxyacetone phosphate (DHAP), which are the key molecules to break symmetry in phospholipids. The advantages of homochiral membranes compared to those of heterochiral membranes were analysed in terms of specific recognition, optimal functions of enzymes, membrane fluidity and topological packing. All biological membranes contain enantiomerically pure lipids in modern bacteria, eukarya and archaea. The contemporary archaea, comprising of methanogens, halobacteria and thermoacidophiles, are living under extreme conditions reminiscent of primitive environment and may indicate the origin of one ancient evolution path of lipid biosynthesis. The analysis of the known lipid metabolism reveals that all modern cells including archaea synthetize enantiomerically pure lipid precursors from prochiral DHAP. Sn-glycerol-1-phosphate dehydrogenase (G1PDH), usually found in archaea, catalyses the formation of sn-glycerol-1-phosphate (G1P), while sn-glycerol-3-phosphate dehydrogenase (G3PDH) catalyses the formation of sn-glycerol-3-phosphate (G3P) in bacteria and eukarya. The selective enzymatic activity seems to be the main strategy that evolution retained to obtain enantiomerically pure lipids. The occurrence of two genes encoding for G1PDH and G3PDH served to build up an evolutionary tree being the basis of our hypothesis article focusing on the evolution of these two genes. Gene encoding for G3PDH in eukarya may originate from G3PDH gene found in rare archaea indicating that archaea appeared earlier in the evolutionary tree than eukarya. Archaea and bacteria evolved probably separately, due to their distinct respective genes coding for G1PDH and G3PDH. We propose that prochiral DHAP is an essential molecule since it provides a convergent link between G1DPH and G3PDH. The synthesis of enantiopure phospholipids from DHAP appeared probably firstly in the presence of chemical catalysts, before being catalysed by enzymes which were the products of later Darwinian selection. The enzymes were probably selected for their efficient catalytic activities during evolution from large libraries of vesicles containing amino acids, carbohydrates, nucleic acids, lipids, and meteorite components that induced symmetry imbalance.
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Kazemi, Mosstafa, Massoud Ghobadi e Ali Mirzaie. "Cobalt ferrite nanoparticles (CoFe2O4 MNPs) as catalyst and support: magnetically recoverable nanocatalysts in organic synthesis". Nanotechnology Reviews 7, n.º 1 (23 de fevereiro de 2018): 43–68. http://dx.doi.org/10.1515/ntrev-2017-0138.
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AbstractRecovery and reusability of catalysts is an important aspect in modern catalysis research especially in organic synthesis. Compared to the conventional separation, magnetic separation has emerged as a robust, highly efficient, easy and rapid separation technique for products and catalysts. Cobalt ferrite nanoparticles are a well-known material, recognized as CoFe2O4MNPs, and can be used as both catalyst and a versatile support for functionalization of metals, organocatalysts. In recent times, catalysis research has clearly experienced a renaissance in the area of utility of cobalt ferrite (CoFe2O4MNPs) nanocatalysts based on their ability for recovery and reusability; the activity of these CoFe2O4MNPs was investigated in a category of organic reactions. In this review, the fabrication, characterization, and application of cobalt ferrite (CoFe2O4MNPs) nanocatalysts (CF-MNPs) in organic reactions have well summarized.
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Mori, Margherita. "Modern finance: a catalyst for truly modern agriculture". Review on Agriculture and Rural Development 7, n.º 1-2 (1 de novembro de 2019): 5–10. http://dx.doi.org/10.14232/rard.2018.1-2.5-10.
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This paper aims at investigating the crucial role that the three pillars of the financial system – i.e. financial markets, products and institutions – are likely to play in order to speed up the process of modernization in agriculture, especially in agri-food chains. Four main areas of interest can be identified that consist of sustainable, inclusive, blended and rural finance, and that embody a set of strategic tools: their support to the agricultural sector ranges from its most traditional side to unprecedented forward steps, such as those pertaining to novel foods and to farming on Mars. While innovation allows for progress both in the financial industry and in agribusiness, glocal co-opetitive challenges surface from what can be found at the crossroads: a growing concern for sustainability issues is just an example, which leads to emphasize the 17 Sustainable Development Goals and the underlying generation pact. Focusing on finance, this is a qualitative research that draws upon empirical evidence and success stories; a framework for analysis is outlined, in an attempt at promoting rural finance as a specialized discipline from a theoretical point of view and a peculiar market segment for operating purposes, with relevant sub-sets such as agricultural finance, agricultural value chain finance and agricultural microfinance. Conclusions encompass recommendations that unveil academic implications; supporting arguments stem from – among others – the widely recognized need for upgrading financial education and literacy, especially in rural areas and even within the context of lifelong learning.
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Hernández Pezzi, Emilia. "Adolf Behne y la arquitectura moderna = Adolf Behne and the modern architecture". Cuaderno de Notas, n.º 15 (28 de novembro de 2014): 83. http://dx.doi.org/10.20868/cn.2014.2959.
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Adolf Behne fue un lúcido crítico alemán de entreguerras. Participó activamente en la evolución de las corrientes culturales de ese tiempo y, pese a su implicación en ellas, las interpretó y valoró con objetividad y acierto. Relacionó arte y arquitectura, entendiendo que sólo un fuerte compromiso social podía fundamentar este vínculo, y así logró detectar la continuidad entre experiencias tan aparentemente distantes como el expresionismo y el racionalismo moderno y enlazarlas con las tendencias funcionalistas ortodoxas de finales de los veinte. Desde sus privilegiados contactos con artistas y arquitectos observó, analizó, juzgó y actuó como agente catalizador de las intensas transformaciones que caracterizaron aquel tiempo convulso, seleccionando con hábil criterio los personajes que mejor las representaron. Abstract Adolf Behne was a lucid German critic from the period between the wars. He was actively involved in the evolution of the cultural trends of the time and, despite his own implication, he interpreted and valued them correctly. He related art and architecture, and understood that only a strong social compromise could found this link, being able this way to detect the continuity between aparently distant experiences such as modern expresionism and rationalism and link them with the ortodox funcionalists trends from the end of the 1920s. From his privileged contacts with artists and architects he observed, analized, judged and acted as a catalyst for the intense transformations that marked those turbulent times, skilfully selecting the characters that pictured them best.
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Nicholls, Peter. "Classical catalase: Ancient and modern". Archives of Biochemistry and Biophysics 525, n.º 2 (setembro de 2012): 95–101. http://dx.doi.org/10.1016/j.abb.2012.01.015.
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Teng, Yingyue, Dingze Liu, Qiang Li, Xue Bai e Yinmin Song. "Research Progress on Application in Energy Conversion of Silicon Carbide-Based Catalyst Carriers". Catalysts 13, n.º 2 (19 de janeiro de 2023): 236. http://dx.doi.org/10.3390/catal13020236.
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In modern industrial production, heterogeneous catalysts play an important role. A catalyst carrier, as a constituent of heterogeneous catalysts, is employed for supporting and loading active components. The catalyst carrier has a considerable impact on the overall acting performance of the catalysts in actual production. Therefore, a catalyst carrier should have some necessary properties such as a high specific surface area, excellent mechanical strength and wear resistance, and better thermal stability. Among the candidate materials, silicon carbide (SiC) has excellent physical and chemical properties due to its special crystal structure; these properties include outstanding thermal conductivity and remarkable mechanical strength and chemical stability. Therefore, SiC materials with a high specific surface area basically meet the requirements of catalyst carriers. Accordingly, SiC has broad application prospects in the field of catalysis and is an ideal material for preparing catalyst carriers. In the present study, we reviewed the preparation methods and the variation in the raw materials used for preparing SiC-based catalyst carriers with high specific surface areas, in particular the research progress on the application of SiC-based catalyst carriers in the field of energy-conversion in recent years. The in-depth analysis indicated that the construction of SiC with a special structure, large-scale synthesis of SiC by utilizing waste materials, low-temperature synthesis of SiC, and exploring the interaction between SiC supports and active phases are the key strategies for future industrial development; these will have far-reaching significance in enhancing catalytic efficiency, reutilization of resources, ecological environmental protection, energy savings, and reductions in energy consumption.
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Bulavchenko, Olga A., e Zakhar S. Vinokurov. "In Situ X-ray Diffraction as a Basic Tool to Study Oxide and Metal Oxide Catalysts". Catalysts 13, n.º 11 (7 de novembro de 2023): 1421. http://dx.doi.org/10.3390/catal13111421.
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X-ray diffraction (XRD) is a standard technique that is widely applied in heterogeneous catalysis to determine phase composition, atomic structure, and size of crystallites. This review is focused on the application of in situ XRD for studying the catalysts during their “lifetime” (under synthesis, activation, operation, and deactivation conditions), limiting the objects of research to oxide and metal oxide catalysts. Also included is a brief overview of modern techniques and instruments and the latest works illustrating different aspects of this technique in catalyst research. The main conclusion is that the field of heterogeneous catalysis research would benefit substantially from the application of in situ XRD for the structural, phase, and morphological characterization of solid catalysts. Even more useful information can be obtained if XRD is combined with other techniques that are more sensitive at length scales different from that of XRD.
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Xiao, Tiancun, Tara Shirvani, Oliver Inderwildi, Sergio Gonzalez-Cortes, Hamid AlMegren, David King e Peter P. Edwards. "The Catalyst Selectivity Index (CSI): A Framework and Metric to Assess the Impact of Catalyst Efficiency Enhancements upon Energy and CO2 Footprints". Topics in Catalysis 58, n.º 10-11 (2 de julho de 2015): 682–95. http://dx.doi.org/10.1007/s11244-015-0401-1.
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AbstractHeterogeneous catalysts are not only a venerable part of our chemical and industrial heritage, but they also occupy a pivotal, central role in the advancement of modern chemistry, chemical processes and chemical technologies. The broad field of catalysis has also emerged as a critical, enabling science and technology in the modern development of “Green Chemistry”, with the avowed aim of achieving green and sustainable processes. Thus a widely utilized metric, the environmental E factor—characterizing the waste-to-product ratio for a chemical industrial process—permits one to assess the potential deleterious environmental impact of an entire chemical process in terms of excessive solvent usage. As the many (and entirely reasonable) societal pressures grow, requiring chemists and chemical engineers not only to develop manufacturing processes using new sources of energy, but also to decrease the energy/carbon footprint of existing chemical processes, these issues become ever more pressing. On that road to a green and more sustainable future for chemistry and energy, we note that, as far as we are aware, little effort has been directed towards a direct evaluation of the quantitative impacts that advances or improvements in a catalyst’s performance or efficiency would have on the overall energy or carbon (CO2) footprint balance and corresponding greenhouse gas (GHG) emissions of chemical processes and manufacturing technologies. Therefore, this present research was motivated by the premise that the sustainability impact of advances in catalysis science and technology, especially heterogeneous catalysis—the core of large-scale manufacturing processes—must move from a qualitative to a more quantitative form of assessment. This, then, is the exciting challenge of developing a new paradigm for catalysis science which embodies—in a truly quantitative form—its impact on sustainability in chemical, industrial processes. Towards that goal, we present here the concept, definition, design and development of what we term the Catalyst Sensitivity Index (CSI) to provide a measurable index as to how efficiency or performance enhancements of a heterogeneous catalyst will directly impact upon the fossil energy consumption and GHG emissions balance across several prototypical fuel production and conversion technologies, e.g. hydrocarbon fuels synthesized using algae-to-biodiesel, algae-to-jet biofuel, coal-to-liquid and gas-to-liquid processes, together with fuel upgrading processes using fluidized catalytic cracking of heavy oil, hydrocracking of heavy oil and also the production of hydrogen from steam methane reforming. Traditionally, the performance of a catalyst is defined by a combination of its activity or efficiency (its turnover frequency), its selectivity and stability (its turnover number), all of which are direct manifestations of the intrinsic physicochemical properties of the heterogeneous catalyst itself under specific working conditions. We will, of course, retain these definitions of the catalytic process, but now attempt to place discussions about a catalyst’s performance onto a new foundation by investigating the effect of improvements in the catalyst’s efficiency or performance on the resulting total energy and total CO2 footprint for these prototypical fuel production and fuel conversion processes. The CSI should help the academic and industrial chemical communities, not only to highlight the current ‘best practice catalysts’, but also draw specific conclusions as to what energy and CO2 emissions saving one could anticipate with higher efficiency/higher performance from heterogeneous catalysts in a particular fuel synthesis or conversion process or technology. Our aim is to place discussions about advances in the science and technology of catalysis onto a firm foundation in the context of GHG emissions. We believe that thinking about (and attempting to quantify) total energy and CO2 emissions reductions associated with advances in catalysis science from a complete energy life cycle analysis perspective is extremely important. The CSI will help identify processes where the most critical advances in catalyst efficiency are needed in terms of their potential impact in the transition to a more sustainable future for fuel production and conversion technologies.
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MacDonald, M. Jason, e Godwin B. D’Cunha. "A modern view of phenylalanine ammonia lyase". Biochemistry and Cell Biology 85, n.º 3 (junho de 2007): 273–82. http://dx.doi.org/10.1139/o07-018.
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Phenylalanine ammonia lyase (PAL; E.C.4.3.1.5), which catalyses the biotransformation of l-phenylalanine to trans-cinnamic acid and ammonia, was first described in 1961 by Koukol and Conn. Since its discovery, much knowledge has been gathered with reference to the enzyme’s catabolic role in microorganisms and its importance in the phenyl propanoid pathway of plants. The 3-dimensional structure of the enzyme has been characterized using X-ray crystallography. This has led to a greater understanding of the mechanism of PAL-catalyzed reactions, including the discovery of a recently described cofactor, 3,5-dihydro-5-methyldiene-4H-imidazol-4-one. In the past 3 decades, PAL has gained considerable significance in several clinical, industrial, and biotechnological applications. The reversal of the normal physiological reaction can be effectively employed in the production of optically pure l-phenylalanine, which is a precursor of the noncalorific sweetener aspartame (l-phenylalanyl-l-aspartyl methyl ester). The enzyme’s natural ability to break down l-phenylalanine makes PAL a reliable treatment for the genetic condition phenylketonuria. In this mini-review, we discuss prominent details relating to the physiological role of PAL, the mechanism of catalysis, methods of determination and purification, enzyme kinetics, and enzyme activity in nonaqueous media. Two topics of current study on PAL, molecular biology and crystal structure, are also discussed.
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van Slagmaat, Christian A. M. R., Khi Chhay Chou, Lukas Morick, Darya Hadavi, Burgert Blom e Stefaan M. A. De Wildeman. "Synthesis and Catalytic Application of Knölker-Type Iron Complexes with a Novel Asymmetric Cyclopentadienone Ligand Design". Catalysts 9, n.º 10 (22 de setembro de 2019): 790. http://dx.doi.org/10.3390/catal9100790.
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Asymmetric catalysis is an essential tool in modern chemistry, but increasing environmental concerns demand the development of new catalysts based on cheap, abundant, and less toxic iron. As a result, Knölker-type catalysts have emerged as a promising class of iron catalysts for various chemical transformations, notably the hydrogenation of carbonyls and imines, while asymmetric versions are still under exploration to achieve optimal enantio-selectivities. In this work, we report a novel asymmetric design of a Knölker-type catalyst, in which the C2-rotational symmetric cyclopentadienone ligand possesses chiral substituents on the 2- and 5-positions near the active site. Four examples of the highly modular catalyst design were synthesized via standard organic procedures, and their structures were confirmed with NMR, IR, MS, and polarimetry analysis. Density functional theory (DFT) calculations were conducted to elucidate the spatial conformation of the catalysts, and therewith to rationalize the influence of structural alterations. Transfer- and H2-mediated hydrogenations were successfully established, leading to appreciable enantiomeric excesses (ee) values up to 70%. Amongst all reported Knölker-type catalysts, our catalyst design achieves one of the highest ee values for hydrogenation of acetophenone and related compounds.
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Zhao, Xiaodan, e Lihao Liao. "Modern Organoselenium Catalysis: Opportunities and Challenges". Synlett 32, n.º 13 (11 de maio de 2021): 1262–68. http://dx.doi.org/10.1055/a-1506-5532.
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AbstractOrganoselenium catalysis has attracted increasing interest in recent years. This Cluster highlights recent key advances in this area regarding the functionalization of alkenes, alkynes, and arenes by electrophilic selenium catalysis, selenonium salt catalysis, selenium-based chalcogen-bonding catalysis, and Lewis basic selenium catalysis. These achievements might inspire and help future research.1 Introduction2 Electrophilic Selenium Catalysis3 Selenonium Salt Catalysis4 Selenium-Based Chalcogen-Bond Catalysis5 Lewis Basic Selenide Catalysis6 Conclusion
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Gelabertó Vilagran, Martín. "La sorcellerie catalane à l’époque moderne". Heresis 39, n.º 1 (2003): 115–28. http://dx.doi.org/10.3406/heres.2003.2013.
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Catalan sorcery in modem times. This document wants to accomplish a research on the issue of sorcery in Cataluña in modern times through the analysis of different historical sources concerning missionary predication littérature. This research tends to interpret this phenomenon in a new way, as something included in a wider movment of cultural transformation of Ancien Regime society. Modern catalan Church will tend to manipulate archaic peasant creeds to serve the official religious views, of which ultimate aim is to subject human consciences to the norms of postridentine Church Triumphant.
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Leclair, Alexandre, Rubén O. Torres-Ochoa, Qian Wang e Jieping Zhu. "Iron-Catalysed Remote C(sp3)-H Azidation of O-Acyl Oximes and N -Acyloxy Imidates". CHIMIA International Journal for Chemistry 75, n.º 4 (28 de abril de 2021): 329–32. http://dx.doi.org/10.2533/chimia.2021.329.
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The azido group occupies an important position in modern organic chemistry, broadly used as amine surrogates and as anchors in bioconjugation. Despite their importance, examples of selective direct azidation of inert C(sp3)–H bonds remain limited and often require strong oxidative conditions. Herein, we highlight the use of O-acyl oximes and N-acyloxy imidates as directing groups for the selective iron-catalysed azidation of C(sp3)–H bond with trimethylsilyl azide, giving access to various γ-azido ketones and β-azido alcohols in moderate to excellent yields. The iron catalyst is assumed to play a dual role in these catalytic processes: as a reductant to generate the reactive iminyl and imidate radicals, respectively, and as a redox centre to mediate the azido transfer to the translocated carbon radical.
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Gai, Pratibha L. "In Situ Electron Microscopy in catalysis research and related surface reactions". Proceedings, annual meeting, Electron Microscopy Society of America 47 (6 de agosto de 1989): 614–15. http://dx.doi.org/10.1017/s0424820100155049.
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Catalysis plays a major role in the modern oil and chemical industries. Solid state catalysts are most common, whilst the reactants are commodity gases and liquids. The performance of the catalysts depends strongly on their microstructure, chemistry and surface structures on a fine (nanometer) scale and electron microscopy (EM) plays an increasingly important role in the characterization. In-situ EM with an environmental cell permits direct observations of chemical reactions under near operating conditions and in conjunction with HREM and AEM can provide in favorable cases, significant atomic level information about the surface/microstructural changes and about possible reaction with substrates. In this paper, examples of catalyst materials in chemical technology and the nature of catalysis in alloy steels with applications in nuclear reactors are shown to elucidate this.A variety of supported metallic catalysts were examined: Ni/carbon, Cu/alumina and bimetallic Cu-Pd/C (both of interest in methanol synthesis), Cu-Ru/C (incyclohexane conversions) and Cu-Ni/alumina.
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Yuldashev, Khayot Khurmatovich, Yulbarsxon Nabievich Mansurov, Abdulaziz Ilkhomjon ugli Jurayev e Navruzbek Abdullayevich Mirzayev. "MODERN CATALYST BASED ON CERIUM OXIDE." Theoretical & Applied Science 103, n.º 11 (30 de novembro de 2021): 940–47. http://dx.doi.org/10.15863/tas.2021.11.103.112.
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Iverson, Gregory. "Korean as Catalyst in Modern Phonology". Korean Linguistics 11 (1 de janeiro de 2002): 53–91. http://dx.doi.org/10.1075/kl.11.04gki.
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Saha, Debasree, e Chhanda Mukhopadhyay. "Metal Nanoparticles: An Efficient Tool for Heterocycles Synthesis and Their Functionalization via C-H Activation". Current Organocatalysis 6, n.º 2 (24 de junho de 2019): 79–91. http://dx.doi.org/10.2174/2213337206666181226152743.
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Background: Metal nanoparticles have been extensively used in the synthesis of organic molecules during the last few decades especially due to their high catalytic activity. Organic reactions involving C-H functionalisations are very much in demand as they provide a direct method of derivatisation of organic molecules, thus making the process economical. In the recent years, metal nanoparticles catalysed C-H activation reactions have led to the design of useful molecules especially heterocyclic motifs which form the core structure of drugs and thus have high biological and industrial importance. Methods: In this review, we present a collection of reactions where metal nanoparticles are instrumental in the synthesis and functionalization of heterocycles via C-H activation. The review consists of three units namely, Nano-copper catalysed C-H activation reactions, nano-palladium catalysed CH activation reactions and other nano-metals catalysed C-H activation reactions. Results: The discussion reflects the scope of nano-metals as effective catalysts for the synthesis and functionalization of heterocycles as well as the efficiency of nano-metals towards catalysing economic and environmentally viable reaction protocols. Conclusion: The theme of this review is to correlate nanometal catalysis, heterocyclic synthesis and C-H activation, each of which in itself forms an integral part of modern day chemical research. Thus, the review will hopefully highlight the need for future development and research in this area and be instrumental in guiding researchers towards fulfilling that goal.
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Castro, Mario, Grant Lythe, Carmen Molina-París e Ruy M. Ribeiro. "Mathematics in modern immunology". Interface Focus 6, n.º 2 (6 de abril de 2016): 20150093. http://dx.doi.org/10.1098/rsfs.2015.0093.
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Mathematical and statistical methods enable multidisciplinary approaches that catalyse discovery. Together with experimental methods, they identify key hypotheses, define measurable observables and reconcile disparate results. We collect a representative sample of studies in T-cell biology that illustrate the benefits of modelling–experimental collaborations and that have proven valuable or even groundbreaking. We conclude that it is possible to find excellent examples of synergy between mathematical modelling and experiment in immunology, which have brought significant insight that would not be available without these collaborations, but that much remains to be discovered.
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Martins, Juliana Timbó. "A construção de uma literatura moderna nas obras de Charles Perrault em meio a querela dos Antigos e dos Modernos * The construction of a modern literature in Charles Perrault's works in the middle of the quarrel of the Ancients and the Moderns". História e Cultura 7, n.º 2 (2 de dezembro de 2018): 120. http://dx.doi.org/10.18223/hiscult.v7i2.2682.
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Conhecida, já no século XVII, como querela dos Antigos e dos Modernos, a série de debates entre membros da Academia Francesa opôs, de um lado, aqueles que defendiam a exemplaridade da Antiguidade na produção artística e literária do período e, de outro, os partidários da legitimidade da criatividade dos artistas modernos. Entre os letrados que em pleno reinado de Luís XIV deram ensejo a essa disputa, Charles Perrault se destacou não apenas como porta-voz dos autointitulados Modernos, mas também como o estopim e catalisador do debate. Nesse sentido, este trabalho tem como objetivo apresentar as ideias e argumentos do poeta francês durante a querela a fim de evidenciar em suas obras tanto a defesa de uma literatura moderna, entendida como arte que expressa a singularidade de seu tempo, quanto o exercício de suas premissas na escrita de Contos da Mamãe Gansa, obra de maior sucesso do autor e da literatura francesa.*Already known in the seventeenth century as the quarrel of the Ancients and the Moderns, the series of debates between members of the French Academy opposed, from one side, those who defended the exemplarity of antiquity in the artistic and literary production in that age and, on the other side, the legitimacy partisans of the modern artists’ creativity. Among the scholars who, during Louis XIV’s reign, created the occasion to such dispute, Charles Perrault stood out not only as an advocate to Moderns, but also as the trigger and the catalyst of the debate. In this regard, this paper aims to present the ideas and arguments of the French poet during the quarrel in order to highlight in his works both the defense of modern literature whereas art that expresses its time’s singularity, and the exercise of his premises in the writing of Tales of Mother Goose, the most successful work of the author and French literature.
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Navrotsky, Alexandra, Richard Hervig, James Lyons, Dong-Kyun Seo, Everett Shock e Albert Voskanyan. "Cooperative formation of porous silica and peptides on the prebiotic Earth". Proceedings of the National Academy of Sciences 118, n.º 2 (29 de dezembro de 2020): e2021117118. http://dx.doi.org/10.1073/pnas.2021117118.
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Modern technology has perfected the synthesis of catalysts such as zeolites and mesoporous silicas using organic structure directing agents (SDA) and their industrial use to catalyze a large variety of organic reactions within their pores. We suggest that early in prebiotic evolution, synergistic interplay arose between organic species in aqueous solution and silica formed from rocks by dynamic dissolution–recrystallization. The natural organics, for example, amino acids, small peptides, and fatty acids, acted as SDA for assembly of functional porous silica structures that induced further polymerization of amino acids and peptides, as well as other organic reactions. Positive feedback between synthesis and catalysis in the silica–organic system may have accelerated the early stages of abiotic evolution by increasing the formation of polymerized species.
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Mazitova, Aliya K., Irina N. Vikhareva, Guliya K. Aminova e Juliya N. Savicheva. "Application of Zinc Oxide to Obtain and Modify Properties of Adipate Plasticizer of Polyvinyl Chloride". Polymers 12, n.º 8 (1 de agosto de 2020): 1728. http://dx.doi.org/10.3390/polym12081728.
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Heterogeneous catalysts are widely used in basic research and in the petrochemical industry due to their effectiveness. In modern times, interest in this type of catalyst and, in particular, in mineral oxides is associated with the technological design of the process, namely: The absence of waste emissions, and the possibility of regeneration and reuse of the catalyst, which meets the criteria of green chemistry. For this reason, the preparation of non-toxic adipate plasticizers is expediently carried out under conditions of heterogeneous catalysis. Zinc oxide was chosen for this purpose, and as initial reagents: Adipic acid, butoxyethanol, and phenoxyethanol. For synthesized butoxyethylphenoxyethyl adipate by thermogravimetry on a TGA-DSC-combined thermal analysis instrument and differential scanning calorimetry on a DSC-1 instrument («Mettler Toledo»), the following properties were studied: Thermal stability, melting and crystallization temperatures, polymer compatibility. An analysis of the data in comparison with di-2-ethylhexylphthalate confirmed the possibility of using it as a plasticizing additive in PVC compositions. The zinc compound obtained in situ as part of the developed plasticizing composition contributes to increasing the color and thermal stability of the obtained PVC compositions.
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Santoliquido, Oscar, Francesco Camerota, Marco Pelanconi, Davide Ferri, Martin Elsener, Panayotis Dimopoulos Eggenschwiler e Alberto Ortona. "Structured Alumina Substrates for Environmental Catalysis Produced by Stereolithography". Applied Sciences 11, n.º 17 (6 de setembro de 2021): 8239. http://dx.doi.org/10.3390/app11178239.
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Modern catalysts for internal combustion engine applications are traditionally constituted by honeycomb substrates on which a coating of the catalytically active phase is applied. Due to the laminar flow of the gases passing through their straight channels, these structures present low heat and mass transfer, thus leading to relatively large catalyst sizes to compensate for the low catalytic activity per unit of volume. Better conversion efficiency can be achieved if three-dimensional periodic structures are employed, because of the resulting gases’ tortuous paths. Furthermore, the increased catalytic activity implies a reduction in the overall catalyst volume, which can translate to a decreased usage of precious metals as active phase. By exploiting the ceramic Stereolithography technique (i.e., SLA) it is nowadays possible to accurately 3D print complex alumina-based lattices to be used as ceramic substrates for catalysis. In this work, closed-walls lattices consisting of a rotated cubic cell of 2 mm dimensions were designed, 3D printed via SLA and finally washcoated with V2O5-WO3-TiO2. The samples were tested for the selective catalytic reduction of NO by NH3 in a heated quartz glass reactor and the performance of the innovative 3D-printed substrate was compared with the catalytic efficiency of the conventional cordierite honeycombs.
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Ratushnyak, Georgy, Katerina Anokhina e Vyacheslav Datsyuk. "FEASIBILITY OF USING HEAT PUMPS IN ENERGYSUPPLY OF THERMOCATALYTIC REACTORS". Modern technology, materials and design in construction 33, n.º 2 (22 de março de 2023): 198–202. http://dx.doi.org/10.31649/2311-1429-2022-2-198-202.
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Modern thermocatalytic rreactors for cleaning of gases must have high yield and to provide continuity of process. For the catalytic cleaning the different on a method co-operating is used with a catalyst and functional setting vehicles. For the increase of energy efficiency of thermocatalytic reactors it is expedient to apply alternative energy sources, in particular, heat-pumps. Taking into account advantages of heat-pumps, in particular, simplicity of editing, economy, automation, universality, compactness, quite, ecofriendlyness, reliability, longevity, a thermocatalytic reactor offers for rendering of harmful extrass harmless with a heat-pump in that due to introduction of alternative energy source, the process of heating of catalyst comes true. It will allow to promote power efficiency of process of heatsupply of thermocatalytic reactors
Comparison of different energy sources is executed, it is set as a result, that a geothermal heat-pump has considerable power efficiency. Application of heat-pump substantially reduces the charges of traditional energy sources on heating of components of mixture in a , thermocatalytic reactor and allows to promote energy efficiency of cleaning process. Depending on the sizes of reactor, necessary temperature of catalysis, amount of components in him and volume of muddy mixture that clears up, it is expedient to elect power of heat-pump.
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Mytareva, A. I., D. A. Bokarev e A. Yu Stakheev. "Seven Modern Trends in the DeNOx Catalyst Development". Kinetics and Catalysis 62, n.º 1 (janeiro de 2021): 1–32. http://dx.doi.org/10.1134/s0023158420060105.
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Ratushnyak, Georgy, e Kateryna Anokhina. "WAYS TO INCREASE THE ENERGY EFFICIENCY OF THERMOCATALYTIC REACTORS". Modern technology, materials and design in construction 31, n.º 2 (6 de junho de 2022): 88–93. http://dx.doi.org/10.31649/2311-1429-2021-2-88-93.
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Modern thermocatalytic reactors for gas cleaning must have high productivity and ensure continuity of the process. For catalytic purification, devices with different methods of interaction with the catalyst and functional purpose are used. To increase the energy efficiency of thermocatalytic reactors, it is advisable to use alternative energy sources, in particular, solar panels. Taking into account the advantages of solar panels, in particular, economy, reliability, environmental friendliness, availability, durability, safety, efficiency and energy saving, a thermocatalytic reactor with a solar battery is proposed. emissions.
The equation of heat balance is proposed, according to which it is possible to clearly identify the main sources of heat inflow and outflow in a thermocatalytic reactor. Heat costs for the catalysis process should be compensated by the converted energy of the Sun in the solar cell. The amount of energy produced in a solar cell depends largely on its power and insolation. The installation of solar panels increases the energy efficiency of thermocatalytic reactors, which improves the process of cleaning emissions and makes catalysis more cost-effective, especially in the summer. Given the characteristics of emissions from a single source, it is possible to determine the required number and capacity of solar panels for a catalytic reactor in each case.
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Eliasz, Jacek, Tomasz Osipowicz, Karol Franciszek Abramek, Zbigniew Matuszak e Łukasz Mozga. "Fuel Pretreatment Systems in Modern CI Engines". Catalysts 10, n.º 6 (20 de junho de 2020): 696. http://dx.doi.org/10.3390/catal10060696.
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The article concerns the possibility of using a fuel pretreatment system in modern compression ignition CI engines, the main task of which is the reduction of toxic emissions in the form of exhaust gases. This fuel pretreatment system consists of a catalytic reactor used in common rail (CR), and a modified fuel atomizer into spiral‒elliptical channels covered with catalytic material. In the system presented here, platinum was the catalyst. The catalyst’s task is to cause the dehydrogenation reaction of paraffin hydrocarbons contained in the fuel to create an olefin form, with the release of a free hydrogen molecule. In the literature, the methods of using catalysts in the exhaust systems of engines, or in combustion chambers, injection pumps, or fuel injectors, are known. However, the use of a catalytic reactor in the CR system in a high-pressure fuel atomizer rail is an innovative project proposed by the authors. Conditions in the high-pressure CR system are favorable for the catalyst’s operation. In addition, the spiral‒elliptical channels made on the inoperative part of the fuel atomizer needle increase the flow turbulence and contact surface for the catalyst.
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Nesterov, Dmytro S., e Oksana V. Nesterova. "Catalytic Oxidations with Meta-Chloroperoxybenzoic Acid (m-CPBA) and Mono- and Polynuclear Complexes of Nickel: A Mechanistic Outlook". Catalysts 11, n.º 10 (25 de setembro de 2021): 1148. http://dx.doi.org/10.3390/catal11101148.
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Selective catalytic functionalization of organic substrates using peroxides as terminal oxidants remains a challenge in modern chemistry. The high complexity of interactions between metal catalysts and organic peroxide compounds complicates the targeted construction of efficient catalytic systems. Among the members of the peroxide family, m-chloroperoxybenzoic acid (m-CPBA) exhibits quite complex behavior, where numerous reactive species could be formed upon reaction with a metal complex catalyst. Although m-CPBA finds plenty of applications in fine organic synthesis and catalysis, the factors that discriminate its decomposition routes under catalytic conditions are still poorly understood. The present review covers the advances in catalytic C–H oxidation and olefine epoxidation with m-CPBA catalyzed by mono- and polynuclear complexes of nickel, a cheap and abundant first-row transition metal. The reaction mechanisms are critically discussed, with special attention to the O–O bond splitting route. Selectivity parameters using recognized model hydrocarbon substrates are summarized and important factors that could improve further catalytic studies are outlined.
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Gafiatullin, Bulat, Aigul Akchurina, Angelina Fedoseeva, Elza Sultanova, Daut Islamov, Konstantin Usachev, Vladimir Burilov, Svetlana Solovieva e Igor Antipin. "PEPPSI-Type Pd(II)—NHC Complexes on the Base of p-tert-Butylthiacalix[4]arene: Synthesis and Catalytic Activities". Inorganics 11, n.º 8 (1 de agosto de 2023): 326. http://dx.doi.org/10.3390/inorganics11080326.
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The creation of effective catalytic systems for cross-coupling reactions, reduction, etc., capable of working in water-organic or pure aqueous media is in great demand. The article presents the synthesis of NHC-palladium complexes of the PEPPSI type based on monoimidazolium derivatives of thiacalix[4]arene. The structure of the imidazolium precursors, obtained in 81–88% yields and the complexes themselves, obtained in 40–50% yields, is established using modern methods, including X-ray structural analysis and high-resolution mass spectrometry. It is shown that the obtained complex with bulk substituents near the palladium atom is not inferior to the well-known PEPPSI-type Organ’s catalyst in the catalysis of Suzuki-Miyaura coupling and is four times superior to the latter in the p-nitrophenol reduction reaction. Given the presence of free phenolic hydroxyl groups in the macrocycle, the obtained complexes are of interest for further post-modification or for immobilization on a carrier.
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Kuznetsov, N. Yu, e I. P. Beletskaya. "Application of CO2 as С1-Synthon in Organic Chemistry: II: Catalytic Synthesis of Cyclic Carbonates (Carbamates) from CO2 and Epoxides (Aziridines)". Журнал органической химии 59, n.º 8 (15 de agosto de 2023): 973–1011. http://dx.doi.org/10.31857/s0514749223080013.
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CO2 composes cheap, easily available and practically inexhaustible source of synthetic carbon (C1-synthon). Among the various transformations of carbon dioxide, synthesis of cyclic carbonates from epoxides and carbamates from aziridines can be referred to the priority areas in the development of contemporary chemical synthesis and catalysis. Cyclic carbonates found wide application in modern industry (electrolytes, solvents, reagents, polymers) and their use and production will be constantly increased. At the forefront of research appears the development of effective catalytic processes, allowing carry out the synthesis of carbonates under mild conditions (atmospheric pressure of CO2 or lower, temperature - 25°С) with low catalyst loads, which sustains its high activity for a long time and is affordable. In the current review we analyze the existing directions of research and catalytic systems based on salts of cheap and earth-abundant metals Al3+, Fe2+(3+) and Zn2+ for the preparation of cyclic carbonates from epoxides and carbamates from aziridines.
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Blinov, Artem, Nikolay Malastowski e Leonid Myagkov. "Development of the model for a diesel engine catalytic converter". E3S Web of Conferences 140 (2019): 06013. http://dx.doi.org/10.1051/e3sconf/201914006013.
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One of the key issues of the modern engine development is to comply with today’s stringent emission standards. It forces the manufacturers to enhance in-engine and after treatment emission reduction technologies continuously. The selective catalytic reduction (SCR) is still the most effective technique for nitrogen oxides removal from exhaust gases of vehicles with diesel engines. Numerical modelling is widely used for SCR systems development and assessment. In this paper, a simplified one-dimensional numerical model of diesel SCR catalyst, which was implemented in Matlab, is described. The algorithm for automatic mesh generation describing real cross-section geometry of the catalyst block and the calculation procedure allowing to take into account non-uniform distribution of the gas flow parameters at the catalyst inlet are presented. Model was validated by the experimental data available in the literature. Numerical simulations for the full-scale modern SCR catalyst were carried out. The effect of the gas velocity non-uniformity at the catalyst inlet on the overall NOx reduction efficiency was evaluated.
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Ramazani, Ali, Hamideh Ahankar, Zahra T. Nafeh e Sang W. Joo. "Modern Catalysts in A3- Coupling Reactions". Current Organic Chemistry 23, n.º 25 (14 de janeiro de 2020): 2783–801. http://dx.doi.org/10.2174/1385272823666191113160643.
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: Propargylamines are an important constituent of diverse, biologically active and industrially valuable compounds. These useful, convenient and effective compounds can be synthesized via the A3-coupling reactions between an aldehyde, amine, and alkyne in the presence of a catalyst. In the past years, most of the catalysts containing transition metals were applied in these reactions, but today, various heterogeneous catalysts, especially nanocatalysts are used. The purpose of this review was to introduce some modern catalysts for the A3-coupling reaction.
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Kovtunov, Kirill V., Oleg G. Salnikov, Ivan V. Skovpin, Nikita V. Chukanov, Dudari B. Burueva e Igor V. Koptyug. "Catalytic hydrogenation with parahydrogen: a bridge from homogeneous to heterogeneous catalysis". Pure and Applied Chemistry 92, n.º 7 (28 de julho de 2020): 1029–46. http://dx.doi.org/10.1515/pac-2020-0203.
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AbstractOne of the essential themes in modern catalysis is that of bridging the gap between its homogeneous and heterogeneous counterparts to combine their individual advantages and overcome shortcomings. One more incentive can now be added to the list, namely the ability of transition metal complexes to provide strong nuclear magnetic resonance (NMR) signal enhancement upon their use in homogeneous hydrogenations of unsaturated compounds with parahydrogen in solution. The addition of both H atoms of a parahydrogen molecule to the same substrate, a prerequisite for such effects, is implemented naturally with metal complexes that operate via the formation of a dihydride intermediate, but not with most heterogeneous catalysts. Despite that, it has been demonstrated in recent years that various types of heterogeneous catalysts are able to perform the required pairwise H2 addition at least to some extent. This has opened a major gateway for developing highly sensitive and informative tools for mechanistic studies of heterogeneous hydrogenations and other processes involving H2. Besides, production of catalyst-free fluids with NMR signals enhanced by 3-4 orders of magnitude is essential for modern applications of magnetic resonance imaging (MRI), including biomedical research and practice. The ongoing efforts to design heterogeneous catalysts which can implement the homogeneous (pairwise) hydrogenation mechanism are reported.
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Harrison, Stuart A., William L. Webb, Hanadi Rammu e Nick Lane. "Prebiotic Synthesis of Aspartate Using Life’s Metabolism as a Guide". Life 13, n.º 5 (12 de maio de 2023): 1177. http://dx.doi.org/10.3390/life13051177.
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A protometabolic approach to the origins of life assumes that the conserved biochemistry of metabolism has direct continuity with prebiotic chemistry. One of the most important amino acids in modern biology is aspartic acid, serving as a nodal metabolite for the synthesis of many other essential biomolecules. Aspartate’s prebiotic synthesis is complicated by the instability of its precursor, oxaloacetate. In this paper, we show that the use of the biologically relevant cofactor pyridoxamine, supported by metal ion catalysis, is sufficiently fast to offset oxaloacetate’s degradation. Cu2+-catalysed transamination of oxaloacetate by pyridoxamine achieves around a 5% yield within 1 h, and can operate across a broad range of pH, temperature, and pressure. In addition, the synthesis of the downstream product β-alanine may also take place in the same reaction system at very low yields, directly mimicking an archaeal synthesis route. Amino group transfer supported by pyridoxal is shown to take place from aspartate to alanine, but the reverse reaction (alanine to aspartate) shows a poor yield. Overall, our results show that the nodal metabolite aspartate and related amino acids can indeed be synthesised via protometabolic pathways that foreshadow modern metabolism in the presence of the simple cofactor pyridoxamine and metal ions.
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Slavetskiy, V. Y., А. К. Satpayev e К. А. Bekeschev. "MODERN INTERNATIONAL POLICY IN A PANDEMIC". BULLETIN Series of Sociological and Political sciences 72, n.º 4 (30 de dezembro de 2020): 15–20. http://dx.doi.org/10.51889/2020-4.1728-8940.02.
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The global coronavirus pandemic has become a catalyst for a previously unheard-of pace of world change. The way of life of a person has already objectively become different, and similar changes have taken place in all spheres of the functioning of our society. The changes that have begun in the international political sphere are only gaining momentum and are at the initial stage. In the near future, there will be serious shifts in the state and trade policy of the countries and the desire for maximum self-sufficiency in resource and production terms.
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Tsukanov, Maksim. "MODERN ENVIRONMENTAL REQUIREMENTS FOR SYNTHETIC FUEL". Technical Sciences 4, n.º 1 (30 de janeiro de 2021): 36–41. http://dx.doi.org/10.26739/2181-9696-2021-1-6.
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The article discusses the possibilities of solving the problem of using connected petroleum gas using GTL technologies. The most important difference between hydrocarbon products of Fisher-Tropsh synthesis and petroleum products is that they do not contain sulfur, nitrogen, and in some cases aromatic compounds, which determines their environmental importance. Synthetic oil is a mixture of normal and isostrotic hydrocarbons C5-C19used for processing in paraffin and motor fuels, as a rawmaterial for the chemical and petrochemical industries, or as a commercial product.Key words:synthesis gas, utilization, GTL technologies, Euro-5, synthetic fuel, reactor, torch, catalyst
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Milton, Ross D. "Electron-Transferring Metalloenzymes and their Potential Biotechnological Applications". CHIMIA 78, n.º 1/2 (28 de fevereiro de 2024): 13–21. http://dx.doi.org/10.2533/chimia.2024.13.
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Modern societies rely heavily on centralized industrial processes to generate a multitude of products ranging from electrical energy to synthetic chemical building blocks to construction materials. To date, these processes have relied extensively on energy produced from fossil fuels, which has led to dramatically increased quantities of greenhouse gases (including carbon dioxide) being released into the atmosphere; the effects of the ensuing change to our climate are easily observed in day-to-day life. Some of the reactions catalyzed by these industrial processes can be catalyzed in nature by metal-containing enzymes (metalloenzymes) that have evolved over the course of up to 3.8 billion years to do so under mild physiological conditions using Earth-abundant metals. While such metalloenzymes could in principle facilitate the implementation of carbon-neutral processes around the globe, either in “bio-inspired” catalyst design or even by direct exploitation, many remaining questions surrounding their mechanisms often preclude both options. Here, our recent efforts in understanding and applying metalloenzymes that catalyze reactions such as dinitrogen reduction to ammonia or proton reduction to molecular hydrogen are discussed. In closing, an opinion on the question: “Can these types of enzymes really be used in new biotechnologies?” is offered.
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Cary, Eve Oleta. "Explaining Overheating in China through Institutional Analysis (1992–2010)". Asian Survey 51, n.º 3 (1 de maio de 2011): 540–58. http://dx.doi.org/10.1525/as.2011.51.3.540.
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Economic overheating is a significant and recurring problem in modern China. This paper analyzes the many factors causing overheating and argues that there are systemic and largely structural explanations for overheating that arise from a number of theorized catalysts, including a bureaucratic catalyst and a historical catalyst.
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Kwon, Hyuk Jae, Joon Hyun Baik, Sung Bong Kang, In-Sik Nam, Byung Jun Yoon e Se H. Oh. "Simulation of a Nonisothermal Modern Three-Way Catalyst Converter". Industrial & Engineering Chemistry Research 49, n.º 15 (4 de agosto de 2010): 7039–51. http://dx.doi.org/10.1021/ie1007486.
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Zhang, Chenyang. "3D printing: A catalyst for innovation in modern industries". Applied and Computational Engineering 9, n.º 1 (25 de setembro de 2023): 241–46. http://dx.doi.org/10.54254/2755-2721/9/20230103.
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3D printing, also known as additive manufacturing, has the potential to revolutionize various areas of society. This technology uses a layer-by-layer approach to transform digital designs into physical objects, allowing individuals and small businesses to easily produce prototypes, custom products, and replacement parts. This significantly reduces the barriers to entry that previously existed in the manufacturing industry. The democratization of product creation through 3D printing has significant implications for intellectual property and manufacturing. There are concerns about the ease with which 3D printing can be used to reproduce copyrighted designs, leading to debates on how to protect intellectual property rights in the digital age. Additionally, the technology may disrupt established manufacturing processes and threaten jobs in traditional manufacturing industries. Despite these concerns, the benefits of 3D printing cannot be ignored. The technology allows for efficient and cost-effective production of complex geometries that would be difficult or impossible to create using traditional manufacturing techniques. It also enables the creation of customizable and personalized products, reducing waste and increasing sustainability. To maximize the potential benefits of 3D printing while addressing its challenges, policymakers, stakeholders, and researchers are working together to develop solutions. These include developing new intellectual property laws and regulations, designing new manufacturing processes that combine traditional techniques with 3D printing, and promoting education and training programs to help ensure that individuals and businesses have the necessary skills to use 3D printing technology effectively.
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Petrovic, Slobodan, Milica Misic-Vukovic e Dusan Mijin. "Modern catalysis in the synthesis of some pharmaceuticals and fine chemicals". Chemical Industry 56, n.º 1 (2002): 10–16. http://dx.doi.org/10.2298/hemind0201010p.
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Catalysis in the synthesis of Pharmaceuticals and line chemicals nowadays becomes more and more important. Synthesis that minimizes wastes is important from the economical aspect, as well as from the environmental aspect. "Green chemistry" or "green technology" is an effort to protect the environment by increasing the efficiency of the overall synthetic processes in the chemical industry by minimizing or eliminating wasteful by-products. Modern catalytic methods in the synthesis of some Pharmaceuticals and fine chemicals are discussed such as phase-transfer catalysis, biocatalysis asymmetric catalysis and, generally, solid-phase chemistry.
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Zhang, Zhe, Jie Huang, Wei Chen, Jufang Hao, Jiangbo Xi, Jian Xiao, Baojiang He e Jun Chen. "Probing the Activity Enhancement of Carbocatalyst with the Anchoring of Atomic Metal". Nanomaterials 13, n.º 17 (27 de agosto de 2023): 2434. http://dx.doi.org/10.3390/nano13172434.
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Enhanced catalysis for organic transformation is essential for the synthesis of high-value compounds. Atomic metal species recently emerged as highly effective catalysts for organic reactions with high activity and metal utilization. However, developing efficient atomic catalysts is always an attractive and challenging topic in the modern chemical industry. In this work, we report the preparation and activity enhancement of nitrogen- and sulfur-codoped holey graphene (NSHG) with the anchoring of atomic metal Pd. When employed as the catalyst for nitroarenes reduction reactions, the resultant Pd/NSHG composite exhibits remarkably high catalytic activity due to the co-existence of dual-active components (i.e., catalytically active NSHG support and homogeneous dispersion of atomic metal Pd). In the catalytic 4-nitrophenol (4-NP) reduction reaction, the efficiency (turnover frequency) is 3.99 × 10−2 mmol 4-NP/(mg cat.·min), which is better than that of metal-free nitrogen-doped holey graphene (NHG) (2.3 × 10−3 mmol 4-NP/(mg cat.·min)) and NSHG carbocatalyst (3.8 × 10−3 mmol 4-NP/(mg cat.·min)), the conventional Pd/C and other reported metal-based catalysts. This work provides a rational design strategy for the atomic metal catalysts loaded on active doped graphene support. The resultant Pd/NSHG dual-active component catalyst (DACC) is also anticipated to bring great application potentials for a broad range of organic fields, such as organic synthesis, environment treatment, energy storage and conversion.
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Tyrański, Mariusz, Jakub Michał Bujalski, Wojciech Orciuch e Łukasz Makowski. "Computational Fluid Dynamics of Ammonia Synthesis in Axial-Radial Bed Reactor". Energies 16, n.º 18 (18 de setembro de 2023): 6680. http://dx.doi.org/10.3390/en16186680.
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Ammonia synthesis by the Haber–Bosch method is a typical and effective implementation of the chemical process in the large-scale fertiliser industry. Due to the growing demand for fertilisers and food, it is desirable to study this process thoroughly using modern numerical methods to improve the operation of existing devices and facilitate the design of new devices in industrial installations. This manuscript focuses on the influence of the catalyst bed parameters on the ammonia synthesis process. Variants with different sizes of catalyst particles and modifications of the geometry of catalytic beds were considered. The axial-radial Topsoe converter with magnetite as a catalyst, commonly used in modern fertiliser industry beds, was investigated using Computational Fluid Dynamics. As a result, contours of velocity, pressure, concentration, and rate of ammonia formation were obtained. The analysis of the obtained results made it possible to determine the gradient of ammonia production rate in the catalyst bed and designate zones with negligible reaction rates. The authors also proposed possible bed geometry modifications to reduce bed volumes without affecting the converter’s performance.