Journal articles: 'Reactivity and catalysis'

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Dagorne, Samuel. "Recent Developments on N-Heterocyclic Carbene Supported Zinc Complexes: Synthesis and Use in Catalysis." Synthesis 50, no. 18 (June 28, 2018): 3662–70. http://dx.doi.org/10.1055/s-0037-1610088.

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The present contribution reviews the synthesis, reactivity, and use in catalysis of NHC–Zn complexes reported since 2013. NHC-stabilized Zn(II) species typically display enhanced stability relative to common organozinc species (such as Zn dialkyls), a feature of interest for the mediation of various chemical processes and the stabilization of reactive Zn-based species. Their use in catalysis is essentially dominated by reduction reactions of various unsaturated small molecules (including CO2), thus primarily involving Zn–H and Zn–alkyl derivatives as catalysts. Simple NHC adducts of Zn(II) dihalides also appear as effective catalysts for the reduction amination of CO2 and borylation of alkyl/aryl halides. Stable and well-defined Zn alkoxides have also been prepared and behave as effective catalysts in the polymerization of cyclic esters/carbonates for the production of well-defined biodegradable materials. Overall, the attractive features of NHC-based Zn(II) species include ready access, a reasonable stability/reactivity balance, and steric/electronic tunability (through the NHC source), which should promote their further development.1 Introduction2 NHC-Supported Zinc Alkyl/Aryl Species2.1 Synthesis2.2 Reactivity and Use in Catalysis3 NHC-Supported Zinc Hydride Species3.1 Synthesis3.2 Reactivity and Use in Catalysis4 NHC-Supported Zinc Amido/Alkoxide Species4.1 Synthesis4.2 Use in Catalysis5 NHC-Supported Zinc Dihalide Species5.1 Synthesis5.2 Use in Catalysis6 Other NHC-Stabilized Zn Species7 Conclusion

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De Coster, Valentijn, Hilde Poelman, Jolien Dendooven, Christophe Detavernier, and Vladimir V. Galvita. "Designing Nanoparticles and Nanoalloys for Gas-Phase Catalysis with Controlled Surface Reactivity Using Colloidal Synthesis and Atomic Layer Deposition." Molecules 25, no. 16 (August 15, 2020): 3735. http://dx.doi.org/10.3390/molecules25163735.

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Supported nanoparticles are commonly applied in heterogeneous catalysis. The catalytic performance of these solid catalysts is, for a given support, dependent on the nanoparticle size, shape, and composition, thus necessitating synthesis techniques that allow for preparing these materials with fine control over those properties. Such control can be exploited to deconvolute their effects on the catalyst’s performance, which is the basis for knowledge-driven catalyst design. In this regard, bottom-up synthesis procedures based on colloidal chemistry or atomic layer deposition (ALD) have proven successful in achieving the desired level of control for a variety of fundamental studies. This review aims to give an account of recent progress made in the two aforementioned synthesis techniques for the application of controlled catalytic materials in gas-phase catalysis. For each technique, the focus goes to mono- and bimetallic materials, as well as to recent efforts in enhancing their performance by embedding colloidal templates in porous oxide phases or by the deposition of oxide overlayers via ALD. As a recent extension to the latter, the concept of area-selective ALD for advanced atomic-scale catalyst design is discussed.

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Konsolakis, Michalis, and Maria Lykaki. "Facet-Dependent Reactivity of Ceria Nanoparticles Exemplified by CeO2-Based Transition Metal Catalysts: A Critical Review." Catalysts 11, no. 4 (March 31, 2021): 452. http://dx.doi.org/10.3390/catal11040452.

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The rational design and fabrication of highly-active and cost-efficient catalytic materials constitutes the main research pillar in catalysis field. In this context, the fine-tuning of size and shape at the nanometer scale can exert an intense impact not only on the inherent reactivity of catalyst’s counterparts but also on their interfacial interactions; it can also opening up new horizons for the development of highly active and robust materials. The present critical review, focusing mainly on our recent advances on the topic, aims to highlight the pivotal role of shape engineering in catalysis, exemplified by noble metal-free, CeO2-based transition metal catalysts (TMs/CeO2). The underlying mechanism of facet-dependent reactivity is initially discussed. The main implications of ceria nanoparticles’ shape engineering (rods, cubes, and polyhedra) in catalysis are next discussed, on the ground of some of the most pertinent heterogeneous reactions, such as CO2 hydrogenation, CO oxidation, and N2O decomposition. It is clearly revealed that shape functionalization can remarkably affect the intrinsic features and in turn the reactivity of ceria nanoparticles. More importantly, by combining ceria nanoparticles (CeO2 NPs) of specific architecture with various transition metals (e.g., Cu, Fe, Co, and Ni) remarkably active multifunctional composites can be obtained due mainly to the synergistic metalceria interactions. From the practical point of view, novel catalyst formulations with similar or even superior reactivity to that of noble metals can be obtained by co-adjusting the shape and composition of mixed oxides, such as Cu/ceria nanorods for CO oxidation and Ni/ceria nanorods for CO2 hydrogenation. The conclusions derived could provide the design principles of earth-abundant metal oxide catalysts for various real-life environmental and energy applications.

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Wang, Danfeng, Robert Malmberg, Indrek Pernik, Shyamal K. K. Prasad, Max Roemer, Koushik Venkatesan, Timothy W. Schmidt, Sinead T. Keaveney, and Barbara A. Messerle. "Development of tethered dual catalysts: synergy between photo- and transition metal catalysts for enhanced catalysis." Chemical Science 11, no. 24 (2020): 6256–67. http://dx.doi.org/10.1039/d0sc02703k.

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A series of tethered dual catalysts were developed, with catalytic investigations demonstrating that tethering enhances photocatalysis and thermally activated Ir catalysis. In addition, sequential and switchable catalytic reactivity was achieved.

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de Bruin, Bas, and Colet te Grotenhuis. "Radical-type Reactions Controlled by Cobalt: From Carbene Radical Reactivity to the Catalytic Intermediacy of Reactive o-Quinodimethanes." Synlett 29, no. 17 (July 19, 2018): 2238–50. http://dx.doi.org/10.1055/s-0037-1610204.

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In this account, we summarize our recent efforts in the fields of ‘open-shell organometallic chemistry’ and ‘metalloradical catalysis’. We focus in particular on the use of so-called ‘carbene radicals’ for the synthesis of a variety of useful synthons for organic chemistry. We further show that unexpected reactivity arises from catalytic synthesis of unusual o-quinone methide and o-quinodimethane intermediates that undergo subsequent rearrangements to uncommon products.1 Introduction2 General (Fischer-Type) Carbene and Nitrene Reactivity and Their Relation to Carbene and Nitrene Radical Reactivity3 Carbene and Nitrene (Radical) Precursors4 Formation and Intrinsic Radical-Type Reactivity of Carbene and Nitrene Radicals5 Types of Cobalt Catalysts Used in Reactions Involving Carbene and Nitrene Radicals6 Applications of Cobalt-Catalyzed Ring-Closure Reactions via Carbene Radicals7 Intermediacy of o-Quinone Methide and o-Quidodimethanes in Carbene Ring-Closing Reactions8 Conclusion

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Dong, Xiao-Yun, Zi-Wei Gao, Ke-Fang Yang, Wei-Qiang Zhang, and Li-Wen Xu. "Nanosilver as a new generation of silver catalysts in organic transformations for efficient synthesis of fine chemicals." Catalysis Science & Technology 5, no. 5 (2015): 2554–74. http://dx.doi.org/10.1039/c5cy00285k.

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Silver nanoparticles catalysis has been of great interest in organic synthesis and has expanded rapidly in the past ten years because of nanosilver catalysts' unique reactivity and selectivity, stability, as well as recyclability in catalytic reactions.

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Mosinska, Magdalena, Natalia Stępińska, Waldemar Maniukiewicz, Jacek Rogowski, Agnieszka Mierczynska-Vasilev, Krasimir Vasilev, Malgorzata I. Szynkowska, and Pawel Mierczynski. "Hydrogen Production on Cu-Ni Catalysts via the Oxy-Steam Reforming of Methanol." Catalysts 10, no. 3 (March 1, 2020): 273. http://dx.doi.org/10.3390/catal10030273.

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In this work, bimetallic Cu-Ni catalysts supported on binary oxides containing ZnO, ZrO2, CeO2 and Al2O3 were investigated in hydrogen production via the oxidative steam reforming of methanol (OSRM). Their physicochemical properties were extensively studied using various methods such as BET, TPR-H2, TPD-NH3, XRD, SEM-EDS, ToF-SIMS and XPS. The reactivity measurements showed that the active phase and support composition played an important role in the activity of the catalyst in the OSRM. The most active system at higher temperatures was 30% Cu–10% Ni/CeO2·Al2O3, with high catalytic activity attributed to the Cu0.8Ni0.2 alloy formation. In addition, the reactivity results showed that the most active catalyst exhibited high acidity and was easily reduced. At low temperatures, the best catalytic properties were exhibited by 30% Cu–10% Ni/ZrO2·Al2O3. The reactivity and physicochemical properties of the studied catalysts confirmed the crucial role of alloy composition on their catalytic properties in the oxy-steam reforming of methanol. The obtained results validate the possibility of using Cu-Ni catalysts for hydrogen production.

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Dare, Nicola A., and Timothy J. Egan. "Heterogeneous catalysis with encapsulated haem and other synthetic porphyrins: Harnessing the power of porphyrins for oxidation reactions." Open Chemistry 16, no. 1 (August 15, 2018): 763–89. http://dx.doi.org/10.1515/chem-2018-0083.

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AbstractEncapsulated metalloporphyrins have been widely studied for their use as efficient heterogeneous catalysts, inspired by the known catalytic activity of porphyrins in haemoproteins. The oxidation of organic substrates by haemoproteins is one of the well-known roles of these proteins, in which the haem (ferriprotoporphyrin IX = FePPIX) cofactor is the centre of reactivity. While these porphyrins are highly efficient catalysts in the protein environment, once removed, they quickly lose their reactivity. It is for this reason that they have garnered much interest in the field of heterogeneous catalysis of oxidation reactions. This review details current research in the field, focusing on the application of encapsulated haem, and other synthetic metalloporphyrins, applied to oxidation reactions.

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Park, Jongmin, Hyo Seok Kim, Won Bo Lee, and Myung-June Park. "Trends and Outlook of Computational Chemistry and Microkinetic Modeling for Catalytic Synthesis of Methanol and DME." Catalysts 10, no. 6 (June 11, 2020): 655. http://dx.doi.org/10.3390/catal10060655.

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The first-principle modeling of heterogeneous catalysts is a revolutionarily approach, as the electronic structure of a catalyst is closely related to its reactivity on the surface with reactant molecules. In the past, detailed reaction mechanisms could not be understood, however, computational chemistry has made it possible to analyze a specific elementary reaction of a reaction system. Microkinetic modeling is a powerful tool for investigating elementary reactions and reaction mechanisms for kinetics. Using a microkinetic model, the dominant pathways and rate-determining steps can be elucidated among the competitive reactions, and the effects of operating conditions on the reaction mechanisms can be determined. Therefore, the combination of computational chemistry and microkinetic modeling can significantly improve computational catalysis research. In this study, we reviewed the trends and outlook of this combination technique as applied to the catalytic synthesis of methanol (MeOH) and dimethyl ether (DME), whose detailed mechanisms are still controversial. Although the scope is limited to the catalytic synthesis of limited species, this study is expected to provide a foundation for future works in the field of catalysis research based on computational catalysis.

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Minaev, Boris F., and Hans Ågren. "Spin-Orbit Coupling Induced Chemical Reactivity and Spin-Catalysis Phenomena." Collection of Czechoslovak Chemical Communications 60, no. 3 (1995): 339–71. http://dx.doi.org/10.1135/cccc19950339.

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The crucial role of electron spin in the control of the reaction channels in the region of activated complexes can easily be inferred from the general principles of chemical bonding. Magnetic perturbations could change spin at the intermediate stages of a reaction or in the region of activation barriers and could hence influence the reaction rate through spin switching of the reaction paths. Spin-orbit coupling is one of the most important intrinsic magnetic perturbations in molecules; its role in chemical reactivity is here shown by a few typical examples. Spin-orbit coupling induced spin flip could also be important in catalysis by transition metals. General qualitative arguments predict great enhancements of the spin-orbit coupling in catalytic complexes with transition metal compounds. The concept of spin-catalysis is introduced in order to describe and classify a wide range of phenomena in which chemical reactions are promoted by substances assisting in inducing spin changes and overcoming spin-prohibition. This concept is based on results of quantum chemical calculations with account of spin-orbit coupling and configuration interaction in the intermediate complexes. Besides spin-orbit coupling, the role of intermolecular exchange interaction with open shell catalysts is stressed. The catalytic action would definitely depend on the efficiency of spin uncoupling inside the reacting substrate molecule and this could be induced by magnetic and exchange perturbations.

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Shubina, Tatyana E., and Timothy Clark. "Catalysis of the Quadricyclane to Norbornadiene Rearrangement by SnCl2 and CuSO4." Zeitschrift für Naturforschung B 65, no. 3 (March 1, 2010): 347—r369. http://dx.doi.org/10.1515/znb-2010-0319.

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Ab initio and density-functional theory (DFT) calculations have been used to investigate the model rearrangements of quadricyclane to norbornadiene catalysed by single CuSO4 and SnCl2 molecules. The isolated reactions with the two molecular catalysts proceed via electron-transfer catalysis in which the hydrocarbon is oxidised, in contrast to systems investigated previously in which the substrate was reduced. The even-electron SnCl2-catalysed reaction shows singlet-triplet two-state reactivity. Solvation by a single methanol molecule changes the mechanism of the rearrangement to a classical Lewis acid-base process.

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Schmal, Martin, and Hans-Joachim Freund. "Towards an atomic level understanding of niobia based catalysts and catalysis by combining the science of catalysis with surface science." Anais da Academia Brasileira de Ciências 81, no. 2 (June 2009): 297–318. http://dx.doi.org/10.1590/s0001-37652009000200016.

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The science of catalysis and surface science have developed, independently, key information for understanding catalytic processes. One might argue: is there anything fundamental to be discovered through the interplay between catalysis and surface science? Real catalysts of monometallic and bimetallic Co/Nb2O5 and Pd-Co/Nb2O5 catalysts showed interesting selectivity results on the Fischer-Tropsch synthesis (Noronha et al. 1996, Rosenir et al. 1993). The presence of a noble metal increased the C+5 selectivity and decreased the methane formation depending of the reduction temperature. Model catalyst of Co-Pd supported on niobia and alumina were prepared and characterized at the atomic level, thus forming the basis for a comparison with "real" support materials. Growth, morphology and structure of both pure metal and alloy particles were studied. It is possible to support the strong metal support interaction suggested by studies on real catalysts via the investigation of model systems for niobia in comparison to alumina support in which this effect does not occur. Formation of Co2+ penetration into the niobia lattice was suggested on the basis of powder studies and can be fully supported on the basis of model studies. It is shown for both real catalysts and model systems that oxidation state of Co plays a key role in controlling the reactivity in Fischer-Tropsch reactions systems and that the addition of Pd is a determining factor for the stability of the catalyst. It is demonstrated that the interaction with unsaturated hydrocarbons depends strongly on the state of oxidation.

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Bím, Daniel, Mauricio Maldonado-Domínguez, Lubomír Rulíšek, and Martin Srnec. "Beyond the classical thermodynamic contributions to hydrogen atom abstraction reactivity." Proceedings of the National Academy of Sciences 115, no. 44 (September 25, 2018): E10287—E10294. http://dx.doi.org/10.1073/pnas.1806399115.

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Hydrogen atom abstraction (HAA) reactions are cornerstones of chemistry. Various (metallo)enzymes performing the HAA catalysis evolved in nature and inspired the rational development of multiple synthetic catalysts. Still, the factors determining their catalytic efficiency are not fully understood. Herein, we define the simple thermodynamic factor η by employing two thermodynamic cycles: one for an oxidant (catalyst), along with its reduced, protonated, and hydrogenated form; and one for the substrate, along with its oxidized, deprotonated, and dehydrogenated form. It is demonstrated that η reflects the propensity of the substrate and catalyst for (a)synchronicity in concerted H+/e− transfers. As such, it significantly contributes to the activation energies of the HAA reactions, in addition to a classical thermodynamic (Bell–Evans–Polanyi) effect. In an attempt to understand the physicochemical interpretation of η, we discovered an elegant link between η and reorganization energy λ from Marcus theory. We discovered computationally that for a homologous set of HAA reactions, λ reaches its maximum for the lowest |η|, which then corresponds to the most synchronous HAA mechanism. This immediately implies that among HAA processes with the same reaction free energy, ΔG0, the highest barrier (≡ΔG≠) is expected for the most synchronous proton-coupled electron (i.e., hydrogen) transfer. As proof of concept, redox and acidobasic properties of nonheme FeIVO complexes are correlated with activation free energies for HAA from C−H and O−H bonds. We believe that the reported findings may represent a powerful concept in designing new HAA catalysts.

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Fallah, Amirhossein, Davood Kordestani, Abdolhamid Alizadeh, and Salasiah Endud. "Supported Palladium Catalysis Using a Biguanide N-Donor Motif on Mesoporous Silica for Suzuki-Miyaura Coupling Reaction." Advanced Materials Research 622-623 (December 2012): 757–61. http://dx.doi.org/10.4028/www.scientific.net/amr.622-623.757.

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A supported Pd(II)/biguanide complex on ordered mesoporous SBA-15 material (Pd@SBA-15/Met) exhibited catalytic activity in the cross-coupling reaction. The structural and surface characteristics of the prepared catalysts were investigated by various techniques (XRD, SEM, FT-IR and AAS). The catalytic performance of the catalysts was evaluated in Suzuki-Miyaura coupling reaction and it was proved to act as a recoverable catalyst in green media with excellent reactivity combined with recyclability.

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Li, Haobo, Jianping Xiao, Qiang Fu, and Xinhe Bao. "Confined catalysis under two-dimensional materials." Proceedings of the National Academy of Sciences 114, no. 23 (May 22, 2017): 5930–34. http://dx.doi.org/10.1073/pnas.1701280114.

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Confined microenvironments formed in heterogeneous catalysts have recently been recognized as equally important as catalytically active sites. Understanding the fundamentals of confined catalysis has become an important topic in heterogeneous catalysis. Well-defined 2D space between a catalyst surface and a 2D material overlayer provides an ideal microenvironment to explore the confined catalysis experimentally and theoretically. Using density functional theory calculations, we reveal that adsorption of atoms and molecules on a Pt(111) surface always has been weakened under monolayer graphene, which is attributed to the geometric constraint and confinement field in the 2D space between the graphene overlayer and the Pt(111) surface. A similar result has been found on Pt(110) and Pt(100) surfaces covered with graphene. The microenvironment created by coating a catalyst surface with 2D material overlayer can be used to modulate surface reactivity, which has been illustrated by optimizing oxygen reduction reaction activity on Pt(111) covered by various 2D materials. We demonstrate a concept of confined catalysis under 2D cover based on a weak van der Waals interaction between 2D material overlayers and underlying catalyst surfaces.

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Lehn, J. M. "Supramolecular reactivity and catalysis." Applied Catalysis A: General 113, no. 2 (June 1994): 105–14. http://dx.doi.org/10.1016/0926-860x(94)80017-0.

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Ponce, Adrian. "Radionuclide-induced defect sites in iron-bearing minerals may have accelerated the emergence of life." Interface Focus 9, no. 6 (October 18, 2019): 20190085. http://dx.doi.org/10.1098/rsfs.2019.0085.

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The emergence of life on Earth (and elsewhere) must have occurred in a milieu that is far from equilibrium, such as at alkaline hydrothermal vents that would have harboured built-in gradients in temperature, redox potential and pH along with precipitated iron-bearing minerals capable of separating these gradients, concentrating reactants and catalysing requisite protobiotic reactions. Iron-bearing minerals such as mackinawite, greenalite and fougèrite have been investigated as catalysts for protobiotic reactions, including amino acid synthesis. In the field of heterogeneous catalysis, it is well known that defect sites in the crystal structure are often the most active sites for catalysis, and mineral catalysts that have been exposed to ionizing radiation are known to exhibit increased reactivity due to radiation-induced defect sites. In this work, we (i) review the literature on the radioactive environment of the Hadean era, (ii) highlight the role of radionuclide ionizing radiation from 238 U, 232 Th and 40 K in generating defect sites with high catalytic activity for the chemical evolution of organic molecules, and (iii) hypothesize that these processes accelerated the emergence of life.

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Zhang, Yuwei, J. Matthew Lucas, Ping Song, Brandon Beberwyck, Qiang Fu, Weilin Xu, and A. Paul Alivisatos. "Superresolution fluorescence mapping of single-nanoparticle catalysts reveals spatiotemporal variations in surface reactivity." Proceedings of the National Academy of Sciences 112, no. 29 (July 6, 2015): 8959–64. http://dx.doi.org/10.1073/pnas.1502005112.

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For the practical application of nanocatalysts, it is desirable to understand the spatiotemporal fluctuations of nanocatalytic activity at the single-nanoparticle level. Here we use time-lapsed superresolution mapping of single-molecule catalysis events on individual nanoparticles to observe time-varying changes in the spatial distribution of catalysis events on Sb-doped TiO2 nanorods and Au triangle nanoplates. Compared with the active sites on well-defined surface facets, the defects of the nanoparticle catalysts possess higher intrinsic reactivity but lower stability. Corners and ends are more reactive but also less stable than flat surfaces. Averaged over time, the most stable sites dominate the total apparent activity of single nanocatalysts. However, the active sites with higher intrinsic activity but lower stability show activity at earlier time points before deactivating. Unexpectedly, some active sites are found to recover their activity (“self-healing”) after deactivation, which is probably due to desorption of the adsorbate. Our superresolution measurement of different types of active catalytic sites, over both space and time, leads to a more comprehensive understanding of reactivity patterns and may enable the design of new and more productive heterogeneous catalysts.

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Hooley, Richard J. "No, Not That Way, the Other Way: Creating Active Sites in Self-Assembled Host Molecules." Synlett 31, no. 15 (May 28, 2020): 1448–63. http://dx.doi.org/10.1055/s-0040-1707125.

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This Account describes our efforts over the last decade to synthesize self-assembled metal–ligand cage complexes that display reactive functional groups on their interiors. This journey has taken us down a variety of research avenues, including studying the mechanism of reversible self-assembly, analyzing ligand self-sorting properties, post-assembly reactivity, molecular recognition, and binding studies, and finally reactivity and catalysis. Each of these individual topics are discussed here, as are the lessons learned along the way and the future research outlook. These self-assembled hosts are the closest mimics of enzymes to date, as they are capable of size- and shape-selective molecular recognition, substrate activation and turnover, as well as showing less common ‘biomimetic’ properties such as the ability to employ cofactors in reactivity, and alter the prevailing mechanism of the catalyzed reactions.1 Introduction2 Paddlewheels and Self-Sorting Behavior3 First-Row Transition-Metal-Mediated Assembly: Sorting and Stereochemical Control4 Post-Assembly Reactivity5 Molecular Recognition and Catalysis6 Conclusions and Outlook

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Friščić, Tomislav, and Jean-Louis Do. "Chemistry 2.0: Developing a New, Solvent-Free System of Chemical Synthesis Based on Mechanochemistry." Synlett 28, no. 16 (August 17, 2017): 2066–92. http://dx.doi.org/10.1055/s-0036-1590854.

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Mechanochemistry by grinding or milling has grown from a laboratory curiosity to a versatile approach for the synthesis and discovery of molecules, materials and reactivity. Focusing on organic synthesis and the chemistry of organic solids in general, we now provide a snapshot of this exciting, rapidly developing area, with the intention to illustrate its potential in establishing a more efficient and environmentally friendly system of chemical and materials synthesis, based on solid-state transformations rather than conventional, solution-dependent chemistry.1 What is Chemistry 2.0?2 Introduction2.1 Why Mechanochemistry Now?2.2 What’s in a Mechanochemistry Laboratory?3 Liquid-Assisted Grinding (LAG): Controlling Mechanochemistry4 The Solvent-Free Research Laboratory5 Medicinal Mechanochemistry6 Exploring Molecular Recognition7 Some Myths to Dispel8 Catalytic Reactions by Mechanochemistry8.1 Catalysis and Reactivity Involving Bulk Metals8.2 Enzyme Catalysis in Mechanochemistry8.3 Coupling of Mechanochemistry, Photochemistry and Supramolecular Catalysis9 Organometallic Mechanochemistry10 New Opportunities10.1 Stoichiometric Control10.2 ‘Impossible’ Molecules10.3 Reaction Discovery by Mechanochemistry11 Energetics of Mechanochemistry12 Mechanistic Understanding13 Real-Time Reaction Monitoring14 Conclusions

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Popovic, Janko, Lorenz Lindenthal, Raffael Rameshan, Thomas Ruh, Andreas Nenning, Stefan Löffler, Alexander Karl Opitz, and Christoph Rameshan. "High Temperature Water Gas Shift Reactivity of Novel Perovskite Catalysts." Catalysts 10, no. 5 (May 22, 2020): 582. http://dx.doi.org/10.3390/catal10050582.

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High temperature water-gas shift (HT-WGS) is an industrially highly relevant reaction. Moreover, climate change and the resulting necessary search for sustainable energy sources are making WGS and reverse-WGS catalytic key reactions for synthetic fuel production. Hence, extensive research has been done to develop improved or novel catalysts. An extremely promising material class for novel highly active HT-WGS catalysts with superior thermal stability are perovskite-type oxides. With their large compositional flexibility, they enable new options for rational catalyst design. Particularly, both cation sites (A and B in ABO3) can be doped with promoters or catalytically active elements. Additionally, B-site dopants are able to migrate to the surface under reducing conditions (a process called exsolution), forming catalytically active nanoparticles and creating an interface that can strongly boost catalytic performance. In this study, we varied A-site composition and B-site doping (Ni, Co), thus comparing six novel perovskites and testing them for their HT-WGS activity: La0.9Ca0.1FeO3-δ, La0.6Ca0.4FeO3-δ, Nd0.9Ca0.1FeO3-δ, Nd0.6Ca0.4FeO3-δ, Nd0.6Ca0.4Fe0.9Ni0.1O3-δ and Nd0.6Ca0.4Fe0.9Co0.1O3-δ. Cobalt and Nickel doping resulted in the highest activity observed in our study, highlighting that doped perovskites are promising novel HT-WGS catalysts. The effect of the compositional variations is discussed considering the kinetics of the two partial reactions of WGS-CO oxidation and water splitting.

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Li, Yang, Yan Peng Ban, Quan Sheng Liu, Meng Zhang, Ke Duan Zhi, Yang Liu, and Lei Wang. "Effects of Several Metals Species on Steam Gasification Behavior of Lignite from Inner Mongolia." Advanced Materials Research 953-954 (June 2014): 1176–79. http://dx.doi.org/10.4028/www.scientific.net/amr.953-954.1176.

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The purpose of this study is to investigate the catalytic effects of different metals in Shengli lignite on the char reactivity. The pyrolysis of Shengli lignite and various metal catalyst loaded coal was investigated in a small fixed-bed reactor, and the gasification activity with steam for different chars was compared as well. The results show that Fe, Ni, Ca and K could effectively lowering the gasification temperature, enhancing the gasification reactivity of SL char. Alkali (K) and alkaline earth (Ca) could be feasibly used as catalysis for the catalytic steam gasification at relatively low temperatures (550~700°C) to produce gases with high H2 (63.2~63.8 v%) and low CO (below 0.9%), and promoting the carbon-water reaction, the water-gas shift reaction to some extent.

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Zhang, Yu, Dongdong Feng, Yijun Zhao, Heming Dong, Guozhang Chang, Cui Quan, Shaozeng Sun, and Yukun Qin. "Evolution of Char Structure During In-Situ Biomass Tar Reforming: Importance of the Coupling Effect Among the Physical-Chemical Structure of Char-Based Catalysts." Catalysts 9, no. 9 (August 24, 2019): 711. http://dx.doi.org/10.3390/catal9090711.

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In order to illustrate the importance of a coupling effect in the physical-chemical structure of char-based catalysts on in-situ biomass tar reforming, three typical char-based catalysts (graphite, Zhundong coal char, and sawdust biochar) were studied in the fixed-bed/fluidized-bed reactor. The physical-chemical properties of carbon-based catalysts associated with their catalytic abilities were characterized by inductively coupled plasma-atomic emission spectroscopy (ICP-AES), Raman, X-ray photoelectron spectroscopy (XPS), scanning electron microscope–energy dispersive spectrometer (SEM-EDS) and N2 adsorption. The relationship between the specific reactivity and tar reforming ability of carbon-based catalysts was discussed through a micro fluidized bed reaction analyzer (MFBRA–MR). The results indicate that the char-based catalyst has a certain removal ability for in-situ biomass tar of corn straw in an inert atmosphere, which is as follows: sawdust biochar > Zhundong (ZD) coal char > graphite. During the in-situ tar reforming, the alkali and alkaline earth metal species (AAEMs) act as adsorption/reaction sites, affecting the evolution of the aromatic ring structure and oxygen-containing functional groups of the char-based catalyst, and also its pore structure. AAEM species on the surface of char-based catalysts are the active sites for tar reforming, which promotes the increase of active intermediates (C-O bond and C-O-AAEMs), and enhances the interactions between char-based catalysts and biomass tar. The abundant AAEMs may lead to the conversion of O=C–O and C=O to C–O. For tar reforming, the internal pore structure of char-based catalysts is little changed, mainly with the carbon deposit forming on the surface pore structure. The carbon deposit from the reformation of straw tar on the char surface has better reactivity than the inherent carbon structure of ZD coal char and sawdust biochar. There is a positive relationship between the MFBRA–MR specific reactivity and tar catalytic reforming ability of char-based catalysts (decided by the coupling effect in their physical-chemical structure), which can be used to determine the catalytic ability of char-based catalysts on tar reforming directly.

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Zinn, Fabiano Kauer, Mihai S. Viciu, and Steven P. Nolan. "10 Carbenes: reactivity and catalysis." Annu. Rep. Prog. Chem., Sect. B: Org. Chem. 100 (2004): 231–49. http://dx.doi.org/10.1039/b401751j.

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Ross, Julian. "Surface reactivity and catalysis group." Applied Catalysis A: General 117, no. 2 (September 1994): N19. http://dx.doi.org/10.1016/0926-860x(94)85100-x.

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Weber, Sebastian, Sebastian Schäfer, Mattia Saccoccio, Nils Ortner, Marko Bertmer, Karsten Seidel, Stefan Berendts, et al. "Mayenite-Based Electride C12A7e−: A Reactivity and Stability Study." Catalysts 11, no. 3 (March 5, 2021): 334. http://dx.doi.org/10.3390/catal11030334.

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Ru supported on mayenite electride, [Ca24Al28O64]4+(e−)4 a calcium aluminum oxide denoted as C12A7e−, are described in the literature as highly active catalysts for ammonia synthesis, especially under conditions of low absolute pressure. In this study, we investigated the application of recently reported plasma arc melting synthesized C12A7e− (aluminum solid reductant) as supports of Ru/C12A7e− catalysts in ammonia synthesis up to pressures of 7.6 MPa. Together with the plasma-arc-melting-based catalyst support, we investigated a similar plasma-synthesized C12A7e− (graphite solid reductant) and a vacuum-sintering-based C12A7e−. Complementary to the catalytic tests, we applied 2H solid-state NMR spectroscopy, DRUVVis-spectroscopy, thermal analysis and PXRD to study and characterize the reactivity of different plasma-synthesized and vacuum-sintered C12A7e− towards H2/D2 and H2O. The catalysts showed an immediate deactivation at pressures > 1 MPa, which can be explained by irreversible hydride formation at higher pressures, as revealed by reactivity tests of C12A7e− towards H2/D2. The direct formation of C12A7:D from C12A7e− is proven. It can be concluded that the application of Ru/C12A7e− catalysts at the industrial scale has limited prospects due to irreversible hydride formation at relevant pressures > 1 MPa. Furthermore, we report an in-depth study relating to structural changes in the material in the presence of H2O.

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Boekell, Nicholas, Dana Cerone, Maria Boucher, Phong Quach, Wilfried Tentchou Nganyak, Christine Reavis, Ifeanyi Okoh, et al. "Triarylmethyl Cation Catalysis: A Tunable Lewis Acid Organocatalyst for the Synthesis of Bisindolylmethanes." SynOpen 01, no. 01 (March 2017): 0097–102. http://dx.doi.org/10.1055/s-0036-1588559.

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Triarylmethyl cations serve as tunable organocatalysts for the synthesis of bisindolylmethanes. The catalyst structure can be modified to increase or decrease reactivity as needed to match the requirements of the substrate. High yields are achieved for a variety of substrates by using these green catalysts. Catalyst tuning allows for the use of less reactive electrophiles by increasing the reactivity of the catalyst. Acid-sensitive products can be isolated under these mild reaction conditions.

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Levi, Samuel M., Qiuhan Li, Andreas R. Rötheli, and Eric N. Jacobsen. "Catalytic activation of glycosyl phosphates for stereoselective coupling reactions." Proceedings of the National Academy of Sciences 116, no. 1 (December 17, 2018): 35–39. http://dx.doi.org/10.1073/pnas.1811186116.

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Glycosyl phosphates are shown to be activated to stereospecific nucleophilic substitution reactions by precisely tailored bis-thiourea catalysts. Enhanced reactivity and scope is observed with phosphate relative to chloride leaving groups. Stronger binding (Km) to the H-bond donor and enhanced reactivity of the complex (kcat) enables efficient catalysis with broad functional group compatibility under mild, neutral conditions.

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Petersen, Haley A., Tessa H. T. Myren, and Oana R. Luca. "Redox-Active Manganese Pincers for Electrocatalytic CO2 Reduction." Inorganics 8, no. 11 (November 11, 2020): 62. http://dx.doi.org/10.3390/inorganics8110062.

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The decrease of total amount of atmospheric CO2 is an important societal challenge in which CO2 reduction has an important role to play. Electrocatalytic CO2 reduction with homogeneous catalysts is based on highly tunable catalyst design and exploits an abundant C1 source to make valuable products such as fuels and fuel precursors. These methods can also take advantage of renewable electricity as a green reductant. Mn-based catalysts offer these benefits while incorporating a relatively cheap and abundant first-row transition metal. Historically, interest in this field started with Mn(bpy-R)(CO)3X, whose performance matched that of its Re counterparts while achieving substantially lower overpotentials. This review examines an emerging class of homogeneous Mn-based electrocatalysts for CO2 reduction, Mn complexes with meridional tridentate coordination also known as Mn pincers, most of which contain redox-active ligands that enable multi-electron catalysis. Although there are relatively few examples in the literature thus far, these catalysts bring forth new catalytic mechanisms not observed for the well-established Mn(bpy-R)(CO)3X catalysts, and show promising reactivity for future studies.

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Sun, Qian, Chun Zeng, Meng-Meng Xing, Bo Chen, Dan Zhao, San-Guo Hong, and Ning Zhang. "Efficiently Engineering Cu-Based Oxide by Surface Embedding of Ce for Selective Catalytic Reduction of NO with NH3." Nano 14, no. 06 (June 2019): 1950079. http://dx.doi.org/10.1142/s1793292019500796.

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Deliberately engineering oxide composites on constructing and manipulating interactive structures particularly in surface layers was highly desirable for heterogeneous catalysis. Herein, upon the redox replacement reaction between Ce(IV) precursor (Ce(NO[Formula: see text] and Cu2O nano-substrate, an attempt to directly engineer the surface structure of Cu-based substrate was performed by the Ce(IV)–Cu2O etching-embedding process, then the obtained powders were thermo-treated to get a series of Ce–O–Cu catalysts with different Ce:Cu molar ratios for NH3 selective catalytic reduction (NH3-SCR) of NO. Characterized by ICP-OES, XRD, Raman, XPS, SEM, BET, H2-TPR, NO- and NH3-TPD measurements, it was demonstrated that the Cu–O–Ce catalysts were structured as CuO matrix with an interactive surface composed by co-present Cu(I)–Cu(II) and Ce(III)–Ce(IV) species, even the introduction of Ce was confined in a quite low loading range (0.83–2.3[Formula: see text]wt.%); such a surface exhibited the distinct synergistic effect with positively manipulated physical-chemistry properties such as active site distributions, redox features and surface reactivity compared to pure CuO and traditional Cu–Ce composite catalyst, leading to attractive catalytic performance such as [Formula: see text]% NO conversion with [Formula: see text]% N2 selectivity and the two-fold TOF enhancement versus traditional catalysts, even SO2 was present in reactant mixture on well-manipulated catalyst (Ce loading at 1.6[Formula: see text]wt.%) These results indicated that the etching-embedding strategy illuminated in this work could be referred as a feasible method to directly engineer and construct interactive oxide composite surface for advanced application as well as current efficient Ce–O–Cu catalytic interface for heterogeneous catalysis.

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Eisenberger, P., and C. M. Crudden. "Borocation catalysis." Dalton Transactions 46, no. 15 (2017): 4874–87. http://dx.doi.org/10.1039/c6dt04232e.

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Konsolakis, Michalis, and Maria Lykaki. "Recent Advances on the Rational Design of Non-Precious Metal Oxide Catalysts Exemplified by CuOx/CeO2 Binary System: Implications of Size, Shape and Electronic Effects on Intrinsic Reactivity and Metal-Support Interactions." Catalysts 10, no. 2 (February 1, 2020): 160. http://dx.doi.org/10.3390/catal10020160.

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Catalysis is an indispensable part of our society, massively involved in numerous energy and environmental applications. Although, noble metals (NMs)-based catalysts are routinely employed in catalysis, their limited resources and high cost hinder the widespread practical application. In this regard, the development of NMs-free metal oxides (MOs) with improved catalytic activity, selectivity and durability is currently one of the main research pillars in the area of heterogeneous catalysis. The present review, involving our recent efforts in the field, aims to provide the latest advances—mainly in the last 10 years—on the rational design of MOs, i.e., the general optimization framework followed to fine-tune non-precious metal oxide sites and their surrounding environment by means of appropriate synthetic and promotional/modification routes, exemplified by CuOx/CeO2 binary system. The fine-tuning of size, shape and electronic/chemical state (e.g., through advanced synthetic routes, special pretreatment protocols, alkali promotion, chemical/structural modification by reduced graphene oxide (rGO)) can exert a profound influence not only to the reactivity of metal sites in its own right, but also to metal-support interfacial activity, offering highly active and stable materials for real-life energy and environmental applications. The main implications of size-, shape- and electronic/chemical-adjustment on the catalytic performance of CuOx/CeO2 binary system during some of the most relevant applications in heterogeneous catalysis, such as CO oxidation, N2O decomposition, preferential oxidation of CO (CO-PROX), water gas shift reaction (WGSR), and CO2 hydrogenation to value-added products, are thoroughly discussed. It is clearly revealed that the rational design and tailoring of NMs-free metal oxides can lead to extremely active composites, with comparable or even superior reactivity than that of NMs-based catalysts. The obtained conclusions could provide rationales and design principles towards the development of cost-effective, highly active NMs-free MOs, paving also the way for the decrease of noble metals content in NMs-based catalysts.

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Raja Shahruzzaman, Raja Mohamad Hafriz, Salmiaton Ali, Robiah Yunus, and Taufiq Yap Yun-Hin. "Green Biofuel Production via Catalytic Pyrolysis of Waste Cooking Oil using Malaysian Dolomite Catalyst." Bulletin of Chemical Reaction Engineering & Catalysis 13, no. 3 (December 4, 2018): 489. http://dx.doi.org/10.9767/bcrec.13.3.1956.489-501.

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Malaysian Dolomite has shown potential deoxygenation catalyst due to high capacity in removing oxygen compound and produce high quality of biofuel with desirable lighter hydrocarbon (C8-C24). The performance of this catalyst was compared with several commercial catalysts in catalytic pyrolysis of Waste Cooking Oil. Calcination at 900 °C in N2 produced catalyst with very high activity due to decomposition of CaMg(CO3)2 phase and formation of MgO-CaO phase. The liquid product showed similar chemical composition of biofuel in the range of gasoline, kerosene and diesel fuel. Furthermore, Malaysian Dolomite showed high reactivity with 76.51 % in total liquid hydrocarbon and the ability to convert the oxygenated compounds into CO2, CO, CH4, H2, hydrocarbon fuel gas, and H2O. Moreover, low acid value (33 mg KOH/g) and low aromatic hydrocarbon content were obtained in the biofuel. Thus, local calcined carbonated material has a potential to act as catalyst in converting waste cooking oil into biofuel. Copyright © 2018 BCREC Group. All rights reservedReceived: 13rd December 2017; Revised: 11st June 2018; Accepted: 3rd July 2018How to Cite: Hafriz, R.S.R.M., Salmiaton, A., Yunus, R., Taufiq-Yap, Y.H. (2018). Green Biofuel Production via Catalytic Pyrolysis of Waste Cooking Oil using Malaysian Dolomite Catalyst. Bulletin of Chemical Reaction Engineering & Catalysis, 13 (3): 489-501 (doi:10.9767/bcrec.13.3.1956.489-501)Permalink/DOI: https://doi.org/10.9767/bcrec.13.3.1956.489-501

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Piccardi, Riccardo, Serge Turcaud, Erica Benedetti, and Laurent Micouin. "Synthesis and Reactivity of Mixed Dimethylalkynylaluminum Reagents." Synthesis 51, no. 01 (November 20, 2018): 97–106. http://dx.doi.org/10.1055/s-0037-1610392.

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Organoaluminum derivatives are mostly appreciated for their Lewis acidity properties, but generally not considered as reagents of choice in synthetic transformations involving the creation of C–C bonds. Among these species, dimethylalkynylaluminum reagents represent a special class of compounds, with, in many cases, unique reactivity. This review summarizes the preparation and reactivity of these organometallic reagents with a focus on their synthetic potential.1 Introduction2 Preparation of Dimethylalkynylaluminum Reagents3 Reactivity of Dimethylalkynylaluminum Reagents3.1 Reactions with Csp3 Electrophiles3.2 Reactions with Csp2 Electrophiles4 Transition-Metal-Catalyzed Reactions4.1 Addition to α,β-Unsaturated Enones4.2 Coupling Reactions5 Triple Bond Reactivity6 Conclusion

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Brown, Ronald W., Farzad Zamani, Michael G. Gardiner, Haibo Yu, Stephen G. Pyne, and Christopher J. T. Hyland. "Divergent Pd-catalyzed cross-coupling of allenyloxazolidinones to give chiral 1,3-dienes and vinyloxazolidinones." Chemical Science 10, no. 39 (2019): 9051–56. http://dx.doi.org/10.1039/c9sc03215k.

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Gao, Xin-Qian, Wei Song, Wen-Cui Li, and An-Hui Lu. "Anti-coke behavior of an alumina nanosheet supported Pt–Sn catalyst for isobutane dehydrogenation." Catalysis Science & Technology 11, no. 7 (2021): 2597–603. http://dx.doi.org/10.1039/d0cy02154g.

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Alumina nanosheet supported platinum-based catalysts exhibited excellent catalytic reactivity and stability with an anti-coke capacity in the isobutane dehydrogenation process due to the abundant defect sites and decreased acidity.

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37

Smith, Louise R., Paul J. Smith, Karl S. Mugford, Mark Douthwaite, Nicholas F. Dummer, David J. Willock, Mark Howard, David W. Knight, Stuart H. Taylor, and Graham J. Hutchings. "New insights for the valorisation of glycerol over MgO catalysts in the gas-phase." Catalysis Science & Technology 9, no. 6 (2019): 1464–75. http://dx.doi.org/10.1039/c8cy02214c.

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Zaccaria, Francesco, Peter H. M. Budzelaar, Cristiano Zuccaccia, Roberta Cipullo, Alceo Macchioni, Vincenzo Busico, and Christian Ehm. "Chain Transfer to Solvent and Monomer in Early Transition Metal Catalyzed Olefin Polymerization: Mechanisms and Implications for Catalysis." Catalysts 11, no. 2 (February 5, 2021): 215. http://dx.doi.org/10.3390/catal11020215.

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Even after several decades of intense research, mechanistic studies of olefin polymerization by early transition metal catalysts continue to reveal unexpected elementary reaction steps. In this mini-review, the recent discovery of two unprecedented chain termination processes is summarized: chain transfer to solvent (CTS) and chain transfer to monomer (CTM), leading to benzyl/tolyl and allyl type chain ends, respectively. Although similar transfer reactions are well-known in radical polymerization, only very recently they have been observed also in olefin insertion polymerization catalysis. In the latter context, these processes were first identified in Ti-catalyzed propene and ethene polymerization; more recently, CTS was also reported in Sc-catalyzed styrene polymerization. In the Ti case, these processes represent a unique combination of insertion polymerization, organic radical chemistry and reactivity of a M(IV)/M(III) redox couple. In the Sc case, CTS occurs via a σ-bond metathesis reactivity, and it is associated with a significant boost of catalytic activity and/or with tuning of polystyrene molecular weight and tacticity. The mechanistic studies that led to the understanding of these chain transfer reactions are summarized, highlighting their relevance in olefin polymerization catalysis and beyond.

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Monkcom, Emily C., Pradip Ghosh, Emma Folkertsma, Hidde A. Negenman, Martin Lutz, and Robertus J. M. Klein Gebbink. "Bioinspired Non-Heme Iron Complexes: The Evolution of Facial N, N, O Ligand Design." CHIMIA International Journal for Chemistry 74, no. 6 (June 24, 2020): 450–66. http://dx.doi.org/10.2533/chimia.2020.450.

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Iron-containing metalloenzymes that contain the 2-His-1-Carboxylate facial triad at their active site are well known for their ability to activate molecular oxygen and catalyse a broad range of oxidative transformations. Many of these reactions are synthetically challenging, and developing small molecular iron-based catalysts that can achieve similar reactivity and selectivity remains a long-standing goal in homogeneous catalysis. This review focuses on the development of bioinspired facial N,N,O ligands that model the 2-His-1-Carboxylate facial triad to a greater degree of structural accuracy than many of the polydentate N-donor ligands commonly used in this field. By developing robust, well-defined N,N,O facial ligands, an increased understanding could be gained of the factors governing enzymatic reactivity and selectivity.

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40

Zhou, Chuan, Binghu Zhang, P. Hu, and Haifeng Wang. "An effective structural descriptor to quantify the reactivity of lattice oxygen in CeO2 subnano-clusters." Physical Chemistry Chemical Physics 22, no. 3 (2020): 1721–26. http://dx.doi.org/10.1039/c9cp05805b.

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Capdevila-Cortada, Marçal, Gianvito Vilé, Detre Teschner, Javier Pérez-Ramírez, and Núria López. "Reactivity descriptors for ceria in catalysis." Applied Catalysis B: Environmental 197 (November 2016): 299–312. http://dx.doi.org/10.1016/j.apcatb.2016.02.035.

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Baral, Ek Raj, Dongwook Kim, Sunwoo Lee, Myung Hwan Park, and Jeung Gon Kim. "Tin(IV)-Porphyrin Tetracarbonyl Cobaltate: An Efficient Catalyst for the Carbonylation of Epoxides." Catalysts 9, no. 4 (March 29, 2019): 311. http://dx.doi.org/10.3390/catal9040311.

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Cationic tin(IV) porphyrins with tetracarbonyl cobaltates were synthesized, exhibiting bifunctional catalytic reactivity. The Lewis acidic tin-porphyrin center activated epoxides; concurrently, cobalt carbonyl anions efficiently opened epoxides and delivered carbonyl moieties. Thus, a series of β-lactones with a high synthetic value were obtained. This catalytic system showed excellent efficiency exceeding a turnover number of one thousand with a broad substrate scope. In addition, the presented tin porphyrin-based catalyst exhibited exclusive chemoselectivity to terminal epoxides over internal ones. The selective carbonylation of di-epoxides demonstrated the usefulness of these catalysts in the synthesis of complex molecular structures.

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Yin, Congcong, Yingmin Pan, Longsheng Zheng, Bijin Lin, Jialin Wen, and Xumu Zhang. "Iridium-catalyzed asymmetric hydrogenation of N-phosphinoylimine." Organic Chemistry Frontiers 8, no. 6 (2021): 1223–26. http://dx.doi.org/10.1039/d0qo01286f.

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On catalysis with an iridium tridentate catalyst, prochiral N-phosphinoylimines were hydrogenated with high enantioselectivity and reactivity. An outer-sphere reaction model was proposed in this hydrogenation of CN bonds.

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Yang, Gang, and Lijun Zhou. "Mechanisms and reactivity differences of proline-mediated catalysis in water and organic solvents." Catalysis Science & Technology 6, no. 10 (2016): 3378–85. http://dx.doi.org/10.1039/c6cy00033a.

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Wen, Jinjun, Chunlei Huang, Yuhai Sun, Long Liang, Yudong Zhang, Yujun Zhang, Mingli Fu, Junliang Wu, Limin Chen, and Daiqi Ye. "The Study of Reverse Water Gas Shift Reaction Activity over Different Interfaces: The Design of Cu-Plate ZnO Model Catalysts." Catalysts 10, no. 5 (May 12, 2020): 533. http://dx.doi.org/10.3390/catal10050533.

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CO2 hydrogenation to methanol is one of the main and valuable catalytic reactions applied on Cu/ZnO-based catalysts; the interface formed through Zn migration from ZnO support to the surface of Cu nanoparticle (ZnOx-Cu NP-ZnO) has been reported to account for methanol synthesis from CO2 hydrogenation. However, the accompanied reverse water gas shift (RWGS) reaction significantly decreases methanol selectivity and deactivates catalysts soon. Inhibition of RWGS is thus of great importance to afford high yield of methanol. The clear understanding of the reactivity of RWGS reaction on both the direct contact Cu-ZnO interface and ZnOx-Cu NP-ZnO interface is essential to reveal the low methanol selectivity in CO2 hydrogenation to methanol and look for efficient catalysts for RWGS reaction. Cu doped plate ZnO (ZnO:XCu) model catalysts were prepared through a hydrothermal method to simulate direct contact Cu-ZnO interface and plate ZnO supported 1 wt % Cu (1Cu/ZnO) catalyst was prepared by wet impregnation for comparison in RWGS reaction. Electron paramagnetic resonance (EPR), XRD, SEM, Raman, hydrogen temperature-programmed reduction (H2-TPR) and CO2 temperature-programmed desorption (CO2-TPD) were employed to characterize these catalysts. The characterization results confirmed that Cu incorporated into ZnO lattice and finally formed direct contact Cu-ZnO interface after H2 reduction. The catalytic performance revealed that direct contact Cu-ZnO interface displays inferior RWGS reaction reactivity at reaction temperature lower than 500 °C, compared with the ZnOx-Cu NP-ZnO interface; however, it is more stable at reaction temperature higher than 500 °C, enables ZnO:XCu model catalysts superior catalytic activity to that of 1Cu/ZnO. This finding will facilitate the designing of robust and efficient catalysts for both CO2 hydrogenation to methanol and RWGS reactions.

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Bordet, Alexis, Sami El Sayed, Matthew Sanger, Kyle J. Boniface, Deepti Kalsi, Kylie L. Luska, Philip G. Jessop, and Walter Leitner. "Selectivity control in hydrogenation through adaptive catalysis using ruthenium nanoparticles on a CO2-responsive support." Nature Chemistry 13, no. 9 (July 5, 2021): 916–22. http://dx.doi.org/10.1038/s41557-021-00735-w.

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AbstractWith the advent of renewable carbon resources, multifunctional catalysts are becoming essential to hydrogenate selectively biomass-derived substrates and intermediates. However, the development of adaptive catalytic systems, that is, with reversibly adjustable reactivity, able to cope with the intermittence of renewable resources remains a challenge. Here, we report the preparation of a catalytic system designed to respond adaptively to feed gas composition in hydrogenation reactions. Ruthenium nanoparticles immobilized on amine-functionalized polymer-grafted silica act as active and stable catalysts for the hydrogenation of biomass-derived furfural acetone and related substrates. Hydrogenation of the carbonyl group is selectively switched on or off if pure H2 or a H2/CO2 mixture is used, respectively. The formation of alkylammonium formate species by the catalytic reaction of CO2 and H2 at the amine-functionalized support has been identified as the most likely molecular trigger for the selectivity switch. As this reaction is fully reversible, the catalyst performance responds almost in real time to the feed gas composition.

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Battaglia, Lorenzo, Francesco Pinna, and Giorgio Strukul. "Thioacetalization of aldehydes and ketones in the presence of hydroxo complexes of platinum(II): An example of Lewis acid catalytic activity." Canadian Journal of Chemistry 79, no. 5-6 (May 1, 2001): 621–25. http://dx.doi.org/10.1139/v01-067.

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The complex [(dppb)Pt(µ-OH)]2(BF4)2 displays high catalytic activity in the thioacetalization of a variety of aldehydes and ketones with mercaptoethanol under very mild conditions. The reaction rate is greatly enhanced by the addition to the reaction mixture of magnesium perchlorate as drying agent and molar turnovers as high as 9700 can be observed. The effect of different desiccating agents is also reported. The reactivity pattern observed, the similarity with other reactions and NMR spectroscopic investigations confirm the possible role of the complex as Lewis acid catalyst in promoting the reaction.Key words: thioacetalization, catalysis, aldehydes, ketones, platinum complex.

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Pike, Sebastian D., and Andrew S. Weller. "Organometallic synthesis, reactivity and catalysis in the solid state using well-defined single-site species." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 373, no. 2037 (March 13, 2015): 20140187. http://dx.doi.org/10.1098/rsta.2014.0187.

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Acting as a bridge between the heterogeneous and homogeneous realms, the use of discrete, well-defined, solid-state organometallic complexes for synthesis and catalysis is a remarkably undeveloped field. Here, we present a review of this topic, focusing on describing the key transformations that can be observed at a transition-metal centre, as well as the use of well-defined organometallic complexes in the solid state as catalysts. There is a particular focus upon gas–solid reactivity/catalysis and single-crystal-to-single-crystal transformations.

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Yang, Dong, Shengjie Zhang, Pinghong Xu, Nigel D. Browning, David A. Dixon, and Bruce C. Gates. "Single-Site Osmium Catalysts on MgO: Reactivity and Catalysis of CO Oxidation." Chemistry - A European Journal 23, no. 11 (January 30, 2017): 2532–36. http://dx.doi.org/10.1002/chem.201605131.

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Poudyal, Samiksha, and Siris Laursen. "Photocatalytic CO2 reduction by H2O: insights from modeling electronically relaxed mechanisms." Catalysis Science & Technology 9, no. 4 (2019): 1048–59. http://dx.doi.org/10.1039/c8cy02046a.

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Understanding of the ground-state surface reaction mechanism for photocatalytic CO₂ reduction and new connections between catalyst surface reactivity and experimentally observed activity and selectivity are presented to facilitate the development of catalysts that exhibit improved activity, controlled product distributions, and enhanced quantum yield.

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Journal articles on the topic 'Reactivity and catalysis'

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