École d'Ingénieurs en Chimie et Sciences du Numérique

Replacement of part of the fossil fuel consumption by renewable energy, in particular in the chemical industry, is a central strategy for resource and energy efficiency. This perspective will show that CO2 is the key molecule to proceed effectively in this direction. The routes, opportunities and barriers in increasing the share of renewable energy by using CO2 reaction and their impact on the chemical and energy value chains are discussed after introducing the general aspects of this topic evidencing the tight integration between the CO2 use and renewable energy insertion in the value chain of the process industry. The focus of this perspective article is on the catalytic aspects of the chemistries involved, with an analysis of the state-of-the-art, perspectives and targets to be developed. The reactions discussed are the production of short-chain olefins (ethylene, propylene) from CO2, and the conversion of carbon dioxide to syngas, formic acid, methanol and dimethyl ether, hydrocarbons via Fischer–Tropsch synthesis and methane. The relevance of availability, cost and environmental footprints of H2 production routes using renewable energies is addressed. The final part discusses the possible scenario for CO2 as an intermediary for the incorporation of renewable energy in the process industry, with a concise roadmap for catalysis needs and barriers to reach this goal.

Surface organometallic chemistry is an area of heterogeneous catalysis which has recently emerged as a result of a comparative analysis of homogeneous and heterogeneous catalysis. The chemical industry has often favored heterogeneous catalysis, but the development of better catalysts has been hindered by the presence of numerous kinds of active sites and also by the low concentration of active sites. These factors have precluded a rational improvement of these systems, hence the empirical nature of heterogeneous catalysis. Catalysis is primarily a molecular phenomenon, and it must involve well-defined surface organometallic intermediates and/or transition states. Thus, one must be able to construct a well-defined active site, test its catalytic performance, and assess a structure-activity relationship, which will be used, in turn-as in homogeneous catalysis-to design better catalysts. By the transfer of the concepts and tools of molecular organometallic chemistry to surfaces, surface organometallic chemistry can generate well-defined surface species by understanding the reaction of organometallic complexes with the support, which can be considered as a rigid ligand. This new approach to heterogeneous catalysis can bring molecular insight to the design of new catalysts and even allow the discovery of new reactions (Ziegler-Natta depolymerization and alkane metathesis). After more than a century of existence, heterogeneous catalysis can still be improved and will play a crucial role in solving current problems. It offers an answer to economical and environmental problems faced by industry in the production of molecules (agrochemicals, petrochemicals, pharmaceuticals, polymers, basic chemicals).

Transition-metal-catalyzed C-H bond arylation has recently emerged as a powerful tool for the functionalization of organic molecules that may complement or even replace traditional catalytic cross-couplings. While many efforts have focused on the arylation of arenes and heteroarenes in the past two decades, less studies have been devoted to the arylation of nonacidic C-H bonds of alkyl groups. This tutorial review highlights recent work in this active area.

Dinitrogen cleavage and hydrogenation by transition-metal centers to produce ammonia is central in industry and in Nature. After an introductory section on the thermodynamic and kinetic challenges linked to N2 splitting, this tutorial review discusses three major classes of transition-metal systems (homogeneous, heterogeneous and biological) capable of achieving dissociation and hydrogenation of dinitrogen. Molecular complexes, solid-state Haber-Bosch catalytic systems, silica-supported tantalum hydrides and nitrogenase will be discussed. Emphasis is focused on the reaction mechanisms operating in the process of dissociation and hydrogenation of dinitrogen, and in particular on the key role played by metal hydride bonds and by dihydrogen in such reactions.

Image denoising is an important problem in image processing since noise may interfere with visual or automatic interpretation. This paper presents a new approach for image denoising in the case of a known uncorrelated noise model. The proposed filter is an extension of the nonlocal means (NL means) algorithm introduced by Buades , which performs a weighted average of the values of similar pixels. Pixel similarity is defined in NL means as the Euclidean distance between patches (rectangular windows centered on each two pixels). In this paper, a more general and statistically grounded similarity criterion is proposed which depends on the noise distribution model. The denoising process is expressed as a weighted maximum likelihood estimation problem where the weights are derived in a data-driven way. These weights can be iteratively refined based on both the similarity between noisy patches and the similarity of patches extracted from the previous estimate. We show that this iterative process noticeably improves the denoising performance, especially in the case of low signal-to-noise ratio images such as synthetic aperture radar (SAR) images. Numerical experiments illustrate that the technique can be successfully applied to the classical case of additive Gaussian noise but also to cases such as multiplicative speckle noise. The proposed denoising technique seems to improve on the state of the art performance in that latter case.

This Perspective describes the recent developments of polymerization-induced self-assembly of amphiphilic block copolymers based on controlled/living free-radical polymerization (CRP) in water. This method relies on the use of a hydrophilic living polymer precursor prepared via CRP that is extended with a hydrophobic second block in an aqueous environment. The process thus leads to amphiphilic block copolymers that self-assemble in situ into self-stabilized nano-objects in the frame of an emulsion or dispersion polymerization process. Depending on the nature and the structure of the so-formed copolymer, not only spherical particles can be achieved but also all morphologies that can be found in the phase diagram of an amphiphilic block copolymer in a selective solvent. This paper focuses mainly on aqueous emulsion or dispersion polymerization and gives an overview of the CRP techniques used, the general conditions, and the morphologies obtained.

Because the Roman god Janus was usually represented with two heads placed back to back, the term Janus is used for the description of particles whose surfaces of both hemispheres are different from a chemical point of view. So, they could be used as building blocks for supraparticular assemblies, as dual-functionalized devices, as particular surfactants if one hemisphere is hydrophilic and the other hydrophobic, etc. If they could allow the segregation of negative charges on one hemisphere and positive charges on the other one, they would display a giant dipole moment allowing their remote positioning by rotation in an electric field as a function of field polarity. This review deals with the great and imaginative efforts which were devoted to the synthesis of Janus particles in the last fifteen years. A special emphasis is made on scalable techniques and on those which apply to the preparation of Janus particles in the nanometer range. Specific properties and applications of Janus particles are discussed.

This Review introduces this special issue of ChemSusChem dedicated to CO(2) recycling. Its aim is to offer an up-to-date overview of CO(2) chemical utilization (inorganic mineralization, organic carboxylation, reduction reactions, and biochemical conversion), as a continuation and extension of earlier books and reviews on this topic, but with a specific focus on large-volume routes and projects/pilot plants that are currently emerging at (pre-)industrial level. The Review also highlights how some of these routes will offer a valuable opportunity to introduce renewable energy into the existing energy and chemical infrastructure (i.e., "drop-in" renewable energy) by synthesis of chemicals from CO(2) that are easy to transport and store. CO(2) conversion therefore has the potential to become a key pillar of the sustainable and resource-efficient production of chemicals and energy from renewables.

It is shown that surface NMR spectra can be greatly enhanced using dynamic nuclear polarization. Polarization is transferred from the protons of the solvent to the rare nuclei (here carbon-13 at natural isotopic abundance) at the surface, yielding at least a 50-fold signal enhancement for surface species covalently incorporated into a silica framework.

Ionization is the dominant response of atoms and molecules to intense laser fields and is at the basis of several important techniques, such as the generation of attosecond pulses that allow the measurement of electron motion in real time. We present experiments in which metastable xenon atoms were ionized with intense 7-micrometer laser pulses from a free-electron laser. Holographic structures were observed that record underlying electron dynamics on a sublaser-cycle time scale, enabling photoelectron spectroscopy with a time resolution of almost two orders of magnitude higher than the duration of the ionizing pulse.

After a brief history that positions polymerization-induced self-assembly (PISA) in the field of polymer chemistry, this Review will cover the fundamentals of the PISA mechanism. Furthermore, this Review will also give an overview of some of the features and limitations of RAFT-mediated PISA in terms of the choice of the components involved, the nature of the nanoobjects that can be obtained and how the syntheses can be controlled, as well as some potential applications.

This review is an extensive update to the comprehensive review on controlled/living radical polymerization (CLRP) in dispersed systems published in 2008.

Abstract This review highlights some remarkable recently made achievements in the application of palladium‐mediated processes to the design of multicomponent one‐pot syntheses of heterocyclic compounds. Palladium‐catalysed cascade reactions are surveyed, together with processes based on sequential, one‐pot performance of individual transformations in which at least one is catalysed by palladium. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

ADVERTISEMENT RETURN TO ISSUEPREVReviewNEXTC−H Bond Activation and Organometallic Intermediates on Isolated Metal Centers on Oxide SurfacesChristophe Coperet*View Author Information Université de Lyon, Institut de Chimie de Lyon, C2P2, UMR 5265 (CNRS-CPE—Université Lyon 1), CPE Lyon F308, 43 Boulevard du 11 Novembre 1918, F-69616 Villeurbanne Cedex, France E-mail: [email protected]Cite this: Chem. Rev. 2010, 110, 2, 656–680Publication Date (Web):October 12, 2009Publication History Received30 March 2009Published online12 October 2009Published inissue 10 February 2010https://pubs.acs.org/doi/10.1021/cr900122phttps://doi.org/10.1021/cr900122preview-articleACS PublicationsCopyright © 2009 American Chemical SocietyRequest reuse permissionsArticle Views11729Altmetric-Citations398LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Bond activation,Catalysts,Hydrocarbons,Metathesis,Oxides Get e-Alerts

Combining experiments and DFT calculations, we show that tricoordinate Al(III) Lewis acid sites, which are present as metastable species exclusively on the major (110) termination of γ- and δ-Al(2)O(3) particles, correspond to the "defect" sites, which are held responsible for the unique properties of "activated" (thermally pretreated) alumina. These "defects" are, in fact, largely responsible for the adsorption of N(2) and the splitting of CH(4) and H(2). In contrast, five-coordinate Al surface sites of the minor (100) termination cannot account for the observed reactivity. The Al(III) sites, which are formed upon partial dehydroxylation of the surface (the optimal pretreatment temperature being 700 °C for all probes), can coordinate N(2) selectively. In combination with specific O atoms, they form extremely reactive Al,O Lewis acid-base pairs that trigger the low-temperature heterolytic splitting of CH(4) and H(2) to yield Al-CH(3) and Al-H species, respectively. H(2) is found overall more reactive than CH(4) because of its higher acidity, hence it also reacts on four-coordinate sites of the (110) termination. Water has the dual role of stabilizing the (110) termination and modifying (often increasing) both the Lewis acidity of the aluminum and the basicity of nearby oxygens, hence the high reactivity of partially dehyxdroxylated alumina surfaces. In addition, we demonstrate that the presence of water enhances the acidity of certain four-coordinate Al atoms, which leads to strong coordination of the CO molecule with a spectroscopic signature similar to that on Al(III) sites, thus showing the limits of this widely used probe for the acidity of oxides. Overall, the dual role of water translates into optimal water coverage, and this probably explains why in many catalyst preparations, optimal pretreatment temperatures are typically observed in the "activation" step of alumina.

Abstract Because of its high lipophilicity, the CF 3 S group has always interested chemists. However, strategies to introduce it into organic molecules have been, for the most part, reserved to specialized “fluorine chemists”. Recent published work has demystified these preconceived ideas by proposing new efficient methods or easy‐to‐handle reagents to enrich the toolbox of chemists. However, all these new concepts arise from the pioneering works of the past! In this review, we will do a “back to the future” by remembering the most significant results of the past and by presenting extensions and novelties of the present and for the future.

In several recent field campaigns the existence of a strong daytime source of nitrous acid was demonstrated. The mechanism of this source remains unclear. Accordingly, in the present laboratory study, the effect of light (in the range 300-500 nm) on the uptake kinetics of NO2 on various surfaces taken as proxies for organic surfaces encountered in the troposphere (as organic aerosol but also ground surfaces) was investigated. In this collaborative study, the uptake kinetics and product formation rate were measured by different flow tube reactors in combination with a sensitive HONO instrument. Uptake on light absorbing aromatic compounds was significantly enhanced when irradiated with light of 300-420 nm, and HONO was formed with high yield when the gas was humidified. Especially organic substrates containing a combination of electron donors, such as phenols, and of compounds yielding excited triplet states, such as aromatic ketones, showed a high reactivity towards NO2. Based on the results reported a mechanism is suggested, in which photosensitised electron transfer is occurring. The results show that HONO can be efficiently formed during the day in the atmosphere at much longer wavelengths compared to the recently proposed nitrate photolysis.

Abstract Membrane emulsification has received increasing attention over the last 10 years, with potential applications in many fields. In the membrane emulsification process, a liquid phase is pressed through the membrane pores to form droplets at the permeate side of a membrane; the droplets are then carried away by a continuous phase flowing across the membrane surface. Under specific conditions, monodispersed emulsions can be produced using this technique. The purpose of the present paper is to provide a review on the membrane emulsification process including: principles of membrane emulsification, influence of process parameters and industrial applications. Small‐scale applications such as drug delivery systems, food emulsions, and the production of monodispersed microspheres are also included. Compared with conventional techniques for emulsification, membrane processes offer advantages such as control of average droplet diameter by average membrane pore size and lower energy input. Copyright © 2004 Society of Chemical Industry

Organ in vitro synthesis is one of the last bottlenecks between tissue engineering and transplantation of synthetic organs. Bioprinting has proven its capacity to produce 3D objects composed of living cells but highly organized tissues such as full thickness skin (dermis + epidermis) are rarely attained. The focus of the present study is to demonstrate the capability of a newly developed ink formulation and the use of an open source printer, for the production of a really complete skin model. Proofs are given through immunostaining and electronic microscopy that the bioprinted skin presents all characteristics of human skin, both at the molecular and macromolecular level. Finally, the printability of large skin objects is demonstrated with the printing of an adult-size ear.

The Cramér-Rao lower bounds (CRBs) are the lowest possible standard deviations of all unbiased model parameter estimates obtained from the data. Consequently they give insight into the potential performance of quantitation estimators. Using analytical CRB expressions for spectral parameters of singlets and doublets in noise, one is able to judge the precision as a function of spectral and experimental parameters. We point out the usefulness of these expressions for experimental design. The influence of constraints (chemical prior knowledge) on spectral parameters of the peaks of doublets is demonstrated and the inherent benefits for quantitation are shown. Abbreviations used: CRB Cramér-Rao lower bounds