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Pera-Titus M.,CNRS Research on Catalysis and Environment in Lyon | Pera-Titus M.,Solvay Group
Chemical Reviews | Year: 2014

CO2 capture, transport, and long-term storage or sequestration (CCS) is visualized as a promising strategy for mitigating CO2 emissions at short- and midterms, especially in stationary sources. In the case of precombustion CO2 capture, carbon-templated microporous silica and MFI membranes constitute the most mature materials for membrane design on the basis not only of the reproducibility of their synthesis protocols, but also of their narrow thickness down to the micrometer level. In the case of postcombustion CO2 capture, MFI membranes can find suitable applications for CO2/N2 separations driven by preferential CO2 adsorption. The presence of moderate Si/Al ratios in these materials provides a trade-off for preferential CO2 adsorption and moderate poisoning by moisture below a threshold value. Finally, in the case of CO2/CH4 separations, the SAPO-34 membranes prepared by Noble and Falconer can show potentials with a proven reproducibility of synthesis protocols.

Platon M.,CNRS Molecular Chemistry Institute of Burgundy University | Amardeil R.,CNRS Molecular Chemistry Institute of Burgundy University | Djakovitch L.,CNRS Research on Catalysis and Environment in Lyon | Hierso J.-C.,CNRS Molecular Chemistry Institute of Burgundy University
Chemical Society Reviews | Year: 2012

A survey highlighting the most recent palladium catalytic systems produced and their performances for progress in direct synthesis of indole backbones by heterocarbocyclization of reactive substrates is provided. The discussion is developed in relation with the principles of sustainable chemistry concerning atom and mass economy. In this respect, the general convergent character of the syntheses is of particular interest (one-pot, domino, cascade or tandem reactions), and the substrates accessibility and reactivity, together with the final waste production, are also important. This critical review clearly indicates that the development of ligand chemistry, mainly phosphines and carbenes, in the last few decades gave a significant impetus to powerful functionalization of indoles at virtually all positions of this ubiquitous backbone (118 references). © 2012 The Royal Society of Chemistry.

Canivet J.,CNRS Research on Catalysis and Environment in Lyon | Fateeva A.,CNRS Materials Sciences and Technologies Laboratory | Guo Y.,CNRS Research on Catalysis and Environment in Lyon | Coasne B.,Massachusetts Institute of Technology | Farrusseng D.,CNRS Research on Catalysis and Environment in Lyon
Chemical Society Reviews | Year: 2014

This review article presents the fundamental and practical aspects of water adsorption in Metal-Organic Frameworks (MOFs). The state of the art of MOF stability in water, a crucial issue to many applications in which MOFs are promising candidates, is discussed here. Stability in both gaseous (such as humid gases) and aqueous media is considered. By considering a non-exhaustive yet representative set of MOFs, the different mechanisms of water adsorption in this class of materials are presented: reversible and continuous pore filling, irreversible and discontinuous pore filling through capillary condensation, and irreversibility arising from the flexibility and possible structural modifications of the host material. Water adsorption properties of more than 60 MOF samples are reported. The applications of MOFs as materials for heat-pumps and adsorbent-based chillers and proton conductors are also reviewed. Some directions for future work are suggested as concluding remarks. This journal is © the Partner Organisations 2014.

Gallezot P.,CNRS Research on Catalysis and Environment in Lyon
Chemical Society Reviews | Year: 2012

This critical review provides a survey illustrated by recent references of different strategies to achieve a sustainable conversion of biomass to bioproducts. Because of the huge number of chemical products that can be potentially manufactured, a selection of starting materials and targeted chemicals has been done. Also, thermochemical conversion processes such as biomass pyrolysis or gasification as well as the synthesis of biofuels were not considered. The synthesis of chemicals by conversion of platform molecules obtained by depolymerisation and fermentation of biopolymers is presently the most widely envisioned approach. Successful catalytic conversion of these building blocks into intermediates, specialties and fine chemicals will be examined. However, the platform molecule value chain is in competition with well-optimised, cost-effective synthesis routes from fossil resources to produce chemicals that have already a market. The literature covering alternative value chains whereby biopolymers are converted in one or few steps to functional materials will be analysed. This approach which does not require the use of isolated, pure chemicals is well adapted to produce high tonnage products, such as paper additives, paints, resins, foams, surfactants, lubricants, and plasticisers. Another objective of the review was to examine critically the green character of conversion processes because using renewables as raw materials does not exempt from abiding by green chemistry principles (368 references). © 2012 The Royal Society of Chemistry.

Besson M.,CNRS Research on Catalysis and Environment in Lyon | Gallezot P.,CNRS Research on Catalysis and Environment in Lyon | Pinel C.,CNRS Research on Catalysis and Environment in Lyon
Chemical Reviews | Year: 2014

The catalytic conversion of biosourced feedstocks into chemicals in the presence of monometallic, multimetallic, and multifunctional catalysts is reviewed. An alternative value-chain based on one-pot processes starting from biopolymers or plant oils could be more effective for mass production and accelerate greatly the industrial development of chemicals and materials based on renewable carbon. Metals and supporting materials employed in conventional hydrocarbon processing and organic synthesis are often not adapted to convert biomass-derived feedstocks. Various challenges should be met for the design of catalysts employed in biomass processing. one of the major issues for the industrial development of the biomass-to-chemical value-chain is the need for catalytic systems and engineering processes able to cope with the presence of residual impurities of feedstocks that may poison the activity or modify the selectivity of metal catalysts.

Piccolo L.,CNRS Research on Catalysis and Environment in Lyon
Chemical Communications | Year: 2013

The hydrogenation of butadiene has been investigated for the first time on Al13Fe4. The model (010) surface of this non-noble metal combination appears to be both active and selective under mild reaction conditions. The performances of Al13Fe4 for CC bond hydrogenation are compared with those of the reference noble metal, palladium. © 2013 The Royal Society of Chemistry.

Sorokin A.B.,CNRS Research on Catalysis and Environment in Lyon
Chemical Reviews | Year: 2013

Phthalocyanine metal complexes are structurally related to porphyrin complexes. The principal motivation for the preparation of heterogeneous catalysts is the possibility of their easy separation from the reaction mixture and their reuse for successive reactions, provided that the catalysts retain their catalytic properties. However, too few papers focus on rigorous studies of the catalysts' stability and recycle. Both organic polymers and inorganic materials can be used as supports. More robust inorganic solids are more suitable, in particular, for oxidation reactions and should be preferred. Several factors should be considered for the appropriate choice of the support: stability of the support under reaction conditions, possible involvement with the reaction, capacity to readily introduce functionality for covalent anchoring, degree of functionalization, and availability and cost of the support.

Herrmann J.-M.,CNRS Research on Catalysis and Environment in Lyon
Applied Catalysis B: Environmental | Year: 2010

Photocatalysis has presently become a major discipline owing to two factors: (i) the intuition of the pioneers of last 20th century and (ii) the mutual enrichment of scientists arising from different fields: photochemistry, electrochemistry, analytical chemistry, radiochemistry, material chemistry, surface science, electronics, and hopefully catalysis. Since heterogeneous photocatalysis belongs to catalysis, all the bases of this discipline must be respected: (i) proportionality of the reaction rate to the mass of catalyst (below the plateau due to a full absorption of photons); (ii) implication of the Langmuir-Hinshelwood mechanism of kinetics with the initial rate being proportional to the coverages θ in reactants;(iii) conversions obtained above the stoichiometric threshold defined as the maximum number of potential active sites initially present at the surface of a mass m of titania used in the reaction. In addition, one should respect photonics, with the photocatalytic activity, i.e. the reaction rate being (i) parallel to the absorbance of the photocatalyst and (ii) proportional to the radiant flux Φ. In every study, one should determine the quantum yield (QY) (or efficiency), which, although dimensionless, is a "doubly kinetic" magnitude defined as the ratio of the reaction rate r (in molecules converted/second) to the efficient photonic flux (in photons/second) received by the solid. This is an instantaneous magnitude directly linked to the parameters mentioned above, in particular to the concentration. It can vary from a maximum value of ca. 40% in pure liquid phase to very low values (10-2%) in diluted media (pollutants trace eliminations). To establish true photocatalytic normalized tests, the above recommendations must be observed with a real catalytic activity independent of non-catalytic side-reaction. In particular, dye decolorization, especially in the visible, provides an apparent "disappearance" of the dye, due to a limited stoichiometric electron transfer from the photo-excited dye molecule to titania, subsequently compensated by an additional ionosorption of molecular oxygen. The energetics of photocatalysis on TiO2, being based on the energy E of the photons, i.e. E≥3.2eV, enables one to produce OH radicals, the second best oxidizing agent. The decrease of energy E to the visible may be thermodynamically detrimental for the generation of such highly cracking and degrading species. Concerning solid state chemistry, it is now finally admitted that cationic doping is detrimental for photocatalysis. In conclusion, all these recommendations have to be addressed and experiments have to be operated in suitable conditions before claiming that one deals with a true photocatalytic reaction. © 2010 Elsevier B.V.

Afanasiev P.,CNRS Research on Catalysis and Environment in Lyon
Journal of Catalysis | Year: 2010

Unsupported MoS2 catalysts were obtained from the decomposition of ammonium tetrathiomolybdate (ATM) at variable temperatures (400-700 °C) and under different gas compositions, from pure H2S to pure H2. The catalysts were further studied in the non-promoted state or promoted by Ni and Co. Catalytic activity and selectivity were studied in the model reaction of thiophene hydrodesulfurization (HDS). Surface areas, crystalline phase and particle size distributions were determined by Brunauer-Emmet-Teller (BET), X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. A comparison of average values calculated from these techniques has enabled the understanding of the morphology of the solids. The catalysts were characterized before and after catalytic tests by X-ray photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS) and temperature-programmed reduction (TPR). Comparison of catalytic activity trends with the results of the characterizations show that over-stoichiometric sulfur, present in the fresh catalysts in the form of edge-located S2 2 - species, plays a key role for the activity of unsupported MoS2 and for its ability to be promoted. Direct hydrogenation (HYD) of thiophene to butane occurs presumably with the participation of -SH groups, produced from the opening of S-S bridges by hydrogen. Whatever the gas atmosphere, any treatment leading to the removal of over-stoichiometric sulfur leads to a decrease in HYD selectivity. Thus, very similar catalytic properties were observed for MoS2 annealed at 700 °C in pure H2, H2S or N2 gases. Ni and Co introduced by means of reflux with acetylacetonates, gave identical promotion trends for all the MoS2 samples. The solids treated in pure H2S could not take up promoter atoms at the edges, whereas for the H2-reduced samples high promotion levels were achieved. The degree of stacking does not seem to have a significant impact on the thiophene HDS activity and selectivity of the unsupported MoS2 catalysts. © 2009 Elsevier Inc. All rights reserved.

Afanasiev P.,CNRS Research on Catalysis and Environment in Lyon
Journal of Physical Chemistry C | Year: 2012

Formation of anisotropic structures by oriented attachment of inorganic nanoparticles in ionic melts has been evidenced for the first time for the case study example of ZnO growth. Hollow microtubules of ZnO were prepared from the reaction of zinc nitrate in alkali metal nitrate-chloride (or nitrate-bromide) mixed fluxes. A series of snapshots of the morphology evolution versus temperature and reaction duration straightforwardly demonstrate oriented attachment of ZnO nanocrystallites and progressive formation of voids. The reactivity in the melts was studied by mass spectrometry of evolved gases, X-ray diffraction (XRD), and extended X-ray absorption fine structure (EXAFS) of solidified melts. The presence of chloride or bromide in the flux is essential for the manifestation of oriented attachment. Chloride decreases the reactivity of Zn species toward nitrate due to formation of ZnCl 4 2- ions. Primary nanoparticles of the precipitate are nanosheets of ZnO exposing (0001) planes and containing residual halogenide on the surface. Further stacking of primary nanosheets might occur in the melts as illustrated by molecular dynamics simulations. External diffusion of Zn from the interior of stacks toward the reactive melt creates hollow tubules. The resulting ZnO microtubules are oriented along the [0001] axis and absorb visible light due to abundant defects, formed probably because of a stacking misfit of the primary nanosheets. © 2011 American Chemical Society.

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