Влияние состояния TiO2 на окислительную делигнификацию древесины осины и соломы пшеницы

The influence of preparation methods on structural characteristics of TiO2 catalysts was studied by the XRD, SEM, BET, DTA-DSC, FTIR techniques. Catalytic activity of obtained titanium dioxide samples was compared in reaction of oxidative delignification of aspen wood and wheat straw by hydrogen peroxide in acetic acid- water medium. The use of titanium dioxide in rutile modification allows to produce a cellulose product with lower content of a residual lignin, as compared to TiO2 in anatase modification. The increase of surface area of the TiO2 catalyst reduces its activity in wood and wheat straw delignificationМетодами РФА, СЭМ, БЭТ, ДТА-ДСК, ИКС изучено влияние способов получения катализаторов TiO2 на их структурные характеристики. Сопоставлена каталитическая активность полученных образцов диоксида титана в реакции окислительной делигнификации древесины осины и соломы пшеницы пероксидом водорода в среде «уксусная кислота–вода». Использование диоксида титана в модификации рутил позволяет получить целлюлозный продукт с более низким содержанием остаточного лигнина, чем при использовании TiO2 в модификации анатаз. Увеличение удельной поверхности катализатора приводит к уменьшению степени делигнификации древесины осины и соломы пшениц

A Landscape of Lignocellulosic Biopolymer Transformations into Valuable Molecules by Heterogeneous Catalysis in C’Durable Team at IRCELYON

This review article highlights part of the research activity of the C’Durable team at IRCELYON in the field of sustainable chemistry. This review presents a landscape of the work performed on the valorization of lignocellulosic biopolymers. These studies intend to transform cellulose, hemicellulose and lignin into valuable molecules. The methodology usually consists in evaluating the behavior of the biopolymers in the absence of catalyst under various conditions (solvent, temperature), and then to assess the influence of a catalyst, most often a heterogeneous catalyst, on the reactivity. The most significant results obtained on the upgrading of cellulose and lignin, which have been mainly investigated in the team, will be presented with an opening on studies involving raw lignocellulose

Recent Advances in the Synthesis of N-Containing Heteroaromatics via Heterogeneously Transition Metal Catalysed Cross-Coupling Reactions

N-containing heteroaromatics are important substructures found in numerous natural or synthetic alkaloids. The diversity of the structures encountered, as well as their biological and pharmaceutical relevance, have motivated research aimed at the development of new economical, efficient and selective synthetic strategies to access these compounds. Over more than 100 years of research, this hot topic has resulted in numerous so-called “classical synthetic methods” that have really contributed to this important area. However, when the selective synthesis of highly functional heteroaromatics like indoles, quinolones, indoxyls, etc. is considered these methods remain limited. Recently transition metal-catalysed (TM-catalysed) procedures for the synthesis of such compounds and further transformations, have been developed providing increased tolerance toward functional groups and leading generally to higher reaction yields. Many of these methods have proven to be the most powerful and are currently applied in target- or diversity-oriented syntheses. This review article aims at reporting the recent developments devoted to this important area, focusing on the use of heterogeneous catalysed procedures that include either the formation of the heterocyclic ring towards the nuclei or their transformations to highly substituted compounds

From the grafting of NHC-based Pd(II) complexes onto TiO 2 to the in situ generation of Mott-Schottky heterojunctions: the boosting effect in the Suzuki-Miyaura reaction. Do the evolved Pd NPs act as reservoirs?

International audienceThe assumption that the real active species involved in the Suzuki-Miyaura reaction are homogeneous, heterogeneous or both is often proposed. However a lack of characterization of the true catalytic entities and their monitoring makes assumptions somewhat elusive. Here, with the aim of getting new insights into the formation of active species in the Suzuki-Miyaura reaction, a family of palladium(II) complexes bearing bis(NHC) ligands was synthesized for immobilization at the surface of TiO 2 .The studies reveal that once the complexes are anchored onto TiO 2 , the mechanism governing the catalytic reaction is different from that observed for the non-anchored complexes. All complexes evolved to Pd NPs at the surface of TiO 2 under reaction conditions and released Pd species in the liquid phase. Also, this reactivity was boosted by the in situ generation of Mott-Schottky heterojunctions, opening new routes towards the design of heterogenized catalysts for their further implementation in reverse-flow reactors

Copper-free heterogeneous catalysts for the Sonogashira cross-coupling reaction: Preparation, characterisation, activity and applications for organic synthesis

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First study on telomerization of chitosan and guar hemicellulose with butadiene: Influence of reaction parameters on the substitution degree of the biopolymers

SSCI-VIDE+CDFA+CPI:LDJ:FRAInternational audienceThe direct functionalization of biopolymers is an important route towards the formation of new biosourced materials. This work describes for the first time the modification of two largely available biopolymers, chitosan and a guar hemicellulose, using the Pd-catalyzed telomerization reaction with butadiene. The reactions with butadiene formed new materials by grafting a long hydrocarbon chain at the surface of the biopolymers. These new biobased compounds were structurally characterized using 1 H and 13 C NMR spectroscopy. The telomerization was possible in green media like water or aqueous iso-propanol using water soluble catalytic systems. The study shows the possibility of adjusting the substitution degree (DS) by combining the effect of some reaction parameters and catalyst composition. For chitosan, it was possible to get DS from 0.03 to 0.60, while for guar hemicellulose a tighter range was obtained with DS between 0.025-0.3. Wettability experiments and contact angle measurements indicate that the transformation induced new hydrophobic-hydrophilic balance within the materials of highest DS that can find potential applications for example in the field of biosourced amphiphilic materials

First Example of the Use of Biosourced Alkyl Levulinates as Solvents for Synthetic Chemistry: Application to the Heterogeneously Catalyzed Heck Coupling

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Diffusion of modified vegetables oils in thermoplastic polymers

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