Catalytic Properties of 3D Graphene-Like Microporous Carbons Synthesized in a Zeolite Template

[EN] The inherent properties of a single atomic carbon layer in graphene offer opportunities for the creation of catalytically active centers tailored on a molecular level on a support with high thermal stability and very high specific surface area. We demonstrate that organization of the two-dimensional system of the carbon layer into three-dimensional (3D) graphene-like catalytic materials with the connectivity of a pore network providing good accessibility to the active centers allows the preparation of catalytic materials that exploit the properties of graphene. In this study, 3D graphene-like microporous carbons, denoted as)6 beta-carbon and Y-carbon, were synthesized by nanocasting of beta (*BEA) and faujasite (FAU) zeolite templates. Structural analyses show that the materials are characterized by 3D-assembled and highly stable single-atom graphene an open porous system resembling the regular channel system of the zeolites with a specific surface area comparable to the surface area of graphene. The materials effectively catalyze the hydrogenation of alkenes, alkynes, and cycloalkenes into the corresponding alkanes and cycloalkanes. The materials facilitate catalytic intramolecular rearrangements, including the selective isomerization of double bonds and branching of linear chains, as well as stereoselective isomerization of unsaturated hydrocarbons. layers that formThis work was supported by the Grant Agency of the Czech Republic under project No. 15-12113S. The authors acknowledge the assistance provided by the Research Infrastructures NanoEnviCz (Project No. LM2015073) and Pro-NanoEnviCz (Project No. CZ.02.1.01/0.0/0.0/16_013/0001821), supported by the Ministry of Education, Youth and Sports of the Czech Republic.Sazama, P.; Pastvova, J.; Rizescu, C.; Tirsoaga, A.; Parvulescu, VI.; García Gómez, H.; Kobera, L.... (2018). Catalytic Properties of 3D Graphene-Like Microporous Carbons Synthesized in a Zeolite Template. ACS Catalysis. 8(3):1779-1789. https://doi.org/10.1021/acscatal.7b04086S177917898

Analyse structurale d'endotoxines bactériennes par spectrométrie de masse

Du point de vue chimique les endotoxines sont des lipopolysaccharides (LPS) constitués d une chaîne de sucres, caractéristique de chaque espèce bactérienne, et d une structure lipidique, le lipide A. Nous avons mis au point des méthodes d analyse structurale et de purification permettant des avancées importantes dans le domaine de la relation structure-activité. La première est une micro-méthode d analyse qui peut être appliquée à des quantités de bactéries de l ordre du milligramme. Elle conduit à l obtention de spectres de lipide A en une journée, au lieu d une semaine par les techniques classiques. La seconde permet d établir la structure et le positionnement des acides gras sur des quantités de lipide A minimes. Cette technologie a été appliquée aux lipides A de Citrobacter, une Entérobactérie responsable de maladies nosocomiales. Enfin, une méthode de purification permet d obtenir des échantillons hautement purifiés pour les tests biologiques. Elle permettra des comparaisons plus fiables entre différentes préparations purifiées dans différents laboratoires. Nous avons aussi mis en évidence la présence de nouveaux substituants au niveau de la région lipidique des lipides A du genre Bordetella, dont B. pertussis, la coqueluche. Il s agit de la présence d une glucosamine sur chaque phosphate dont l implication sur les activités biologiques seront majeurs au niveau de l action des peptides antibactériennes, car ces structures viennent neutraliser les charges du lipide A, la molécule responsable des activités endotoxiques du LPS.Endotoxins are lipopolysaccharides (LPS) made up of a lipid - (called lipid A) and a sugar - chain, both characteristic of each bacterial species. We developed methods of structure analysis and a purification method representing an important improvement for studies of structure/activity relationships. The first one is a micro analytical method that can be applied to milligram quantities of bacteria. With it, one can obtain spectra of the lipid A in one day, instead of a week as for previous techniques. The second one leads to the determination of the structure and the positions of the fatty acids with a little amount of lipid A. This technology was applied to Citrobacter, an Enterobacterium causing nosocomial diseases. A LPS purification method gave highly purified samples suitable for biological tests. This method will give preparation having identical activities in different laboratories. We also have established the existence of new constituents on the lipid A of B. bronchiseptica, from which the whooping cough originated. The presence of a glucosamine on the phosphate group(s) was demonstrated and its effect on the biological activities will be of high impact particularly on the activity of anti-bacterial peptides, as glucosamines neutralise the lipid A structure responsible for the endotoxic activities of LPS.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Analyse structurale d'endotoxines bactériennes par spectrométrie de masse

Du point de vue chimique les endotoxines sont des lipopolysaccharides (LPS) constitués d une chaîne de sucres, caractéristique de chaque espèce bactérienne, et d une structure lipidique, le lipide A. Nous avons mis au point des méthodes d analyse structurale et de purification permettant des avancées importantes dans le domaine de la relation structure-activité. La première est une micro-méthode d analyse qui peut être appliquée à des quantités de bactéries de l ordre du milligramme. Elle conduit à l obtention de spectres de lipide A en une journée, au lieu d une semaine par les techniques classiques. La seconde permet d établir la structure et le positionnement des acides gras sur des quantités de lipide A minimes. Cette technologie a été appliquée aux lipides A de Citrobacter, une Entérobactérie responsable de maladies nosocomiales. Enfin, une méthode de purification permet d obtenir des échantillons hautement purifiés pour les tests biologiques. Elle permettra des comparaisons plus fiables entre différentes préparations purifiées dans différents laboratoires. Nous avons aussi mis en évidence la présence de nouveaux substituants au niveau de la région lipidique des lipides A du genre Bordetella, dont B. pertussis, la coqueluche. Il s agit de la présence d une glucosamine sur chaque phosphate dont l implication sur les activités biologiques seront majeurs au niveau de l action des peptides antibactériennes, car ces structures viennent neutraliser les charges du lipide A, la molécule responsable des activités endotoxiques du LPS.Endotoxins are lipopolysaccharides (LPS) made up of a lipid - (called lipid A) and a sugar - chain, both characteristic of each bacterial species. We developed methods of structure analysis and a purification method representing an important improvement for studies of structure/activity relationships. The first one is a micro analytical method that can be applied to milligram quantities of bacteria. With it, one can obtain spectra of the lipid A in one day, instead of a week as for previous techniques. The second one leads to the determination of the structure and the positions of the fatty acids with a little amount of lipid A. This technology was applied to Citrobacter, an Enterobacterium causing nosocomial diseases. A LPS purification method gave highly purified samples suitable for biological tests. This method will give preparation having identical activities in different laboratories. We also have established the existence of new constituents on the lipid A of B. bronchiseptica, from which the whooping cough originated. The presence of a glucosamine on the phosphate group(s) was demonstrated and its effect on the biological activities will be of high impact particularly on the activity of anti-bacterial peptides, as glucosamines neutralise the lipid A structure responsible for the endotoxic activities of LPS.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Impact of Deactivation Phenomena on Kinetics of the C–N Coupling Reaction over Supported Cu₂O Catalysts in Continuous-Flow Conditions

Heterogeneous C–N coupling of bromobenzene with aniline was investigated in flow conditions, with emphasis on kinetic evolution of the catalyst (1% Cu₂O/support) deactivation. A kinetic model including parallel and sequential steps leading to the formation of three reaction products (diphenylamine, triphenylamine, and aminodiphenyl) has been established. It was found that the support is not inert in this reaction, and changing its composition induced the following order of catalytic activity: 1% Cu₂O/Al₂O₃ > 1% Cu₂O/TiO₂ > 1% Cu₂O/ZnO. Conversely, the resistance to deactivation varied in the reverse order. This was merely assigned to the nature of the interaction of copper with the catalyst support. Among these, Cu₂O/TiO₂ highlighted the best compromise between catalytic activity and resistance to deactivation. It was also found that a larger excess of aniline improved the selectivity in diphenylamine and enhanced catalyst (1% Cu₂O/TiO₂) resistance to deactivation. Structural characterization of these catalysts by X-ray diffraction, X-ray photoelectron spectroscopy, and H₂ temperature-programmed reduction provided support for the evidenced kinetic results

The activation of C–O bonds in lignin Miscanthus over acidic heterogeneous catalysts: towards lignin depolymerisation to monomer units

peer reviewedOne-pot depolymerisation of lignin, extracted from Miscanthus plants under acidic (formic acid lignin, FAL) or basic (ammonia lignin, AL) conditions, over Ni- and/or Nb-doped SBA-15, was the subject of this study. The aforementioned acid catalysts prepared by sol–gel method were characterized by SEM–EDX, ATR-FTIR, Raman, XRD, N2 adsorption/desorption isotherms, CO2-TPD and NH3-TPD techniques. The increase in acidity due to the insertion of Nb into the SBA-15 structure promoted the selective cleavage of β–O–4 from ammonia lignin, leading to aromatic monomer yields up to 22 wt% in 6 h at 180 °C under 50 atm H2. The catalytic performances of Ni-Nb-SBA-15 as well as its stability were influenced by the chemical composition of the lignin sample as results of its extraction from the Miscanthus plant

Hydrogenolysis of lignin over Ru-based catalysts: The role of the ruthenium in a lignin fragmentation process

peer reviewedThe catalytic performances of two different classes of catalysts containing nickel or/and ruthenium as the active sites were studied in the depolymerisation of lignin isolated from Miscanthus × giganteus. The catalysts were prepared either by coprecipitation (ie, (RuNiMgAlO)x, (RuNiAlO)x, (NiAlO)x, (NiMgAlO)x) or by wet impregnation (ie, Ru/Al2O3) and characterized by nitrogen physisorption (BET), XRD, XPS, NH3-TPD, Raman and H2-TPR techniques. The experimental results indicate that the presence of ruthenium led to dimers as dominant products. © 2018 Elsevier B.V