Academic literature on the topic 'Catalyse or'
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Journal articles on the topic "Catalyse or":
1
Rajesh, Nimmakuri, and Dipak Prajapati. "Indium(iii) catalysed regio- and stereoselective hydrothiolation of bromoalkynes." RSC Adv. 4, no. 61 (2014): 32108–12. http://dx.doi.org/10.1039/c4ra04359f.
Abstract:
Hydrothiolation of bromoalkynes has been reported for the first time under metal catalysed conditions. Indium(iii) trifluoromethanesulfonate was demonstrated as the first catalyst which can catalyse the hydrothiolation of bromoalkynes with absolute regio- and stereoselectivity to generate synthetically valuable (Z)-β-bromo vinyl sulfides in good yields.
2
Khan, Mohammad Niyaz, and Ibrahim Isah Fagge. "Kinetics and Mechanism of Cationic Micelle/Flexible Nanoparticle Catalysis: A Review." Progress in Reaction Kinetics and Mechanism 43, no. 1 (March 2018): 1–20. http://dx.doi.org/10.3184/146867818x15066862094905.
Abstract:
The aqueous surfactant (Surf) solution at [Surf] > cmc (critical micelle concentration) contains flexible micelles/nanoparticles. These particles form a pseudophase of different shapes and sizes where the medium polarity decreases as the distance increases from the exterior region of the interface of the Surf/H2O particle towards its furthest interior region. Flexible nanoparticles (FNs) catalyse a variety of chemical and biochemical reactions. FN catalysis involves both positive catalysis ( i.e. rate increase) and negative catalysis ( i.e. rate decrease). This article describes the mechanistic details of these catalyses at the molecular level, which reveals the molecular origin of these catalyses. Effects of inert counterionic salts (MX) on the rates of bimolecular reactions (with one of the reactants as reactive counterion) in the presence of ionic FNs/micelles may result in either positive or negative catalysis. The kinetics of cationic FN (Surf/MX/H2O)-catalysed bimolecular reactions (with nonionic and anionic reactants) provide kinetic parameters which can be used to determine an ion exchange constant or the ratio of the binding constants of counterions.
3
Avigliano, L., V. Carelli, A. Casini, A. Finazzi-Agrò, and F. Liberatore. "Oxidation of NAD dimers by horseradish peroxidase." Biochemical Journal 226, no. 2 (March 1, 1985): 391–95. http://dx.doi.org/10.1042/bj2260391.
Abstract:
Horseradish peroxidase catalyses the oxidation of NAD dimers, (NAD)2, to NAD+ in accordance with a reaction that is pH-dependent and requires 1 mol of O2 per 2 mol of (NAD)2. Horseradish peroxidase also catalyses the peroxidation of (NAD)2 to NAD+. In contrast, bacterial NADH peroxidase does not catalyse the peroxidation or the oxidation of (NAD)2. A free-radical mechanism is proposed for both horseradish-peroxidase-catalysed oxidation and peroxidation of (NAD)2.
4
ABBADI, Amine, Monika BRUMMEL, Burkhardt S. SCHüTT, Mary B. SLABAUGH, Ricardo SCHUCH, and Friedrich SPENER. "Reaction mechanism of recombinant 3-oxoacyl-(acyl-carrier-protein) synthase III from Cuphea wrightii embryo, a fatty acid synthase type II condensing enzyme." Biochemical Journal 345, no. 1 (December 17, 1999): 153–60. http://dx.doi.org/10.1042/bj3450153.
Abstract:
A unique feature of fatty acid synthase (FAS) type II of higher plants and bacteria is 3-oxoacyl-[acyl-carrier-protein (ACP)] synthase III (KAS III), which catalyses the committing condensing reaction. Working with KAS IIIs from Cuphea seeds we obtained kinetic evidence that KAS III catalysis follows a Ping-Pong mechanism and that these enzymes have substrate-binding sites for acetyl-CoA and malonyl-ACP. It was the aim of the present study to identify these binding sites and to elucidate the catalytic mechanism of recombinant Cuphea wrightii KAS III, which we expressed in Escherichia coli. We engineered mutants, which allowed us to dissect the condensing reaction into three stages, i.e. formation of acyl-enzyme, decarboxylation of malonyl-ACP, and final Claisen condensation. Incubation of recombinant enzyme with [1-14C]acetyl-CoA-labelled Cys111, and the replacement of this residue by Ala and Ser resulted in loss of overall condensing activity. The Cys111Ser mutant, however, still was able to bind acetyl-CoA and to catalyse subsequent binding and decarboxylation of malonyl-ACP to acetyl-ACP. We replaced His261 with Ala and Arg and found that the former lost activity, whereas the latter retained overall condensing activity, which indicated a general-base action of His261. Double mutants Cys111Ser/His261Ala and Cys111Ser/His261Arg were not able to catalyse overall condensation, but the double mutant containing Arg induced decarboxylation of [2-14C]malonyl-ACP, a reaction indicating the role of His261 in general-acid catalysis. Finally, alanine scanning revealed the involvement of Arg150 and Arg306 in KAS III catalysis. The results offer for the first time a detailed mechanism for a condensing reaction catalysed by a FAS type II condensing enzyme.
5
Ortega-Caballero, Fernando, and Mikael Bols. "Cyclodextrin derivatives with cyanohydrin and carboxylate groups as artificial glycosidases." Canadian Journal of Chemistry 84, no. 4 (April 1, 2006): 650–58. http://dx.doi.org/10.1139/v06-039.
Abstract:
Two cyclodextrin derivatives (1 and 2) were prepared in an attempt to create glycosidase mimics with a general acid catalyst and a nucleophilic carboxylate group. The catalysts 1 and 2 were found to catalyse the hydrolysis of 4-nitrophenyl β-D-glucopyranoside at pH 8.0, but rapidly underwent decomposition with loss of hydrogen cyanide to convert the cyanohydrin to the corresponding aldehyde. The initial rate of the catalysis shows that the cyanohydrin group in these molecules functions as a good catalyst, but that the carboxylate has no positive effect. The decomposition product aldehydes display little or no catalysis. A mechanism for the decomposition is suggested.Key words: biomimicry, enzyme model, kinetics, intramolecular reaction.
6
Jia, Yunhua, Takeo Tomita, Kazuma Yamauchi, Makoto Nishiyama, and David R. J. Palmer. "Kinetics and product analysis of the reaction catalysed by recombinant homoaconitase from Thermus thermophilus." Biochemical Journal 396, no. 3 (May 29, 2006): 479–85. http://dx.doi.org/10.1042/bj20051711.
Abstract:
HACN (homoaconitase) is a member of a family of [4Fe-4S] cluster-dependent enzymes that catalyse hydration/dehydration reactions. The best characterized example of this family is the ubiquitous ACN (aconitase), which catalyses the dehydration of citrate to cis-aconitate, and the subsequent hydration of cis-aconitate to isocitrate. HACN is an enzyme from the α-aminoadipate pathway of lysine biosynthesis, and has been identified in higher fungi and several archaea and one thermophilic species of bacteria, Thermus thermophilus. HACN catalyses the hydration of cis-homoaconitate to (2R,3S)-homoisocitrate, but the HACN-catalysed dehydration of (R)-homocitrate to cis-homoaconitate has not been observed in vitro. We have synthesized the substrates and putative substrates for this enzyme, and in the present study report the first steady-state kinetic data for recombinant HACN from T. thermophilus using a (2R,3S)-homoisocitrate dehydrogenase-coupled assay. We have also examined the products of the reaction using HPLC. We do not observe HACN-catalysed ‘homocitrate dehydratase’ activity; however, we have observed that ACN can catalyse the dehydration of (R)-homocitrate to cis-homoaconitate, but HACN is required for subsequent conversion of cis-homoaconitate into homoisocitrate. This suggests that the in vivo process for conversion of homocitrate into homoisocitrate requires two enzymes, in simile with the propionate utilization pathway from Escherichia coli. Surprisingly, HACN does not show any activity when cis-aconitate is substituted for the substrate, even though other enzymes from the α-aminoadipate pathway can accept analogous tricarboxylic acid-cycle substrates. The enzyme shows no apparent feedback inhibition by L-lysine.
7
Liu, Yansheng, Xinlin Li, Xuanduong Le, Wei Zhang, Hao Gu, Ruiwen Xue, and Jiantai Ma. "Catalysis of the hydro-dechlorination of 4-chlorophenol by Pd(0)-modified MCM-48 mesoporous microspheres with an ultra-high surface area." New Journal of Chemistry 39, no. 6 (2015): 4519–25. http://dx.doi.org/10.1039/c5nj00617a.
8
Gu, Nina X., Gaël Ung, and Jonas C. Peters. "Catalytic hydrazine disproportionation mediated by a thiolate-bridged VFe complex." Chemical Communications 55, no. 37 (2019): 5363–66. http://dx.doi.org/10.1039/c9cc00345b.
Abstract:
A heterobimetallic VFe complex is demonstrated to catalyse hydrazine disproportionation with yields of up to 1073 equivalents of NH3 per catalyst, comparable to the highest turnover known for any molecular catalyst.
9
Boucher, Guillaume, Bilal Said, Elizabeth L. Ostler, Marina Resmini, Keith Brocklehurst, and Gerard Gallacher. "Evidence that the mechanism of antibody-catalysed hydrolysis of arylcarbamates can be determined by the structure of the immunogen used to elicit the catalytic antibody." Biochemical Journal 401, no. 3 (January 12, 2007): 721–26. http://dx.doi.org/10.1042/bj20060551.
Abstract:
A kinetically homogeneous anti-phosphate catalytic antibody preparation was shown to catalyse the hydrolysis of a series of O-aryl N-methyl carbamates containing various substituents in the 4-position of the O-phenyl group. The specific nature of the antibody catalysis was demonstrated by the adherence of these reactions to the Michaelis–Menten equation, the complete inhibition by a hapten analogue, and the failure of the antibody to catalyse the hydrolysis of the 2-nitrophenyl analogue of the 4-nitrophenylcarbamate substrate. Hammett σ–ρ analysis suggests that both the non-catalysed and antibody-catalysed reactions proceed by mechanisms in which development of the aryloxyanion of the leaving group is well advanced in the transition state of the rate-determining step. This is probably the ElcB (elimination–addition) mechanism for the non-catalysed reaction, but for the antibody-catalysed reaction might be either ElcB or BAc2 (addition–elimination), in which the elimination of the aryloxy group from the tetrahedral intermediate has become rate-determining. This result provides evidence of the dominance of recognition of phenolate ion character in the phosphate hapten in the elicitation process, and is discussed in connection with data from the literature that suggest a BAc2 mechanism, with rate-determining formation of the tetrahedral intermediate for the hydrolysis of carbamate substrates catalysed by an antibody elicited by a phosphonamidate hapten in which phenolate anion character is minimized. The present paper contributes to the growing awareness that small differences in the structure of haptens can produce large differences in catalytic characteristics.
10
Giger, Rudolf, and Pascal Hoffmann. "Design and synthesis of a transition state analog of a metalloporphyrin-catalysed oxidation reaction." Journal of Porphyrins and Phthalocyanines 06, no. 05 (May 2002): 362–65. http://dx.doi.org/10.1142/s1088424602000439.
Abstract:
A hapten that mimics the transition state of a metalloporphyrin-catalysed oxidation reaction was synthesized in order to generate antibodies that might be able to catalyse the regioselective metalloporphyrin-co-catalysed reaction of cyclosporin A to [D-Ser8]cyclosporin A.
Dissertations / Theses on the topic "Catalyse or":
1
Nguyen, Thi Xuan Phuong. "La catalyse hétérogène." Paris 5, 1994. http://www.theses.fr/1994PA05P039.
2
Roudier, Mylène. "Catalyse duale pour une synthèse énantiosélective éco-compatible." Electronic Thesis or Diss., Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4347.
Abstract:
Ce mémoire de thèse se concentre sur le développement de réactions multicatalysées impliquant une activation iminium et un transfert d’hydrogène réversible rédox-neutre pour la synthèse de briques moléculaires complexes énantioenrichies à partir de composés 1,3-dicarbonylés et d’alcools allyliques.Une cascade réactionnelle combinant un complexe de fer et une pyrrolidine chirale a été développée pour la préparation d’alcools g-fonctionnalisés énantioenrichis par une approche impliquant économie d’étapes et d’atomes. L’efficacité de cette méthode impliquant une catalyse duale ainsi qu’une étape de rétro-Claisen a été démontré dans la synthèse de fragments clés de produits naturels. Cette méthodologie a ensuite été complétée par une étude mécanistique expérimentale aboutissant à une meilleure compréhension du mécanisme de cette transformation et conduisant également au développement d’une catalyse triple impliquant deux complexes métalliques et un organocatalyseur. Par la suite, une nouvelle approche pour la synthèse de lactones énantioenrichies de taille de cycles moyens a été mise au point. Cette stratégie de synthèse est basée sur une addition-1,4- organocatalysée énantiosélective de Michael, suivie d’une réduction chimiosélective qui engendre une fragmentation de Claisen.Enfin, grâce aux méthodologies développées au cours de cette thèse, la synthèse totale d’un produit naturel, la floribundane B, a été étudiéeThis manuscript is focus on the development of multicatalyzed reactions involving iminium activation and reversible neutral hydrogen transfer reaction for the synthesis of complexe enantioenriched building blocks from allyl alcohols and 1,3-dicarbonyls.An unprecedented cascade catalysis combining an iron catalyst and a pyrrolidine-base catalyst is developed for the preparation of g-fonctionalized enantioenriched alcohols in a formal redox-, atom- and step-economical approach. The efficiency of this method involving a dual catalysis and a retro-Claisen xas further demonstrated in the short synthesis of several key fragments of biologically active natural products or odorant molecule. This methodolgy was then incremented by a experimental mechanistic study allowing a better understanding of the mechanism of this transformation and leading to a new catalytic systeminvolving three different catalysts (iron complex, copper and organocatalyst). Then, we focused on the development of a new synthetic approach to enantioenriched medium-sized lactones. This methodology is based on a 1,4-Michael addition of cycloalkane-1,3-diones to a,b-insaturated aldehydes. Then, a key chemoselective reductively triggered Claisen fragmentation occurred to generate desired lactones in a rapid manner.Finally, thanks to our methodology developed during this thesis, the total synthesis of floribundane B was studied
3
Sierra, salazar Andrés Felipe. "Waterborne catalytic materials with original design." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2017. http://www.theses.fr/2017ENCM0014/document.
Abstract:
Catalysis is one of the Green Chemistry Principles given its importance for limiting environmental impacts and improving current processes, as well as for developing new sustainable processes and products. In order to provide more performant catalysts, this study provides a novel preparation method for controlling the distribution of metal nanoparticles (NPs) within hierarchically meso- and macroporous catalysts. It consists of the combination of latex synthesis, sonochemistry and sol-gel process. All these steps can be carried out in water, reducing environmental impact. The first step is the synthesis of latex, typically polystyrene. The second step is the sonochemical synthesis and deposition of noble metal NPs on the surface of the latex polymer. The third step is the synthesis of the support by sol-gel process using tetraethyl orthosilicate (TEOS) under controlled conditions to modulate the porosity of the final silica matrix. As a result, an original catalyst morphology is obtained with active sites preferentially located within the macropores, which are surrounded by a mesoporous matrix. Using this approach, a monodisperse polystyrene latex (~130 nm) was prepared by emulsion polymerisation and then decorated with Pt NPs (~2.3 nm) by sonochemical reduction. The mesoporous silica support was prepared by sol-gel synthesis in the presence of the decorated latex. After calcination, the organic template left behind macropores with the Pt NPs within the generated macropores. Mesopores (2-15 nm) connecting these macropores (110-400 nm) were tuned by varying the synthesis conditions. Typically, specific surface areas of 615 m2/g and total pore volumes of 0.74 cm3/g were obtained. In a first case of study, hierarchically porous Pt/SiO2 catalysts were evaluated in the selective hydrogenation of p-chloronitrobenzene (p-CNB) to produce p-chloroaniline. They exhibited activities up to 91.7 ± 2.9 molCNB/(min molPt) and selectivity values up to 100 ± 2% at 80% of conversion, in comparison with 47.7 ± 2.9 molCNB/(min molPt) and 91 ± 2%, respectively, obtained with a commercial catalyst under the same conditions. Moreover, in a second case of study, it was possible to prepare silica-supported Pd, Pd-Pt and Pd-CeO2 catalysts with hierarchical porosity (meso and macro). These materials were tested in the direct synthesis of hydrogen peroxide from hydrogen and oxygen. The best productivity of H2O2 was obtained with the bimetallic Pd-Pt catalyst with 32500 molH2O2/(h molmetal) in batch, and the best selectivity was obtained with Pd-CeO2/SiO2 catalyst (63 ± 2%) in semi-batch. In summary, this thesis proposes a new aqueous preparation method for hierarchically porous functional materials by the combination of latex synthesis, sonochemical reduction and sol-gel process. It has been demonstrated that this preparation technique provides a very powerful and versatile toolbox for catalyst tailoring and optimisation. Further perspectives to achieve improved morphologies and controlled active sites distribution are also proposedLa catalyse est l'un des piliers pour le développement de procédés durables, car elle permet d'utiliser moins de ressources en accélérant les réactions chimiques. Afin de fournir des catalyseurs plus performants, cette étude propose une nouvelle méthode de préparation de catalyseurs pour contrôler la distribution de nanoparticules (NPs) métalliques au sein des catalyseurs hiérarchiquement poreux (méso et macro) en combinant la synthèse de latex, la réduction sonochimique et le procédé sol-gel. La première étape est la synthèse d'une empreinte porogène de billes de polystyrène (latex) obtenues par polymérisation en émulsion aqueuse. La deuxième étape est la synthèse et le dépôt de NPs de métaux nobles sur la surface des billes de polymère par voie sonochimique dans l’eau. La troisième étape est la synthèse du support catalytique par un procédé sol-gel en milieu aqueux en utilisant le latex décoré et l’orthosilicate de tétraéthyle (TEOS) dans des conditions contrôlées pour moduler la porosité finale de la matrice de silice (mésoporeuse). Toutes les étapes de cette approche sont effectuées dans l'eau, ce qui limite les impacts environnementaux de la préparation du catalyseur. L'élimination du porogène (latex) par calcination génère les macropores. Le matériau résultant possède alors une morphologie inédite pour un catalyseur, avec des macropores fonctionnalisés par des NPs métalliques, dans une matrice de silice mésoporeuse. Ainsi, il a été possible de synthétiser un latex monodisperse de polystyrène (~130 nm), lequel a été décoré avec des NPs de Pt (~2.3 nm) par réduction sonochimique. Le matériau final de silice a présenté des mésopores (2-15 nm) reliant les macropores (110-400 nm) contenant les NPs de Pt. Il a été possible d'obtenir des surfaces spécifiques et des volumes poreux totaux de 615 m2/g et 0,74 cm3/g, respectivement. Dans un premier cas d'étude, des catalyseurs de Pt/SiO2 à porosité hiérarchique ont été évalués dans l'hydrogénation sélective du p-chloronitrobenzene (p-CNB) pour produire la p-chloroaniline. Ils ont présenté des activités catalytiques allant jusqu'à 91,7 ± 2,9 molCNB/(min molPt) et des sélectivités jusqu'à 100 ± 2% à 80% de conversion, par rapport à 47,7 ± 2,9 molCNB/(min molPt) et 91 ± 2%, respectivement, obtenus dans les mêmes conditions avec un catalyseur commercial. Dans un deuxième cas d'étude, des catalyseurs à base de Pd, Pd-Pt et Pd-CeO2 supportés sur de la silice à porosité hiérarchique ont été préparés et testés dans la synthèse directe du peroxyde d'hydrogène. La meilleure productivité a été obtenue avec le catalyseur bimétallique Pd-Pt avec 32500 molH2O2/(h molmétal) en batch, et la meilleure sélectivité a été obtenue avec le catalyseur Pd-CeO2/SiO2 (63 ± 2%) en semi-continu. En résumé, cette thèse propose une nouvelle méthode de préparation dans l’eau de matériaux fonctionnels à porosité hiérarchique en combinant la synthèse de latex, la réduction sonochimique et le procédé sol-gel. Il a été démontré que cette technique de préparation fournit une boîte à outils très puissante et polyvalente pour la préparation et l'optimisation des catalyseurs. Des perspectives pour améliorer davantage les morphologies et la distribution contrôlée des sites actifs sont également proposées
4
Roudier, Mylène. "Catalyse duale pour une synthèse énantiosélective éco-compatible." Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4347.
Abstract:
Ce mémoire de thèse se concentre sur le développement de réactions multicatalysées impliquant une activation iminium et un transfert d’hydrogène réversible rédox-neutre pour la synthèse de briques moléculaires complexes énantioenrichies à partir de composés 1,3-dicarbonylés et d’alcools allyliques.Une cascade réactionnelle combinant un complexe de fer et une pyrrolidine chirale a été développée pour la préparation d’alcools g-fonctionnalisés énantioenrichis par une approche impliquant économie d’étapes et d’atomes. L’efficacité de cette méthode impliquant une catalyse duale ainsi qu’une étape de rétro-Claisen a été démontré dans la synthèse de fragments clés de produits naturels. Cette méthodologie a ensuite été complétée par une étude mécanistique expérimentale aboutissant à une meilleure compréhension du mécanisme de cette transformation et conduisant également au développement d’une catalyse triple impliquant deux complexes métalliques et un organocatalyseur. Par la suite, une nouvelle approche pour la synthèse de lactones énantioenrichies de taille de cycles moyens a été mise au point. Cette stratégie de synthèse est basée sur une addition-1,4- organocatalysée énantiosélective de Michael, suivie d’une réduction chimiosélective qui engendre une fragmentation de Claisen.Enfin, grâce aux méthodologies développées au cours de cette thèse, la synthèse totale d’un produit naturel, la floribundane B, a été étudiéeThis manuscript is focus on the development of multicatalyzed reactions involving iminium activation and reversible neutral hydrogen transfer reaction for the synthesis of complexe enantioenriched building blocks from allyl alcohols and 1,3-dicarbonyls.An unprecedented cascade catalysis combining an iron catalyst and a pyrrolidine-base catalyst is developed for the preparation of g-fonctionalized enantioenriched alcohols in a formal redox-, atom- and step-economical approach. The efficiency of this method involving a dual catalysis and a retro-Claisen xas further demonstrated in the short synthesis of several key fragments of biologically active natural products or odorant molecule. This methodolgy was then incremented by a experimental mechanistic study allowing a better understanding of the mechanism of this transformation and leading to a new catalytic systeminvolving three different catalysts (iron complex, copper and organocatalyst). Then, we focused on the development of a new synthetic approach to enantioenriched medium-sized lactones. This methodology is based on a 1,4-Michael addition of cycloalkane-1,3-diones to a,b-insaturated aldehydes. Then, a key chemoselective reductively triggered Claisen fragmentation occurred to generate desired lactones in a rapid manner.Finally, thanks to our methodology developed during this thesis, the total synthesis of floribundane B was studied
5
Chenneberg, Ludwig. "Nouvelles avancées en catalyse photoredox : applications en chimie radicalaire de synthèse et en catalyse duale." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066305/document.
Abstract:
L’objectif principal des travaux de recherche décrits dans ce manuscrit de thèse, est de concevoir de nouvelles méthodes de synthèse en chimie radicalaire et organométallique, de les associer dans une catalyse duale afin qu’elles puissent être appliquées à l’élaboration de briques moléculaires élaborées. Nous avons développé dans une première étude une alternative photocatalytique à la réaction de désoxygénation classique de Barton-McCombie d’alcools secondaires et tertiaires par l’hydrure de tributylétain. Celle-ci repose sur l’utilisation d’un précurseur O-thiocarbamate dérivé d’alcools pouvant être réduit par catalyse photorédox. Une étude mécanistique, basée sur des expériences de fluorescence et de voltammétrie cyclique, est aussi présentée. Dans une seconde étude, une élégante méthode de génération de radicaux alkyles non stabilisés, par photooxydation de « ate-complexes » de bore ou d’espèces hypervalentes à base de silicium est présentée. Ces radicaux sont piégés en présence d’accepteurs radicalaires ou engagés dans une catalyse duale avec des complexes de NickelVisible-light photoredox catalysis has emerged as a very powerful strategy to generate radical species replacing more and more tin-mediated or stoichiometric redox methodologies. The main objective of the research described in this Ph. D. thesis is to develop new synthetic methodologies in radical and organometallic chemistry, and merge them in a dual catalysis process for the preparation of elaborated molecular building blocks. In a first study, we report a photocatalytic alternative of Barton-McCombie deoxygenation based on a visible-light photoreduction of O-thiocarbamates derived from secondary and tertiary alcohols. A mechanistic investigation is presented based on fluorescence quenching and cyclic voltammetry experiments. In a second study, a challenging method of generation of unstabilized alkyl radicals by photooxidation of borate salts or hypervalent silicon species is reported. These radicals are trapped by free radical scavengers or engaged in a photoredox/nickel dual catalysis
6
Dandachi, Hiba. "Nouveaux Complexes Oligomères Cycliques de Salens Chiraux pour la Catalyse Asymétrique." Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLS106/document.
Abstract:
Les ligands de type salen constituent la pierre angulaire des travaux décrits dans cette thèse. L’attention particulière portée aux complexes chiraux correspondants est due à leur utilisation comme catalyseurs énantiosélectives versatiles pour promouvoir une large gamme de réactions d’intérêt. Dans le contexte de la catalyse asymétrique hétérogène, nous nous focalisons plus particulièrement sur l’élaboration de catalyseurs polymères cycliques de salens chiraux, appelés complexes calixsalens. Ainsi, nous avons mis au point une voie d’accès directe aux calixsalens de cobalt (III) par polycondensation. Ces complexes testés en tant que catalyseurs dans le dédoublement cinétique dynamique hydrolytique de l’épibromohydrine peuvent être facilement récupérés par simple filtration du milieu réactionnel et réutilisés dans une nouvelle transformation. Ces ligands cycliques permettent donc la préparation de complexes homobimétalliques capables de réaliser une double activation efficace de l’époxyde et de l’eau, conduisant au produit ciblé avec des rendements et des sélectivités élevés.Nous avons également rapporté l’utilisation de ces mêmes calixsalens de cobalt (III) en présences des complexes analogues de manganèse (III) dans la réaction d’hydrolyse des époxydes méso. Ce système de catalyse hétérobimétallique s’est révélé encore plus sélectif que le système homobimétallique impliquant les catalyseurs de cobalt seuls.Suite à ces résultats, nous avons tenté de préparer des complexes de salens hétérobimétalliques, dans lesquels deux métaux différents sont présents sur le même macrocycle. Pour ce faire, nous avons choisi d’explorer la chimie click pour coupler des complexes salens porteurs de différents métaux, modifiés les uns par des fonctions alcynes, les autres par des groupements azoturesThis thesis work takes place in the broad context of salen chemistry. A special attention is given to corresponding chiral complexes used as versatile enantioselective catalysts for a wide range of reactions of interest. In the context of heterogeneous asymmetric catalysis, we focus specifically on the development of polymeric, cyclic, chiral salen catalysts, named calixsalen complexes. Thus, we have developed an easy access to calixsalen cobalt (III) complexes by a facile polycondensation route. These calixsalens were used as catalysts to promote the dynamic hydrolytic kinetic resolution of epibromohydrin. They are easily recovered from the reaction mixture by a simple filtration. These cyclic complexes allowed the formation of homobimetallic species responsible for an efficient dual activation of both the epoxide and water, delivering the targeted product in both high yield and selectivity.We have also reported the use of a combination of cobalt and manganese calixsalen complexes in the hydrolysis of meso epoxydes. This dual heterobimetallic system proved to be even more selective than the homobimetallic one, in which cobalt complexes were only engaged. Based on these results, we have attempted preparing heterobimetallic salen complexes, wherein two different metals should be closely associated into the same macrocycle. Towards this aim, we explored click chemistry to couple alkyne- and azide-functionalized monomeric salen complexes coordinated to two different metals
7
Giuseppone, Nicolas. "Les iodures de lanthanides en catalyse et catalyse asymetrique." Paris 11, 2000. http://www.theses.fr/2000PA112122.
Abstract:
La premiere partie de cette these a trait a l'utilisation du diiodure de samarium en tant que promoteur catalytique de reactions d'aldolisation et de michael de type mukaiyama. Une etude du mecanisme reactionnel a ete menee de maniere a determiner si leur transposition vers la catalyse asymetrique etait envisageable. La seconde partie decrit la catalyse de reactions tandem entre des acetals de cetenes silyles, des cetones ,-insaturees et des aldehydes, promues par le diiodure de samarium. Ces reactions permettent la formation de deux liaisons carbone-carbone ainsi que l'introduction de trois centres asymetriques lors d'une meme sequence reactionnelle. L'efficacite de cette methode a ete montree a travers la synthese formelle de produits d'interet biologique. La troisieme partie presente la synthese et la caracterisation d'iodoalcoolates enantiopurs de lanthanides trivalents. Deux voies d'acces a ces derniers ont ete etudiees a partir des triiodures de lanthanides. Dans la premiere, un echange direct entre un alcoolate de potassium et un (ou deux) iodes a permis d'acceder de facon selective et avec de tres bons rendements a des complexes binaphtolates mono- et bidentes ou 3,3-bis(o-anisyl)binaphtolates polydentes de lanthanides. Dans la seconde, un echange entre un binaphtol et un complexe amidure de lanthanide a ete envisage. Dans une derniere partie, les differents complexes enantiopurs de lanthanides ont ete testes dans des reactions de diels-alder asymetriques. Les derives 3,3-bis(o-anisyl)binaphtolates du samarium et de l'ytterbium conduisent a l'obtention d'exces enantiomeriques eleves. Ils permettent d'acceder preferentiellement a l'un ou l'autre des enantiomeres suivant le choix des conditions reactionnelles (temperature, solvant) et ce, a partir d'un ligand chiral de meme purete optique. Une etude des effets non lineaires a differentes temperatures a permis de montrer la presence de processus d'associations entre especes catalytiques.
8
Carrée, Fabien. "Catalyse et catalyse asymétrique par les dérivés des lanthanides." Paris 11, 2004. http://www.theses.fr/2004PA112208.
Abstract:
Ce travail de these s'est articule autour de deux themes principaux : la preparation de complexes de type iodobinaphtolate de lanthanides ainsi que leur evaluation pour la catalyse des reactions de diels-alder et leur valorisation en tant que catalyseurs dans des reactions variees. Diverses methodes de synthese ont ete mises au point pour preparer les complexes. Deux d'entre elles impliquent le passage par la formation intermediaire d'un binaphtolate de potassium, la derniere consiste en un echange de ligands. La preparation des complexes par deprotonation du ligand en utilisant le sel de potassium du diphenylmethane a conduit aux meilleurs resultats. Nous nous sommes interesses a l'optimisation des conditions de la reaction d'iminoaldolisation entre une imine glyoxylique et un acetal de cetene silyle catalysee par l'iodo-binaphtolate de samarium. L'importance des conditions operatoires a ete mis en evidence, permettant ainsi d'obtenir un excellent exces enantiomerique. Les complexes synthetises ont egalement ete utilises pour la catalyse de la reaction d'aminolyse d'ouverture d'epoxydes meso. Dans cette reaction, des complexes de lanthane et de samarium ont permis d'obtenir des ?-aminoalcools avec des exces enantiomeriques superieurs a 90%. Le complexe de samarium a permis d'elargir la gamme d'aminoalcools obtenus avec de tres bons exces enantiomeriques. Des phenomenes de variations des exces enantiomeriques non monotones avec la temperature ont ete observes. Nous avons montre que le diiodure de samarium et les iodobinaphtolates de lanthanides catalysent egalement l'addition d'amines sur des n-acyloxazolidinones ou l'ouverture d'aziridines par des amines aromatiquesThis work deals with the preparation of a novel class of lanthanides iodo-binaphtoxides complexes and their evaluation as lewis acid catalysts in various organic reactions. The structure of our complexes is very interesting since they bear ionic lanthanide-oxygen bonds. Various methods have been tested to carry out the synthesis of our catalysts. Among these, two of them involve the formation of a potassium binaphtoxide as an intermediar,. The other system uses a different strategy which consists in a ligand exchange. Among these methods, the bests results have been observed by using the diphenylmethane potassium salt as base for ligands deprotonation. Catalytic activity of lanthanides iodo-binaphtoxides has then been tested in the imino-aldol reaction involving a glyoxilic imine and ketene silyl dimethyl acetal (ksa). Very high enantiomeric excesses have been observed by optimising condition reactions. Our complexes have also shown an interesting catalytic activity in primary aromatic amines meso epoxides ring-opening reactions. Lanthanum as well as samarium iodo-binaphtoxides have allowed formation of ?-amino-alcohols with up to 90% enantiomeric excesses. Moreover, use of the samarium complex has furnished a wide range of amino-alcohols, also with very good enantiomeric excesses. Finally, non-linear temperature dependant variations of enantiomeric excesses have been highlighted in our system. It has been also shown that samarium diiodide as well as samarium iodo-binaphtoxides are efficient catalysts in addition of amines on n-acyloxazolidinones or ring-opening of aziridines by aromatic amines
9
Motos, Blanca. "Silices fonctionnalisées contenant des espèces ioniques pour la catalyse hétérogène." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2011. http://www.theses.fr/2011ENCM0015.
Abstract:
La catalyse hétérogène est en plein développement pour des raisons économiques, de santé et de protection environnementale. Les travaux de cette thèse s'intéressent à la préparation des silices fonctionnalisées par des sous-structures ioniques pour leur application en catalyse hétérogène. D'abord, des matériaux mésoporeux fonctionnalisés par des entités di-aryl imidazoliums ont été préparés par des réactions de post-greffage. En plus, films de type PMO contenant des entités di-aryl imidazoliums ont été synthétisés en présence d'un surfactant anionique. Ensuite, complexes carbéniques N-hétérocycliques du cuivre et du palladium supportés ont été préparés et appliqués en tant que catalyseurs organométalliques dans des réactions A3 (Cu-NHC) et de couplage de Suzuki (Pd-NHC). Les silices fonctionnalisées avec des entités imidazoliums ont également été utilisées en tant qu'organocatalyseurs des réactions de Henry et dans de cycloaddition du dioxyde de carbone aux époxydes. Des matériaux de type ‘PMO' contenant des entités amines/ammoniums ainsi que des sous-structures zwitterioniques ont été utilisés en réactions organocatalysées de Henry et BiginelliHeterogenous catalysis is an area in continuous development due to economical, health and environmental issues. This thesis deals with the preparation of i-silica materials for the posterior application in heterogeneous catalysis. First, di-aryl imidazolium containing silica materials were synthesized by post-grafting reactions on mesoporous SBA-15. Moreover, di-alkyl imidazolium containing PMO films were prepared in presence of an anionic surfactant. Then, supported copper and palladium N-heterocyclic carbenes were synthesized from di-aryl imidazolium silica and applied to A3 reactions (Cu-NHC) and Suzuki cross-coupling reactions (Pd-NHC). Imidazolium functionalized silicas were also utilized as heterogeneous organocatalysts in Henry reactions and in reactions of cycloaddition of carbon dioxide to epoxides. Finally, PMO type materials containing amine/ammonium and zwitterionic substructures were applied to Henry and Biginelli organocatalysed reactions, respectively
10
Leone, Matteo. "Development of novel synthetic methodologies in photocatalysis for the preparation of (a)chiral amine derivatives." Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASF021.
Abstract:
La lumière visible, reconnue pour être une source d'énergie abondante et économique, est devenue récemment un élément crucial dans l'avancement des processus chimiques catalytiques durables. Les importantes contributions de la communauté scientifique ont mis en lumière un large éventail de transformations, comme décrit dans le premier chapitre. Malgré les diverses applications synthétiques développées à ce jour, la réalisation de réactions photocatalysées de manière asymétrique demeure un défi considérable. Dans ce contexte, nous visons non seulement à développer de nouvelles méthodologies durables et efficaces basées sur la lumière, mais aussi à innover dans le développement de processus asymétriques. Le deuxième chapitre de ce manuscrit est consacré à l'introduction d'une nouvelle catégorie de catalyseurs organocatalytiques chiraux sensibles à la lumière visible. Ces catalyseurs sont caractérisés par un squelette covalent dérivé du BINOL lié à divers photosensibilisateurs, tels que les cétones aryles et la phénothiazine. Plusieurs CPAs, intégrant un ou deux groupes photosensibilisateurs, ont été synthétisés facilement en quelques étapes à partir du BINOL. Les propriétés photophysiques et électrochimiques de ces catalyseurs photocatalytiques chiraux symétriques C1 et C2 ont été étudiées. Les catalyseurs chiraux à base de cétones ont été appliqués avec succès dans un processus tandem multicomposant énantiosélectif, permettant la synthèse efficace de 1,2-diamines entièrement substituées avec d'excellentes énantiosélectivités. Le troisième chapitre expose une approche alternative pour le développement de processus asymétriques à travers la photocatalyse, en exploitant des auxiliaires chiraux. Il met en lumière la création d'une méthodologie photocatalysée durable et efficace spécifiquement conçue pour l'alkylation radicalaire stéréosélective de sulfinyl-imines chirales. En utilisant des précurseurs radicaux non préfonctionnalisés et du TBADT comme photocatalyseur pour générer des radicaux par transfert direct d'atome d'hydrogène (HAT), cette méthode a permis d'obtenir diverses amines chirales avec des rendements et d'excellentes diastéréosélectivités dans des conditions douces. Cette approche s'avère efficace pour l'accès à une gamme variée de composés médicalement pertinents, incluant à la fois des acides α-aminés naturels et synthétiques ainsi que d'autres composés α-aminés couramment présents dans les produits pharmaceutiques approuvés et les produits naturels. Le quatrième chapitre décrit un couplage électrophile croisé déoxygénant entre des esters redox actifs dérivés d'acides carboxyliques facilement disponibles et des sulfonylhydrazones d'aldéhyde avec l'utilisation de l'Eosine Y comme organophotocatalyseur sous irradiation de lumière visible. Ce couplage C(sp3)−C(sp3) croisé, sans métaux, se présente comme une plateforme polyvalente. Son utilité synthétique a été démontrée en mettant au point par une homologation C1 d'acides carboxyliques, offrant ainsi une alternative plus sûre et largement applicable à la réaction traditionnelle d'Arndt-Eistert. De plus, cette approche permet la synthèse directe d'amines β-aryléthylcycliques et acycliques en utilisant diverses sulfonylhydrazones d'aldéhyde. Il convient de noter que cette méthode est parfaitement compatible avec la fonctionnalisation en fin de phase des peptides en phase solide, simplifiant ainsi la modification de peptides complexes sans nécessiter de longues et fastidieuses synthèses de novoVisible light, known for being an abundant and economical energy source, has recently become crucial in advancing sustainable catalytic chemical processes. The scientific community's substantial contributions have disclosed a broad spectrum of transformations, as outlined in the initial chapter. Among the various synthetic applications developed so far, achieving photocatalysed reactions in an asymmetric fashion remains a considerable challenge. In this specific context, our focus extends beyond the creation of new sustainable and efficient light-mediated methodologies; we are also dedicated to pioneering innovative asymmetric processes. Within this manuscript, the second chapter is dedicated to introducing a novel category of visible-light-sensitive chiral organocatalysts. These catalysts feature a covalently linked backbone of BINOL-derived Chiral Phosphoric Acids (CPAs) with various photosensitizers, such as aryl ketones and phenothiazine. Several CPAs, incorporating one or two photosensitizer moieties, were easily synthesized in a few steps from BINOL. The photophysical and electrochemical properties of these C1- and C2-symmetric chiral photocatalysts were investigated. The ketone-based chiral photocatalysts were applied in an enantioselective multicomponent tandem process, enabling the efficient synthesis of fully substituted 1,2-diamines with excellent enantioselectivities. The third chapter presents an alternative strategy for the development of asymmetric processes through photocatalysis, exploiting chiral auxiliaries. It highlights the needs of a sustainable and efficient photocatalysed methodology specifically designed for the stereoselective radical alkylation of chiral sulfinyl-imines. By utilizing readily available non-prefunctionalized radical precursors and TBADT as a photocatalyst to generate radicals through direct hydrogen atom transfer (HAT), this method has enabled the synthesis of diverse chiral amines with high yields and excellent diastereoselectivities under mild conditions. This approach proves to be effective for accessing a varied range of medically relevant compounds, encompassing both natural and synthetic α-amino acids and other α-amino compounds commonly present in approved pharmaceuticals and natural products. The fourth chapter describes a deoxygenative cross-electrophile coupling technique that combines readily available carboxylic acid-derived redox-active esters (RAEs) with aldehyde derived sulfonyl hydrazones, employing Eosin Y as an organophotocatalyst under visible light irradiation. This methodology serves as a versatile, metal-free C(sp3)−C(sp3) cross-coupling platform. Its synthetic utility as a safer and widely applicable C1 homologation of carboxylic acids was demonstrated, providing an alternative to the traditional Arndt-Eistert reaction. Furthermore, the approach allows for the direct synthesis of cyclic and acyclic β-arylethylamines using various aldehyde-derived sulfonyl hydrazones. Notably, the method is compatible with late-stage functionalization of peptides on solid-phase, simplifying the modification of intricate peptides without the need for time demanding de novo synthesis
Books on the topic "Catalyse or":
1
Pellissier, Hélène. Enantioselective titanium-catalysed transformations. New Jersey: Imperial College Press, 2015.
2
Thomas, J. M. Principles and practice of heterogeneous catalysis. Weinheim: VCH, 1996.
3
Ross, J. R. H. Heterogeneous catalysis: Fundamentals and applications. Amsterdam: Elsevier, 2012.
4
S. S. E. H. Elnashaie. Modelling, simulation, and optimization of industrial fixed bed catalytic reactors. Yverdon, Switzerland: Gordon and Breach Science Publishers, 1993.
5
Farrauto, Robert J. Fundamentals of industrial catalytic processes. 2nd ed. Hoboken, N.J: Wiley, 2005.
6
1959-, Regalbuto John R., ed. Handbook of catalyst preparation. Boca Raton: Taylor & Francis, 2007.
7
1960-, Jacobsen Eric N., Pfaltz Andreas 1948-, and Yamamoto Hisashi, eds. Comprehensive asymmetric catalysis. Berlin: Springer, 2004.
8
Eley, D. D. Advances in catalysis. San Diego, Calif: Academic Press, 1998.
9
M, Starks Charles, American Chemical Society Meeting, and American Chemical Society. Division of Petroleum Chemistry., eds. Phase-transfer catalysis: New chemistry, catalysts, and applications. Washington, DC: American Chemical Society, 1987.
10
L, Liotta Charles, Starks Charles M, and Halpern Marc, eds. Phase-Transfer Catalysis: Fundamentals, Applications and Industrial Perspectives. New York: Chapman & Hall, 1993.
Book chapters on the topic "Catalyse or":
1
Engel, Paul. "2. Making things happen—catalysis." In Enzymes: A Very Short Introduction, 12–26. Oxford University Press, 2020. http://dx.doi.org/10.1093/actrade/9780198824985.003.0002.
Abstract:
‘Making things happen—catalysis’ examines chemical catalysis, considering what makes a reaction go or not go and how enzymes catalyse particular chemical reactions. This process is not unique to living systems, although enzymes are both more potent and more selective than catalysts encountered elsewhere in chemistry. A catalyst is an agent that speeds up a chemical reaction but remains unchanged itself at the end of the process. Since a catalyst is not altered or used up, it can be used over and over again.
2
"Catalyse." In Encyclopedia of Astrobiology, 262. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-11274-4_5018.
3
"3 Catalyse." In Chimie verte, 133–276. EDP Sciences, 2020. http://dx.doi.org/10.1051/978-2-7598-2002-3-004.
4
"3 Catalyse." In Chimie verte, 133–276. EDP Sciences, 2020. http://dx.doi.org/10.1051/978-2-7598-2002-3.c004.
5
"catalyse, v." In Oxford English Dictionary. 3rd ed. Oxford University Press, 2023. http://dx.doi.org/10.1093/oed/8577801088.
6
Dobson, C. M., J. A. Gerrard, and A. J. Pratt. "Proteins as catalysts." In Foundations of Chemical Biology. Oxford University Press, 2001. http://dx.doi.org/10.1093/hesc/9780199248995.003.0005.
Abstract:
This chapter reviews how proteins adopt well-defined three-dimensional structures and are capable of binding small molecules reversibly at one or more specific sites on their surfaces. It refers to enzymes that generally catalyse specific reactions of particular molecules and the enhancements of the reaction rate that are often remarkably high. It also emphasizes the efficiency of enzymes as the rate-limiting factor in the catalysed reaction is the diffusion of the reactants to the enzyme. The chapter focuses on the appreciation of the chemistry of enzyme catalysis that provides insights into the biochemical details of cells and chemical catalysis. It looks at features of enzyme catalysis by illustrating triose phosphate isomerase in great detail.
7
Shao, Z., and Y. H. Deng. "2.1.1 General Principles of Metal/Organocatalyst Dual Catalysis." In Dual Catalysis in Organic Synthesis 2. Stuttgart: Georg Thieme Verlag, 2020. http://dx.doi.org/10.1055/sos-sd-232-00002.
Abstract:
AbstractMetal/organocatalyst dual catalysis is a privileged catalytic strategy which involves both a metal-based catalyst and an organocatalyst to catalyze the organic transformation. Based on the type of activation of substrates with both catalysts, there are seven kinds of dual catalysis; namely cooperative catalysis, cascade catalysis, sequential catalysis, double activation catalysis, restorative catalysis, bifunctional catalysis, and multiple relay catalysis. The generic activation of the metal-based catalyst and the organocatalyst applied in the dual-catalytic system is summarized. In these dual-catalytic approaches, the advantages of both metal catalysis and organocatalysis are converged to achieve many transformations that were previously inaccessible or challenging by any single-catalyst paradigm, to develop new reactions, to discover unique reaction mechanisms, and even to allow for stereodivergent synthesis.
8
"8 Catalyse hétérogène." In Les agrégats, 327–56. EDP Sciences, 2020. http://dx.doi.org/10.1051/978-2-7598-2176-1-010.
9
"8 Catalyse hétérogène." In Les agrégats, 327–56. EDP Sciences, 2020. http://dx.doi.org/10.1051/978-2-7598-2176-1.c010.
10
Maskill, Howard. "Catalysis of organic reactions in solution by small molecules and ions." In Structure and Reactivity in Organic Chemistry. Oxford University Press, 1999. http://dx.doi.org/10.1093/hesc/9780198558200.003.0004.
Abstract:
This chapter focuses on the catalysis of organic reactions in solution by small molecules and ions. Catalysis is the enhancement of the rate of a reaction by a compound (the catalyst) not generally present in the chemical equation which describes the reaction. Normally, a catalyst remains unchanged by the chemical reaction it catalyzes. It brings about the rate enhancement by providing a reaction pathway additional to the one which occurs in its absence. This additional pathway will have its own rate law, and the total rate of reaction in the presence of the catalyst is the sum of the catalysed and uncatalyzed pathways. The chapter then looks at electrophile catalysis, specific acid catalysis, general acid catalysis, nucleophile catalysis, specific base catalysis, and general base catalysis. It also considers the Brønsted equation.
Conference papers on the topic "Catalyse or":
1
Kulić Mandić, Aleksandra, Milena Bečelić-Tomin, Đurđa Kerkez, Gordana Pucar Milidrag, Vesna Pešić, and Miljana Prica. "A mini review: Optimal dye removal by fenton process catalysed with waste materials." In 10th International Symposium on Graphic Engineering and Design. University of Novi Sad, Faculty of technical sciences, Department of graphic engineering and design,, 2020. http://dx.doi.org/10.24867/grid-2020-p21.
Abstract:
Large quantities of solid waste from different industries are commonly disposed in landfills, where can generate wide range of environmental problems. Therefore, the aim of this paper is to give insight on the usage of various waste materials as oxidation catalysts in different Fenton processes for dye removal. In that manner the circular value chain of these materials will be reinforced, obtaining disposal cost reduction and further value addition. Some of industrial wastes (fly ash, electric arc furnace dust, red mud, coal bottom ash, activated carbon from biomass, etc.) that have been used to catalyse Fenton reaction in various researches are reviewed from optimization point of view. Both types of optimization, one-factor-at-a-time (OFAT) and response surface methodology (RSM) are investigated. The study revealed that factors as catalyst concentration, pH value, hydrogen peroxide concentration, dye concentration and reaction time are main factors that influence final Fenton capacity as oxidation process catalysed with reviewed waste materials.
2
Appleyard, N., and Z. Lock. "Connect and catalyse - our strategy [innovation management]." In IET Seminar on the Directions and Funding of Robotics Research in the UK. IEE, 2008. http://dx.doi.org/10.1049/ic:20080553.
3
Bond, Gary, A. Halman, H. Eccles, R. Mao, S. Pollington, P. Hinde, V. Demidyuk, and A. Gkelios. "A COMPARATIVE STUDY OF MICROWAVE AND BARRIER DISCHARGE PLASMA FOR THE REGENERATION OF SPENT ZEOLITE CATALYSTS." In Ampere 2019. Valencia: Universitat Politècnica de València, 2019. http://dx.doi.org/10.4995/ampere2019.2019.9936.
Abstract:
Due to their acid characteristics and pore structure, which can induce high product selectivity; zeolite catalysts are used extensively in industry to catalyse reactions involving hydrocarbons. However, these catalysts can suffer from deactivation due to cracking reactions that result in the deposition of carbon leading to poisoning of the acid sites and blocking of the pores [1]. Depending upon the reaction and the particular catalyst involved this deactivation may take place over several months or even years but in some cases occurs in minutes. Therefore, zeolite catalysts are frequently reactivated / regenerated. This generally involves a thermal treatment involving air which results in oxidation of the carbon [2]. However, the oxidation of carbon is highly exothermic, and if not carefully controlled, results in the generation of exceedingly high localized temperatures which can destroy the zeolite structure and result in subsequent loss of catalyst activity. More conservative thermal treatments can result in incomplete regeneration and again a catalyst displaying inferior activity. This paper explores the use of non-thermal plasma which had been either generated using microwaves or via a barrier discharge to regenerate spent zeolite catalysts. The catalyst, H-mordenite, was tested for the disproportionation of toluene (Figure 1) using conventional heating. The spent catalyst was then regenerated using a plasma or conventional thermal treatment before having its activity re-evaluated for the toluene disproportionation reaction as previous. Fig. 1. Reaction Scheme for Toluene Disproportionation. Interestingly, not only is plasma regeneration highly effective but also catalysts can be regenerated in greatly reduced times. There is an additional advantage in that plasma regeneration can impart physical properties that result in a zeolite that is resistant to further deactivation. However, the results are highly dependent upon the experimental conditions involved for plasma regeneration. References Wu J, Leu L., Appl. Catal., 1983; 7:283-294. M. Guisnet and P. Magnoux, Deactivation of Zeolites by Coking. Prevention of Deactivation and Regeneration. In: Zeolite Microporous Solids: Synthesis, Structure, and Reactivity. E.G. Derouane, F Lemos, C. Naccache, F. Ramôa Ribeiro, Eds. Pages 437-456. Springer 1992.
4
Audhali, Nadia, Anna Moore, Tim Martin, Charlotte Munro, and Florence Wedmore. "181 Harnessing staff values to catalyse workplace change." In Leaders in Healthcare Conference, 17–20 November 2020. BMJ Publishing Group Ltd, 2020. http://dx.doi.org/10.1136/leader-2020-fmlm.181.
5
Jobic, H. "Catalyse localisée : étude de molécules adsorbées et de systèmes catalytiques." In JDN 16 – Diffusion Inélastique des Neutrons pour l'Etude des Excitations dans la Matiére Condensée. Les Ulis, France: EDP Sciences, 2010. http://dx.doi.org/10.1051/sfn/2010018.
6
Audhali, Nadia, Florence Wedmore, Anna Moore, and Charlotte Monro. "1427 Harnessing staff values to catalyse workplace change. Towards 2040, NHS net-zero." In Royal College of Paediatrics and Child Health, Abstracts of the RCPCH Conference–Online, 15 June 2021–17 June 2021. BMJ Publishing Group Ltd and Royal College of Paediatrics and Child Health, 2021. http://dx.doi.org/10.1136/archdischild-2021-rcpch.636.
7
Ofosu, F. A., G. J. Modi, M. A. Blajchman, M. R. Buchanan, and E. A. Johnson. "INCREASED SULFATION IMPROVES THE ABILITY OF VESSEL WALL GLYCOSA-MINOGLYCANS TO REGULATE THROMBIN ACTIVITY AND PROTHROMBIN ACTIVATION IN PLASMA." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643252.
Abstract:
Studies have shown that dermatan sulfate (DS), heparan sulfate (HS) and chondroitin-4-sulfate (C4S), have antithrombotic properties. The sulfate to carboxylate ratios of these three glycosaminoglycans (GAGs) are approximately half that of heparin (HEP) and the gravimetric dose of each of the three GAGs required to achieve antithrombotic effects in vivo comparable to HEP can be 10 times or more than that of HEPT Since antithrombotic effects depend on the ability of a GAG to catalyse thrombin inhibition and/or to inhibit prothrombin activation, we determined the relationship between the extent of sulfation of various GAGs and their effects on these two reactions in normal plasma. In addition to the three GAGs, DS, HS and C4S were resulfated in vitro to yield DS-S, HS-S and C4S-S, each with a sulfate to carboxylate ratio comparable to that of heparin. As summarized below, increased sulfation improved the ability of a GAG to catalyse thrombin inhibition and to inhibit prothrombin activation. Increasing the degree of sulfation primarily improved the ability of a GAG to accelerate the inhibition of thrombin by heparin cofactor II. The degree of sulfation, therefore, appears to be an important functional attribute of the ability of vessel wall GAGs to regulate the formation and activity of thrombin in plasma.
8
Lou, Diming, Yajuan Chen, Yunhua Zhang, Peng Wan, Piqiang Tan, Zhiyuan Hu, Liang Fang, and Tong Wang. "Study on Soot Oxidation Characteristics of Ce and La Modified Pt-Pd CDPF Catalysts." In WCX SAE World Congress Experience. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2023. http://dx.doi.org/10.4271/2023-01-0390.
Abstract:
<div class="section abstract"><div class="htmlview paragraph">The catalyzed diesel particulate filter with Pt and Pd noble metals as the main loaded active components are widely used in the field of automobile engines, but the high cost makes it face huge challenges. Rare earth element doping can improve the soot oxidation performance of the catalyzed diesel particulate filter and provide a new way to reduce its cost. In this paper, thermogravimetric tests and chemical reaction kinetic calculations were used to explore the effect of Pt-Pd catalysts doped Ce, and La rare earth elements on the oxidation properties of soot. The results shown that, among Pt-Pd-5%Ce, Pt-Pd-5%La, and Pt-Pd-5%Ce-5%La catalysts, Pt-Pd-5%La catalyst has the highest soot conversion, the highest low-temperature oxidation speed, and the activation energy is the smallest. Compared with soot, this catalyst reduced <i>T<sub>10</sub></i> and <i>T<sub>20</sub></i> by 82% and 26%, respectively, meaning the catalytic activity of Pt-Pd-5%La catalyst was the best. With the decrease of catalyst/soot ratios, the soot conversion and oxidation speed of Pt-Pd and Pt-Pd-5%La catalysts decreased, and characteristic temperature increased. In both catalyst formulations, samples with catalyst/soot ratio of 5 showed the best catalytic activity, and the other samples with smaller catalyst/soot ratios showed less difference. The study revealed the influence of doping elements and catalyst/soot ratios on the oxidation characteristics and reaction kinetics of soot, which has a guiding significance for optimizing the doping scheme of rare earth elements and realizing the reduction of noble metals.</div></div>
9
Zhang, Aihua. "EXPERIMENTAL STUDY ON THE APPLICATION OF MACHINE LEARNING METHOD IN CATALYTIC MATERIALS." In Topics In Chemical & Material Engineering (TCME). Volkson Press, 2023. http://dx.doi.org/10.26480/smmp.01.2023.24.27.
Abstract:
Machine learning has emerged as a powerful tool for analyzing complex data sets and making predictions in a wide range of applications, including catalysis. Bycombining statistical methods, algorithms, and computational power, machine learning can help identify patterns and relationships in catalytic systems that are difficult or impossible to discern using traditional approaches. This can lead to more efficient and effective catalyst design, optimization, and prediction of catalytic activity. Machine learning has already been successfully applied to various aspects of catalysis, including catalyst discovery, reaction mechanism identification, and kinetic modeling. The continued integration of machine learning with catalysis research holds great promise for advancing our understanding of catalytic systems and developing new and improved catalysts for important industrial processes.
10
Henriksen, Jesper, Susanne Bendsen, Tony Ao Han, Jin Wang, Tine Holmboe, and Catherine Merlo. "Experience as Incentive: Promoting Sustainable Urban Mobility Through Bridge Design." In IABSE Congress, New Delhi 2023: Engineering for Sustainable Development. Zurich, Switzerland: International Association for Bridge and Structural Engineering (IABSE), 2023. http://dx.doi.org/10.2749/newdelhi.2023.0978.
Abstract:
<p>Bicycle infrastructure creates environmental, social, and economic value in urban environments across cultures. Cities that invest in bicycle infrastructure reduce the number of cars on the road, save on infrastructure maintenance costs, and preserve greenspace within development plans. A bridge must not only solve specific traffic challenges but catalyse value creation and incentivize sustainable urban transport.</p><p>Exploring the intersection of architecture and user experience across bicycle bridges in Copenhagen, Denmark and Xiamen, China - Dissing+Weitling demonstrates how cycling infrastructure is a powerful tool for cities to incentivize sustainable urban mobility.</p>
Reports on the topic "Catalyse or":
1
Olsen, Daniel, Bryan Hackleman, and Rodrigo Bauza Tellechaea. PR-179-16207-R01 Oxidation Catalyst Degradation on a 2-Stroke Lean-Burn NG Engine - Washing. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), May 2019. http://dx.doi.org/10.55274/r0011586.
Abstract:
Oxidation catalysts are often utilized to reduce carbon monoxide, formaldehyde, and volatile organic compounds in order to meet emissions regulations for large bore natural gas engines. These catalysts degrade over time and need to be replaced or regenerated to maintain emissions compliance. This work evaluates the effectiveness of catalyst regeneration, or catalyst washing. The evaluation is performed by utilizing field and laboratory slip streams combined with catalyst module performance (reduction efficiency) measurements and catalyst material surface analysis to quantify catalyst poisons.
2
Stevens and Olsen. PR-179-12214-R01 CO Sensor Experimental Evaluation for Catalyst Health Monitoring. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), September 2014. http://dx.doi.org/10.55274/r0010827.
Abstract:
Oxidation catalysts and three-way catalysts can be used to reduce the amount of CO present in engine exhaust. For 2-stroke lean-burn engines, the oxidation catalyst degrades over time be-cause of the buildup of poisons such as sulfur, zinc, phosphorous, and calcium. Three-way cata-lysts used with stoichiometric engines also degrade over time. Emissions analyzers are often used to evaluate the degradation of oxidation catalysts and three-way catalysts, but it can be very time consuming and expensive. Ideally, a simple sensor system would be beneficial for operating companies to determine if the catalyst were out of compliance according to normal operating standards. An ECM CO sensor and recording device was acquired for testing. The CO sensor system was evaluated for its ability to monitor post-catalyst CO concentration. The results show that this CO sensor system is ineffective at monitoring post-catalyst CO concentration.
3
Badrinarayanan and Olsen. PR-179-11201-R01 Performance Evaluation of Multiple Oxidation Catalysts on a Lean Burn Natural Gas Engine. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), August 2012. http://dx.doi.org/10.55274/r0010772.
Abstract:
Two-way catalysts or oxidation catalysts are the common after-treatment systems used on lean burn natural gas engines to reduce CO, VOCs and formaldehyde emissions. The study evaluates the performance of oxidation catalysts from commercial vendors for varying catalyst temperature and space velocity. For this study, a part of the exhaust from a Waukesha VGF-18 GL lean burn natural gas engine was flowed through a catalyst slipstream system to assess the performance of the oxidation catalysts. The slipstream is used to reduce the size of the catalysts and to allow precise control of temperature and space velocity. Analyzers used include Rosemount 5-gas emissions bench, Nicolet Fourier Transform Infra-Red spectrometer and HP 5890 Series II Gas Chromatograph. The oxidation catalysts were degreened at 1200oF (650oC) for 24 hours prior to performance testing. The reduction efficencies for the emission species varied among the oxidation catalysts tested from different vendors. Most oxidation catalysts showed over 90% maximum reduction efficiencies on CO, VOCs and formaldehyde. VOC reduction efficiency was limited by poor propane emission reduction efficiency at the catalyst temperatures tested. Saturated hydrocarbons such as propane showed low reduction efficiencies on all oxidation catalysts due to high activation energy. Variation in space velocity showed very little effect on the conversion efficiencies. Most species showed over 90% conversion efficiency during the space velocity sweep. Adding more catalyst volume may not increase the reduction efficiency of emission species. Varying cell density showed very little effect on performance of the oxidation catalysts. The friction factor correlation showed the friction factor for flow through a single channel is inversely proportional to cell density.
4
Olsen and Neuner. PR-179-12207-R01 Performance Measurements of Oxidation Catalyst on an Exhaust Slipstream. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), August 2013. http://dx.doi.org/10.55274/r0010800.
Abstract:
Oxidation catalysts are effective at reducing CO, formaldehyde, and VOCs as long as the catalyst temperature is above the light-off temperature for each species. It is important to understand the effects of temperature and space velocity on regulated species in order to effectively apply oxidation catalyst technology to lean burn engines, in particular 2-stroke engines that typically have lower exhaust temperatures. Various catalysts were tested on an exhaust slipstream coupled to a 4-stroke lean-burn engine which allows tests to be conducted at different temperatures and flow rates. The effect of the oxidation catalysts on NO2 and odor are also discussed.
5
Taylor, Joe, Peter Taylor, and Louise Clark. Covid Collective Learning Report. Institute of Development Studies, March 2024. http://dx.doi.org/10.19088/cc.2024.001.
Abstract:
This report provides an overview the Covid Collective research platform, how it was operationalised, and the learning which emerged from the three-year programme. The foundation of the Covid Collective’s theory of change was the network and relationships that were established and developed to harness collaboration and sharing of knowledge across a platform of global research partners. We acknowledged the critical role knowledge sharing, learning and engagement played in creating a culture that could enable and catalyse evidence-based, transformative action in response to Covid-19. The network that was developed in forming the Covid Collective could then facilitate comparative learning and collective action, and generate new insights and knowledge on the factors that support more or less effective responses to Covid-19 and help to build resilience to address future global development challenges.
6
de Brauw, Alan, Shalini Roy, and Mulugeta Tefera. Financial services in refugee hosting areas: Can they promote inclusion? Lessons from the SHARPE project in Ethiopia. Centre for Excellence and Development Impact and Learning (CEDIL), December 2022. http://dx.doi.org/10.51744/ceb4.
Abstract:
Digital financial inclusion is important to achieving the Sustainable Development Goals. Digital financial tools, such as mobile money, can, in principle, be used by anyone with a cell phone. Mobile money and services surrounding mobile money can help reduce poverty by helping increase remittances from labour migrants, helping households to weather negative shocks to income, and encouraging investments such as in farms or in self-employment activities. An extension of this logic is that, in refugee hosting areas, digital financial inclusion through mobile money can potentially play a role in improving the economic inclusion of refugees. This evidence brief shares findings from a project developing a mobile money system in the Somali region of Ethiopia and discusses ways that policies can help catalyse the use of mobile money in such regions.
7
Defoort, Willson, and Olsen. L51849 Performance Evaluation of Exhaust Catalysts During the Initial Aging on Large Industrial Engines. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), June 2001. http://dx.doi.org/10.55274/r0011213.
Abstract:
An investigation of catalyst performance during the initial aging process, providing insight into the deactivation rate of the catalyst and assisting in predicting the operational lifetime of the catalyst was preformed. The information gained through the test program provides a mechanism to assist in developing new technologies geared at reducing engine emission while providing improvements in efficiency, reliability, and operability for the aging industrial reciprocating engine fleet. Two natural gas lean burn engines, a 2-stroke, large bore slow speed and a 4-stroke medium bore medium speed, were operated at pre-determined conditions in conjunction with an oxidation catalyst. The aging process of the catalysts was observed. The research concluded that the catalyst performance is much lower than anticipated,particularly in relation to the aging process. During the aging process for the large bore 2-stroke engine (about 200 hours) the catalyst efficiency drops from 95% to 80% for CO and from 75% to 45% for CH2O. Results for the medium bore 4-stroke engine are better as a result of nearly 200°F higher catalyst temperatures. During aging (approximately 150 hours) the catalyst efficiencies are reduced from 99.2 to 97.7% for CO and from undetectable post catalyst levels (essentially 100% removal) to 67% for CH2O.
8
de Brauw, Alan, Daniel Gilligan, Laura Leavens, Fekadu Moges, Shalini Roy, and Mulugeta Tefera. Impact Evaluation of the SHARPE Programme in Ethiopia: Academic Report. Centre for Excellence and Development Impact and Learning (CEDIL), March 2023. http://dx.doi.org/10.51744/crpp6.
Abstract:
The Strengthening Host and Refugee Populations in Ethiopia (SHARPE) programme uses a market systems development approach to promote increased self-reliance and economic opportunities for refugees and host communities through the piloting and scaling of interventions across different sectors. This approach is based upon understanding the economic barriers that refugee and host communities face, and working with key stakeholders – including businesses, government, and service providers – to improve market function for people in these regions. This report focuses on evaluating the impacts of investments SHARPE has made in the financial market system, which have focused on developing markets for digital financial services in refugee hosting areas. A highlight of the evaluation are two co-developed randomized control trials, designed to help SHARPE and its partners overcome constraints found while implementing the programme. The report finds evidence that robust markets for digital financial services are emerging in refugee hosting areas near Jijiga and are a little farther behind in Dollo Ado. Enrolment in the mobile money product, HelloCash, has been quite robust, though lower among women and refugees. HelloCash users are more likely to report financial inclusion (beyond inclusion through Hello Cash); they are 8.8 percentage points more likely to report being self-employed; they are 6.1 percentage points more likely to report typically having enough income; and they appear less food insecure than non-users. To try to enrol more women and refugees and catalyse HelloCash use among those groups, we conducted two randomized trials, one which allowed high volume customers to refer customers and receive a small bonus for doing so, and one which provided inactive customers with small incentives to start using the system. The former trial led to increased enrolment, but the share of women and refugees enrolling did not change; the latter led to increased use among women, but not refugees. We conclude with some ideas about further experiments to catalyse more use among refugees.
9
Swanson, Dr Larry, and Christopher Samuelson. PR-362-06208-R01 Evaluation of Byproduct Emissions from Gas Turbine SCR Catalyst. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), February 2009. http://dx.doi.org/10.55274/r0010978.
Abstract:
The primary objective of the test program was to evaluate byproduct emissions at steady state and transient operating conditions for two commercially available SCR catalysts used in gas turbine applications. Both NOX removal efficiency and ammonia slip behavior were also examined to validate expected catalyst trends and activity. Even though the study replicated expected field catalyst process conditions as well as possible (e.g., flue gas temperatures, space velocities, and inlet species concentrations), the data and results are from pilot-scale testing only, and consequently may differ from actual gas turbine field tests.
10
Bauza, Rodrigo, and Daniel Olsen. PR-179-20200-R01 Improved Catalyst Regeneration Process to Increase Poison Removal. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), June 2021. http://dx.doi.org/10.55274/r0012106.
Abstract:
In this work, the details of catalyst poison deposition are studied, and new catalyst restoration methods are explored. Lubrication oil makes its way through the combustion chamber and into the exhaust system, depositing poisons onto the catalyst and degrading catalyst performance. To estimate the degradation rate of the units and to find the best restoration method, two identical alumina-platinum oxidation catalysts were used in a dual setting, combining a field degradation engine and a laboratory testing engine. In order to find the best restoration process, the combination of both baking and washing is tested with poison deposition and performance analysis, and a hydrogen reduction is tested for the restoration of the platinum crystallites. The units were aged, then restored with the industry-standard washing procedure, then aged again until reaching non-compliance with emissions standards, and then restored a second time with a modified version of the industry-standard washing process that combines baking and washing. There is a related webinar.