115-18-4Relevant academic research and scientific papers
Tailoring the framework composition of carbon nitride to improve the catalytic efficiency of the stabilised palladium atoms
Vorobyeva,Chen,Mitchell,Leary,Midgley,Thomas,Hauert,Fako,López,Pérez-Ramírez
, p. 16393 - 16403 (2017)
Graphitic carbon nitride (g-C3N4) exhibits unique properties for the preparation of single-atom heterogeneous catalysts (SAHCs) due to the presence of sixfold nitrogen-based coordination sites in the lattice. Despite the potential to profoundly affect the metal stabilisation and resulting catalytic properties, no work has previously investigated the effect of modifying the carrier composition. Here, we study the impact of doping carbon in g-C3N4 on the interaction with palladium. This is achieved by introducing carbon-rich heterocycles (barbituric acid or 2,4,6-triaminopyrimidine) during the synthesis of bulk and mesoporous g-C3N4. Palladium is subsequently introduced via microwave-irradiation-assisted deposition, which emerges as a highly effective route for the dispersion of single atoms. Detailed characterisation confirms the controlled variation of the C/N ratio of the lattice and reveals the complex interplay with the crystal size, surface area, amount of defects, basic properties and thermal stability of the carrier. Atomic dispersions of palladium with similar surface densities could be obtained on both the stoichiometric and carbon-doped carriers in mesoporous form, but appreciable differences are observed in the ratio of Pd2+/Pd4+. The latter, which provides a measure of the degree of electron transfer from the metal to the carrier, is found to correlate with the activity in the continuous flow semi-hydrogenation of 2-methyl-3-butyn-2-ol. Density functional theory calculations support the decreased adsorption energy of palladium upon doping with carbon and reveal the potentially significant impact of oxygen-containing defects. The findings demonstrate the importance of understanding the metal-carrier interaction to optimise the catalytic efficiency of SAHCs.
Precursor Nuclearity and Ligand Effects in Atomically-Dispersed Heterogeneous Iron Catalysts for Alkyne Semi-Hydrogenation
Faust Akl, Dario,Ruiz-Ferrando, Andrea,Fako, Edvin,Hauert, Roland,Safonova, Olga,Mitchell, Sharon,López, Núria,Pérez-Ramírez, Javier
, p. 3247 - 3256 (2021)
Nanostructuring earth-abundant metals as single atoms or clusters of controlled size on suitable carriers opens new routes to develop high-performing heterogeneous catalysts, but resolving speciation trends remains challenging. Here, we investigate the potential of low-nuclearity iron catalysts in the continuous liquid-phase semi-hydrogenation of various alkynes. The activity depends on multiple factors, including the nuclearity and ligand sphere of the metal precursor and their evolution upon interaction with the mesoporous graphitic carbon nitride scaffold. Density functional theory predicts the favorable adsorption of the metal precursors on the scaffold without altering the nuclearity and preserving some ligands. Contrary to previous observations for palladium catalysts, single atoms of iron exhibit higher activity than larger clusters. Atomistic simulations suggest a central role of residual carbonyl species in permitting low-energy paths over these isolated metal centers.
Scale up study of capillary microreactors in solvent-free semihydrogenation of 2‐methyl‐3‐butyn‐2‐ol
Cherkasov, Nikolay,Al-Rawashdeh, Ma ’moun,Ibhadon, Alex O.,Rebrov, Evgeny V.
, p. 205 - 212 (2016)
A 2.5 wt.% Pd/ZnO catalytic coating has been deposited onto the inner wall of capillary reactors with a diameter of 0.53 and 1.6 mm. The coatings were characterised by XRD, SEM, TEM and elemental analysis. The performance of catalytic reactors was studied in solvent-free hydrogenation of 2-methyl-3-butyn-2-ol. No mass transfer limitations was observed in the reactor with a diameter of 0.53 mm up to a catalyst loading of 1.0 kg(Pd) m?3. The activity and selectivity of the catalysts has been studied in a batch reactor to develop a kinetic model. The kinetic model was combined with the reactor model to describe the obtained data in a wide range of reaction conditions. The model was applied to calculate the range of reaction conditions to reach a production rate of liquid product of 10–50 kg a day in a single catalytic capillary reactor.
A Stable Single-Site Palladium Catalyst for Hydrogenations
Vilé, Gianvito,Albani, Davide,Nachtegaal, Maarten,Chen, Zupeng,Dontsova, Dariya,Antonietti, Markus,López, Núria,Pérez-Ramírez, Javier
, p. 11265 - 11269 (2015)
We report the preparation and hydrogenation performance of a single-site palladium catalyst that was obtained by the anchoring of Pd atoms into the cavities of mesoporous polymeric graphitic carbon nitride. The characterization of the material confirmed the atomic dispersion of the palladium phase throughout the sample. The catalyst was applied for three-phase hydrogenations of alkynes and nitroarenes in a continuous-flow reactor, showing its high activity and product selectivity in comparison with benchmark catalysts based on nanoparticles. Density functional theory calculations provided fundamental insights into the material structure and attributed the high catalyst activity and selectivity to the facile hydrogen activation and hydrocarbon adsorption on atomically dispersed Pd sites.
Palladium-bismuth intermetallic and surface-poisoned catalysts for the semi-hydrogenation of 2-methyl-3-butyn-2-ol
Cherkasov, Nikolay,Ibhadon, Alex O.,McCue, Alan J.,Anderson, James A.,Johnston, Shaun K.
, p. 22 - 30 (2015)
The effects of poisoning of Pd catalysts with Bi and annealing in a polyol (ethylene glycol) were studied on the semi-hydrogenation of 2-methyl-3-butyn-2-ol (MBY). An increase in the Pd:Bi ratio from 7 to 1 in the Bi-poisoned catalysts decreased the hydrogenation activity due to blocking of active sites, but increased maximum alkene yield from 91.5% for the Pd catalyst to 94-96% for all Bi-poisoned Pd catalysts, by decreasing the adsorption energy of alkene molecules and suppressing the formation of β-hydride phase. Annealing of the catalysts induced the formation of intermetallic phases and decreased its activity due to sintering of the catalytic particles and low activity of intermetallic compounds. Langmuir-Hinshelwood kinetic modelling of the experimental data showed that poisoning of Pd with Bi changed the relative adsorption constants of organic species suggesting ligand effects at high Bi content.
Synthesis of (±) debenzoyl analogs of norsampsones as potential anticancer agents
Jadhav, Amol R.,Thombal, Raju S.,Nigam, Preeti,Jadhav, Vrushali H.
, p. 5235 - 5237 (2015)
Synthesis of (±) debenzoyl analogs of norsampsones 1 and 2 is reported starting from commercially available 1,3-cyclohexadione in six steps with overall yields of 37% and 36%, respectively. Compounds 1 and 2 were tested for their anticancer activity and showed moderate anticancer activity against HeLa cell lines.
Solvent-free semihydrogenation of acetylene alcohols in a capillary reactor coated with a Pd-Bi/TiO2 catalyst
Cherkasov, Nikolay,Ibhadon, Alex O.,Rebrov, Evgeny V.
, p. 108 - 115 (2016)
A solvent-free semihydrogenation of 2-methyl-3-butyn-2-ol (MBY) to 2-methyl-3-buten-2-ol was performed in a capillary reactor (10 m long, 0.53 mm i.d.) coated with a titania supported Pd-Bi catalyst. Several coatings with different Pd/Bi ratio have been prepared. The catalysts have been characterized with SEM, TEM, EDX, XRD analysis and N2 adsorption-desorption measurements. The maximum alkene yield of 90% was obtained at a molar Pd/Bi ratio of 11. The yield was increased to 95% in the presence of 10 mol.% pyridine in the reaction mixture. The alkene selectivity decreased with time due to leaching of Bi. The leaching was fully suppressed in the presence of 1 vol.% acetic acid in the reaction mixture. The catalyst remained stable for 100 h of continuous operation. The results demonstrate that capillary reactors provide alkene selectivity the same compared to ideal stirred tank batch reactors.
Novel synthesis of thick wall coatings of titania supported Bi poisoned Pd catalysts and application in selective hydrogenation of acetylene alcohols in capillary microreactors
Cherkasov, Nikolay,Ibhadon, Alex O.,Rebrov, Evgeny V.
, p. 1952 - 1960 (2015)
Catalysis in microreactors allows reactions to be performed in a very small volume, reducing the environmental problems and greatly intensifying the processes through easy pressure control and the elimination of heat- and mass-transfer limitations. In this study, we report a novel method for the controlled synthesis of micrometre-thick mesoporous TiO2 catalytic coatings on the walls of long channels (>1 m) of capillary microreactors in a single deposition step. The method uses elevated temperature and introduces a convenient control parameter of the deposition rate (displacement speed controlled by a stepper motor), which allows deposition from concentrated and viscous sols without channel clogging. A capillary microreactor wall-coated with titania supported Bi-poisoned Pd catalyst was obtained using the method and used for the semihydrogenation of 2-methyl-3-butyn-2-ol providing 93 ± 1.5% alkene yield for 100 h without deactivation. Although the coating method was applied only for TiO2 deposition, it is nonetheless suitable for the deposition of volatile sols.
Structural and functional insights into asymmetric enzymatic dehydration of alkenols
Nestl, Bettina M.,Geinitz, Christopher,Popa, Stephanie,Rizek, Sari,Haselbeck, Robert J.,Stephen, Rosary,Noble, Michael A.,Fischer, Max-Philipp,Ralph, Erik C.,Hau, Hoi Ting,Man, Henry,Omar, Muhiadin,Turkenburg, Johan P,Van Dien, Stephen,Culler, Stephanie J.,Grogan, Gideon,Hauer, Bernhard
, p. 275 - 281 (2017)
The asymmetric dehydration of alcohols is an important process for the direct synthesis of alkenes. We report the structure and substrate specificity of the bifunctional linalool dehydratase isomerase (LinD) from the bacterium Castellaniella defragrans that catalyzes in nature the hydration of β-myrcene to linalool and the subsequent isomerization to geraniol. Enzymatic kinetic resolutions of truncated and elongated aromatic and aliphatic tertiary alcohols (C5-C15) that contain a specific signature motif demonstrate the broad substrate specificity of LinD. The three-dimensional structure of LinD from Castellaniella defragrans revealed a pentamer with active sites at the protomer interfaces. Furthermore, the structure of LinD in complex with the product geraniol provides initial mechanistic insights into this bifunctional enzyme. Site-directed mutagenesis confirmed active site amino acid residues essential for its dehydration and isomerization activity. These structural and mechanistic insights facilitate the development of hydrating catalysts, enriching the toolbox for novel bond-forming biocatalysis.
Palladium-Phosphorus Nanoparticles as Effective Catalysts of the Chemoselective Hydrogenation of Alkynols
Belykh, L. B.,Dashabylova, T. M.,Gvozdovskaya, K. L.,Schmidt, F. K.,Skripov, N. I.,Sterenchuk, T. P.,Zherdev, V. V.
, p. 575 - 588 (2020)
Abstract: The effect of the composition of the catalytic system and reaction conditions on the properties of phosphorus-modified palladium catalysts in hydrogenations of alkynols was studied. Modification with phosphorus increased the activity and turnover number of palladium catalysts in the hydrogenation of the model compound 2-methyl-3-butyn-2-ol (MBY) without any reduction in the selectivity to 2-methyl-3-butene-2-ol at 95–98percent MBY conversion. The promoting effect of phosphorus on the properties of the palladium catalyst is caused not only by an increase in the particle size, but also, probably, by a change in the energy of interaction of reagents with the active sites. Hypotheses on the nature of the carriers of catalytic activity in Pd–P particles were discriminated using kinetic methods with the differential selectivity of catalytic systems as the main measured parameter under the conditions of competition between two alkynols. The hydrogenation of acetylenic alcohols involves only one of the two potentially active forms in Pd–P nanoparticles—Pd(0) clusters, whereas the hydrogenation of the resulting allyl alcohols involves both Pd(0) clusters and palladium phosphides.
