- Tailoring the framework composition of carbon nitride to improve the catalytic efficiency of the stabilised palladium atoms
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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.
- Vorobyeva,Chen,Mitchell,Leary,Midgley,Thomas,Hauert,Fako,López,Pérez-Ramírez
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- Precursor Nuclearity and Ligand Effects in Atomically-Dispersed Heterogeneous Iron Catalysts for Alkyne Semi-Hydrogenation
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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.
- Faust Akl, Dario,Ruiz-Ferrando, Andrea,Fako, Edvin,Hauert, Roland,Safonova, Olga,Mitchell, Sharon,López, Núria,Pérez-Ramírez, Javier
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- Scale up study of capillary microreactors in solvent-free semihydrogenation of 2‐methyl‐3‐butyn‐2‐ol
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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.
- Cherkasov, Nikolay,Al-Rawashdeh, Ma ’moun,Ibhadon, Alex O.,Rebrov, Evgeny V.
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- A Stable Single-Site Palladium Catalyst for Hydrogenations
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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.
- Vilé, Gianvito,Albani, Davide,Nachtegaal, Maarten,Chen, Zupeng,Dontsova, Dariya,Antonietti, Markus,López, Núria,Pérez-Ramírez, Javier
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- Palladium-bismuth intermetallic and surface-poisoned catalysts for the semi-hydrogenation of 2-methyl-3-butyn-2-ol
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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.
- Cherkasov, Nikolay,Ibhadon, Alex O.,McCue, Alan J.,Anderson, James A.,Johnston, Shaun K.
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- Synthesis of (±) debenzoyl analogs of norsampsones as potential anticancer agents
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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.
- Jadhav, Amol R.,Thombal, Raju S.,Nigam, Preeti,Jadhav, Vrushali H.
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- Solvent-free semihydrogenation of acetylene alcohols in a capillary reactor coated with a Pd-Bi/TiO2 catalyst
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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.
- Cherkasov, Nikolay,Ibhadon, Alex O.,Rebrov, Evgeny V.
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- Novel synthesis of thick wall coatings of titania supported Bi poisoned Pd catalysts and application in selective hydrogenation of acetylene alcohols in capillary microreactors
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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.
- Cherkasov, Nikolay,Ibhadon, Alex O.,Rebrov, Evgeny V.
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- Structural and functional insights into asymmetric enzymatic dehydration of alkenols
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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.
- 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
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- Palladium-Phosphorus Nanoparticles as Effective Catalysts of the Chemoselective Hydrogenation of Alkynols
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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.
- Belykh, L. B.,Dashabylova, T. M.,Gvozdovskaya, K. L.,Schmidt, F. K.,Skripov, N. I.,Sterenchuk, T. P.,Zherdev, V. V.
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- Novel Fe–Pd/γ-Al2O3 catalysts for the selective hydrogenation of C≡C bonds under mild conditions
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Novel promising Fe–Pd/γ-Al2O3 catalysts for the selective liquid-phase hydrogenation of unsaturated compounds (phenylacetylene and 2-methylbut-3-yn-2-ol) under ambient conditions have been prepared. They were characterized by low temperature nitrogen adsorption, XRD, SEM, TEM, TPR-H2 and DRIFTS-CO techniques. The presence of Pd–Fe nanoparticles led to increased reactivity and selectivity of the new catalysts in hydrogenation of the C≡C bond to the C=C one as compared to those of the Pd/Al2O3 system.
- Shesterkina, Anastasiya A.,Kozlova, Ludmila M.,Mishin, Igor V.,Tkachenko, Olga P.,Kapustin, Gennady I.,Zakharov, Viktor P.,Vlaskin, Mikhail S.,Zhuk, Andrei Z.,Kirichenko, Olga A.,Kustov, Leonid M.
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- Internal Surface Coating of a Capillary Microreactor for the Selective Hydrogenation of 2-Methyl-3-Butyn-2-Ol Using a PdZn/TiO2 Catalyst. The Effect of the Catalyst’s Activation Conditions on Its Catalytic Properties
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Finely divided polymer-stabilized PdZn bimetallic nanoclusters are prepared by the polyol method. TiO2 matrix-impregnated nanoclusters coated on the inner surface of a capillary microreactor are used as catalysts for the selective hydrogenation of 2-methyl-3-butyn-2-ol. The effect of the activation conditions (duration, temperature, and gas medium composition) on the physicochemical and catalytic properties of the coatings is studied. It is shown that their catalytic activities decrease and the reaction’s selectivity increases with an increase in the reaction time and the time of hydrogen reduction at 573 K. The highest selectivity (96.5% at a conversion rate of 99%) is reached on the coatings reduced with hydrogen for 6 h. The coatings remain highly active and stable for 1 month in the continuous flow mode of the reaction. Kinetic simulation showed that a high selectivity level is ensured by a decrease in the rate constants of hydrogenation of 2-methyl-3-buten-2-ol and the ratio of the alkene/alkyne adsorption constants after reductive treatment.
- Okhlopkova,Kerzhentsev,Ismagilov
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- Efficient synthesis of 3-sulfolenes from allylic alcohols and 1,3-dienes enabled by sodium metabisulfite as a sulfur dioxide equivalent
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We present herein an efficient and practical method for a gram scale synthesis of 3-sulfolenes using sodium metabisulfite as a safe, inexpensive, and easy to handle sulfur dioxide equivalent. Diversely-substituted 3-sulfolenes can be prepared by reacting a variety of 1,3-dienes or allylic alcohols with sodium metabisulfite in aqueous hexafluoroisopropanol (HFIP) or in aqueous methanol in the presence of potassium hydrogen sulfate. Advantageously, the method enables conversion of allylic alcohols directly to 3-sulfolenes, bypassing intermediate 1,3-dienes.
- Dang, Hang T.,Nguyen, Vu T.,Nguyen, Viet D.,Arman, Hadi D.,Larionov, Oleg V.
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- Magnetically recoverable catalysts based on polyphenylenepyridyl dendrons and dendrimers
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Here, a systematic study of magnetite nanoparticle (NP) formation in the presence of functional polyphenylenepyridyl dendrons and dendrimers of different generations and structures (such as focal groups, periphery and a combination of phenylene and pyridyl moieties) has been reported. For certain dendron/dendrimer concentrations and structures, well-dispersible, multi-core, flower-like crystals are formed which display ferrimagnetic-like behavior. It is noteworthy that the least complex second generation polyphenylenepyridyl dendrons with a carboxyl focal group already allow formation of flower-like crystals. Magnetically recoverable catalysts were obtained via Pd NP formation in the dendron/dendrimer shells of magnetite NP and tested in selective hydrogenation of dimethylethynylcarbinol to dimethylvinylcarbinol. Dependences of catalytic activity and selectivity on the dendron/dendrimer generation and structure, type of Pd species, and Pd NP size have been demonstrated. High selectivity and activity of these catalysts along with easy catalyst recovery and successful repeated use make them promising in catalytic hydrogenation.
- Yuzik-Klimova,Kuchkina,Sorokina,Morgan,Boris,Nikoshvili,Lyubimova,Matveeva,Sulman,Stein,Mahmoud,Al-Ghamdi,Kostopoulou,Lappas,Shifrina,Bronstein
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- Ligand ordering determines the catalytic response of hybrid palladium nanoparticles in hydrogenation
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Supported palladium nanoparticles, prepared by reducing the active metal in the presence of the hexadecyl(2-hydroxyethyl)dimethylammonium dihydrogen-phosphate (HHDMA) ligand and depositing the resulting colloids on titanium silicate (TiSi2O6), represent a proven alternative to the archetypal poisoned catalysts in industrially-relevant selective hydrogenations. To date, a key aspect in the design of these hybrid nanocatalysts remains unaddressed, namely the impact of the ligand content on the catalytic behaviour. In order to assess the structural and associated catalytic implications of this variable, we have prepared a series of Pd-HHDMA/TiSi2O6 catalysts with different HHDMA content (0.3-16.8 wt%), keeping the average particle size (5 nm) and Pd content (0.3 wt%) constant. The materials are characterised with a toolbox of methods, including advanced microscopy and solid-state nuclear magnetic resonance, in order to assess the structure metal-ligand interface and the mobility of the alkyl chain. Continuous-flow three-phase hydrogenations of short-chain acetylenic compounds, nitriles, and carbonyls reveal an increase in the catalytic activity with the ligand content. Density Functional Theory indicates that the ligand behaves as a self-assembled monolayer, changing its adsorption configuration as a function of the HHDMA concentration. At low coverage, the organic layer lies almost flat on the surface of the metal nanoparticle blocking a large number of metal sites and resembling a two-dimensional catalyst; high HHDMA coverages favour an extended three-dimensional configuration of the alkyl chain, and consequently a lower fraction of Pd sites are poisoned. These results provide new fundamental insights into the role of the ligand on the catalytic activity and can enable the design of hybrid nanocatalysts with optimised performance.
- Albani, Davide,Vilé, Gianvito,Mitchell, Sharon,Witte, Peter T.,Almora-Barrios, Neyvis,Verel, René,López, Núria,Pérez-Ramírez, Javier
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- Gas-Phase Protonation of Spiropentane. A Novel Entry into the C5H9+ Potential Energy Surface
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The structures, stabilities, and isomerization patterns of C5H9+ ions arising from the gas-phase protonation of spiropentane have been investigated by nuclear-decay, radiolytic, and FT-ICR techniques combined with ab initio calculations.The experimental and theoretical results are consistent with the initial formation of a corner-protonated spiropentane intermediate 17, whose lifetime in the gas phase exceeds 7E-9 s.This local C5H9+ minimum is separated from ca. 30 kcal mol-1 more stable cyclopentyl cation as well as from dimethylallyl open-chain isomers by significant energy barriers.Persistency of 17 in the gas phase does not find any correspondence in solution.Solvation and ion-pairing effects may explain the failure to detect C5H9+ structures retaining the spirobicyclic framework of spiropentane in the condensed phase.
- Cecchi, Patrizio,Pizzabiocca, Adriano,Renzi, Gabriele,Grandinetti, Felice,Sparapani, Cinzia,et al.
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- A novel one-pot conversion of allyl alcohols into primary allyl halides mediated by acetyl halide
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A new and simple method for the synthesis of the primary allyl chlorides and bromides 9-16 from the secondary or tertiary allyl alcohols 3-8 and acyl halide was developed (Scheme 2, Table 1). Non-commercially available secondary and tertiary allyl alcohols were synthesized from the related ketones and aldehydes via the addition of vinylmagnesium chloride. Mechanistic studies indicate that the alcohols were first acetylated by the acetyl halide and then protonated prior to substitution by the halide, Cl- or Br -, via an 5N2′ reaction, to yield the primary halides (Scheme 5).
- Kishali, Nurhan,Polat, M. Fatih,Altundas, Ramazan,Kara, Yunus
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- Atom-by-Atom Resolution of Structure–Function Relations over Low-Nuclearity Metal Catalysts
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Controlling the structure sensitivity of catalyzed reactions over metals is central to developing atom-efficient chemical processes. Approaching the minimum ensemble size, the properties enter a non-scalable regime in which each atom counts. Almost all trends in this ultra-small frontier derive from surface science approaches using model systems, because of both synthetic and analytical challenges. Exploiting the unique coordination chemistry of carbon nitride, we discriminate through experiments and simulations the interplay between the geometry, electronic structure, and reactivity of palladium atoms, dimers, and trimers. Catalytic tests evidence application-dependent requirements of the active ensemble. In the semi-hydrogenation of alkynes, the nuclearity primarily impacts activity, whereas the selectivity and stability are affected in Suzuki coupling. This powerful approach will provide practical insights into the design of heterogeneous catalysts comprising well-defined numbers of atoms.
- Vorobyeva, Evgeniya,Fako, Edvin,Chen, Zupeng,Collins, Sean M.,Johnstone, Duncan,Midgley, Paul A.,Hauert, Roland,Safonova, Olga V.,Vilé, Gianvito,López, Núria,Mitchell, Sharon,Pérez-Ramírez, Javier
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- Hydrophobic periphery tails of polyphenylenepyridyl dendrons control nanoparticle formation and catalytic properties
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(Figure Presented) Here we report control of iron oxide and palladium nanoparticle (NP) formation via stabilization with polyphenylenepyridyl dendrons of the second and third generations with dodecyl periphery. These nanomaterials are developed as magnetically recoverable catalysts. To accurately assess the influence of the dodecyl exterior for the same dendron generation, we also designed a second generation dendron with partial dodecyl periphery. For all dendrons studied, the multicore iron oxide mesocrystals were formed, the sizes and morphology of which were controlled by the dendron generation. Analysis of the static and dynamic magnetic properties, in combination with transmission electron microscopy observations, demonstrate that magnetism is sensitive on the structure-directing capabilities of the type of the dendron which was employed for the mesocrystal stabilization. Close proximity of single cores in such multicore mesocrystals promotes the coupling of the neighboring magnetic moments, thus boosting their magnetization and allowing easy crossover between superparamagnetic and ferrimagnetic behaviors at room temperature. The particularly dramatic role of the dendron structure was also witnessed via the Pd NP formation, which was found to depend on both the dendron generation and its dodecyl periphery. In the case of the catalyst based on the second generation dendron with full dodecyl periphery, no Pd NPs were observed by TEM indicating that these species are of a subnanometer size and are not visible on or near the iron oxide NPs. For the catalyst based on the second generation dendron with partial dodecyl periphery, hydrogen reduction leads to much larger Pd NPs (2.7 nm) due to an unimpeded exchange of Pd species between dendrons and nondense dendron coating with asymmetrical dendrons. The third generation dendron with full dodecyl periphery allows nearly monodisperse 1.2 nm Pd NPs in the shells of iron oxide mesocrystals and the best catalytic properties in selective hydrogenation of dimethylethynylcarbinol. This study suggests a robust approach to control NP formation in magnetically recoverable catalysts for a wide variety of catalytic reactions using dendrons combining rigidity and flexibility in one molecule.
- Kuchkina, Nina V.,Morgan, David Gene,Kostopoulou, Athanasia,Lappas, Alexandros,Brintakis, Konstantinos,Boris, Bethany S.,Yuzik-Klimova, Ekaterina Yu.,Stein, Barry D.,Svergun, Dmitri I.,Spilotros, Alessandro,Sulman, Mikhaill G.,Nikoshvili, Linda Zh.,Sulman, Esther M.,Shifrina, Zinaida B.,Bronstein, Lyudmila M.
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- Stabilization of Pd3?xIn1+x Polymorphs with Pd-like Crystal Structure and their Superior Performance as Catalysts for Semi-Hydrogenation of Alkynes
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Selective hydrogenation (semi-hydrogenation) reactions of alkynes rely on Pd-based catalysts to provide the correct pathway to favour formation of double bonds and avoid full hydrogenation to single bonds. Here, we present the preparation and characterisation of “Pd3In”/TiO2 nanocatalysts, which show improved activity and selectivity compared to pure Pd catalysts, towards the liquid phase semi-hydrogenation of 2-methyl-3-butyn-2-ol (MBY) to 2-methyl-3-buten-2-ol (MBE), a fundamental step in the preparation of pharmaceuticals, and other industrially produced substances, as well as a model reaction for the semi-hydrogenation of alkynes. For both the supported and unsupported “Pd3In” alloys (later re-defined as Pd3?xIn1+x), we stabilised two new cubic polymorphs with a Pd-like structure, instead of the tetragonal structure as reported so far in the literature. The stabilisation of these new polymorphs was made possible by using a solution-based synthesis and, thanks to the use of different solvents, the reaction was carried out at different temperatures and the Pd/In ratio could be tuned. The same synthetic approach was adapted to prepare two “Pd3In”/TiO2 catalysts by adding the TiO2 support to the reaction mixture, in a practical one-step, one-pot reaction. HREM and X-Ray maps show that the cubic crystal structure of “Pd3In” is maintained when prepared in the presence of the support, however, the support seems to influence the Pd/In ratio.
- Johnston, Shaun K.,Bryant, Thomas A.,Strong, Jonathan,Lazzarini, Laura,Ibhadon, Alex O.,Francesconi, Maria Grazia
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- Selective hydrogenation of 2-methyl-3-butyne-2-ol in a wall-coated capillary microreactor with a Pd25Zn75/TiO2 catalyst
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Continuous flow capillary microreactors with embedded monometallic (Pd) or bimetallic (Pd25Zn75) catalysts have been tested in the selective hydrogenation of alkyne reagents. The catalysts were prepared in two steps. At first, polymer- stabilized metal nanoparticles (either Pd or Pd 25Zn75) were prepared by the reduction by solvent method. Then, a solution of colloidal nanoparticles with a desired concentration was added into a titania sol, which was destabilized by solvent evaporation during dip-coating of the inner wall of a fused silica capillary with an internal diameter of 250 μm. The wall-coated microreactors were tested in the hydroge- nation of 2-methyl-3-butyne-2-ol (0.011-0.45 M solution in methanol) in the 328-337 K temperature range. The highest selectivity towards the alkene product of 90% was obtained at 99.9% conversion on the Pd25Zn 75/TiO2 catalyst. The selectivity was further increased to 97% by addition of pyridine into the reactant solution. No deactivation of the wall-coated catalysts was observed during one month of continuous operation at 333 K.
- Rebrov, Evgeny V.,Klinger, Ekaterina A.,Berenguer-Murcia, Angel,Sulman, Esther M.,Schouten, Jaap C.
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- Preparation of semi-hydrogenation catalysts by embedding Pd in layered double hydroxides nanocages via sacrificial template of ZIF-67
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In this work a Pd/Fe-Co-Ni layered double hydroxide (LDH) composite was prepared and investigated in the semi-hydrogenation of 2-methyl-3-butyn-2-ol (MBY). Hollow nanocages of ternary Fe-Co-Ni LDH were constructed by stacking the LDH nanosheets edge-to-face which inherited the rhombic dodecahedral structure of ZIF-67 templates. Uniform palladium (Pd) nanocrystals with cubic shapes were imbedded in the LDH nanocages via a solvothermal method. The hydroxyl groups on LDH supports were critical to inhibit the association of excess hydrogen atoms on the catalyst, so less MBY molecules were converted to 2-methyl-2-butanol (MBA) during the hydrogenation catalysis. Under optimized reaction conditions the hydrogenation activity of Pd/Fe-Co-Ni LDH was significantly improved, and the conversion of MBY was higher than 99% with selectivity of 2-methyl-3-buten-2-ol (MBE) exceeding 99%. The catalyst was easily recovered and had little reduction in catalytic performance during the cycling reactions.
- Li, Lina,Li, Wenqing,Miao, Shiding,Wang, Jian,Wang, Ziyan,Wei, Cundi,Zhang, Peiping,Zhang, Peng,Zhang, Yan
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- PdPt Alloy Nanocatalysts Supported on TiO2: Maneuvering Metal–Hydrogen Interactions for Light-Driven and Water-Donating Selective Alkyne Semihydrogenation
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Low power consumption and minimal potential hazards are ultimate goals for the modern development of chemical manufact? however, it often reduces the selectivity of chemical reactions by implementing a new reaction system. A nanocatalyst design is reported for achieving efficient and selective alkyne semihydrogenation through the photocatalytic hydrogen transfer from water, which avoids the use of a heat source and explosive H2. The PdPt catalytic sites that are implemented on the TiO2 photocatalyst hold the key to achieving both high activity and selectivity. As compared with pure Pd or Pt, the alloy cocatalysts can better harness H diffusion/desorption for selective semihydrogenation as well as suppress competitive H2 evolution. This work opens up new possibilities for green and selective alkyne semihydrogenation and highlights the importance of lattice engineering to catalytic selectivity.
- Li, Mengqiao,Zhang, Ning,Long, Ran,Ye, Wei,Wang, Chengming,Xiong, Yujie
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- Capillary microreactor with a catalytic coating based on mesoporous titanium dioxide for the selective hydrogenation of 2-methyl-3-butyn-2-ol
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A continuously working capillary microreactor with a catalytic coating based on mesoporous titanium dioxide with embedded Pd nanoparticles was tested in a reaction of the selective hydrogenation of 2-methyl-3-butyn-2-ol (MBI). The catalytic coatings were obtained by the supporting of a carrier sol, which contained colloidal Pd nanoparticles, onto the internal wall of a quartz capillary with a diameter of 250 μm in the dynamic mode. The effects of the concentration of MBI in methanol (0.05–0.2 mol/L), the partial pressure of hydrogen (0.28–1.0 atm), and the reaction temperature (308–333 K) on the catalyst activity and the selectivity of reaction were studied. High selectivity for the formation of the semi-hydrogenated product 2-methyl-3-buten-2-ol was reached at 313 K in an atmosphere of pure hydrogen. At a conversion of 99.9%, the selectivity was 92.3%, which is 15.5% higher than that in a batch reactor. The rate of hydrogenation on the Pd/TiO2 coating was higher by one order of magnitude than that on a commercial Lindlar catalyst. The coating remained stable upon the continuous passage of the flow of a reaction mixture for 500 h.
- Okhlopkova,Kerzhentsev,Ismagilov
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- Pd3Sn nanoparticles on TiO2 and ZnO supports as catalysts for semi-hydrogenation: Synthesis and catalytic performance
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The two catalysts Pd3Sn/TiO2 and Pd3Sn/ZnO were prepared via a one-pot procedure based on the “polyol method” with the addition of a capping agent (polyvinylpyrrolidone) to control the particle size distribution. The same procedure was used to prepare Pd/TiO2 and Pd/ZnO for comparison. All four catalysts showed high activity and selectivity for the selective hydrogenation of 2-methyl-3-butyn-2-ol (MBY) to 2-methyl-3-buten-2-ol (MBE) in the liquid phase under identical conditions. However, Pd3Sn/TiO2 and Pd3Sn/ZnO show selectivities to alkene significantly higher than that of the Pd catalysts. Specifically, the selectivity increases from 96.4% to 97.4% on TiO2 support, and 96.2% to 97.6% on ZnO support, at 90% conversion. Transition electron microscopy shows nanoparticles evenly dispersed on the support, with mean particle sizes as low as 4.1 (±0.8) nm when Sn is incorporated into the catalyst. Unsupported Pd3Sn was prepared using the same method and characterised by powder X-Ray diffraction followed by the Rietveld refinement. Pd3Sn was found to be single-phase and isostructural to Pd metal with a face centred cubic unit cell.
- Johnston, Shaun K.,Cherkasov, Nikolay,Pérez-Barrado, Elena,Aho, Atte,Murzin, Dmitry Y.,Ibhadon, Alex O.,Francesconi, M. Grazia
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- Coating the Internal Surface of a Capillary Microreactor for the Selective Hydrogenation of 2-Methyl-3-Butyn-2-ol by PdxZn1 – x/TiO2 Catalysts: A Kinetic Study
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The kinetics of the liquid-phase hydrogenation of 2-methyl-3-butyn-2-ol (MBI) on the thin films of Pd50Zn50/TiO2, Pd80Zn20/TiO2, and Pd/TiO2 was studied in a temperature range of 308–333 K at MBI concentrations of 0.1–0.6 mol/L. The films were applied to the internal walls of silica capillaries with an inside diameter of 530 μm. The reaction of MBI hydrogenation at its initial stage was of first order with respect to hydrogen, and the orders of reaction with respect to MBI on Pd50Zn50/TiO2, Pd80Zn20/TiO2, and Pd/TiO2 were 0.3, 0.4, and 0.5, respectively. The yield of the target product 2-methyl-3-buten-2-ol on the bimetallic films was higher than that on Pd/TiO2. The highest yield (94%) was achieved on the film of Pd50Zn50/TiO2 at a conversion of 99%, a temperature of 313 K, and a partial hydrogen pressure of 1 atm. The higher selectivity of the reaction, which occurred according to the Langmuir–Hinshelwood mechanism, on the bimetallic films was explained by a decrease in the alkene/alkyne and alkene/alkane ratios of adsorption constants and by a decrease in the rate constants of 2-methyl-3-buten-2-ol hydrogenation.
- Okhlopkova,Kerzhentsev,Ismagilov
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- Tuning the catalytic performance for the semi-hydrogenation of alkynols by selectively poisoning the active sites of Pd catalysts
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Semi-hydrogenation of alkynols to alkenols with Pd-based catalysts is of great significance in fine chemical industries. Industrial Lindlar catalysts, employing Pb to modify the Pd nanoparticles for higher selectivity toward alkenols, however, generally suffer from both a severe activity decrease and environment pollution caused by using heavy metal Pb and additives. Therefore, how to overcome the selectivity-activity paradox remains a great challenge in industry. Here, we report a controllable strategy for the synthesis of semi-hydrogenation catalysts, which successfully improves the catalytic performance through selectively poisoning the edge and corner sites of Pd nanoparticles. When the integrity of the crystal face is reserved, both higher activity (～1340 h-1) and selectivity (～95% at 99% conversion) are achieved in the semi-hydrogenation of 2-methyl-3-butyn-2-ol (MBY) in ethanol, an industrially important intermediate product for the synthesis of vitamin E, without adding any toxic additives. What's more, the yield could exceed 98% at 99% conversion under no solvent and organic adsorbate conditions, which had never been achieved before. This work provides a different perspective to design and develop high performance catalysts for semi-hydrogenation of alkenols or even substituted alkynes.
- Mao, Shanjun,Zhao, Bowen,Wang, Zhe,Gong, Yutong,Lü, Guofeng,Ma, Xiao,Yu, Lili,Wang, Yong
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- Development, Synthesis, and Study of Nanomaterials of Titania Doped by Zirconium for Selective Hydrogenation of 2-Methyl-3-Butyn-2-ol in a Microcapillary Reactor
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Abstract: An ordered mesoporous titanium–zirconium TixZr1–xO2 matrix for introducing catalytic nanoparticles was synthesized by self-assembly using titanium isopropoxide and zirconium oxychloride as precursors and amphiphilic triblock copolymer F127 as a template. The process of self-assembly occurs without the addition of an acid to preserve the morphology and structure of the catalytic nanoparticles. When controlling the initial molar ratios of the copolymer to metal precursors, titanium–zirconium nanocomposites with controlled texture and composition were obtained in a wide range of titania content, from 15 to 80 mol % TiO2. The structural and phase properties of the composites were studied by X-ray diffraction, low-temperature nitrogen adsorption, and transmission electron microscopy. Composites have an ordered mesoporous structure, a high specific surface area, a large pore volume, and a uniform pore size distribution. Catalytic coatings of 1 wt % Pd–Zn/TixZr1–xO2 (x = 1.0, 0.8, 0.5) on the inner surface of a capillary reactor were prepared by the dip-coating method using a colloidal solution of Pd–Zn nanoparticles. The developed catalytic coatings based on titanium–zirconium composites exhibit high activity and selectivity (> 96%) in the hydrogenation of 2-methyl-3-butyn-2-ol.
- Okhlopkova,Kerzhentsev,Ismagilov
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- Tailoring Nitrogen-Doped Carbons as Hosts for Single-Atom Catalysts
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The application of nitrogen-doped carbons (NDCs) as host materials for single-atom catalysts (SACs) is increasing because of the strong binding affinity of the heteroatom with transition metals. Establishment of the relation between the properties of NDCs, their interaction with metals, and the performance of the resulting catalysts is crucial to guide the design of more effective SACs but has not been critically addressed. Here, a series of NDCs is prepared and studied as hosts for palladium atoms. The amount of nitrogen incorporated primarily depends on the choice of carbon followed by the doping temperature and nitrogen source. Pyridinic and pyrrolic species predominate in all cases, especially at lower doping temperatures. The stabilization of palladium atoms is successful above a critical nitrogen content that depends on the carbon type. Evaluation in the catalytic semi-hydrogenation of 2-methyl-3-butyn-2-ol readily distinguishes the reactivity of single atoms and nanoparticles, which correlates with the electronic properties of palladium described by the average oxidation state. Comparison with SACs based on compositionally-related carbon nitride hosts shows that similarly high stability and tunability of the metal is achievable over NDCs, despite their lower nitrogen contents and greater heterogeneity of coordination sites.
- Büchele, Simon,Chen, Zupeng,Mitchell, Sharon,Hauert, Roland,Krumeich, Frank,Pérez-Ramírez, Javier
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- Selective hydrogenation of 2-methyl-3-butyn-2-ol over Pd-nanoparticles stabilized in hypercrosslinked polystyrene: Solvent effect
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Selective hydrogenation of 2-methyl-3-butyn-2-ol (MBY) to 2-methyl-3-butene-2-ol (MBE) over Pd supported on hypercrosslinked polystyrene was studied in polar (ethanol, isopropanol, water) and non-polar (cyclohexane, toluene, octane, hexane, heptane and m-xylene) solvents. The catalytic activity and selectivity were found to be strongly affected by solvent properties such as dipole moment and dielectric constant, but cannot be explained by solvent polarity only. Hydrogen solubility and solvent-catalyst interaction also influential factors. The catalyst activity decreases in the series: alcohols > cyclohexane > water/ethanol mixture > octane ≥ hexane ≥ xylene > toluene > heptane. The highest values of MBE selectivity of 99.6% and 98.7% at 95% MBY conversion were obtained in toluene and in ethanol, respectively.
- Nikoshvili, Linda,Shimanskaya, Elena,Bykov, Alexey,Yuranov, Igor,Kiwi-Minsker, Lioubov,Sulman, Esther
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- Highly selective semi-hydrogenation of alkynes with a Pd nanocatalyst modified with sulfide-based solid-phase ligands
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Soluble small molecular/polymeric ligands are often used in Pd-catalyzed semi-hydrogenation of alkynes as an efficient strategy to improve the selectivity of targeted alkene products. The use of soluble ligands requires their thorough removal from the reaction products, which adds significant extra costs. In the paper, commercially available, inexpensive, metallic sulfide-based solid-phase ligands (SPL8-4 and SPL8-6) are demonstrated as simple yet high-performance insoluble ligands for a heterogeneous Pd nanocatalyst (Pd@CaCO3) toward the semi-hydrogenation of alkynes. Based on the reactions with a range of terminal and internal alkyne substrates, the use of the solid-phase ligands has been shown to markedly enhance the selectivity of the desired alkene products by efficiently suppressing over-hydrogenation and isomerization side reactions, even during the long extension of the reactions following full substrate conversion. A proper increase in the dosage or a reduction in the average size of the solid-phase ligands enhances such effects. With their insoluble nature, the solid-phase ligands have the distinct advantage in their simple, convenient recycling and reuse while without contaminating the products. A ten-cycle reusability test with the SPL8-4/Pd@CaCO3 catalyst system confirms its well-maintained activity and selectivity over repeated uses. A mechanistic study with x-ray photoelectron spectroscopy indicates that the solid-phase ligands have electronic interactions with Pd in the supported catalyst, contributing to inhibit the binding and further reaction of the alkene products. This is the first demonstration of solid-phase ligands for highly selective semi-hydrogenation of alkynes, which show strong promise for commercial applications.
- Huang, Lingqi,Hu, Kecheng,Ye, Ganggang,Ye, Zhibin
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- Reasons for the Inverse Dependence of the Turnover Frequency of Hydrogenation of Unsaturated Compounds on Palladium Catalyst Concentration
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Abstract: The hypotheses about reasons for the inverse dependence of the turnover frequency of hydrogenation of unsaturated compounds (alkyne, alkynol, olefin) on the catalyst concentration were discriminated by kinetic methods combined with electron microscopy. The reasons are: dissociation of polycrystalline Pd–P particles, equilibrium shift (stabilized cluster–cluster + stabilizer), and aggregation–disaggregation of Pd–P particles, the latter being the main reason for the concentration range 0.125–1 mmol/L. The effect of aggregation–disaggregation of Pd–P particles on the catalyst activity differs depending on the substrate. The proposed kinetic model was shown to be consistent with the experimental data for styrene hydrogenation used as an example. The rate constants of some stages were determined.
- Skripov,Belykh,Sterenchuk,Levchenko,Schmidt
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p. 299 - 306
(2021/04/26)
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- Method for preparing allyl alcohol compound by reduction of propargyl alcohol compound
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A hydrazide compound is used as a reducing agent, an organic amine is used as an auxiliary, and the propargyl alcohol compound is selectively reduced to obtain an allyl alcohol compound under the presence of a solvent and a certain temperature. The method does not need Pd catalyst which is expensive, and the reducing agent and auxiliary agent are cheap and easily available, easy to separate, free of residue in the product, simple in reaction operation process, mild in reaction condition, high in target product selectivity and the like.
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Paragraph 0043-0056; 0065-0068
(2021/11/10)
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- Generation of Stable Isopentenyl Monophosphate Aryloxy Triester Phosphoramidates as Activators of Vγ9Vδ2 T Cells
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Aryloxy triester phosphoramidate prodrugs of the monophosphate derivatives of isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP) were synthesized as lipophilic derivatives that can improve cell uptake. Despite the structural similarity of IPP and DMAPP, it was noted that their phosphoramidate prodrugs exhibited distinct stability profiles in aqueous environments, which we show is due to the position of the allyl bond in the backbones of the IPP and DMAPP monophosphates. As the IPP monophosphate aryloxy triester phosphoramidates showed favorable stability, they were subsequently investigated for their ability to activate Vγ9/Vδ2 T cells and they showed promising activation of this subset of T cells. Together, these findings represent the first report of IPP and DMAPP monophosphate prodrugs and the ability of IPP aryloxy triester phosphoramidate prodrugs to activate Vγ9/Vδ2 T cells highlighting their potential as possible immunotherapeutics.
- Xu, Qin,Taher, Taher E.,Ashby, Elizabeth,Sharif, Maria,Willcox, Benjamin E.,Mehellou, Youcef
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p. 2375 - 2380
(2021/05/26)
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- Novel nickel nanoparticles stabilized by imidazolium-amidinate ligands for selective hydrogenation of alkynes
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The main challenge in the hydrogenation of alkynes into (E)- or (Z)-alkenes is to control the selective formation of the alkene, avoiding the over-reduction to the corresponding alkane. In addition, the preparation of recoverable and reusable catalysts is of high interest. In this work, we report novel nickel nanoparticles (Ni NPs) stabilized by three different imidazolium-amidinate ligands (ICy·(Ar)NCN; L1: Ar = p-tol, L2: Ar = p-anisyl and L3: Ar = p-ClC6H4). The as-prepared Ni NPs were fully characterized by (HR)-TEM, XRD, WASX, XPS and VSM. The nanocatalysts are active in the hydrogenation of various substrates. They present a remarkable selectivity in the hydrogenation of alkynes towards (Z)-alkenes, particularly in the hydrogenation of 3-hexyne into (Z)-3-hexene under mild reaction conditions (room temperature, 3% mol Ni and 1 bar H2). The catalytic behaviour of Ni NPs was influenced by the electron donor/acceptor groups (-Me, -OMe, -Cl) in the N-aryl substituents of the amidinate moiety of the ligands. Due to the magnetic character of the Ni NPs, recycling experiments were successfully performed after decantation in the presence of an external magnet, which allowed us to recover and reuse these catalysts at least 3 times preserving both activity and chemoselectivity.
- López-Vinasco, Angela M.,Martínez-Prieto, Luis M.,Asensio, Juan M.,Lecante, Pierre,Chaudret, Bruno,Cámpora, Juan,Van Leeuwen, Piet W. N. M.
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p. 342 - 350
(2020/02/04)
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- Creation of Redox-Active PdSx Nanoparticles Inside the Defect Pores of MOF UiO-66 with Unique Semihydrogenation Catalytic Properties
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Semihydrogenation of alkynes to produce alkenes is very important in the industry; however, over-hydrogenation heavily complicates the postprocesses, which are highly energy consuming and not environmentally friendly. One of the most efficient pathways to solve this challenging issue is to develop highly selective catalysts that could only hydrogenate alkynes and are inactive in hydrogenation of alkenes. This work presents herein an efficient catalyst, consisting of in situ created PdS0.53 nanoparticles as the redox-active sites inside the defect pores of metal–organic framework UiO-66, which demonstrates very high alkene selectivity (up to 99.5%) in semihydrogenation of easily over-hydrogenated terminal alkynes. In contrast to the traditional catalysts, strict control over the reaction time becomes the nonessential condition because the catalyst system is almost inactive in hydrogenation of alkenes. Therefore, this paradigm work provides a practically applicable pathway for the development of efficient catalysts with unique catalytic properties for selective semihydrogenation reactions.
- Dong, Ming-Jie,Wang, Xuan,Wu, Chuan-De
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- Fast and Selective Semihydrogenation of Alkynes by Palladium Nanoparticles Sandwiched in Metal–Organic Frameworks
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The semihydrogenation of alkynes into alkenes rather than alkanes is of great importance in the chemical industry. Unfortunately, state-of-the-art heterogeneous catalysts hardly achieve high turnover frequencies (TOFs) simultaneously with almost full conversion, excellent selectivity, and good stability. Here, we used metal–organic frameworks (MOFs) containing Zr metal nodes (“UiO”) with tunable wettability and electron-withdrawing ability as activity accelerators for the semihydrogenation of alkynes catalyzed by sandwiched palladium nanoparticles (Pd NPs). Impressively, the porous hydrophobic UiO support not only leads to an enrichment of phenylacetylene around the Pd NPs but also renders the Pd surfaces more electron-deficient, which leads to a remarkable catalysis performance, including an exceptionally high TOF of 13835 h?1, 100 % phenylacetylene conversion 93.1 % selectivity towards styrene, and no activity decay after successive catalytic cycles. The strategy of using molecularly tailored supports is universal for boosting the selective semihydrogenation of various terminal and internal alkynes.
- Choe, Kwanghak,Li, Guodong,Qiu, Xueying,Ri, Myonghak,Shi, Xinghua,Tang, Zhiyong,Wang, Hui,Wang, Yinglong,Xue, Guangxin,Yuan, Yi,Zhao, Wenshi,Zheng, Fengbin
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supporting information
p. 3650 - 3657
(2020/02/04)
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- Production method of 2-methyl-3-buten-2-ol
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The invention relates to a production method of 2-methyl-3-buten-2-ol. The production method comprises the following steps that: isoprene is used as a raw material, and hydrogen chloride is selectively added to obtain 3-methyl-3-chlorobutene; then the 3-methyl-3-chlorobutene is esterified with carboxylate under the action of a catalyst; and then hydrolysis is performed to obtain 2-methyl-3-buten-2-ol. Under reaction conditions of the method, a byproduct 1-chloroisopentene is prevented from being generated in the process of adding hydrogen chloride into isoprene; and 3-methyl-3-chlorobutene adopts is subjected to esterification at first and then to hydrolysis, and a cuprous ion catalyst is synthesized in situ to catalyze a reaction, so the generation of a byproduct isopentenol ether is avoided. The method has the advantages of high selectivity, simple process, low separation cost and the like.
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Paragraph 0032-0036
(2020/06/09)
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- Hydroxypyridine ligand and preparation method and catalytic application thereof (by machine translation)
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The invention provides a hydroxypyridine ligand, a preparation method thereof and application, for catalyzing allyl alcohol isomerism, wherein the structural formula of the hydroxypyridine ligand is as follows : One or more, R wherein, R represents the substituent C1 - C20 selected from, alkyl, phenyl, naphthyl, heteroaryl, methoxy, fluoro, chloro, bromo, trifluoromethyl, methoxycarbonyl, amine has a higher catalytic activity, than that of a ligand 2 - such as an amine alcohol α, ω - hydroxyquinoline reported in the known literature and having a double-tooth chelating effect, and a metal tungsten bonding capability. The present invention provides, a; ligand 1,3 - and a, dihalide coupling, which can be rapidly, efficiently obtained . The, ligand has, a higher catalytic activity than the, metal tungsten bonding capability. (by machine translation)
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Paragraph 0083-0085
(2020/05/11)
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- An α-Cyclopropanation of Carbonyl Derivatives by Oxidative Umpolung
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The reactivity of iodine(III) reagents towards nucleophiles is often associated with umpolung and cationic mechanisms. Herein, we report a general process converting a range of ketone derivatives into α-cyclopropanated ketones by oxidative umpolung. Mechanistic investigation and careful characterization of side products revealed that the reaction follows an unexpected pathway and suggests the intermediacy of non-classical carbocations.
- Bauer, Adriano,Di Mauro, Giovanni,Li, Jing,Maulide, Nuno
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supporting information
p. 18208 - 18212
(2020/08/21)
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- Ensemble Design in Nickel Phosphide Catalysts for Alkyne Semi-Hydrogenation
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Modification of transition metals with p-block elements is known to be effective to tune the ensemble characteristics of catalysts for the semi-hydrogenation of alkynes. To further explore this approach, here we prepare two nickel phosphides, namely Ni2P and Ni5P4. Assessment in the semi-hydrogenation of 1-hexyne and 2-methyl-3-butyn-2-ol shows that the phosphides present higher rate and selectivity than unmodified nickel catalysts. While no activity and selectivity differences are displayed in the semi-hydrogenation of 1-hexyne over Ni2P and Ni5P4, in the case of 2-methyl-3-butyn-2-ol a higher rate and lower selectivity to 2-methyl-3-buten-2-ol are observed over Ni2P. Density functional theory reveals that the hydroxyl group facilitates the reaction, but also increases the barrier for product desorption. Detailed analyses of the ensemble show the potential of phosphorus to create spatially-isolated nickel trimers that surpass the performance of unmodified nickel, but also its limited ability to modulate the electronic properties and related binding energies of organic intermediates, which is key to preventing undesired side reactions.
- Albani, Davide,Karajovic, Konstantin,Tata, Bharath,Li, Qiang,Mitchell, Sharon,López, Núria,Pérez-Ramírez, Javier
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p. 457 - 464
(2018/11/27)
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- METHOD FOR PRODUCING CONJUGATED DIENE
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Provided is a method of producing a conjugated diene, including a step of dehydrating a γ,δ-unsaturated alcohol in the presence of a solid acid catalyst having a Hammett acidity function (H0) of ?12.2 or less.
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Paragraph 0058-0059
(2019/05/18)
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- Additive-modulated switchable reaction pathway in the addition of alkynes with organosilanes catalyzed by supported Pd nanoparticles: Hydrosilylation: versus semihydrogenation
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We herein report supported Pd nanoparticles on N,O-doped hierarchical porous carbon as a single operation catalyst-enabled additive-modulated reaction pathway for alkynes addition with organosilanes between hydrosilyation and semihydrogenation. In the case of alkynes hydrosilylation, a simple iodide ion as an additive has a promotion effect on the activity and regio- and stereoselectivity, where iodide can coordinate with Pd NPs via strong δ donation to increase the electron density of the Pd atom, resulting in an increased ability for the oxidative addition of hydrosilane as the rate-determining step to make the reaction proceed efficiently to afford vinylsilanes in high yields with excellent regio- and stereoselectivity. For the catalytic transfer semihydrogenation of alkynes, water was introduced to mix with organosilane to form a silanol together with the generation of hydrogen atoms on the Pd NPs surface or the liberation of H2 gas as a reducing agent, whereby the quantitative reduction of alkynes was achieved with exclusive selectivity to alkenes. In both cases, the catalyst could be recycled several times without a significant loss in activity or selectivity. A broad range of alkyl and aryl alkynes with various functional groups are compatible with the reaction conditions. The role the additive exerted in each reaction was extensively investigated through control experiments as well as the kinetic isotopic effect along with spectroscopic characterization. In addition, the respective mechanism operating in both reactions was proposed.
- Duan, Yanan,Ji, Guijie,Zhang, Shaochun,Chen, Xiufang,Yang, Yong
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p. 1039 - 1050
(2018/03/05)
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- IMPROVED PROCESS TO DEPOSIT PD- NANOPARTICLES
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The present invention relates to an improved process to prepare and deposit Pd-nanoparticles onto a metal oxide.
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Page/Page column 5-6
(2018/11/26)
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- METAL POWDERDOUS CATALYST FOR HYDROGENATION PROCESSES
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The present invention is related to a new metal powder catalytic system (catalyst), its production and its use in hydrogenation processes.
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Page/Page column 17-20
(2018/12/03)
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- Unconventional Pd@Sulfonated Silica Monoliths Catalysts for Selective Partial Hydrogenation Reactions under Continuous Flow
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Doubly functionalized, hierarchical-porosity silica monoliths were synthesized by postgrafting of sulfonic groups and in situ growth of Pd nanoparticles in that order. PdNP of 3.1 nm size located in the mesopores of the material showed to be evenly distributed within 4.6 % wt Pd monoliths. The system was explored in the continuous-flow, catalytic partial hydrogenation reaction of 3-halogeno-nitrobenzenes and 3-hexyn-1-ol in the liquid phase, showing remarkable conversion, selectivity, and resistance under very mild conditions.
- Liguori, Francesca,Barbaro, Pierluigi,Said, Bilel,Galarneau, Anne,Santo, Vladimiro Dal,Passaglia, Elisa,Feis, Alessandro
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p. 3245 - 3258
(2017/08/29)
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- PdNP@Titanate Nanotubes as Effective Catalyst for Continuous-Flow Partial Hydrogenation Reactions
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Pd nanoparticles were easily immobilized onto titanate nanotubes by a straightforward procedure. The material (0.50 wt % Pd) was used as catalyst in the continuous-flow, liquid-phase hydrogenation reaction of unsaturated C-C bonds and it showed excellent performance and durability under very mild conditions (room temperature, 1-2 bar H2, residence time 13-36 s). In particular, very high productivity was obtained in the synthesis of the perfumery component cis-3-hexen-1-ol (40.6 mol gPd-1 h-1) without additives or metal contamination, with clear benefits in terms of process economy and environmental impact compared with conventional catalysts. The catalyst performance is discussed in the light of comparable systems.
- Linares, Noemi,Moreno-Marrodan, Carmen,Barbaro, Pierluigi
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p. 1001 - 1011
(2016/03/15)
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- Device useful for hydrogenation reactions (I)
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The present invention relates to a device for treatment of material transported through the device comprising at least one porous element consisting of specific solid metallic structure which allows cross-flow of the material through the porous element and wherein the porous element is coated by a non-acidic metal oxide which is impregnated by palladium (Pd).
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Page/Page column 9
(2016/08/10)
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- 3-methyl-3-buten-1-ol production method
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The invention relates to a 3-methyl-3-buten-1-ol production method and belongs to the technical field of water reducer synthesis. The method comprises that isoprene and hydrogen chloride as raw materials undergo an addition reaction to produce a mixture of 1-chloroisopentene and 3-chloroisopentene, the reaction product undergoes a hydrolysis reaction so that the chloroisopentene is transformed into methyl butenol and prenyl alcohol, and the hydrolysis products undergo an isomerization reaction to produce a finished product. The method is used for 3-methyl-3-buten-1-ol synthesis and has the advantages of simple processes, abundant raw material sources, low production cost and high reaction yield.
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Paragraph 0029; 0038; 0031; 0042; 0044
(2016/12/16)
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- PD ON BOEHMITE CATALYTIC SYSTEM FOR SELECTIVE HYDROGENATION OF TRIPLE BONDS
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The present invention relates to a new catalytic system, furthermore it relates to processes of producing such catalytic systems as well as their use in selective hydrogenations of C-C triple bonds to C-C double bonds.
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Page/Page column 16
(2015/04/15)
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- Structured catalyst
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The present invention relates to novel structured catalysts based on sintered metal fibers (SMF) coated by a basic oxide layer with Pd-nanoparticles, to reactions of organic compounds with hydrogen in the presence of said catalyst and an organic base as well as to vitamins, carotinoids, perfume ingredients, and/or food or feed ingredients prepared by using this reaction.
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Page/Page column 9
(2015/09/22)
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- Kinetic study of selective hydrogenation of 2-methyl-3-butyn-2-ol over Pd-containing hypercrosslinked polystyrene
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Kinetics of the selective hydrogenation of 2-methyl-3-butyn-2-ol (MBY) to 2-methyl-3-buten-2-ol (MBE) over Pd supported on hypercrosslinked polystyrene bearing amino-groups was studied at variation of the MBY-to-Pd ratio and reaction temperature. For the catalyst, containing 0.7?wt.% of Pd, optimal reaction conditions were found providing >98% of the MBE selectivity at 95% of the MBY conversion. Kinetic modeling and temperature variations as well as studies of a hydrogen consumption rate allowed us to suggest that a thermodynamic factor is most likely responsible for the high MBE selectivity.
- Nikoshvili, Linda Zh.,Makarova, Alexandra S.,Lyubimova, Nadezhda A.,Bykov, Alexey V.,Sidorov, Alexander I.,Tyamina, Irina Yu.,Matveeva, Valentina G.,Sulman, Esther M.
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p. 231 - 240
(2016/09/02)
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- Selective hydrogenation of 2-methyl-3-butyn-2-ol over Pd-nanoparticles stabilized in hypercrosslinked polystyrene: Solvent effect
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Selective hydrogenation of 2-methyl-3-butyn-2-ol (MBY) to 2-methyl-3-butene-2-ol (MBE) over Pd supported on hypercrosslinked polystyrene was studied in polar (ethanol, isopropanol, water) and non-polar (cyclohexane, toluene, octane, hexane, heptane and m-xylene) solvents. The catalytic activity and selectivity were found to be strongly affected by solvent properties such as dipole moment and dielectric constant, but cannot be explained by solvent polarity only. Hydrogen solubility and solvent. catalyst interaction also influential factors. The catalyst activity decreases in the series: alcohols > cyclohexane > water/ethanol mixture > octane ≥ hexane ≥ xylene > toluene > heptane. The highest values of MBE selectivity of 99.6% and 98.7% at 95% MBY conversion were obtained in toluene and in ethanol, respectively.
- Nikoshvili, Linda,Shimanskaya, Elena,Bykov, Alexey,Yuranov, Igor,Kiwi-Minsker, Lioubov,Sulman, Esther
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p. 179 - 188
(2015/03/14)
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