821-09-0Relevant articles and documents
Phosphorus and nitrogen-doped palladium nanomaterials support on coral-like carbon materials as the catalyst for semi-hydrogenation of phenylacetylene and mechanism study
Ma, Lei,Jiang, Pengbo,Wang, Kaizhi,Lan, Kai,Huang, Xiaokang,Yang, Ming,Gong, Li,Jia, Qi,Mu, Xiao,Xiong, Yucong,Li, Rong
, (2021/02/26)
In this work, two types of polyporous and coral-like materials (CN) with high specific surface area are prepared using sodium glutamate as a carrier. At the same time, a CN-supported phosphorus-nitrogen-doped palladium nanomaterial CN-P-Pd is synthesized and applied to the preparation of styrene by selective hydrogenation of phenylacetylene under mild conditions. As shown in the TEM images, Pd nanoparticles with a particle size of about 4.4 nm are uniformly dispersed on the surface of the carrier. The results of N2 adsorption–desorption reveal that the surface area of the prepared catalyst (CN-P-Pd) is 1307 m2g?1. In addition, the experimental exploration shows the intervention of P in carbon-nitrogen materials can contribute to improve the selectivity of the reaction, which can be attributed to the fact that P element can change the electron density of Pd. Meanwhile, it is found that the solvent not only affects the activity of catalyst, but also the selectivity of the reaction. Kinetic study shows the activation energy of the reaction is 4.5 kJ/mol. With the increase of the reaction temperature, the dissolution rate of hydrogen in the solvent gradually slows down, which inhibits the progress of the reduction reaction. Mechanistic studies demonstrate that the carbon-nitrogen materials have strong adsorption capacity for substrates, and also provide more adsorption sites for phenylacetylene. Additionally, the optimal catalyst (CN-P-Pd) also has high reaction activity to other alkynes and the conversion can reach at 95%. Moreover, the optimal catalyst can be reused several times without significant reduction in reaction activity.
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 (2021/05/31)
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.
Effect of pretreatment conditions on acidity and dehydration activity of CeO2-MeOx catalysts
Cronauer, Donald C.,Góra-Marek, Kinga,Garcia, Richard,Gnanamani, Muthu Kumaran,Jacobs, Gary,Kropf, A. Jeremy,Marshall, Christopher L.
, (2020/07/10)
A series of MeOx-modified CeO2 (CeO2-MnOx, CeO2-ZnO, CeO2-MgO, CeO2-CaO, and CeO2-Na2O) catalysts were prepared by the impregnation of CeO2 with corresponding metal nitrates. Acidity and oxidation state of cerium were investigated on both oxidized and reduced catalysts by employing Fourier Transform Infrared spectroscopy (FTIR) on adsorbed pyridine and in situ H2-Temperature Programmed Reduction/X-ray Absorption Spectroscopy (H2-TPR/XAS) techniques, respectively. Metal oxide addition tended to alter both type and number of acid sites on ceria. EXAFS data showed a significant difference in NCe-O between unmodified and CeO2-MeOx, suggesting that added MeOx interferes with vacancy formation on ceria during reduction. In comparison with air-pretreated samples, H2-pretreated ones under similar conversion of 1,5 pentanediol exhibited a higher selectivity towards linear alcohols. Alcohol conversion found to correlate with total acidity (i.e., Br?nsted and Lewis). CeO2 benefited from the addition of alkali (Na) or alkaline earth metals (Mg, Ca) by producing unsaturated alcohols.
Chemoselective Electrochemical Hydrogenation of Ketones and Aldehydes with a Well-Defined Base-Metal Catalyst
Fokin, Igor,Siewert, Inke
, p. 14137 - 14143 (2020/10/12)
Hydrogenation reactions are fundamental functional group transformations in chemical synthesis. Here, we introduce an electrochemical method for the hydrogenation of ketones and aldehydes by in situ formation of a Mn-H species. We utilise protons and electric current as surrogate for H2 and a base-metal complex to form selectively the alcohols. The method is chemoselective for the hydrogenation of C=O bonds over C=C bonds. Mechanistic studies revealed initial 3 e? reduction of the catalyst forming the steady state species [Mn2(H?1L)(CO)6]?. Subsequently, we assume protonation, reduction and internal proton shift forming the hydride species. Finally, the transfer of the hydride and a proton to the ketone yields the alcohol and the steady state species is regenerated via reduction. The interplay of two manganese centres and the internal proton relay represent the key features for ketone and aldehyde reduction as the respective mononuclear complex and the complex without the proton relay are barely active.
An Annelated Mesoionic Carbene (MIC) Based Ru(II) Catalyst for Chemo- And Stereoselective Semihydrogenation of Internal and Terminal Alkynes
Bera, Jitendra K.,Choudhury, Joyanta,Das, Shubhajit,Dutta, Indranil,Pati, Swapan K.,Saha, Sayantani,Yadav, Suman
, p. 3212 - 3223 (2020/10/02)
The catalytic utility of [RuL1(CO)2I2] (1), containing an annelated π-conjugated imidazo-naphthyridine-based mesoionic carbene (MIC) ligand (L1), is evaluated for E-selective alkyne semihydrogenation. The precatalyst 1, in combination with 2 equiv of AgBArF, semihydrogenates a broad range of internal alkynes with molecular hydrogen (5 bar) in water. (E)-Alkenes are accessed in high yields, and a number of reducible functional groups are tolerated. A chelate MIC ligand and two cis carbonyls provide a well-defined platform at the Ru center for hydrogenation and isomerization. The loss of two iodides and the presence of two carbonyls render the Ru center electron deficient and thus the formation of metal vinylidenes with terminal alkynes is avoided. This is leveraged for the semihydrogenation of terminal alkynes by the same catalytic system in isopropyl alcohol. Reaction profile, isomerization, kinetic, and DFT studies reveal initial alkyne hydrogenation to a (Z)-alkene, which further isomerizes to an (E)-alkene via metal-catalyzed Z → E isomerization.
Fast and Selective Semihydrogenation of Alkynes by Palladium Nanoparticles Sandwiched in Metal–Organic Frameworks
Choe, Kwanghak,Li, Guodong,Qiu, Xueying,Ri, Myonghak,Shi, Xinghua,Tang, Zhiyong,Wang, Hui,Wang, Yinglong,Xue, Guangxin,Yuan, Yi,Zhao, Wenshi,Zheng, Fengbin
supporting information, p. 3650 - 3657 (2020/02/04)
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.
A General One-Pot Methodology for the Preparation of Mono- and Bimetallic Nanoparticles Supported on Carbon Nanotubes: Application in the Semi-hydrogenation of Alkynes and Acetylene
Lomelí-Rosales, Diego A.,Delgado, Jorge A.,Díaz de los Bernardos, Miriam,Pérez-Rodríguez, Sara,Gual, Aitor,Claver, Carmen,Godard, Cyril
supporting information, p. 8321 - 8331 (2019/06/04)
A facile and straightforward methodology for the preparation of monometallic (copper and palladium) and bimetallic nanocatalysts (NiCu and PdCu) stabilized by a N-heterocyclic carbene ligand is reported. Both colloidal and supported nanoparticles (NPs) on carbon nanotubes (CNTs) were prepared in a one-pot synthesis with outstanding control on their size, morphology and composition. These catalysts were evaluated in the selective hydrogenation of alkynes and alkynols. PdCu/CNTs revealed an efficient catalytic system providing high selectivity in the hydrogenation of terminal and internal alkynes. Moreover, this catalyst was tested in the semi-hydrogenation of acetylene in industrially relevant acetylene/ethylene-rich model gas feeds and showed excellent stability even after 40 h of reaction.
Dehydration of 1,5-Pentanediol over Na-Doped CeO2 Catalysts
Gnanamani, Muthu Kumaran,Jacobs, Gary,Martinelli, Michela,Shafer, Wilson D.,Hopps, Shelley D.,Thomas, Gerald A.,Davis, Burtron H.
, p. 1148 - 1154 (2018/02/12)
The effects of CeO2 doped with Na on the dehydration of 1,5-pentanediol were studied by using a fixed-bed reactor at two different temperatures (350 and 400 °C) and atmospheric pressure. For characterization, BET surface area, hydrogen temperature-programmed reduction, CO2 temperature-programmed desorption, and diffuse reflectance infrared Fourier transform spectroscopy techniques were utilized. The conversion of the diol on CeO2 was found to depend on Na loading. The selectivity to the desired product (i.e., unsaturated alcohol) increased and the selectivity to undesired products (i.e., tetrahydropyran, tetrahydropyran-2-one, cyclopentanol and cylopentanone) decreased with increasing Na content on CeO2. The basicity of hydroxyl groups or surface oxygen on CeO2 was altered with the addition of Na, and controlled the dehydration reaction pathway.
Dehydration of 1,5-Pentanediol over CeO2-MeOx Catalysts
Gnanamani, Muthu Kumaran,Martinelli, Michela,Badoga, Sandeep,Hopps, Shelley D.,Davis, Burtron H.
, p. 4629 - 4635 (2018/09/21)
The dehydration reaction of 1,5-pentanediol was performed over CeO2 and modified CeO2 (CeO2?MnOx, CeO2?ZnO, CeO2?MgO, CeO2?CaO, CeO2?Na2O) catalysts in a fixed-bed tubular reactor at 350 °C and an atmospheric pressure. The undoped CeO2 produced a mixture of the products containing mainly 4-penten-1-ol, 1-pentanol, cyclopentanol, cyclopentanone and tetrahydropyran-2-one from 1,5-pentanediol, while additions of MgO, MnOx, or ZnO to CeO2 was found to enhance the overall production rate of unsaturated alcohol. On the other hand, more basic metals like CaO or Na2O tend to decline the dehydration activity of CeO2. The porous structure of CeO2 did not change appreciably with the addition of metal oxides. Temperature programmed desorption of adsorbed CO2 on an activated catalyst suggest more CO2 remain on the catalyst surface, particularly CeO2?CaO and CeO2?Na2O indicating that fewer defect sites are only available for reaction. The defect sites or oxygen vacancy on CeO2 controls both activity and selectivity for the dehydration of 1,5-pentanediol.
Transfer Hydrogenation of Aldehydes, Allylic Alcohols, Ketones, and Imines Using Molybdenum Cyclopentadienone Complexes
Wu, Weiwei,Seki, Tomohiro,Walker, Katherine L.,Waymouth, Robert M.
, p. 1428 - 1431 (2018/05/23)
The molybdenum tetraphenylcyclopentadienone complex (C5Ph4O)Mo(CO)3(CH3CN) 1a is an effective precatalyst for the transfer hydrogenation of aldehydes, allylic alcohols, ketones, and imines under mild conditions with either 2-propanol or formic acid as reducing reagent. Mechanistic studies suggest that these molybdenum cyclopentadienone complexes can be reduced to the corresponding hydroxycyclopentadienyl Mo hydrides. These complexes, by virtue of the hydroxyl group on the cyclopentadienyl ligand, are more reactive and chemoselective than the analogous cyclopentadienyl molybdenum complexes for the reduction of ketones, aldehydes, and imines.
