110-54-3Relevant articles and documents
Carrier-Induced Modification of Palladium Nanoparticles on Porous Boron Nitride for Alkyne Semi-Hydrogenation
Büchele, Simon,Chen, Zupeng,Fako, Edvin,Hauert, Roland,Krumeich, Frank,López, Núria,Mitchell, Sharon,Pérez-Ramírez, Javier,Safonova, Olga V.
, p. 19639 - 19644 (2020)
Chemical modifiers enhance the efficiency of metal catalysts in numerous applications, but their introduction often involves toxic or expensive precursors and complicates the synthesis. Here, we show that a porous boron nitride carrier can directly modify supported palladium nanoparticles, originating unparalleled performance in the continuous semi-hydrogenation of alkynes. Analysis of the impact of various structural parameters reveals that using a defective high surface area boron nitride and ensuring a palladium particle size of 4–5 nm is critical for maximizing the specific rate. The combined experimental and theoretical analyses point towards boron incorporation from defects in the support to the palladium subsurface, creating the desired isolated ensembles determining the selectivity. This practical approach highlights the unexplored potential of using tailored carriers for catalyst design.
Regio- and Chemoselective Hydrogenation of Dienes to Monoenes Governed by a Well-Structured Bimetallic Surface
Miyazaki, Masayoshi,Furukawa, Shinya,Komatsu, Takayuki
, p. 18231 - 18239 (2017)
Unprecedented surface chemistry, governed by specific atomic arrangements and the steric effect of ordered alloys, is reported. Rh-based ordered alloys supported on SiO2 (RhxMy/SiO2, M = Bi, Cu, Fe, Ga, In, Pb, Sn, and Zn) were prepared and tested as catalysts for selective hydrogenation of trans-1,4-hexadiene to trans-2-hexene. RhBi/SiO2 exhibited excellent regioselectivity for the terminal C=C bond and chemoselective hydrogenation to the monoene, not to the overhydrogenated alkane, resulting in a high trans-2-hexene yield. Various asymmetric dienes, including terpenoids, were converted into the corresponding inner monoenes in high yields. This is the first example of a regio- and chemoselective hydrogenation of dienes using heterogeneous catalysts. Kinetic studies and density functional theory calculations revealed the origin of the high selectivity: (1) one-dimensionally aligned Rh arrays geometrically limit hydrogen diffusion and attack to alkenyl carbons from one direction and (2) adsorption of the inner C=C moiety to Rh is inhibited by steric repulsion from the large Bi atoms. The combination of these effects preferentially hydrogenates the terminal C=C bond and prevents overhydrogenation to the alkane.
Competitive reactions and mechanisms in the simultaneous HDO of phenol and methyl heptanoate over sulphided NiMo/γ-Al2O3
Ryymin, Eeva-Maija,Honkela, Maija L.,Viljava, Tuula-Riitta,Krause, A.Outi I.
, p. 114 - 121 (2010)
Hydrodeoxygenation (HDO) of phenol and methyl heptanoate separately and as mixtures was carried out over a sulphided NiMo catalyst to compare the HDO of aromatic and aliphatic reactants. Some experiments were also carried out in the presence of a sulphur additive. The conversion of phenol was suppressed in the presence of methyl heptanoate, whereas the conversion of methyl heptanoate was practically unaffected by phenol. In addition, distributions of the hydrocarbon products were different for reactants in the mixture and the reactants tested separately. Sulphur additive changed the product distribution of the separate components more than that of the mixture. The findings indicate that reduction (including hydrogenation) reactions occur on coordinatively unsaturated sites (CUS) independently of the aromatic or aliphatic character of the component. Sulphur, too, adsorbs on CUS and competes with other reactants that have an affinity to CUS. Decarbonylation and acid-catalysed reactions are, instead, proposed to occur on sulphur-saturated sites.
Direct Reduction of 1-Bromo-6-chlorohexane and 1-Chloro-6-iodohexane at Silver Cathodes in Dimethylformamide
Rose, John A.,McGuire, Caitlyn M.,Hansen, Angela M.,Karty, Jonathan A.,Mubarak, Mohammad S.,Peters, Dennis G.
, p. 311 - 317 (2016)
Cyclic voltammetry and controlled-potential (bulk) electrolyses have been employed to probe the electrochemical reductions of 1-bromo-6-chlorohexane and 1‐chloro-6-iodohexane at silver cathodes in dimethylformamide (DMF) containing 0.050?M tetra-n-butylammonium tetrafluoroborate (TBABF4). A cyclic voltammogram for reduction of 1-bromo-6-chlorohexane shows a single major irreversible cathodic peak, whereas reduction of 1-chloro-6-iodohexane gives rise to a pair of irreversible cathodic peaks. Controlled-potential (bulk) electrolyses of 1-bromo-6-chlorohexane at a silver gauze cathode reveal that the process involves a two-electron cleavage of the carbon–bromine bond to afford 1-chlorohexane as the major product, along with 6-chloro-1-hexene, n‐hexane, 1‐hexene, and 1,5-hexadiene as minor species. In contrast, bulk electrolyses of 1-chloro-6-iodohexane indicate that the first voltammetric peak corresponds to a one-electron process, leading to production of a dimer (1,12-dichlorododecane) together with 1-chlorohexane and 6-chloro-1-hexene as well as 1‐hexene and 1,5-hexadiene in trace amounts. At potentials corresponding to the second cathodic peak, reduction of 1-chloro-6-iodohexane is a mixture of one- and two-electron steps that yields the same set of products, but in different proportions. Mechanistic schemes are proposed to explain the electrochemical behavior of both 1‐bromo-6-chlorohexane and 1-chloro-6-iodohexane.
Calcium Hydride Cation [CaH]+ Stabilized by an NNNN-type Macrocyclic Ligand: A Selective Catalyst for Olefin Hydrogenation
Schuhknecht, Danny,Lhotzky, Carolin,Spaniol, Thomas P.,Maron, Laurent,Okuda, Jun
, p. 12367 - 12371 (2017)
Reaction of dibenzyl calcium complex [Ca(Me4TACD)(CH2Ph)2], containing the neutral NNNN-type macrocyclic ligand Me4TACD (Me4TACD=1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane), with triphenylsilane gave the cationic dinuclear calcium hydride [Ca2H2(Me4TACD)2](PhCHSiPh3)2 which was characterized by NMR spectroscopy and single-crystal X-ray diffraction. The cation can be regarded as the ligand-stabilized dimeric form of hypothetical [CaH]+. Hydrogenolysis of benzyl calcium cation [Ca(Me4TACD)(CH2Ph)(thf)]+ gave dicationic calcium hydrides [Ca2H2(Me4TACD)2][BAr4]2 (Ar=C6H4-4-tBu; C6H3-3,5-Me2) containing weakly coordinating anions. In THF, they catalyzed the isotope exchange of H2 and D2 to give HD and the hydrogenation of unactivated 1-alkenes.
Intrinsic role of pH in altering catalyst properties of NiMoP over alumino-silicate for the vapour phase hydrodeoxygenation of methyl heptanoate
Ramesh, Arumugam,Tamizhdurai, Perumal,Suthagar, Krishnan,Sureshkumar, Kandhasamy,Theres, Gubert Sonia,Shanthi, Kannan
, p. 3545 - 3555 (2019)
Monometallic and bimetallic Ni2P, MoP, and NiMoP active species were successfully impregnated on thermally stable, high surface area mesoporous alumino-silicate with an Si/Al ratio of 10 at room temperature via a facile wet impregnation method under both acidic and basic conditions using HCl and NH4OH as pH regulators, respectively. Furthermore, the intrinsic role of pH in altering the physicochemical properties of the catalysts was comprehensively evaluated. The catalysts were tested in a high-pressure stainless steel fixed bed reactor at different temperatures ranging from 275-350 °C, under 10-40 bar hydrogen pressure for the hydrodeoxygenation (HDO) of methyl heptanoate. The reaction pathway and product distribution of methyl heptanoate were manifested at different temperatures and pressures. The HDO activity and synergistic factor were found to be remarkably higher for the NiMoP/MAS (10)-A catalyst than the NiMoP/MAS (10)-B catalyst and its monometallic counterparts. This investigation proves that the NiMoP/MAS (10)-A catalyst is a promising catalyst for green fuel production from non-edible oils through hydrodeoxygenation. It was also unequivocally confirmed that the catalytic process does not suffer from any mass transfer resistance; thus, making the scaling up of the reaction more feasible.
Biphasic hydroformylation of 1-hexene with carbon dioxide catalyzed by ruthenium complex in ionic liquids
Tominaga, Ken-Ichi,Sasaki, Yoshiyuki
, p. 14 - 15 (2004)
Hydroformylation of 1-hexene using carbon dioxide as carbonyl carbon source attained high yield and good chemoselectivity in heptanols when a ruthenium complex was used in biphasic ionic liquid-toluene system.
Studies on organolanthanide complexes. XVIII. The reduction and isomerization of olefins with tricyclopentadienyllanthanides/sodium hydride
Qian, Changtao,Ge, Yuanwen,Deng, Daoli,Gu, Yongjie,Zhang, Caihua
, p. 175 - 184 (1988)
Reduction of 1-hexene with Cp3Ln/NaH (Cp=cyclopentadienyl, Ln=rare earth metals) in THF at 45 deg C, after hydrolysis, gives hexane.The reducing activity of Cp3Ln depends strongly upon the ionic radius of the trivalent rare earth ion.The activity and selectivity of early rare earths for 1-hexene reduction are higher than those of heavy rare earths.The Cp3Ln/NaH systems can be used to regioselectively reduce dienes which contain a terminal carbon-carbon double bond as well as an internal one with high yield.Selectivity is 100percent.Moreover, the Cp3Ln/NaH systems are able to catalyze the hydrogenation of olefins.When Cp3Ln/NaH is used as catalyst, 1-hexene was isomerized at 45 deg C to cis-2-hexene and to trans-2-hexene in excellent yields.In contrast to reducing activity, the catalytic activity of heavy rare earths in the isomerization reaction is higher than that of the early earths.Hence, Cp3Sm/NaN and Cp3Y/NaH are new reducing agents and catalysts for 1-hexene reduction and isomerization, respectively.
Cationic pyridyl(benzoazole) ruthenium(II) complexes: Efficient and recyclable catalysts in biphasic hydrogenation of alkenes and alkynes
Ogweno, Aloice O.,Ojwach, Stephen O.,Akerman, Matthew P.
, p. 250 - 258 (2014)
The synthesis, structural characterization of cationic 2-(2-pyridyl)benzoazole)ruthenium(II) complexes and their applications in biphasic hydrogenations of alkenes is reported. Reactions of 2-(2-pyridyl)benzoimidazole (L1), 2-(2-pyridyl)benzothiazole (L2) and 2-(2-pyridyl)benzoxazole (L3) with [η6-(2-phenoxyethanol)RuCl2]2produced the corresponding cationic complexes [η6-(2-phenoxyethanol)RuCl(L1)]Cl (1), [η6-(2-phenoxyethanol)RuCl(L2)]Cl (2) and [η6-(2-phenoxyethanol)RuCl(L3)]Cl (3) in good yields. Solid state structures of 1-3 confirmed the bidentate coordination modes of L1-L3 and formation of cationic species through displacement of one chloride ligand from Ru(II) coordination sphere. Complexes 1-3 produced active catalysts for high pressure hydrogenation of alkenes both in methanol and biphasic conditions. Relatively lower activities were observed in the hydrogenation of terminal alkynes giving a mixture of alkane and alkene products. Complexes 1-3 were recyclable under biphasic conditions and retained significant catalytic activities in six cycles. Reaction parameters such as substrate/catalyst ratio, temperature, and aqueous/organic ratio affected the catalytic trends.
Enhancing catalytic performance of activated carbon supported Rh catalyst on heterogeneous hydroformylation of 1-hexene via introducing surface oxygen-containing groups
Tan, Minghui,Wang, Ding,Ai, Peipei,Liu, Guoguo,Wu, Mingbo,Zheng, Jingtang,Yang, Guohui,Yoneyama, Yoshiharu,Tsubaki, Noritatsu
, p. 53 - 59 (2016)
Activated carbon supported rhodium (Rh/AC) catalysts with different amounts of oxygen-containing functional groups were prepared by nitric acid (HNO3) treatment at varied temperatures. Thermal analyses of Rh/AC catalysts with or without this acidic treatment were characterized by thermogravimetric analysis (TGA) and temperature programmed desorption (TPD). The change of surface oxygen-containing functional groups was characterized by Fourier transform infrared spectrometry (FTIR) and X-ray photoelectron spectroscopy (XPS). These characterization results indicated that the amount of oxygen-containing functional groups increased with the treatment temperature. The influence of these oxygen-containing functional groups on the products selectivities in heterogeneous hydroformylation reaction was investigated in detail. These abundant functional groups were benefited to improve the selectivity of n-heptanal, resulting in higher n/i (normal to iso) ratio of heptanal. The Rh/AC catalyst being treated at 80?°C had the highest n/i ratio of 2.3, due to the maximum amount of oxygen-containing functional groups, which was almost double to that of raw Rh/AC catalyst. Moreover, abundant functional groups on catalyst suppressed hydrogenation of hexene, decreasing the selectivity of hexane from 4.9% of raw Rh/AC to 0.2%. These findings disclosed that these oxygen-containing functional groups on catalysts played an extremely important role in improving the catalytic performance of heterogeneous hydroformylation reaction, providing a new viewpoint for the studies on heterogeneous hydroformylation.
