- Site-specific catalytic activities to facilitate solvent-free aerobic oxidation of cyclohexylamine to cyclohexanone oxime over highly efficient Nb-modified SBA-15 catalysts
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The development of highly active and selective heterogeneous catalysts for efficient oxidation of cyclohexylamine to cyclohexanone oxime is a challenge associated with the highly sensitive nitrogen center of cyclohexylamine. In this work, dispersed Nb oxide supported on SBA-15 catalysts are disclosed to efficiently catalyze the selective oxidation of cyclohexylamine with high conversion (>75%) and selectivity (>84%) to cyclohexanone oxime by O2without any addition of solvent (TOF = 469.8 h?1, based on the molar amount of Nb sites). The role of the active-site structure identity in dictating the site-specific catalytic activities is probed with the help of different reaction and control conditions and multiple spectroscopy methods. Complementary to the experimental results, further poisoning tests (with KSCN or dehydroxylation reagents) and DFT computational studies clearly unveil that the surface exposed active centers toward activation of the reactants are quite different: the surface -OH groups can catch the NH2group from cyclohexylamine by forming a hydrogen bond and lead to a more facile cyclohexylamine oxidation to desired products, while the monomeric or oligomeric Nb sites with a highly distorted structure play a key role in the dissociation of O2molecules beneficial for insertion of active oxygen species into cyclohexylamine. These catalysts exhibit not only satisfactory recyclability for cyclohexylamine oxidation but also efficiently catalyze the aerobic oxidation of a wide range of amines under solvent-free conditions.
- Ding, Wei,Mao, Liqiu,Peng, Haoyu,Yin, Dulin,Zhong, Wenzhou
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p. 3409 - 3422
(2020/06/09)
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- Continuous Production of Dialkylamines by Selective Hydrogenation of Nitriles on a Nickel-Zeolite Catalyst
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Hydrogenation of aliphatic nitriles in the presence of nickel supported by NaX zeolite was studied. The data obtained were used to develop a continuous method for obtaining dialkylamines with the yield of the target product of up to 98%.
- Popov, Yu. V.,Mokhov,Latyshova,Panov,Pletneva, M. Yu.
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p. 1778 - 1782
(2018/03/21)
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- Colloid and nanosized catalysts in organic synthesis: XVI.1 Continuous hydrogenation of carbonitriles catalyzed by nickel nanoparticles applied on a support
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Conversion of the starting nitriles and selectivity of the products formation during continuous hydrogenation of various nitriles catalyzed by Ni0/Ceokar-2 have been studied as functions of temperature. Performing the process at temperature 120–260°С has led to the formation of a mixture of products containing di- and trialkylamines as well as the corresponding imines and enamines.
- Popov, Yu. V.,Mokhov,Latyshova,Nebykov,Panov,Pletneva, M. Yu.
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p. 2276 - 2281
(2017/11/24)
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- The conversion of 1-propanamine on copper-containing MFI and BEA zeolites prepared by aqueous and vapor ion-exchange
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A process has been developed for exchanging one Cu atom per ion exchange site in an MFI zeolite. The material is synthesized by reaction of the acidic zeolite with CuCl vapor, followed by oxidation with oxygen, and conversion of the Cu2+ species to copper hydroxyl ions and copper hydroxyl dimers by reaction of the oxidized material with water upon exposure to humid air. This material, a similarly prepared BEA material, and copper-containing MFI and BEA zeolites prepared by conventional aqueous ion-exchange have been comparatively investigated for the conversion of 1-propanamine. Reaction products include C6 products such as dipropanamine and 1-propanamine, N-(1-propylidene). A bifunctional acid/metal reaction pathway is proposed to account for the observed products.
- Guidry, Trent F.,Price, Geoffrey L.
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- Acetylenes as Potential Antarafacial Components in Concerted Reactions. Formation of Pyrroles from Thermolyses of Propargylamines, of a Dihydrofuran from a Propargylic Ether, and of an Ethylidenepyrrolidine from a β-Amino Acetylene
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A thermal cyclization of acetylenic compounds provides evidence for the ability of acetylenic links to act as antarafacial components in processes.The cyclization competes with the normally favored acetylenic retro-ene reaction.Propargylic amines, without substituents whose presence would hinder a tight cyclic transition state, yield intermediate pyrrolines whose subsequent hydrogen elimination affords pyrroles in small amounts.The same process in 2-ethynyltetrahydropyran affords 8-oxabicyclooctane in 35percent yield.A related thermal reaction of N-methyl-3-hexyn-1-amine provides a quantitative transformation to N-methyl-2-ethylidenepyrrolidine in a nominal s + 2a + 2s + 2s> Moebius process, wherein the acetylenic unit is the antarafacial component.Evidence for concertedness in these reactions is discussed.
- Viola, Alfred,Collins, John J.,Filipp, Nicholas,Locke, John S.
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p. 5067 - 5075
(2007/10/02)
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- Semiconductor Photocatalysis.ZnS-Catalyzed Photoreduction of Aldehydes and Related Derivatives: Two-Electron-Transfer Reduction and Relationship with Spectroscopic Properties
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Photocatalytic activity and spectroscopic properties of ZnS suspensions for the two-electron reduction of aldehydes or related compounds in aqueous medium are described.The ZnS suspension (ZnS-0) prepared by cooling from aqueous ZnSO4 and Na2S solutions catalyzes photoredox reactions of acetaldehyde, giving ethanol without much H2 evolution as a two-electron-reduction product, and acetic acid, biacetyl, and acetoin as oxidation products.When the ZnS-0 suspension is refluxed (giving ZnS-100) or dried to powder, the resulting ZnS shows an increased activity for H2 evolution but a decreased activity for the two-electron reduction.The two-electron photoreduction is ascribed to the sequential transfer of active electrons in the conduction band of defect-free aggregates of ZnS microcrystallites (quantized ZnS).This mechanism is supported by product analysis, energetics at ZnS interfaces, the sharp and blue-shifted onset of absorption and excitation spectra, and the long-life band gap emission of the active ZnS-0 suspension.UV, emission, and ESR spectra, as well as the enhancement of the particle size and crystallinity, suggest that the activity change observed after heating or drying to powder is due to the formation of surface states which may trap active electrons.This interpretation is also supported by the generated activity of ZnS-100 for the H2 photoevolution under >350-nm irradiation.ZnS photocatalysis under >350-nm irradiation and relationship with spectroscopic properties are also discussed.
- Yanagida, Shozo,Ishimaru, Yoshiteru,Miyake, Yoshio,Shiragami, Tsutomu,Pac, Chyongjin,et al.
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p. 2576 - 2582
(2007/10/02)
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- FACILE GENERATION OF DIALKYLAMINYL RADICALS FROM N-HYDROXYPYRIDINE-2-THIONE CARBAMATES. APPLICATION IN KINETIC STUDIES OF SMALL RING CYCLOALKYLAMINYL RADICAL RING OPENINGS
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The preparation of N-hydroxypyridine-2-thione carbamates and the formation of dialkylaminyl radicals from these species are described, and the application of this methodology in kinetic studies of aminyl radical rearrangements is demonstrated.
- Newcomb, Martin,Park, Seung-Un,Kaplan, Jere,Marquardt, Donald J.
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p. 5651 - 5654
(2007/10/02)
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