- Photochemistry of Benzene Isomers. 1. Fulvene and 3,4-Dimethylenecyclobutene
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The photochemical behavior of the benzene isomer fulvene is investigated at various excitation wavelengths.The only observable photoproduct is benzene, produced in high quantum yield below about 275-nm excitation.The quantum yield is dependent upon excitation wavelength indicating the photoisomerization requires vibrational activation.Quenching by various added gases is efficient and suggests that the photochemistry does not invove triplet-state or free-radical mechanisms.Another isomer, 3,4-dimethylenecyclobutene, also shows photochemical behavior upon excitation at 240 and 215 nm to produce a polymeric material.
- Kent, Jay E.,Harman, Peter J.,O'Dwyer, Michael F.
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- Alkylation of benzene by alkyl cations. Stability of the tert-butyl benzenium ion
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The kinetics and eqilibria of the gas phase reaction tert-C4H9+ + C6H6 = tert-C4H9C6H6+ were studied with a high ion source pressure pulsed electron beam mass spectrometer.Equilibria could be observed in the temperature range 285-325 K, van't Hoff plots of the equilibrium constants led to ΔH10 = -22+/-2 kcal mol-1 and ΔS10 = -49+/-5 cal K-1 mol-1.The rate constants at 305 K were k1f = 1.5*10-28 molecules-2 cm6 s-1 and k1r = 2.9*10-19 molecules-1 cm3 s-1. tert-C4H9C6H6+ dissociates easily via not only because of the low dissociation energy (-ΔH10) but also because of the unusually favorable entropy (-ΔS10).The occurence of transalkylation reactions: tert-C4H9C6H6+ + alkylbenzene = tert-C4H9 alkylbenzene+ + benzene, was discovered in the present work.
- Sharma, D. K. Sen,Ikuta, S.,Kebarle, P.
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- Pyrolysis of Styrene. Kinetics and Mechanism of the Equilibrium Styrene Benzene + Acetylene
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The thermal unimolecular decomposition of styrene into benzene and acetylene, C6H5CH=CH2 -> C6H6 + HCCH (1), was investigated in a low pressure (ca. 10 mTorr) flow reactor by on-line mass spectrometry between 1180 and 1350 K.Measured rates can be calculated, via RRKM extrapolation, from the expression log (K1, s-1) = 14.38 - 17076/T, which was derived by detailed balance from high-pressure (ca. 50 Torr) low-temperature (878-973 K) kinetic data for the reverse reaction.This value of E1 = 77.9 kcal/mol allows for the generation of vinylidene, H2C=C:; the carbene isomer of acetylene, as a primary product of the title reaction.A non-radical process involving the rate-determining extrusion of H2C=C: from a -7-methylene cyclohepta-2,4-diene intermediate in equilibrium with styrene is consistent with kinetic and thermochemical considerations.
- Grela, M. A.,Amorebieta, V. T.,Colussi, A. J.
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- Kinetic Parameters for the Unimolecular Dissociation of Styrene Ion
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Time-resolved photodissociation measurements of the laser-induced fragmentation of styrene molecular ion have been carried out at 355 nm.Taking thermal energy content into account, a unimolecular dissociation rate of 6.3 * 103 s-1 at an internal energy of 3.66 eV was derived.The new measurement has been combined with previous data from photodissociation and photoionization to give a dissociation rate-energy curve spanning 2 decades of rate values.By RRKM fitting to this curve, unimolecular kinetic parameters E0 = 2.43 +/- 0.05 eV and ΔS% (1000K) = -3.9 +/- 1 cal mol-1 K-1 were derived.The conclusion that this dissociation proceeds through a rate-limiting thight activated complex at E0 = 2.43 eV was affirmed.
- Dunbar, Robert C.
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- Probing ensemble effects in surface reactions. 3. Cyclohexane adsorption on clean and bismuth-covered Pt(III)
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The adsorption and chemistry of cyclohexane on clean and Bi-covered Pt(111) surfaces have been studied with thermal desorption mass spectroscopy (TDS), deuterium labeling, Auger electron spectroscopy (AES), and X-ray photoelectron spectroscopy (XPS). The thermal experiments show that, on clean Pt(111), cyclohexane is adsorbed in three molecular states with desorption temperatures of approx. 236 (monolayer), approx. 181 (second monolayer), and approx.154 K (multilayer). There is little isotopic exchange in the molecularly desorbing cyclohexane. Benzene is formed at approx. 236 K on the clean Pt(111) surface is a product of the dehydrogenation of adsorbed cyclohexane. This process is 13-fold slower for perdeuterated cyclohexane. An analysis of quantitative XPS data and the effect of Bi poisoning on the chemisorption of cyclohexane shows that an ensemble of about five Pt atoms is necessary to chemisorb C6H12. The dehydrogenation of adsorbed cyclohexane is poisoned at very low bismuth coverages (θ$-Βi$/0.1) according to mechanism dominated by steric, site-blocking effects.
- Rodriguez,Campbell
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- Infrared multiphoton dissociation of styrene ions by low-power continuous CO2 laser irradiation
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The kinetics of infrared multiphoton dissociation of styrene ions under collision-free conditions in the ion cyclotron resonance ion trap were studied as a function of the intensity of the cw CO2 laser at powers up to 6 W.Following the beginning of irradiation an induction time was observed.Followed by dissociation according to a first-order rate constant.The kinetics could be fitted to a random-walk simulation of a master-equation model, in the same way as previous studies.A matrix-algebra solution of the master-equation model is described which gave a better fit with greater computational convenience.From the modeling the rate of radiation of infrared photons (assumed to be at 940 cm-1) from the ions was estimated as 350 s-1 at an ion internal energy of around 3 eV.When the dissociation threshold E, was treated as an unknown it was found that master-equation modeling of the kinetic results could give an estimate of Et, but with large uncertainty.Application of simple thermal kinetic theory via Tolman's theorem gave good qualitative understanding of the results, and predicted the intensity dependence of the dissociation rate with a deviation of about 30percent.
- Dunbar, Robert C.,Zaniewski, Rebecca C.
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- Kinetic Energy Release in Thermal Ion-Molecule Reactions: Single Charge-Transfer Reactions of V2+ and Ta2+ with Benzene
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Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) has been used to study the single charge-transfer reactions of V2+ and Ta2+ with benzene under thermal conditions.Thermal charge-transfer rate constants of 2.0 x 10-9 and 1.2 x 10-9 cm3 molecule-1s-1 were measured for V2+ and Ta2+, respectively.The total kinetic energy of the product ions was determined to be 1.91 +/- 0.50 eV for the V2+ case and 2.82 +/- 0.50 eV for the Ta2+ case.These results and a previous study of the Nb2+ - benzene single charge-transfer system suggest a simple long-distance electron-transfer mechanism proceeding by ionization of the 1a2u orbital of benzene with significant internal excitation of the nascent C6H6+ product.
- Gord, James R.,Freiser, Ben S.,Buckner, Steven W.
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- Methane chemistry in the hot supersonic nozzle
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The combination of pyrolysis and expansion to a supersonic molecular beam was shown to be very effective in conversion of pure CH4 to heavier hydrocarbons. Pure CH4 conversion reached 70% when it reacted in a hot (1000°-1150°C) supersonic nozzle made of quartz with 100 μ dia orifice. Hydrogen, acetylene, benzene, methyl, and propargyl radicals were the major products in the distribution. CH4 conversion rate was not improved with the addition of O2, NO, or CO2 as O2 reacted primarily with surface carbon formed by CH4 decomposition. No oxygen containing hydrocarbon derivatives were observed. The lifetime of the nozzle was longer than pure CH4 as a reactant resulting from surface carbon removal by oxygen. The mechanism involved pyrolytic rather than catalytic surface generation of free hydrocarbon radicals with subsequent coupling to heavier hydrocarbon products prior to desorption to the gas phase and expansion to the supersonic beam.
- Somorjai,Kim,Romm
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- Facile formation of benzene from a novel cyclohexane derivative
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Upon acidification, benzene forms at room temperature from the novel 1,3,5-cis-trisubstituted cyclohexane wherein the substituents are the azido phosphine cage moieties N3P(MeNCH2CH2)3N. The dominant reaction in the decomposition of this unusually thermally stable intermediate in the presence of HA is the formation of nitrogen and the salt [H2N=P(MeNCH2CH2)3N]A in addition to benzene. Evidence for a transannulated cage intermediate is presented.
- Liu, Xiadong,Zhang, Guangtao,Verkade, John G.
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- Reaction of Hydrogen Atom with Benzene: Kinetics and Mechanism
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The rate coefficients for the reactions H + C6H6 -> products (k1) (1), H + C6D6 -> products (k2) (2), D + C6H6 -> products (k3) (3), and D + C6D6 -> products (k4) (4) have been measured in the temperature range of 298-1000 K by using the pulsed photolysis-resonance fluorescence technique.On the basis of the obtained kinetic information, it is shown that the primary path in all these reactions is addition of the atom to the benzene ring form cyclohexadienyl radical.The rate coefficient for the thermal decomposition of the cyclohexadienyl radical has also been measured.When the rate coefficients for the formation and decomposition of the cyclohexadienyl radical are used, the standard heat of formation of cyclohexadienyl radical at 298 K is calculated to be 45.7 kcal/mol.The measured values of k1-k4 are compared with the results of previous investigations.Most of the observed kinetic behavior in these reactions has been explained on the basis of the addition-decomposition reaction scheme.
- Nicovich, J. M.,Ravishankara, A. R.
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- Synergies of surface-interface multiple active sites over Al-Zr oxide solid solution supported nickel catalysts for enhancing the hydrodeoxygenation of anisole
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Currently, the catalytic hydrodeoxygenation (HDO) of oxygen-containing compounds derived from biomass to highly valuable chemicals or hydrocarbon bio-fuels is attracting more and more attention. Concerning the design and synthesis of high-performance supported metal catalysts for HDO, the efficient deposition/immobilization of active metal species on supports, as well as the construction of the favorable properties of supports, is quite necessary. In this work, we fabricated series of aluminum-zirconium oxide solid solution supported Ni-based catalysts by a simple surfactant-assisted homogeneous coprecipitation and applied them in the HDO of anisole. Various structural characterizations showed that surface-interface properties of Ni-based catalysts (i.e., surface acidity, defective structures, and metal-support interactions) could be finely tuned by adjusting the amount of Al introduced into Al-Zr oxide solid solutions, thus profoundly governing their catalytic HDO activities. It was demonstrated that the introduction of an appropriate amount of Al could not only enhance surface acidity and promote the formation of defective Zr-Ov-Al structures (Ov: oxygen vacancy) but also facilitate the generation of interfacial Niδ+ species bound to the support. Over the Ni-based catalyst bearing an Al2O3:ZrO2 mass ratio of 5:2, a high cyclohexane yield of ～77.4% was attained at 230 °C and 1.0 MPa initial hydrogen pressure. The high catalytic HDO efficiency was revealed to be correlated with the catalytic synergy between Ni0 and adjacent interfacial Niδ+ species, together with the promotion of neighboring defective oxygen vacancies and acidic sites, which contributed to the enhanced activation of the methoxy group in anisole and reaction intermediate and thus greatly improved HDO activity. The present findings offer a new and promising guidance for constructing high-performance metal-based catalysts via a rational surface-interface engineering.
- Fan, Guoli,Li, Feng,Lin, Yanjun,Yang, Lan,Zhang, Yaowen
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- Selective catalytic synthesis of bio-based high value chemical of benzoic acid from xylan with Co2MnO4@MCM-41 catalyst
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The efficient synthesis of bio-based chemicals using renewable carbon resources is of great significance to promote sustainable chemistry and develop green economy. This work aims to demonstrate that benzoic acid, an important high added value chemical in petrochemical industry, can be selectively synthesized using xylan (a typical model compound of hemicellulose). This novel controllable transformation process was achieved by selective catalytic pyrolysis of xylan and subsequent catalytic oxidation. The highest benzoic acid selectivity of 88.3 % with 90.5 % conversion was obtained using the 10wt%Co2MnO4@MCM-41 catalyst under the optimized reaction conditions (80 °C, 4 h). Based on the study of the model compounds and catalyst's characterizations, the reaction pathways for the catalytic transformation of xylan to bio-based benzoic acid were proposed.
- Fan, Minghui,He, Yuting,Li, Quanxin,Luo, Yuehui,Yang, Mingyu,Zhang, Yanhua,Zhu, Lijuan
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- Wavelength-Specific Product Desorption as a Key to Raising Nitrile Yield of Primary Alcohol Ammoxidation over Illuminated Pd Nanoparticles
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Research on visible-light photocatalysts of metal nanoparticles (NPs) has focused on increasing the reactant conversion by light-excited charges (electrons and positively charged holes). However, light irradiation can accelerate catalysis by other mechanisms. Here, we report that 650 nm wavelength irradiation of 0.75 W·cm-2 significantly increases nitrile yield of ammoxidation of primary aromatic alcohols with an ammonium salt over supported Pd NPs at 80 °C in air. We found that the desorption of the nitrile product from the catalyst is the rate-determining step; the irradiation promotes not only alcohol oxidation and subsequent aldehyde cyanation over the Pd NPs but also the nitrile desorption selectively via resonance energy transfer to achieve a high nitrile yield. This new mechanism provides a knob for the exquisite control of catalytic reaction pathways for ecofriendly synthesis.
- Han, Pengfei,Tang, Cheng,Sarina, Sarina,Waclawik, Eric R.,Du, Aijun,Bottle, Steven E.,Fang, Yanfen,Huang, Yingping,Li, Kun,Zhu, Huai-Yong
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p. 2280 - 2289
(2022/02/14)
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- One-step conversion of lignin-derived alkylphenols to light arenes by co-breaking of C-O and C-C bonds
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The conversion of lignin-derived alkylphenols to light arenes by a one-step reaction is still a challenge. A 'shortcut' route to transform alkylphenols via the co-breaking of C-O and C-C bonds is presented in this paper. The catalytic transformation of 4-ethylphenol in the presence of H2 was used to test the breaking of C-O and C-C bonds. It was found that the conversion of 4-ethylphenol was nearly 100%, and the main products were light arenes (benzene and toluene) and ethylbenzene under the catalysis of Cr2O3/Al2O3. The conversion of 4-ethylphenol and the selectivity of the products were significantly influenced by the reaction temperature. The selectivity for light arenes reached 55.7% and the selectivity for overall arenes was as high as 84.0% under suitable reaction conditions. Such results confirmed that the co-breaking of the C-O and C-C bonds of 4-ethylphenol on a single catalyst by one step was achieved with high efficiency. The adsorption configuration of the 4-ethylphenol molecule on the catalyst played an important role in the breaking of the C-O and C-C bonds. Two special adsorption configurations of 4-ethylphenol, including a parallel adsorption and a vertical adsorption, might exist in the reaction process, as revealed by DFT calculations. They were related to the breaking of C-O and C-C bonds, respectively. A path for the hydrogenation reaction of 4-ethylphenol on Cr2O3/Al2O3 was proposed. Furthermore, the co-breaking of the C-O and C-C bonds was also achieved in the hydrogenation reactions of several alkylphenols. This journal is
- Di, Yali,Li, Guangyu,Li, Zhiqin,Liu, Weiwei,Qiu, Zegang,Ren, Xiaoxiong,Wang, Ying
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supporting information
p. 2710 - 2721
(2022/02/21)
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- Synthesis of Decorated Carbon Structures with Encapsulated Components by Low-Voltage Electric Discharge Treatment
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Abstract: Polycondensation of complexes of chloromethanes with triphenylphosphine by the action of low-voltage electric discharges in the liquid phase gives nanosized solid products. The elemental composition involving the generation of element distribution maps (scanning electron microscopy–energy dispersive X?ray spectroscopy mapping) and the component composition (by direct evolved gas analysis–mass spectrometry) of the solid products have been studied. The elemental and component compositions of the result-ing structures vary widely depending on the chlorine content in the substrate and on the amount of triphenylphosphine taken. Thermal desorption analysis revealed abnormal behavior of HCl and benzene present in the solid products. In thermal desorption spectra, these components appear at an uncharacteristically high temperature. The observed anomaly in the behavior of HCl is due to HCl binding into a complex of the solid anion HCI-2 with triphenyl(chloromethyl)phosphonium chloride, which requires a relatively high temperature (up to 800 K) to decompose. The abnormal behavior of benzene is associated with its encapsulated state in nanostructures. The appearance of benzene begins at 650 K and continues up to temperatures above 1300?K.
- Bodrikov, I. V.,Pryakhina, V. I.,Titov, D. Yu.,Titov, E. Yu.,Vorotyntsev, A. V.
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- Impact of oxygen vacancies in Ni supported mixed oxide catalysts on anisole hydrodeoxygenation
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The hydrodeoxygenation (HDO) activity of anisole has been investigated over Ni catalysts on mixed metal oxide supports containing Nb–Zr and Ti–Zr in 1:1 and 1:4 ratios. XRD patterns indicate the incorporation of Ti (or Nb) into the ZrO2 framewo
- Ali, Hadi,Kansal, Sushil Kumar,Lauwaert, Jeroen,Saravanamurugan, Shunmugavel,Thybaut, Joris W.,Vandevyvere, Tom
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- Few-Atom Pt Ensembles Enable Efficient Catalytic Cyclohexane Dehydrogenation for Hydrogen Production
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Identification of catalytic active sites is pivotal in the design of highly effective heterogeneous metal catalysts, especially for structure-sensitive reactions. Downsizing the dimension of the metal species on the catalyst increases the dispersion, which is maximized when the metal exists as single atoms, namely, single-atom catalysts (SACs). SACs have been reported to be efficient for various catalytic reactions. We show here that the Pt SACs, although with the highest metal atom utilization efficiency, are totally inactive in the cyclohexane (C6H12) dehydrogenation reaction, an important reaction that could enable efficient hydrogen transportation. Instead, catalysts enriched with fully exposed few-atom Pt ensembles, with a Pt-Pt coordination number of around 2, achieve the optimal catalytic performance. The superior performance of a fully exposed few-atom ensemble catalyst is attributed to its high d-band center, multiple neighboring metal sites, and weak binding of the product.
- Cai, Xiangbin,Deng, Yuchen,Diao, Jiangyong,Dong, Chunyang,Guo, Jinqiu,Guo, Yu,Jia, Zhimin,Jiang, Zheng,Li, Chengyu,Li, Jun,Liu, Hongyang,Liu, Jin-Cheng,Ma, Ding,Wang, Meng,Wang, Ning,Xiao, Hai,Xie, Jinglin,Xu, Bingjun,Zhang, Hongbo
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supporting information
p. 3535 - 3542
(2022/02/16)
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- Mechanistic studies into visible light-driven carboxylation of aryl halides/triflates by the combined use of palladium and photoredox catalysts
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The reaction mechanism of palladium-catalyzed visible light-driven carboxylation of aryl halides and triflates with a photoredox catalyst was examined in detail. Experimental and theoretical studies indicated that the active species for photoredox- catalyzed reduction was cationic ArPd(II)+ species to generate nucleophilic ArPd(I) or its further reduced ArPd(0)- species, which reacted with CO2 to give carboxylic acids. Hydrodehalogenated compounds, main byproducts in this carboxylation, were thought to be generated by protonation of these reduced species.
- Caner, Joaquim,Iwasawa, Nobuharu,Martin, Ruben,Murata, Kei,Shimomaki, Katsuya,Toriumi, Naoyuki
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supporting information
p. 1846 - 1853
(2021/08/13)
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- Metal-Free Photoredox-Catalyzed Hydrodefluorination of Fluoroarenes Utilizing Amide Solvent as Reductant
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A metal-free photoredox-catalyzed hydrodefluorination of fluoroarenes was achieved by using N,N,N’,N’-tetramethyl-para-phenylenediamine (1) as a strong photoreduction catalyst. This reaction was applicable not only to electron-rich monofluoroarenes but also to polyfluoroarenes to afford non-fluorinated arenes. The experimental mechanistic studies indicated that the amide solvent NMP plays an important role for regeneration of the photocatalyst, enabling additive-free photoreduction catalysis.
- Toriumi, Naoyuki,Yamashita, Kazuya,Iwasawa, Nobuharu
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supporting information
p. 12635 - 12641
(2021/08/03)
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- Heterogeneously Catalyzed Selective Decarbonylation of Aldehydes by CeO2-Supported Highly Dispersed Non-Electron-Rich Ni(0) Nanospecies
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Aldehyde decarbonylation has been extensively investigated, primarily using noble-metal catalysts; however, nonprecious-base-metal-catalyzed aldehyde decarbonylation has been hardly reported. We have established an efficient selective aldehyde decarbonylation reaction with a broad substrate scope and functional group tolerance utilizing a heterogeneous Ni(0) nanospecies catalyst supported on CeO2. The high catalytic performance is attributable to the highly dispersed and non-electron-rich Ni(0) nanospecies, which possibly suppress a side reaction producing esters and adsorbed CO-derived inhibition of the catalytic turnover, according to detailed catalyst characterization and kinetic evaluation.
- Matsuyama, Takehiro,Yatabe, Takafumi,Yabe, Tomohiro,Yamaguchi, Kazuya
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p. 13745 - 13751
(2021/11/17)
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- Photo-induced thiolate catalytic activation of inert Caryl-hetero bonds for radical borylation
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Substantial effort is currently being devoted to obtaining photoredox catalysts with high redox power. Yet, it remains challenging to apply the currently established methods to the activation of bonds with high bond dissociation energy and to substrates with high reduction potentials. Herein, we introduce a novel photocatalytic strategy for the activation of inert substituted arenes for aryl borylation by using thiolate as a catalyst. This catalytic system exhibits strong reducing ability and engages non-activated Caryl–F, Caryl–X, Caryl–O, Caryl–N, and Caryl–S bonds in productive radical borylation reactions, thus expanding the available aryl radical precursor scope. Despite its high reducing power, the method has a broad substrate scope and good functional-group tolerance. Spectroscopic investigations and control experiments suggest the formation of a charge-transfer complex as the key step to activate the substrates.
- K?nig, Burkhard,Wang, Hua,Wang, Shun
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supporting information
p. 1653 - 1665
(2021/06/17)
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- Luminescent Platinum(II) Complexes with Bidentate Diacetylide Ligands: Structures, Photophysical Properties and Application Studies
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A series of platinum(II) complexes supported by terphenyl diacetylide as well as diimine or bis-N-heterocyclic carbene (NHC) ligands have been prepared. The diacetylide ligands adopt a cis coordination mode featuring non-planar terphenyl moieties as revealed by X-ray crystallographic analyses. The electrochemical, photophysical and photochemical properties of these platinum(II) complexes have been investigated. These platinum(II) diimine complexes show broad emission with peak maxima from 566 nm to 706 nm, with two of them having emission quantum yields >60% and lifetimes 2 μs in solutions at room temperature, whereas the platinum(II) diacetylide complexes having bis-N-heterocyclic carbene instead of diimine ligand display photoluminescence with quantum yields of up to 28% in solutions and excited state lifetimes of up to 62 μs at room temperature. Application studies revealed that one of the complexes can catalyze photoinduced aerobic dehydrogenation of alcohols and alkenes, and a relatively non-toxic water-soluble Pt(II) complex displays anti-angiogenic activity.
- Luo, Zaoli,Liu, Yungen,Tong, Ka-Chung,Chang, Xiao-Yong,To, Wai-Pong,Che, Chi-Ming
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p. 2978 - 2992
(2021/08/30)
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- A Mononuclear Non-heme Iron(III)-Peroxo Complex with an Unprecedented High O-O Stretch and Electrophilic Reactivity
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A mononuclear non-heme iron(III)-peroxo complex, [Fe(III)(O2)(13-TMC)]+ (1), was synthesized and characterized spectroscopically; the characterization with electron paramagnetic resonance, M?ssbauer, X-ray absorption, and resonance Raman spectroscopies and mass spectrometry supported a high-spin S = 5/2 Fe(III) species binding an O2 unit. A notable observation was an unusually high νO-O at ～1000 cm-1 for the peroxo ligand. With regard to reactivity, 1 showed electrophilic reactivity in H atom abstraction (HAA) and O atom transfer (OAT) reactions. In the HAT reaction, a kinetic isotope effect (KIE) value of 5.8 was obtained in the oxidation of 9,10-dihydroanthracene. In the OAT reaction, a negative ρ value of -0.61 in the Hammett plot was determined in the oxidation of p-X-substituted thioanisoles. Another interesting observation was the electrophilic reactivity of 1 in the oxidation of benzaldehyde derivatives, such as a negative ρ value of -0.77 in the Hammett plot and a KIE value of 2.2. To the best of our knowledge, the present study reports the first example of a mononuclear non-heme iron(III)-peroxo complex with an unusually high νO-O value and unprecedented electrophilic reactivity in oxidation reactions.
- Ezhov, Roman,Guo, Yisong,Jang, Semin,Kim, Taeyeon,Lee, Yong-Min,Li, Xiao-Xi,Nam, Wonwoo,Pushkar, Yulia,Sarangi, Ritimukta,Seo, Mi Sook,Xiong, Jin,Zhu, Wenjuan
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supporting information
p. 15556 - 15561
(2021/10/01)
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- Synthesis, Structure, and Oxidative Reactivity of a Class of Thiolate-Bridged Dichromium Complexes Featuring Antiferromagnetic Coupling Interactions
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Several thiolate-bridged dichromium complexes with Cp* (Cp=η5-C5Me5) as auxiliary ligands were designed and synthesized through the salt metathesis, which all contain two six-coordinate chromium centers in the formal valence of +3. These complexes are all paramagnetic species, which are in good agreement with the experimental results that broad and paramagnetically shifted proton resonances appear in the 1H NMR spectra. Furthermore, variable-temperature solid-state magnetic susceptibility studies reveal the two chromium centers of these complexes are both in an S=3/2 high-spin state with a strong antiferromagnetic coupling. Simulated values of antiferromagnetic coupling constant for these complexes are directly related to the distances of the two CrIII centers confirmed by X-ray crystallography. In addition, in the presence of dehalogenation agent AgPF6, complexes [Cp*CrCl(μ-SR)2CrClCp*] (3, R=Et; 4, R=iPr) and [Cp*Cr(μ-Cl)(μ-SEt)2CrCp*][BPh4] (5) containing easily removable chloride can achieve the catalytic oxidation of organic substrates, such as PPh3, 1,4-cyclohexadiene and 1,2-diphenylhydrazine under an oxygen atmosphere.
- Wei, Nianmin,Yang, Dawei,Zhang, Yixin,Wang, Baomin,Qu, Jingping
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supporting information
p. 923 - 928
(2021/01/21)
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- Investigating reactivity and electronic structure of copper(II)-polypyridyl complexes and hydrogen peroxide
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This work presents a detailed study of the reactivity of three mononuclear CuII complexes supported by derivatives of the tetradentate ligand N,N'-bis(2-pyridylmethyl)-1,2-ethylenediamine (bispicen). The CuII complexes are capable of performing C[sbnd]H bond activation in the presence of NEt3 and H2O2 through what has been proposed computationally to be a [CuO]+ intermediate. A wavefunction-based quantum chemical investigation into the electronic structure of the proposed [CuO]+ intermediate reveals a triplet ground state predominantly consistent with an S = ? CuII center ferromagnetically coupled to an oxyl radical, though contributions from the corresponding biradicaloid CuI-oxene resonance structure may be nontrivial. Furthermore, correlation of the electronic structure of the proposed intermediate with analogous high-valent metal-oxo species capable of olefin epoxidation suggests that the CuII complexes might be also capable of olefin epoxidation in the presence of NEt3 and H2O2. To test this hypothesis experimentally, the CuII complexes are treated with NEt3 and H2O2 in the presence of alkene substrates, resulting in the formation of epoxides.
- Khazanov, Thomas M.,Botcha, Niharika Krishna,Yergeshbayeva, Sandugash,Shatruk, Michael,Mukherjee, Anusree
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- Ligand-Constraint-Induced Peroxide Activation for Electrophilic Reactivity
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μ-1,2-peroxo-bridged diiron(III) intermediates P are proposed as reactive intermediates in various biological oxidation reactions. In sMMO, P acts as an electrophile, and performs hydrogen atom and oxygen atom transfers to electron-rich substrates. In cyanobacterial ADO, however, P is postulated to react by nucleophilic attack on electrophilic carbon atoms. In biomimetic studies, the ability of μ-1,2-peroxo-bridged dimetal complexes of Fe, Co, Ni and Cu to act as nucleophiles that effect deformylation of aldehydes is documented. By performing reactivity and theoretical studies on an end-on μ-1,2-peroxodicobalt(III) complex 1 involving a non-heme ligand system, L1, supported on a Sn6O6 stannoxane core, we now show that a peroxo-bridged dimetal complex can also be a reactive electrophile. The observed electrophilic chemistry, which is induced by the constraints provided by the Sn6O6 core, represents a new domain for metal?peroxide reactivity.
- Ansari, Mursaleem,Chandra, Anirban,Kundu, Subrata,Monte-Pérez, Inés,Rajaraman, Gopalan,Ray, Kallol
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supporting information
p. 14954 - 14959
(2021/06/01)
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- C-H Activation by RuCo3O4Oxo Cubanes: Effects of Oxyl Radical Character and Metal-Metal Cooperativity
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High-valent multimetallic-oxo/oxyl species have been implicated as intermediates in oxidative catalysis involving proton-coupled electron transfer (PCET) reactions, but the reactive nature of these oxo species has hindered the development of an in-depth understanding of their mechanisms and multimetallic character. The mechanism of C-H oxidation by previously reported RuCo3O4 cubane complexes bearing a terminal RuV-oxo ligand, with significant oxyl radical character, was investigated. The rate-determining step involves H atom abstraction (HAA) from an organic substrate to generate a Ru-OH species and a carbon-centered radical. Radical intermediates are subsequently trapped by another equivalent of the terminal oxo to afford isolable radical-trapped cubane complexes. Density functional theory (DFT) reveals a barrierless radical combination step that is more favorable than an oxygen-rebound mechanism by 12.3 kcal mol-1. This HAA reactivity to generate organic products is influenced by steric congestion and the C-H bond dissociation energy of the substrate. Tuning the electronic properties of the cubane (i.e., spin density localized on terminal oxo, basicity, and redox potential) by varying the donor ability of ligands at the Co sites modulates C-H activations by the RuV-oxo fragment and enables construction of structure-activity relationships. These results reveal a mechanistic pathway for C-H activation by high-valent metal-oxo species with oxyl radical character and provide insights into cooperative effects of multimetallic centers in tuning PCET reactivity.
- Amtawong, Jaruwan,Balcells, David,Handford, Rex C.,Skjelstad, Bastian Bjerkem,Suslick, Benjamin A.,Tilley, T. Don
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supporting information
p. 12108 - 12119
(2021/08/20)
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- Formation of cobalt-oxygen intermediates by dioxygen activation at a mononuclear nonheme cobalt(ii) center
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A mononuclear nonheme cobalt(ii) complex, [(TMG3tren)CoII(OTf)](OTf) (1), activates dioxygen in the presence of hydrogen atom donor substrates, such as tetrahydrofuran and cyclohexene, resulting in the generation of a cobalt(ii)-alkylperoxide intermediate (2), which then converts to the previously reported cobalt(iv)-oxo complex, [(TMG3tren)CoIV(O)]2+-(Sc(OTf)3)n(3), in >90% yield upon addition of a redox-inactive metal ion, Sc(OTf)3. Intermediates2and3represent the cobalt analogues of the proposed iron(ii)-alkylperoxide precursor that converts to an iron(iv)-oxo intermediateviaO-O bond heterolysis in pterin-dependent nonheme iron oxygenases. In reactivity studies,2shows an amphoteric reactivity in electrophilic and nucleophilic reactions, whereas3is an electrophilic oxidant. To the best of our knowledge, the present study reports the first example showing the generation of cobalt-oxygen intermediates by activating dioxygen at a cobalt(ii) center and the reactivities of the cobalt-oxygen intermediates in oxidation reaction.
- Chandra, Anirban,Dau, Holger,Farquhar, Erik R.,Lee, Yong-Min,Malik, Deesha D.,Mebs, Stefan,Nam, Wonwoo,Ray, Kallol,Seo, Mi Sook
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supporting information
p. 11889 - 11898
(2021/09/06)
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- Combining Structural with Functional Model Properties in Iron Synthetic Analogue Complexes for the Active Site in Rabbit Lipoxygenase
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Iron complexes that model the structural and functional properties of the active iron site in rabbit lipoxygenase are described. The ligand sphere of the mononuclear pseudo-octahedral cis-(carboxylato)(hydroxo)iron(III) complex, which is completed by a tetraazamacrocyclic ligand, reproduces the first coordination shell of the active site in the enzyme. In addition, two corresponding iron(II) complexes are presented that differ in the coordination of a water molecule. In their structural and electronic properties, both the (hydroxo)iron(III) and the (aqua)iron(II) complex reflect well the only two essential states found in the enzymatic mechanism of peroxidation of polyunsaturated fatty acids. Furthermore, the ferric complex is shown to undergo hydrogen atom abstraction reactions with O-H and C-H bonds of suitable substrates, and the bond dissociation free energy of the coordinated water ligand of the ferrous complex is determined to be 72.4 kcal·mol-1. Theoretical investigations of the reactivity support a concerted proton-coupled electron transfer mechanism in close analogy to the initial step in the enzymatic mechanism. The propensity of the (hydroxo)iron(III) complex to undergo H atom abstraction reactions is the basis for its catalytic function in the aerobic peroxidation of 2,4,6-tri(tert-butyl)phenol and its role as a radical initiator in the reaction of dihydroanthracene with oxygen.
- Bonck, Thorsten,De Waal Malefijt, Matina Elo?se,Dobbelaar, Emiel,Kelm, Harald,Klein, Johannes E. M. N.,Krüger, Hans-J?rg,Rauber, Christian,Schmitz, Markus
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supporting information
p. 13145 - 13155
(2021/09/03)
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- Rapid Iron(III)?Fluoride-Mediated Hydrogen Atom Transfer
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We anticipate high-valent metal–fluoride species will be highly effective hydrogen atom transfer (HAT) oxidants because of the magnitude of the H?F bond (in the product) that drives HAT oxidation. We prepared a dimeric FeIII(F)?F?FeIII(F) complex (1) by reacting [FeII(NCCH3)2(TPA)](ClO4)2 (TPA=tris(2-pyridylmethyl)amine) with difluoro(phenyl)-λ3-iodane (difluoroiodobenzene). 1 was a sluggish oxidant, however, it was readily activated by reaction with Lewis or Br?nsted acids to yield a monomeric [FeIII(TPA)(F)(X)]+ complex (2) where X=F/OTf. 1 and 2 were characterized using NMR, EPR, UV/Vis, and FT-IR spectroscopies and mass spectrometry. 2 was a remarkably reactive FeIII reagent for oxidative C?H activation, demonstrating reaction rates for hydrocarbon HAT comparable to the most reactive FeIII and FeIV oxidants.
- Doyle, Lorna M.,Gericke, Robert,McDonald, Aidan R.,Panda, Chakadola
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p. 26281 - 26286
(2021/11/12)
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- MWW TYPE ZEOLITE, METHOD FOR PRODUCING SAME, AND CRACKING CATALYST
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Provided are the following: an MWW type zeolite which has many Br?nsted acid sites when in the form of a proton type and which is highly suitable as a cracking catalyst for cumene; a method for producing same; and an application of same. The present invention provides an MWW type zeolite in which the ratio (B/A) of the peak intensity (B) attributable to tetracoordinate aluminum relative to the peak intensity (A) attributable to hexacoordinate aluminum is 2 or more in 27Al MAS NMR, when measured as an ammonium type. The present invention also provides a method for producing an MWW type zeolite, the method having a step for carrying out a hydrothermal synthesis reaction in the presence of: a seed crystal of an MWW type zeolite containing no organic structure-directing agent; and a reaction mixture containing a silica source, an alumina source, an alkali source, an organic structure-directing agent, and water. The reaction mixture satisfies the following molar ratio: X/SiO20.15 (here, X denotes the number of moles of the organic structure-directing agent).
- -
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Paragraph 0142-0144
(2021/01/21)
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- New insight into the electrochemical reduction of different aryldiazonium salts in aqueous solutions
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Electrochemical reduction of different aryldiazonium salts in aqueous solution was studied in this work and it is shown that the aryldiazonium salts are converted to the corresponding aryl radical and aryl anion. The results of this research indicate that the reduction of aryldiazonium salts takes place in two single-electron steps. Our data show that when the substituted group on the phenyl ring is H, Cl, OH, NO2, OCH3or SO3?, the corresponding diazonium salt shows poor adsorption characteristics, but when the substituted group is methyl, the corresponding diazonium salt shows strong adsorption characteristics. In the latter case, the voltammogram exhibits three cathodic peaks. In addition, the effect of various substitutions on the aryldiazonium reduction was studied by Hammett's method. The data are show that with increasing electron withdrawing capacity of the substituent, the reduction of corresponding diazonium salt becomes easier.
- Goljani, Hamed,Nematollahi, Davood,Sepehrmansourie, Hassan,Tavakkoli, Zahra,Zolfigol, Mohammad Ali
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p. 25811 - 25815
(2021/08/09)
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- Method of regenerating zeolite catalyst for aromatization of acetylene by plasma treatment
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The present invention relates to a method of preparing an aromatic compound from acetylene, which includes synthesizing an aromatic compound from an acetylene-containing reactant gas in the presence of a zeolite catalyst for the aromatization of acetylene, and subjecting the zeolite catalyst deactivated by the coke formed in the aromatization of acetylene, to plasma treatment at ambient temperature and pressure so as to selectively remove the external cokes and partial internal coke, thereby regenerating the zeolite catalyst; a method of regenerating the zeolite catalyst used in the aromatization of acetylene by plasma treatment; and a regenerated zeolite catalyst for the aromatization of acetylene, prepared thereof.
- -
-
Page/Page column 11; 16-17
(2021/10/20)
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- METHOD TO PRODUCE C4 OLEFINS FROM NATURAL GAS-DERIVED ACETYLENE
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In accordance with the purpose(s) of the present disclosure, as embodied and broadly described herein, the disclosure relates to a method for producing C4 olefins from acetylene using supported metal-based catalysts and metal-based promoters. The method is inexpensive, efficient, and environmentally sound. Additionally, the method is selective for C4 olefins and other value-added products based on changes to reaction parameters including temperature, feed gas composition, and promoter identity. This abstract is intended as a scanning tool for purposes of searching in the particular art and is not intended to be limiting of the present disclosure.
- -
-
Paragraph 0015; 0016; 0019; 0020; 0248
(2021/10/22)
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- KF-Promoted copper-catalyzed highly efficient and selective oxidation of methane and other alkanes with a dramatic additive effect
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Highly efficient oxidation of methane to methyl trifluoroacetate mediated by CuCl/KF/K2S2O8in trifluoroacetic acid (TFA) and trifluoroacetic anhydride (TFAA) is described. The additive effect has been systematically evaluated and potassium fluoride (KF) was identified as the most effective promoter among the salts screened. KF is conjectured to exhibit the salt effect to promote the [SO4˙]?radical to escape the solvent cage based on control experiments. Cyclohexane and adamantane could also be efficiently oxidized into benzene or corresponding trifluoroacetates.
- Chen, Wei,Chen, Xiaoyan,Fan, Wu,Li, Suhua,Liu, Luyao
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p. 4962 - 4968
(2021/07/26)
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- AROMATIZATION CATALYST WITH IMPROVED ISOMERIZATION, REACTOR CONFIGURATIONS AND USE THEREOF
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Processes for dehydroaromatization of C6 paraffins to form aromatic hydrocarbons are disclosed. The processes include contacting a mixture of branched and linear paraffins with at least two catalysts to produce aromatic hydrocarbons. One catalyst has a higher relative aromatization reactivity and another catalyst has a higher relative isomerization activity. In a common example, a mixture of branched and linear hexanes is contacted with aromatization and isomerization catalysts to produce benzene.
- -
-
Paragraph 0043; 0045; 0047
(2021/03/19)
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- Unprecedented high selectivity of: N -hexane dehydroaromatization to benzene over metal-free phosphorus-doped activated carbon catalysts
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Phosphorus-doped activated carbon is reported for the first time as a highly selective catalyst for n-hexane dehydroaromatization to benzene and hydrogen with 100% n-hexane conversion and 97% benzene selectivity. The weak/medium-strength acidic centres composed of (CO)(C)-P(O)(OH) units on the catalyst surface would be the catalytic active sites. This work provides a new alternative in the preparation of metal-free catalysts for the highly selective functionalization of C-H bonds of n-alkanes. This journal is
- Li, Yong,Bao, Shuhao,Zhao, Hong,Feng, Bing,Chen, Siyuan,Gu, Tangjie,Yang, Bo,Jiang, Biao
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supporting information
p. 4166 - 4169
(2021/05/04)
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- Phosphorus-doped activated carbon catalyst for n-hexane dehydroaromatization reaction
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Phosphorus-doped activated carbon (P@AC), prepared by wet impregnation method, can serve as efficient metal-free catalyst for the dehydroaromatization of n-hexane to benzene under mild conditions. The effect of phosphorus amount and phosphorus sources including phenylphosphonic acid (PPOA), phosphorus acid (H3PO4), triphenylphosphine (TPP), and tributylphosphine (TBP) on catalytic performance of P@AC were investigated. Combining with characterization analysis, functional groups containing -P(O)(OH) on the carbon surface are believed to be the active sites for dehydroaromatization catalysis.
- Li, Yong,Zhao, Hong,Chen, Siyuan,Bao, Shuhao,Xing, Feifei,Jiang, Biao
-
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- Eco-friendly preparation of ultrathin biomass-derived Ni3S2-doped carbon nanosheets for selective hydrogenolysis of lignin model compounds in the absence of hydrogen
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Lignin is an abundant source of aromatics, and the depolymerization of lignin provides significant potential for producing high-value chemicals. Selective hydrogenolysis of the C-O ether bond in lignin is an important strategy for the production of fuels and chemical feedstocks. In our study, catalytic hydrogenolysis of lignin model compounds (β-O-4, α-O-4 and 4-O-5 model compounds) over Ni3S2-CS catalysts was investigated. Hence, an array of 2D carbon nanostructure Ni3S2-CSs-X-Yderived catalysts were produced using different compositions at different temperatures (X= 0 mg, 0.2 mg, 0.4 mg, 0.6 mg, and 0.8 mg; Y = 600 °C, 700 °C, 800 °C, and 900 °C) were prepared and applied for hydrogenolysis of lignin model compounds and depolymerization of alkaline lignin. The highest conversion of lignin model compounds (β-O-4 model compound) was up to 100% and the yield of the obtained corresponding ethylbenzene and phenol could achieve 92% and 86%, respectively, over the optimal Ni3S2-CSs-0.4-700 catalyst in iPrOH at 260 °C without external H2. The 2D carbon nanostructure catalysts performed a good dispersion on the surface of the carbon nanosheets, which facilitated the cleavage of the lignin ether bonds. The physicochemical characterization studies were carried out by means of XRD, SEM, TEM, H2-TPR, NH3-TPD, Raman and XPS analyses. Based on the optimal reaction conditions (260 °C, 4 h, 2.0 MPa N2), various model compounds (β-O-4, α-O-4 and 4-O-5 model compounds) could also be effectively hydrotreated to produce the corresponding aromatic products. Furthermore, the optimal Ni3S2-CSs-0.4-700 catalyst could be carried out in the next five consecutive cycle experiments with a slight decrease in the transformation of lignin model compounds.
- Chen, Changzhou,Jiang, Jianchun,Li, Jing,Liu, Peng,Wu, Dichao,Xia, Haihong,Zhou, Minghao
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p. 3090 - 3103
(2021/05/07)
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- Design and preparation of metal-based carbon nanosheets for C–O bond cleavage in the absence of external H2
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A facile yet sustainable approach for the production of Ni3S2-doped ultrathin carbon nanosheets in one-pot with very thin thickness of 30 nm was reported. Reaction of nickel nitrate hexahydrate, sodium lignosulfonate with boric acid could produce ultrathin carbon nanosheets. In comparison with the conventional method for the synthesis of Ni3S2-doped ultrathin carbon nanosheets, this reaction did not require second vulcanization step. Sodium lignosulfonate was used as carbon and sulfur source. Boric acid was used as 2D template and it could also be readily recycled for repeated use by simply evaporative crystallization. Ni3S2-doped ultrathin carbon nanosheets was expected to be an excellent catalyst for C–O bond cleavage under 260°C through catalytic transfer hydrogenation process. In addition, the optimal catalyst could also be recovered in the end.
- Chen, Changzhou,Zhou, Minghao,Jiang, Jianchun
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p. 1181 - 1185
(2021/06/23)
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- Environmentally-friendly and sustainable synthesis of bimetallic NiCo-based carbon nanosheets for catalytic cleavage of lignin dimers
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This paper reports on a study of 2D metal-based (Ni-, NiCo-) carbon nanosheet (CNs) material that were synthesized via a template method and the synthetic materials showed an ultra-thin lamellar structure. The structures were characterized using different analytical methods including XRD, SEM, EDX, TEM, XPS, NH3-TPD. The synthesized NiCo-based CNs are ultrathin sheet shape with good crystallinity and uniform particle distributions. In the synthetic route of NiCo-based CNs, sodium lignosulfonate was employed as carbon and sulfur source and boric acid was used as 2D template to form a perfect lamellar structure. It manifested an environmentally-friendly and sustainable concept for preparation of the 2D NiCo-CNs. Although simple CNs was a poor catalyst, after Ni and NiCo doping, it became highly active in cleavage of β-O-4 ether bond in lignin through a catalytic transfer hydrogenation process and led to very high product yields.
- Chen, Changzhou,Jiang, Jianchun,Liu, Peng,Ren, Jurong,Wu, Dichao,Xia, Haihong,Zhou, Minghao
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- Carbon-Halogen Bond Activation with Powerful Heavy Alkaline Earth Metal Hydrides
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Reaction of [(DIPePBDI)SrH]2 with C6H5X (X=Cl, Br, I) led to hydride-halogenide exchange (DIPePBDI=HC[(Me)CN-2,6-(3-pentyl)phenyl]2). Conversion rates increase with increasing halogen size (FDIPePBDI)SrH]2 with C6H5F was slow and ill-defined but addition of C6H4F2 gave smooth hydride-fluoride exchange. After addition of THF the full range of Sr halogenides was structurally characterized: [(DIPePBDI)SrX ? THF]2 (X=F, Cl, Br, I). Mixtures of AeN“2 and PhSiH3 in situ formed less defined but more robust Ae metal hydride clusters (AexN”yHz, Ae=Ca, Sr, Ba and N“=N(SiMe3)2) which are able to hydrodefluorinate C6H5F. Conversion rates increase with increasing metal size (Ca2/PhSiH3 mixtures also converted SF6 at room temperature to give undefined decomposition products. Addition of Me6Tren to a SrN“2/PhSiH3 led to crystallization of [Sr6N”2H9 ? (Me6Tren)3+][SrN“3?]; Me6Tren=tris[2-(dimethylamino)ethyl]amine). After hydrodefluorination, Sr6N”4F8 ? (Me6Tren)2 was formed and structurally characterized. Dissolution in THF led to cluster growth and the larger cluster Sr16N“8F24 ? (THF)12 is structurally characterized. DFT calculations support that hydrodehalogenation of halobenzenes follows a concerted nucleophilic aromatic substitution mechanism (cSNAr).
- Harder, Sjoerd,Knüpfer, Christian,Langer, Jens,Mai, Jonathan,R?sch, Bastian,Wiesinger, Michael
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p. 3731 - 3741
(2021/08/23)
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- Electrochemical Activation of Diverse Conventional Photoredox Catalysts Induces Potent Photoreductant Activity**
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Herein, we disclose that electrochemical stimulation induces new photocatalytic activity from a range of structurally diverse conventional photocatalysts. These studies uncover a new electron-primed photoredox catalyst capable of promoting the reductive cleavage of strong C(sp2)?N and C(sp2)?O bonds. We illustrate several examples of the synthetic utility of these deeply reducing but otherwise safe and mild catalytic conditions. Finally, we employ electrochemical current measurements to perform a reaction progress kinetic analysis. This technique reveals that the improved activity of this new system is a consequence of an enhanced catalyst stability profile.
- Chernowsky, Colleen P.,Chmiel, Alyah F.,Wickens, Zachary K.
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p. 21418 - 21425
(2021/08/25)
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- Photo-Initiated Cobalt-Catalyzed Radical Olefin Hydrogenation
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Outer-sphere radical hydrogenation of olefins proceeds via stepwise hydrogen atom transfer (HAT) from transition metal hydride species to the substrate. Typical catalysts exhibit M?H bonds that are either too weak to efficiently activate H2 or too strong to reduce unactivated olefins. This contribution evaluates an alternative approach, that starts from a square-planar cobalt(II) hydride complex. Photoactivation results in Co?H bond homolysis. The three-coordinate cobalt(I) photoproduct binds H2 to give a dihydrogen complex, which is a strong hydrogen atom donor, enabling the stepwise hydrogenation of both styrenes and unactivated aliphatic olefins with H2 via HAT.
- Sang, Sier,Unruh, Tobias,Demeshko, Serhiy,Domenianni, Luis I.,van Leest, Nicolaas P.,Marquetand, Philipp,Schneck, Felix,Würtele, Christian,de Zwart, Felix J.,de Bruin, Bas,González, Leticia,V?hringer, Peter,Schneider, Sven
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p. 16978 - 16989
(2021/08/09)
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- Towards the Circular Economy: Converting Aromatic Plastic Waste Back to Arenes over a Ru/Nb2O5 Catalyst
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The upgrading of plastic waste is one of the grand challenges for the 21st century owing to its disruptive impact on the environment. Here, we show the first example of the upgrading of various aromatic plastic wastes with C?O and/or C?C linkages to arenes (75–85 % yield) via catalytic hydrogenolysis over a Ru/Nb2O5 catalyst. This catalyst not only allows the selective conversion of single-component aromatic plastic, and more importantly, enables the simultaneous conversion of a mixture of aromatic plastic to arenes. The excellent performance is attributed to unique features including: (1) the small sized Ru clusters on Nb2O5, which prevent the adsorption of aromatic ring and its hydrogenation; (2) the strong oxygen affinity of NbOx species for C?O bond activation and Br?nsted acid sites for C?C bond activation. This study offers a catalytic path to integrate aromatic plastic waste back into the supply chain of plastic production under the context of circular economy.
- Jing, Yaxuan,Wang, Yanqin,Furukawa, Shinya,Xia, Jie,Sun, Chengyang,Hülsey, Max J.,Wang, Haifeng,Guo, Yong,Liu, Xiaohui,Yan, Ning
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supporting information
p. 5527 - 5535
(2021/02/05)
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- Comparison of Physicochemical Properties and Catalytic Activity in the m-Xylene Isomerization of Catalysts Based on ZSM-12 Zeolites Prepared at Hydrothermal Conditions and under the Action of Microwave Radiation
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The properties of ZSM-12 zeolites prepared under hydrothermal conditions and microwave radiation influence were investigated. The prepared zeolites were characterized by various physicochemical methods of analysis, e.g., X-ray diffraction analysis, low-temperature nitrogen adsorption/desorption, scanning electron microscopy, solid-state 27Al and 29Si NMR spectroscopy, IR spectroscopy, temperature-programmed desorption of ammonia, IR spectroscopy of adsorbed pyridine, and X-ray fluorescence elemental analysis. The calcined zeolites were impregnated with 0.5 wt.% Pt, which performed the hydrogenation function in the reaction under study. The obtained materials were evaluated in the m-xylene isomerization reaction under the following conditions: Т = 300°С–440°С, WHSV = 1/hr, Р(Н2) = 10 atm. On the ZSM-12 MW catalyst, due to its high acidity and fine particles, which promoted high mass transfer, it is possible to increase the yields of m-xylene isomers, in particular p-xylene, to 36%–65%.
- Tsaplin,Ostroumova,Kulikov,Naranov,Egazar’yants,Karakhanov
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p. 1292 - 1301
(2021/12/29)
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- Aromatization Catalyst And Preparation Process And Use Thereof
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An aromatization catalyst and preparation process and use thereof is set forth. The catalyst comprises an inorganic oxide and a modified Ga-ZSM-5 zeolite, which comprises a modified ZSM-5 zeolite with a hierarchical macro-meso-microporosity and gallium deposited in channels of and/or on surfaces of the modified ZSM-5 zeolite. The hierarchical porosity of the modified ZSM-5 zeolite in the catalyst can reduce diffusion resistance of products during the aromatization reaction, thereby retarding carbon depositing rate and substantially improving catalytic activity, aromatic hydrocarbon selectivity, stability and lifetime of the catalyst. When being used in aromatization of propane, the catalyst exhibits a high stability, a lifetime of more than 320 hours, and a selectivity to aromatic hydrocarbons of up to 73.3 wt. %.
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Paragraph 0091-0092
(2021/07/17)
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- Evaluation of the Properties of ZSM-5 Type Zeolites Modified with CexMg1–xAl2O4 Nanopowders in the Toluene Disproportionation Reaction
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Abstract: The effect of CexMg1–xAl2O4 spinel nanopowders on the textural, acidic, and catalytic properties displayed by HZSM-5 zeolite in the toluene disproportionation reaction was examined. Modification with CexMg1–xAl2O4 nanopowders caused a decrease in the concentration of strong protonic sites, formation of new stronger aprotonic sites, and a decrease in the pore volume of HZSM-5, thereby creating more steric hindrance to diffusion of o- and m-xylenes and enhancing para-selectivity of the catalyst. The possibility of achieving high p-xylene selectivity of 65.7–77.3% via toluene disproportionation over the optimal 5% Сe0.1Mg0.9Al2O4/HZSM-5 catalyst at toluene conversion of 20.3–29.7% was demonstrated. [Figure not available: see fulltext.]
- Akhmedov, E. I.,Akhmedova, N. F.,Ilyasli, T. M.,Kerimli, F. Sh.,Makmudova, N. I.,Mammadov, E. S.,Mammadov, S. E.
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p. 895 - 900
(2021/08/13)
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- Selective C-O Bond Reduction and Borylation of Aryl Ethers Catalyzed by a Rhodium-Aluminum Heterobimetallic Complex
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We report the catalytic reduction of a C-O bond and the borylation by a rhodium complex bearing an X-Type PAlP pincer ligand. We have revealed the reaction mechanism based on the characterization of the reaction intermediate and deuterium-labeling experiments. Notably, this novel catalytic system shows steric-hindrance-dependent chemoselectivity that is distinct from conventional Ni-based catalysts and suggests a new strategy for selective C-O bond activation by heterobimetallic catalysis.
- Hara, Naofumi,Nakao, Yoshiaki,Saito, Teruhiko,Seki, Rin
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supporting information
p. 6388 - 6394
(2021/05/31)
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- Non-plasmonic Ni nanoparticles catalyzed visible light selective hydrogenolysis of aryl ethers in lignin under mild conditions
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Light-driven catalysis on catalytically versatile group VIII metals, which has been widely used in thermal catalysis, holds great potential in solar-to-chemical conversion. We report a novel photocatalysis process for the selective hydrogenolysis of aryl ethers in lignin on a heterogeneous catalyst of non-precious Ni nanoparticles supported on ZrO2. Three aryl ether bonds in lignin were successfully cleaved under mild conditions with excellent conversion and good to excellent selectivity under visible light irradiation. We also used solar irradiation to demonstrate a significant reduction in the total energy consumption. The light irradiation excited interband transitions in Ni nanoparticles and the resultant energetic electrons enhanced the activity of reductive cleavage of the aryl ethers. Its application potential was illustrated by the depolymerization of dealkaline lignin to give a total monomer yield of 9.84 wt% with vanillin, guaiacol, and apocynin as the three major products.
- Baeyens, Jan,Li, Peifeng,Ouyang, Yixuan,Sarina, Sarina,Su, Haijia,Xiao, Gang,Zhao, Yilin,Zhu, Huai-Yong
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supporting information
p. 7780 - 7789
(2021/10/12)
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- H2-Free Selective Dehydroxymethylation of Primary Alcohols over Palladium Nanoparticle Catalysts
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The dehydroxymethylation of primary alcohols is a promising strategy to transform biomass-derived oxygenates into hydrocarbon fuels. In this study, a novel, highly efficient, and reusable heterogeneous catalyst system was established for the H2-free dehydroxymethylation of primary alcohol using cerium oxide-supported palladium nanoparticles (Pd/CeO2). A wide range of aliphatic and aromatic alcohols including biomass-derived alcohols were converted into the corresponding one-carbon shorter hydrocarbons in high yields in the absence of any additives, accompanied by the production of H2 and CO. Pd/CeO2 was easily recovered from the reaction mixture and reused, retaining its high activity, thus, providing a simple and sustainable methodology to produce hydrocarbon fuels from biomass-derived oxygenates.
- Yamaguchi, Sho,Kondo, Hiroki,Uesugi, Kohei,Sakoda, Katsumasa,Jitsukawa, Koichiro,Mitsudome, Takato,Mizugaki, Tomoo
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p. 1135 - 1139
(2020/12/29)
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- Aluminum Metal-Organic Framework-Ligated Single-Site Nickel(II)-Hydride for Heterogeneous Chemoselective Catalysis
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The development of chemoselective and heterogeneous earth-abundant metal catalysts is essential for environmentally friendly chemical synthesis. We report a highly efficient, chemoselective, and reusable single-site nickel(II) hydride catalyst based on robust and porous aluminum metal-organic frameworks (MOFs) (DUT-5) for hydrogenation of nitro and nitrile compounds to the corresponding amines and hydrogenolysis of aryl ethers under mild conditions. The nickel-hydride catalyst was prepared by the metalation of aluminum hydroxide secondary building units (SBUs) of DUT-5 having the formula of Al(μ2-OH)(bpdc) (bpdc = 4,4′-biphenyldicarboxylate) with NiBr2 followed by a reaction with NaEt3BH. DUT-5-NiH has a broad substrate scope with excellent functional group tolerance in the hydrogenation of aromatic and aliphatic nitro and nitrile compounds under 1 bar H2 and could be recycled and reused at least 10 times. By changing the reaction conditions of the hydrogenation of nitriles, symmetric or unsymmetric secondary amines were also afforded selectively. The experimental and computational studies suggested reversible nitrile coordination to nickel followed by 1,2-insertion of coordinated nitrile into the nickel-hydride bond occurring in the turnover-limiting step. In addition, DUT-5-NiH is also an active catalyst for chemoselective hydrogenolysis of carbon-oxygen bonds in aryl ethers to afford hydrocarbons under atmospheric hydrogen in the absence of any base, which is important for the generation of fuels from biomass. This work highlights the potential of MOF-based single-site earth-abundant metal catalysts for practical and eco-friendly production of chemical feedstocks and biofuels.
- Antil, Neha,Kumar, Ajay,Akhtar, Naved,Newar, Rajashree,Begum, Wahida,Dwivedi, Ashutosh,Manna, Kuntal
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p. 3943 - 3957
(2021/04/12)
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- Synergistic effect of Ni-Co alloying on hydrodeoxygenation of guaiacol over Ni-Co/Al2O3 catalysts
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The hydrodeoxygenation (HDO) of guaiacol was investigated in a batch reactor using Ni-Co/γ-Al2O3 catalysts prepared by co-impregnation method. The structural and physicochemical properties of the catalysts were investigated using BET, XRD, H2-TPR, FT-IR, and NH3-TPD. The characterization results revealed that the formation of various Ni-Co composite species strongly depend on the Ni/Co mole ratio, total metal loadings, and the calcination/reduction temperature. The 6.1Ni3.05CoAl (Ni/Co = 1:2) catalyst seeds the formation of NiCo2O4 spinel structure and subsequent formation of Ni-Co alloy, which represents as specific active site for direct demethoxylation/deoxygenation reaction. The synergistic interaction of Ni-Co enhances the selectivity of benzene. The benzene selectivity of 35.2 % and cyclohexane selectivity of 59.1 % with complete conversion of guaiacol (98.9 %) were achieved with the 3.05Ni6.1CoAl catalyst at 575 K. A tentative reaction pathway is proposed based on the product distribution accomplished during HDO reaction. The structural property was correlated with activity to explore the mechanistic insights.
- Raikwar, Deepak,Majumdar, Saptarshi,Shee, Debaprasad
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- Poisoning effect of N-containing compounds on performance of Raney nickel in transfer hydrogenation
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The effect of amines, imines and heterocycle compounds on conversion has been studied in transfer hydrogenation of camphor and 2-PrOH catalyzed by Raney nickel. Small amount (5 mol% to nickel) of N-containing compound significantly decreases catalyst activity. It has been shown that the poisoning effect mostly depends on molecular size of amines and heterocyclic compounds. For aniline and cyclohexylamine the dependence of camphor conversion on poison/nickel ratio was obtained. Additionally, benzaldehyde, cinnamaldehyde demonstrated higher reactivity compared corresponding imines under transfer hydrogenation conditions. Obtained data explain low activity of nickel-based catalysts when N-containing compounds are presented in reaction mixture.
- Martyanov, Oleg N.,Philippov, Alexey A.
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- Dual Active Sites on Molybdenum/ZSM-5 Catalyst for Methane Dehydroaromatization: Insights from Solid-State NMR Spectroscopy
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Methane dehydroaromatization (MDA) on Mo/ZSM-5 zeolite catalyst is promising for direct transformation of natural gas. Understanding the nature of active sites on Mo/ZSM-5 is a challenge for applications. Herein, using 1H{95Mo} double-resonance solid-state NMR spectroscopy, we identify proximate dual active sites on Mo/ZSM-5 catalyst by direct observation of internuclear spatial interaction between Br?nsted acid site and Mo species in zeolite channels. The acidic proton–Mo spatial interaction is correlated with methane conversion and aromatics formation in the MDA process, an important factor in determining the catalyst activity and lifetime. The evolution of olefins and aromatics in Mo/ZSM-5 channels is monitored by detecting their host–guest interactions with both active Mo sites and Br?nsted acid sites via 1H{95Mo} double-resonance and two-dimensional 1H–1H correlation NMR spectroscopy, revealing the intermediate role of olefins in hydrocarbon pool process during the MDA reaction.
- Gao, Wei,Qi, Guodong,Wang, Qiang,Wang, Weiyu,Li, Shenhui,Hung, Ivan,Gan, Zhehong,Xu, Jun,Deng, Feng
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supporting information
p. 10709 - 10715
(2021/04/09)
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- Ordered macroporous Co3O4-supported Ru nanoparticles: A robust catalyst for efficient hydrodeoxygenation of anisole
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A three-dimensional ordered macroporous Co3O4 (OM-Co3O4) supported Ru catalyst was developed for the efficient hydrodeoxygenation (HDO) of anisole. It is revealed that small-sized Ru nanoparticles evenly distributed over the surface of OM-Co3O4 with large quantities of oxygen vacancies could strongly capture Ru0 species, thereby resulting in strong Ru-Co3O4 interactions. Compared with commercial Co3O4 supported Ru catalyst, Ru/OM-Co3O4 displays a better catalytic HDO performance, with a high cyclohexane yield of 92.4% at 250 °C and 0.5 MPa hydrogen pressure after 5 h on stream. Such a significant efficiency of Ru/OM-Co3O4 is mainly attributed to both high dispersion of Ru0 species and an enhanced formation of surface defects, as well as the unique macroporous framework of OM-Co3O4 support.
- Wang, An,Shi, Yisheng,Yang, Lan,Fan, Guoli,Li, Feng
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- Synergistic effect for selective hydrodeoxygenation of anisole over Cu-ReOx/SiO2
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Selective hydrodeoxygenation (HDO) of lignin derived oxygenated aromatic compounds has great significance for lignin utilization and chemicals production. Hereby, bifunctional catalysts of Cu-MOx/SiO2 (M = Re, Mo or W) were prepared to study the synergistic effect of Cu and MOx on the performance of anisole HDO. Characterizations indicated that Cu interacted strongly with the second metal species. As a result, more efficient sites exposed on catalysts surface, and metal dispersion and surface properties both were improved. Besides, adsorption strength for both oxygen atom and aromatic ring in reactant were all adjusted due to Cu-MOx interaction. Bimetallic catalyst Cu-ReOx/SiO2 showed the highest HDO activity, while Cu-MoOx/SiO2 and Cu-WOx/SiO2 both preferred transmethylation because of their prominent acid properties. The Cu-ReOx composition was found to evidently affect the anisole conversion and selectivity of benzene, toluene and xylene (BTX). The highest BTX yield of 50.5 % could be achieved when Cu/Re ratio was 3.
- Wang, Xiaofei,Zhou, Wei,Wang, Yue,Huang, Shouying,Zhao, Yujun,Wang, Shengping,Ma, Xinbin
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p. 223 - 234
(2020/04/27)
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- Nonoxidative Methane Conversion on Granulated Mo/ZSM-5 Catalysts
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Abstract: Nonoxidative conversion of methane to aromatic hydrocarbons on granulatedМо/ZSM-5 catalysts was studied. The catalysts prepared using zeolites with thehierarchic pore system surpass in activity the catalysts prepared by thetraditional method, mi
- Stepanov,Kuvatova,Korobitsyna,Travkina,Vosmerikov,Kutepov
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p. 370 - 377
(2021/02/16)
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- Rapid hydrothermal synthesis of hierarchical ZSM-5/beta composite zeolites
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An innovative hydrothermal method has been successfully applied to the synthesis of hierarchical ZSM-5/beta composite zeolites with different mass ratios. Firstly, the ZSM-5 zeolites were coated with amorphous silica and aluminum species by a spray drying process. Then, the precursor powder was hydrothermally crystallized for only 1-2 days with the addition of tetraethyl ammonium hydroxide (TEAOH). The obtained products were characterized by XRD, SEM, TEM, N2physical adsorption-desorption,27Al MAS NMR, ICP, pyridine-IR and NH3-TPD techniques. The characterization results imply that the ZSM-5/beta composite zeolites exhibit hierarchical-pores, higher external surface areas and larger mesopore volumes as compared to those of the pure ZSM-5 and beta zeolite. Moreover, the pore structure and acid sites of the ZSM-5/beta composite can be adjusted by changing the mass ratio of ZSM-5/beta. Finally, the ZSM-5/beta composite catalysts exhibit good catalytic performances in the cracking of 1,3,5-triisopropylbenzene (1,3,5-TIPB).
- Liu, Jiaxu,Liu, Liping,Meng, Feifei,Xiong, Guang,Zhao, Leping
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p. 21235 - 21247
(2021/07/01)
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- Photoredox-catalyzed reduction of halogenated arenes in water by amphiphilic polymeric nanoparticles
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The use of organic photoredox catalysts provides new ways to perform metal-free reactions controlled by light. While these reactions are usually performed in organic media, the application of these catalysts at ambient temperatures in aqueous media is of considerable interest. We here compare the activity of two established organic photoredox catalysts, one based on 10-phenylphenothiazine (PTH) and one based on an acridinium dye (ACR), in the light-activated dehalogenation of aromatic halides in pure water. Both PTH and ACR were covalently attached to amphiphilic polymers that are designed to form polymeric nanoparticles with hydrodynamic diameter DH ranging between 5 and 11 nm in aqueous solution. Due to the hydrophobic side groups that furnish the interior of these nanoparticles after hydrophobic collapse, water-insoluble reagents can gather within the nanoparticles at high local catalyst and substrate concentrations. We evaluated six different amphiphilic polymeric nanoparticles to assess the effect of polymer length, catalyst loading and nature of the catalyst (PTH or ACR) in the dechlorination of a range of aromatic chlorides. In addition, we investigate the selectivity of both catalysts for reducing different types of aryl-halogen bonds present in one molecule, as well as the activity of the catalysts for C-C cross-coupling reactions. We find that all polymer-based catalysts show high activity for the reduction of electron-poor aromatic compounds. For electron-rich compounds, the ACR-based catalyst is more effective than PTH. In the selective dehalogenation reactions, the order of bond stability is C-Cl > C-Br > C-I irrespective of the catalyst applied. All in all, both water-compatible systems show good activity in water, with ACR-based catalysts being slightly more efficient for more resilient substrates.
- Eisenreich, Fabian,Kuster, Tom H. R.,Palmans, Anja R. A.,van Krimpen, David
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supporting information
(2021/10/05)
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