683-73-8Relevant academic research and scientific papers
A Comparative Analysis of the CO-Reducing Activities of MoFe Proteins Containing Mo- and V-Nitrogenase Cofactors
Lee, Chi Chung,Tanifuji, Kazuki,Newcomb, Megan,Liedtke, Jasper,Hu, Yilin,Ribbe, Markus W.
, p. 649 - 653 (2018/04/16)
The Mo and V nitrogenases are structurally homologous yet catalytically distinct in their abilities to reduce CO to hydrocarbons. Here we report a comparative analysis of the CO-reducing activities of the Mo- and V-nitrogenase cofactors (i.e., the M and V clusters) upon insertion of the respective cofactor into the same, cofactor-deficient MoFe protein scaffold. Our data reveal a combined contribution from the protein environment and cofactor properties to the reactivity of nitrogenase toward CO, thus laying a foundation for further mechanistic investigation of the enzymatic CO reduction, while suggesting the potential of targeting both the protein scaffold and the cofactor species for nitrogenase-based applications in the future.
deuterium generation ethylene preparation method
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Paragraph 0027; 0038; 0040; 0041-0049; 0056-0067, (2018/02/04)
The invention discloses a preparation method of deuteroethylene. According to the preparation method, calcium carbide is reacted with D2O to generate deuteroacetylene; a deuteration reaction is performed on the prepared deuteroacetylene and deuterium gas in the presence of a composite catalyst Cu-Ni/SiO2 to obtain the deuteroethylene; the volume ratio of the deuteroacetylene to the deuterium gas is 1: (10-60). The preparation method of the deuteroethylene is applicable to industrial production and has been verified and utilized in an industrial pilot plant already; experimental results prove that the preparation method has the advantages of simple reaction steps, mild reaction conditions, high deuteroethylene yield, recyclability of superfluous deuterium gas in the reaction as the raw material, and great reduction of the production cost.
Metathesis of C5–C8 Terminal Olefins on Re2O7/Al2O3 Catalysts
Kustov, Leonid M.,Furman, Daniil B.,Barkova, Aleksandra P.
, p. 1033 - 1039 (2016/06/01)
Abstract: Primary products of the interaction of terminal olefins C5–C8 with Re2O7/Al2O3 catalysts are established. The rupture of the C=C bond of the olefin occurs with formation of a carbene localized at a rhenium ion, with the alkylidene fragment in the produced carbene being the CH2=group of the terminal alkene molecule. Thus M=CH2 species and lower normal α-olefins are formed. Graphical Abstract: [Figure not available: see fulltext.]
Reaction Mechanism and Kinetics of Olefin Metathesis by Supported ReOx/Al2O3 Catalysts
Lwin, Soe,Wachs, Israel E.
, p. 272 - 278 (2016/01/12)
The self-metathesis of propylene by heterogeneous supported ReOx/Al2O3 catalysts was investigated with in situ Raman spectroscopy, isotopic switch (D-C3= → H-C3=), temperature-programmed surface reaction (TPSR) spectroscopy, and steady-state kinetic studies. The in situ Raman studies showed that two distinct surface ReO4 sites are present on alumina and that the olefins preferentially interact with surface ReO4 sites anchored at acidic surface sites of alumina (olefin adsorption: C4= > C3= > C2=). The isotopic switch experiments demonstrate that surface Re?CH3 and Re?CHCH3 are present during propylene metathesis, with Re? representing activated surface rhenia sites. At low temperatures (3=][Re?]2. At high temperatures (>100 °C), the rate-determining step is the recombination of two surface propylene molecules (rate ≈ [C3=]2[Re?]). To a lesser extent, the recombination of surface Re?CH3 and Re?CHCH3 intermediates also contributes to self-metathesis of propylene at elevated reaction temperatures.
On ethane ODH mechanism and nature of active sites over NiO-based catalysts via isotopic labeling and methanol sorption studies
Skoufa,Heracleous,Lemonidou
, p. 118 - 129 (2015/09/28)
In this paper, the ethane oxidative dehydrogenation (ODH) mechanism is thoroughly investigated via isotopic labeling and methanol sorption studies over NiO and highly selective Ni0.85Nb0.15Ox catalysts. ODH experiments with unlabeled and deuterium labeled ethane demonstrated the existence of strong kinetic isotope effect (KIE) over both NiO and Ni0.85Nb0.15Ox, indicating that C-H bond scission is the rate determining step in ethane ODH. Similar KIE values obtained for NiO and Ni0.85Nb0.15Ox mixed oxide indicate that both catalysts share similar active sites for ethane activation. Methanol adsorption/desorption followed by TGA, MS, and in situ DRIFTS showed that pure and Nb-doped nickel oxide surfaces primarily host the same redox active sites that differ in terms of abundance (i.e. surface concentration) and activity. O2-TPD studies of used catalysts verified the participation of non-stoichiometric oxygen species in the reaction, which proceeds via a redox mechanism. Based on the above, a detailed reaction mechanism is proposed.
Oxidative dehydrogenation of ethane on dynamically rearranging supported chloride catalysts
G?rtner, Christian A.,Van Veen, Andr C.,Lercher, Johannes A.
supporting information, p. 12691 - 12701 (2014/12/10)
Ethane is oxidatively dehydrogenated with a selectivity up to 95% on catalysts comprising a mixed molten alkali chloride supported on a mildly redox-active Dy2O3-doped MgO. The reactive oxyanionic OCl- species acting as active sites are catalytically formed by oxidation of Cl- at the MgO surface. Under reaction conditions this site is regenerated by O2, dissolving first in the alkali chloride melt, and in the second step dissociating and replenishing the oxygen vacancies on MgO. The oxyanion reactively dehydrogenates ethane at the melt-gas phase interface with nearly ideal selectivity. Thus, the reaction is concluded to proceed via two coupled steps following a Mars-van-Krevelen-mechanism at the solid-liquid and gas-liquid interface. The dissociation of O2 and/or the oxidation of Cl- at the melt-solid interface is concluded to have the lowest forward rate constants. The compositions of the oxide core and the molten chloride shell control the catalytic activity via the redox potential of the metal oxide and of the OCl-. Traces of water may be present in the molten chloride under reaction conditions, but the specific impact of this water is not obvious at present. The spatial separation of oxygen and ethane activation sites and the dynamic rearrangement of the surface anions and cations, preventing the exposure of coordinatively unsaturated cations, are concluded to be the origin of the surprisingly high olefin selectivity.
Differential Reduction of CO2 by Molybdenum and Vanadium Nitrogenases
Rebelein, Johannes G.,Hu, Yilin,Ribbe, Markus W.
supporting information, p. 11543 - 11546 (2016/02/19)
The molybdenum and vanadium nitrogenases are two homologous enzymes with distinct structural and catalytic features. Previously, it was demonstrated that the Vnitrogenase was nearly 700 times more active than its Mo counterpart in reducing CO to hydrocarbons. Herein, a similar discrepancy between the two nitrogenases in the reduction of CO2 is reported, with the Vnitrogenase being capable of reducing CO2 to CO, CD4, C2D4, and C2D6, and its Mocounterpart only capable of reducing CO2 to CO. Furthermore, it is shown that the Vnitrogenase may direct the formation of CD4 in part via CO2-derived CO, but that it does not catalyze the formation of C2D4 and C2D6 along this route. The exciting observation of a Vnitrogenase-catalyzed C-C coupling with CO2 as the origin of the building blocks adds another interesting reaction to the catalytic repertoire of this unique enzyme system. The differential activities of the V and Monitrogenases in CO2 reduction provide an important framework for systematic investigations of this reaction in the future.
Kinetics and mechanism of ethanol dehydration on γ-Al 2O3: The critical role of dimer inhibition
DeWilde, Joseph F.,Chiang, Hsu,Hickman, Daniel A.,Ho, Christopher R.,Bhan, Aditya
, p. 798 - 807 (2013/05/21)
Steady state, isotopic, and chemical transient studies of ethanol dehydration on γ-alumina show unimolecular and bimolecular dehydration reactions of ethanol are reversibly inhibited by the formation of ethanol-water dimers at 488 K. Measured rates of ethylene synthesis are independent of ethanol pressure (1.9-7.0 kPa) but decrease with increasing water pressure (0.4-2.2 kPa), reflecting the competitive adsorption of ethanol-water dimers with ethanol monomers; while diethyl ether formation rates have a positive, less than first order dependence on ethanol pressure (0.9-4.7 kPa) and also decrease with water pressure (0.6-2.2 kPa), signifying a competition for active sites between ethanol-water dimers and ethanol dimers. Pyridine inhibits the rate of ethylene and diethyl ether formation to different extents verifying the existence of acidic and nonequivalent active sites for the dehydration reactions. A primary kinetic isotope effect does not occur for diethyl ether synthesis from deuterated ethanol and only occurs for ethylene synthesis when the β-proton is deuterated; demonstrating olefin synthesis is kinetically limited by either the cleavage of a Cβ-H bond or the desorption of water on the γ-alumina surface and ether synthesis is limited by the cleavage of either the C-O bond of the alcohol molecule or the Al-O bond of a surface bound ethoxide species. These observations are consistent with a mechanism inhibited by the formation of dimer species. The proposed model rigorously describes the observed kinetics at this temperature and highlights the fundamental differences between the Lewis acidic γ-alumina and Bronsted acidic zeolite catalysts.
Tracing the hydrogen source of hydrocarbons formed by vanadium nitrogenase
Lee, Chi Chung,Hu, Yilin,Ribbe, Markus W.
experimental part, p. 5545 - 5547 (2011/07/08)
Hydrocarbons from CO: The vanadium-nitrogenase-catalyzed reduction of carbon monoxide involves the adenosine triphosphate (ATP)-dependent protonation of CO and the subsequent formation of C - C bonds, leading to the production of small hydrocarbons, such as C2H4, C2H 6, C3H6, and C3H8 (see picture). Isotope-substitution studies monitored by GC-MS analysis show that protons are the source of hydrogen for the CO reduction. Copyright
Coupling reactions in aldehydes adsorbed on V(100) single-crystal surfaces
Shen, Min,Zaera, Francisco
experimental part, p. 8708 - 8713 (2009/10/23)
The thermal chemistry of formaldehyde on vanadium (100) single-crystal surfaces was characterized under ultrahigh vacuum (UHV) conditions by using temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) in combination with isotope-labeling experiments. Particular emphasis was placed on establishing a mechanism for the formation of ethylene, which was observed to desorb in two temperature regimes, at 290 and 540 K. The low-temperature reaction was determined to occur via the coupling of methylene groups formed on the surface upon dissociation of the C-O bond in adsorbed formaldehyde. The high-temperature ethylene, on the other hand, was proven to require the prior formation of a diolate, -OCH2CH2O-, intermediate. This chemistry was shown to be quite general, also occuring in cross-coupling mode between two different coadsorbed aldehydes.
