Stoichiometric Amount Of CO Research Articles

Mechanistic insights into the electrochemical reduction of CO2 to CO on Ni(salphen) complexes

Ni(salphen) reduces CO2 to CO via a double reduction/protonation mechanism, and the active species binds to CO, only releasing stoichiometric amounts of CO upon exposure to air. This has been confirmed in both experimental and computational studies.

Preparation and characterization of ultra-small, monodisperse CoxFe3-xO4 nanoparticles

The application of magnetite nanoparticles to functional magnetic materials requires the ability to tune their magnetic properties. Doping of transition metals offers the ability to control the magnetic and electron transport properties of magnetite nanoparticles. Herein, we describe a synthetic approach to producing ultra-small (∼6 nm), monodisperse Co-doped magnetite (CoxFe3-xO4) nanoparticles, capped with oleic acid, using a modified co-precipitation method under mild conditions. For stoichiometric amounts of Co corresponding to x = 0.1, 0.3, and 0.5, we measured compositions of Co0.12Fe2.88O4, Co0.33Fe2.67O4, and Co0.58Fe2.42O4, respectively, using XPS analysis. Although a minor impurity of α-FeOOH was detected, this impurity was found to reduce significantly with increasing Co content. The resulting CoxFe3-xO4 nanoparticles showed significant increase in both the coercive field, and the blocking temperatures with increasing Co content, due to increased magnetic anisotropy. Magnetic characterization further revealed saturation magnetization values higher than those reported for CoxFe3-xO4 nanoparticles of similar size, monodispersity and Co content, prepared by other methods.

Ammonia-Assisted Light Alkane Anti-coke Reforming on Isolated ReOxSites in Zeolite

The conventional reforming produces H2 with stoichiometric amounts of CO and CO2 from hydrocarbons. Here, we show that COx-free H2 can be produced from ammonia-assisted reforming (ammoreforming) of natural gas liquids (CnH2n+2 + nNH3 = nHCN + (2n + 1) H2, n = 2 or 3) at the same conditions as the steam reforming. Such a process co-produces HCN, which can be easily separated from H2 and used as value-added chemicals or for NH3 recycling through hydrolysis. The ammoreforming of ethane and propane was realized over the Re-modified HZSM-5 zeolite rather than the traditional Pt-based catalyst for the BMA process (methane ammoreforming). The specific activity of the Re/HZSM-5 catalysts at 650 °C is up to 1 molH2/gRe/min (or 180 min–1) during ethane ammoreforming. The catalyst is highly coke resistant and shows only slight deactivation with a time-on-stream up to 20 h. Characterization of the fresh and used catalysts by X-ray absorption and Raman spectroscopies suggested that the isolated ReOx site grafted by AlO4– tetrahedral in the zeolite framework is responsible for the outstanding catalytic activity and coke resistibility.

In situ CO2 reactivation of FeCrOx/C catalyst in the oxidative dehydrogenation of ethane to ethylene

Catalyst FeCrOx/C in the course of oxidative dehydrogenation of ethane with carbon dioxide to ethylene at temperatures of 600–700 °C was found to undergo in situ regeneration with CO2 to give a stoichiometric amount of CO by the Boudoir–Bell reaction with the surface carbonized material.

Highly selective photocatalytic conversion of CO2 by water over Ag-loaded SrNb2O6 nanorods

Strontium niobates (SrNb2O6 and Sr2Nb2O7) with regular nanostructures were synthesized by a facile flux method. Ag-loaded SrNb2O6 and Sr2Nb2O7 exhibited different performances for the photocatalytic reduction of CO2 in H2O. Compared to Sr2Nb2O7 nanoflakes and SrNb2O6 nanoparticles, SrNb2O6 nanorods exhibited higher photocatalytic activity and selectivity toward CO evolution. Stoichiometric amounts of CO (51.2μmolh−1) and H2 (1.1μmolh−1) as the reduction products, in addition to O2 (24.8μmolh−1) as the oxidation product, were obtained, indicating that H2O serves as an electron donor in the photocatalytic conversion of CO2. In addition, the effect of the Ag cocatalyst on the photocatalytic conversion of CO2 was investigated.

ChemInform Abstract: Intracell Hydrogen Adsorption‐Transmission in a Co2P Solid Hydrogen‐Storage Material.

AbstractCo2P nanoparticles are obtained by ball milling (600 rpm, 6 h) of stoichiometric amounts of Co and red P under argon.

ChemInform Abstract: A Palladium‐Catalyzed Double Carbonylation Approach to Isatins from 2‐Iodoanilines.

AbstractThe Pd‐catalyzed double carbonylation of 2‐iodoanilines using nearly stoichiometric amounts of CO, generated ex situ from solid CO‐surrogate SilaCogen, followed by acid promoted cyclization of intermediates (IV) affords isatine derivatives.

A Palladium‐Catalyzed Double Carbonylation Approach to Isatins from 2‐Iodoanilines

AbstractA high‐yielding procedure for the synthesis of isatins has been developed. Sequential Pd‐catalyzed double carbonylation of 2‐iodoanilines with near stoichiometric amounts of CO followed by acid‐promoted cyclization readily affords an array of isatins. The conversion of 2‐iodoanilines to isatins in good to excellent yields was found to proceed with good functional group tolerance. This protocol proved adaptable to 13C‐isotope labeling of isatins, which was extended to the synthesis of the 13C‐isotope labeled antiviral drug metisazone and the experimental anti‐schizophrenia drug ML137.

ChemInform Abstract: Pd‐Catalyzed Carbonylative Access to Aroyl Phosphonates from (Hetero)aryl Bromides.

AbstractThis is the first transition‐metal catalyzed carbonylation with a phosphorus nucleophile.

Na2CoPO4f As High Voltage Positive Materials for Sodium Ion Batteries

Although Li-ion batteries became the most popular power sources for personal digital assistants, rare-metal free or low-cost materials derived from more abundant resources have become increasingly desirable. Especially, studies of positive materials for sodium-ion batteries (NIBs) have been intensely discussed for past 5 years, some of reported candidates such as layered oxides [1,2] delivered promising outcome for productization of NIBs. However, their overall electrochemical performance is still inferior to the Li system and developing new materials becomes challenging due to its fundamental nature such as lower working voltage, heavier atomic weight, and lager ionic radius, leading to low energy density and poor cycle performance. Despite of these demerits, some phosphate materials [3,4] have demonstrated good electrochemical performance with medium discharge capacity of around 100 mAh/g and high redox voltage close to 4.0 V. We, therefore focused on phosphate materials, Na2CoPO4F, to explore the potential of high voltage positive active materials to achieve higher energy density for the NIBs. Na2CoPO4F was first reported in 2010 in Li system [5] and its performance as active materials was not so attractive because the potential window in the Li system is not satisfactory for operation of this material. In 2014, our group reported its electrochemical performance in the Na system where Na2CoPO4F exhibited high working voltage of 4.3 V with relatively large discharge capacity, and however it suffered from impurity and serious performance degradation during few cycles [6]. In this study, we developed synthesis route for single phase of Na2CoPO4F while adding citric acid and VGCF to increase conductivity and we studied its electrochemical properties. Na2CoPO4F products were obtained by a two-step solid synthesis method. Stoichiometric amounts of Co(NO3)2-H2O, NaNO3 and (NH4)2HPO4 are mixed with critic acid in distilled water to obtain sol-gel precursor mixtures. 20 w/w% of VGCF was added to the precursor and the mixture was heated at 650 oC for 10 hours. And then, stoichiometric amount of NaF was mixed to the obtained material, and the mixture was heated again 600 oC for 3 hours under Ar flow. The electrode for charge and discharge measurement was made of Na2CoPO4F /VGCF composite, acetylene black and polytetrafluoroethylene binder in a weight ratio of 90:5:5 and R2032-type coin cells were assembled with 1 M NaPF6 / EC:DEC (= 1:1) 2 v/v% FEC as electrolyte and sodium metal as a negative material. In addition, ex-situ XRD measurements for the electrodes at various charge and discharge states on the 1st cycle were carried out in order to examine the structural change accompanying Na+extraction/insertion. The ex-situ XRD measurement was done by using an Ar-filled hermetic sample holder. The obtained powder product was identified to be a single phase of Na2CoPO4F with a space group, Pbcn, by XRD. Na2CoPO4F showed the first discharge capacity of ca. 112 mAh/g, with two discharge redox voltages at 4.39 V and 4.46 V, and its average working voltage was 4.3 V with good capacity maintenance in Fig. 1. As shown in Fig. 2, the ex-situ XRD data revealed that diffraction profiles of Na2CoPO4F become broad after charge up to 4.8 V and returned to the original profile located at the original 2 theta position after one cycle, suggesting its reversibility of phase transition during cycles. Although the electrochemical profile indicated the two-phase reaction, obvious second phase in the ex-situ data was not observed. However the ex-situ XRD profile of end-members after 4.8 V charge was quite similar to that previously reported in Na2FePO4F[6]. For investigating more detailed charge and discharge mechanize of Na2FePO4F, we performed in-situ XRD and further measurements. The result will be discussed in the conference. Figure 1

ChemInform Abstract: Palladium‐Catalyzed Carbonylative α‐Arylation of Nitromethane.

AbstractThis method uses a two‐chamber system allowing the reaction to run with near stoichiometric amounts of CO.

Photocatalytic Water Splitting and CO2 Reduction over KCaSrTa5O15 Nanorod Prepared by a Polymerized Complex Method

Abstract Single-crystal KCaSrTa5O15 nanorods were successfully synthesized by a polymerized complex method. SEM and TEM observations revealed that the nanorods growing along the c axis of a tungsten bronze structure measured 40–100 nm in diameter and 100–300 nm in length. Tb(0.03 atom %)-doped KCaSrTa5O15 nanorods gave a green luminescence due to the 5D4 → 7F6 and 5D4 → 7F5 transition of Tb3+, when the KCaSrTa5O15 host was excited. The intensity of the luminescence was much higher than that by polycrystalline KCaSrTa5O15 prepared by a solid-state reaction. This indicates that nonradiative deactivation at grain boundaries was suppressed in the KCaSrTa5O15 nanorods compared to the polycrystalline KCaSrTa5O15. NiO cocatalyst-loaded KCaSrTa5O15 nanorods split water into H2 and O2 with an apparent quantum yield of 6.6% at 254 nm. The efficiency was three times as high as that of the polycrystalline KCaSrTa5O15. The KCaSrTa5O15 nanorods also showed photocatalytic activity for CO2 reduction, when a Ag-cocatalyst was loaded. Stoichiometric amounts of CO and H2 as reduction products and O2 as an oxidation product were obtained. The activity for CO2 reduction was improved by adding NaHCO3 into the reactant solution, giving about 90% CO selectivity (CO/(CO + H2)).

Pd-catalyzed carbonylative access to aroyl phosphonates from (hetero)aryl bromides.

The first transition-metal catalysed carbonylation with a phosphorus nucleophile is presented. This transformation provides efficient and mild access to aroylphosphonates under mild conditions, thus ensuring a broad substrate scope. The utility of aroylphosphonates as useful reagents, capable of participating in a number of transformations, is subsequently demonstrated. Furthermore, access to [(13)C]-carbonyl labelled aroylphosphonates is easily realised for the first time, as only a near stoichiometric amount of CO is required applying this carbonylation.

C–Cl bond activation and catalytic hydrodechlorination of hexachlorobenzene by cobalt and nickel complexes with sodium formate as a reducing agent

A benzyne cobalt complex, Co(η(2)-C6Cl4)(PMe3)3 (2), was generated from the reaction of hexachlorobenzene with 2 equiv. of Co(PMe3)4 through selective activation of two C-Cl bonds of hexachlorobenzene. Meanwhile, the byproduct CoCl2(PMe3)3 was also confirmed by IR spectra. The cobalt(II) complex, CoCl(C6Cl5)(PMe3)3 (1), as an intermediate in the formation of aryne complex 2, was also isolated by the reaction of hexachlorobenzene with the stoichiometric amount of Co(PMe3)4. Complex 2 could be obtained by the reaction of 1 with Co(PMe3)4. Under similar reaction conditions, the reaction of Ni(PMe3)4 with hexachlorobenzene afforded only a mono-(C-Cl) bond activation nickel(II) complex, NiCl(C6H5)(PMe3)2 (5). The expected benzyne nickel complex was not formed. The structures of complexes 2 and 5 were determined by X-ray single crystal diffraction. Successful selective hydrodechlorinations of hexachlorobenzene were studied and in the presence of Co(PMe3)4 or Ni(PMe3)4 as catalysts and sodium formate as a reducing agent pentachlorobenzene and 1,2,4,5-tetrachlorobenzene were obtained. The catalytic hydrodechlorination mechanism is proposed and discussed.

New Dinuclear Cobalt(II) and Zinc(II) Complexes of a Carboxylate-Rich Dinucleating Ligand: Synthesis, Structure, Spectroscopic Characterization, and Their Interactions with Sugars

Sugar-metal ion interactions in aqueous medium are involved in many biochemical processes such as the transport and storage of metals, the function and regulation of sugar-metabolizing metalloenzymes, the mechanism of action of metal-containing pharmaceuticals, and toxic metal metabolism. To understand such interactions we synthesized and fully characterized two new dinuclear cobalt(II) and zinc(II) complexes as carbohydrate binding models for xylose/glucose isomerases (XGI). Synthesis of the dicobalt complex, Na3[Co2(ccdp)(μ-HCO2)]BF4·9H2O·2CH3OH (1), was performed in methanol with stoichiometric amounts of Co(BF4)2·6H2O and the dinucleating ligand, H5ccdp (H5ccdp = N,N'-bis[2-carboxybenzomethyl]-N,N'-bis[carboxymethyl]-1,3-diaminopropan-2-ol), in the presence of NaOH at ambient temperature in an argon glovebox. Similarly, the dizinc complex, [NMe4]2[Zn2(ccdp)(μ-OAc)]·CH3OH (2), was synthesized from Zn(OAc)2·2H2O and H5ccdp in the presence of NMe4OH at ambient temperature in methanol. Binding of the complexes with carbohydrates was investigated under different reaction conditions. In aqueous alkaline media, complexes 1 and 2 showed chelating ability towards the biologically important sugars, d-glucose and d-xylose, and a polyalcohol enzyme inhibitor (xylitol). In solution, each complex forms a 1:1 complex-substrate bound product with specific binding constant values. Synthesis, characterization details, and substrate binding using spectroscopic techniques and single-crystal X-ray diffraction are reported.

Palladium‐Catalyzed Carbonylative α‐Arylation for Accessing 1,3‐Diketones

With a hint of CO: The first Pd-catalyzed carbonylative α-arylations of simple ketones with carbon monoxide is presented for the direct synthesis of 1,3-diketones (see scheme). The method uses only stoichiometric amounts of CO, and hence allows for the simple installment of carbon isotopes into the core structures of heterocyclic compounds. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Crystal structure determination of CoGeTe from powder diffraction data

The crystal structure of cobalt germanium telluride CoGeTe has been determined by direct methods using integrate intensities of conventional X-ray powder diffraction data and subsequently refined with the Rietveld method. The title compound was prepared by heating of stoichiometric amount of Co, Ge and Te in silica glass tube at 670 °C. CoGeTe adopts orthorhombic symmetry, space group Pbca with unit cell parameters a = 6.1892(4) Å, b = 6.2285(4) Å, c = 11.1240(6) Å, V = 428.8(1) Å 3 and Z = 8. Its crystal structure is formed by [CoGe 3Te 3] octahedra sharing both edges and corners. CoGeTe represents a ternary ordered variant of α-NiAs 2 type structure. An important feature present in CoGeTe is an occurrence of short Co–Co distance across the shared edge of [CoGe 3Te 3] octahedra. Differential thermal analysis (DTA) has revealed that CoGeTe melts incongruently at about 725 °C; CoGeTe decomposes into GeTe, CoGe and CoTe 2. Temperature dependence of the electrical conductivity and value of Seebeck coefficient at 300 K are also reported.

PHOTOCATALYTIC REACTION OF ACETONE ON MESOPOROUS CHROMIUM SILICATE

Cr -containing mesoporous silicates ( Cr -FSM-16) were prepared and characterized by several spectroscopic analyses. Their photocatalytic reactivity for acetone under UV- and visible-light irradiations has been investigated and the effect of adsorption on the reactivity was discussed. XPS spectra showed the Cr -oxide moieties were in the mesoporous framework of FSM-16. The UV-VIS spectra of the Cr -FSM-16 exhibited three distinct absorption bands, which could be assigned to charge transfer from O 2- to Cr 6+ of the tetrahedrally coordinated moieties. In particular, the band at 460 nm was assigned to the symmetry-forbidden nature of the 1 A 1 → 1 T 1 transition of tetrahedral Cr -oxide. The absorption showed Cr -FSM-16 has the photocatalytic reactivity under visible light irradiation. Acetone was adsorbed strongly on Cr -FSM-16, and then adsorbed acetone was decomposed to CO 2 and H 2 O on Cr -FSM-16 under visible light irradiation. But the amount of CO 2 produced was much less than the stoichiometric amount of CO 2 calculated from adsorbed acetone. This may be due to adsorption of acetone, and/or CO 2 on Cr -FSM-16.

Re-evaluation of the mechanism of the stoichiometric hydroformylation of olefins with cobalt carbonyls as catalysts

Abstract Two types of stoichiometric hydroformylation reactions have been described in the literature. One was performed using stoichiometric amounts of HCo(CO) 4 as the cobalt complex, and the second using stoichiometric amounts of Co 2 (CO) 8 at high hydrogen pressure. It has been believed that the second reaction follows the mechanism of the first, once HCo(CO) 4 was formed from Co 2 (CO) 8 and hydrogen. However, there have been some serious discrepancies between the expected mechanism of this reaction and its actual experimental behavior. Using a high pressure–high temperature infrared throughput cell, we have examined in situ whether the second type reaction does indeed proceed as a stoichiometric reaction between HCo(CO) 4 and olefin, and hence, in this case, the role of Co 2 (CO) 8 is merely to activate the hydrogen to form HCo(CO) 4 , or whether there is some other mechanism which is more appropriate to describe the reaction.

The Mechanism of Superoxide Scavenging byArchaeoglobus fulgidus Neelaredoxin

Neelaredoxin is a mononuclear iron protein widespread among prokaryotic anaerobes and facultative aerobes, including human pathogens. It has superoxide scavenging activity, but the exact mechanism by which this process occurs has been controversial. In this report, we present the study of the reaction of superoxide with the reduced form of neelaredoxin from the hyperthermophilic archaeon Archaeoglobus fulgidus by pulse radiolysis. This protein reduces superoxide very efficiently (k = 1.5 x 10(9) m(-1)s(-1)), and the dismutation activity is rate-limited, in steady-state conditions, by the much slower superoxide oxidation step. These data show unambiguously that the superfamily of neelaredoxin-like proteins (including desulfoferrodoxin) presents a novel type of reactivity toward superoxide, a result of particular relevance for the understanding of both oxygen stress response mechanisms and, in particular, how pathogens may respond to the oxidative burst produced by the defense cells in eukaryotes. The actual in vivo functioning of these enzymes will depend strongly on the cell redox status. Further insight on the catalytic mechanism was obtained by the detection of a transient intermediate ferric species upon oxidation of neelaredoxin by superoxide, detectable by visible spectroscopy with an absorption maximum at 610 nm, blue-shifted approximately 50 nm from the absorption of the resting ferric state. The role of the iron sixth ligand, glutamate-12, in the reactivity of neelaredoxin toward superoxide was assessed by studying two site-directed mutants: E12Q and E12V.