Presence Of Carbon Monoxide Research Articles

ChemInform Abstract: Enantioselective Total Synthesis of (‐)‐Minovincine in Nine Chemical Steps: An Approach to Ketone Activation in Cascade Catalysis.

ChemInform Abstract: Enantioselective Total Synthesis of (‐)‐Minovincine in Nine Chemical Steps: An Approach to Ketone Activation in Cascade Catalysis.

Heterolytic Cleavage of Dihydrogen by an Iron(II) PNP Pincer Complex via Metal-Ligand Cooperation.

The bis-carbonyl Fe(II) complex trans-[Fe(PNP-iPr)(CO)2Cl]+ reacts with Zn as reducing agent under a dihydrogen atmosphere to give the Fe(II) hydride complex cis-[Fe(PNP-iPr)(CO)2H]+ in 97% isolated yield. A crucial step in this reaction seems to be the reduction of the acidic NH protons of the PNP-iPr ligand to afford H2 and the coordinatively unsaturated intermediate [Fe(PNPH-iPr)(CO)2]+ bearing a dearomatized pyridine moiety. This species is able to bind and heterolytically cleave H2 to give cis-[Fe(PNP-iPr)(CO)2H]+. The mechanism of this reaction has been studied by DFT calculations. The proposed mechanism was supported by deuterium labeling experiments using D2 and the N-deuterated isotopologue of trans-[Fe(PNP-iPr)(CO)2Cl]+. While in the first case deuterium was partially incorporated into both N and Fe sites, in the latter case no reaction took place. In addition, the N-methylated complex trans-[Fe(PNPMe-iPr)(CO)2Cl]+ was prepared, showing no reactions with Zn and H2 under the same reaction conditions. An alternative synthesis of cis-[Fe(PNP-iPr)(CO)2H]+ was developed utilizing the Fe(0) complex [Fe(PNP-iPr)(CO)2]. This compound is obtained in high yield by treatment of either trans-[Fe(PNP-iPr)(CO)2Cl]+ or [Fe(PNP-iPr)Cl2] with an excess of NaHg or a stoichiometric amount of KC8 in the presence of carbon monoxide. Protonation of [Fe(PNP-iPr)(CO)2] with HBF4 gave the hydride complex cis-[Fe(PNP-iPr)(CO)2H]+. X-ray structures of both cis-[Fe(PNP-iPr)(CO)2H]+ and [Fe(PNP-iPr)(CO)2] are presented.

An Efficient and Highly Selective Carbonylative Bisthiolation of Internal Alkynes with Organic Disulfides Catalyzed by [Co2(CO)8

Abstract Although many transition-metal catalysts are ineffective for the addition and carbonylative addition of organic disulfides to internal alkynes, dicobalt octacarbonyl ([Co2(CO)8]) was found to exhibit excellent catalytic activity for the carbonylative bisthiolation of internal alkynes. In the presence of carbon monoxide, a wide variety of organic disulfides successfully underwent addition to internal alkynes to afford the corresponding β-sulfanyl-α,β-unsaturated thioesters in good yields.

Investigation of a proton-conducting SOFC with internal autothermal reforming of methane

This study presents a performance analysis of a proton-conducting SOFC (SOFC-H+) with internal reforming of methane. The autothermal reforming within the SOFC-H+ stack is considered to be a potential solution of the carbon formation problem facing in operation of internal steam reforming SOFC-H+. A one-dimensional, steady-state model of the SOFC-H+ coupled with a detailed electrochemical model is employed to investigate its performance in terms of power density and fuel cell efficiency. The simulation results show that when SOFC-H+ is operated under an autothermal reforming environment, the presence of carbon monoxide, which is a major cause of carbon formation, in the fuel cell stack decreases. Effect of key operating parameters, such as temperature, steam-to-carbon and oxygen-to-carbon feed ratios, current density and fuel utilization, on the SOFC-H+ performance in terms of electrical efficiencies and energy demand is also investigated. The results indicate that operating temperatures have strong influence on SOFC-H+ performance, carbon monoxide production and heat generation.

Atomistic Theory of Ostwald Ripening and Disintegration of Supported Metal Particles under Reaction Conditions

Understanding Ostwald ripening and disintegration of supported metal particles under operating conditions has been of central importance in the study of sintering and dispersion of heterogeneous catalysts for long-term industrial implementation. To achieve a quantitative description of these complicated processes, an atomistic and generic theory taking into account the reaction environment, particle size and morphology, and metal-support interaction is developed. It includes (1) energetics of supported metal particles, (2) formation of monomers (both the metal adatoms and metal-reactant complexes) on supports, and (3) corresponding sintering rate equations and total activation energies, in the presence of reactants at arbitrary temperature and pressure. The thermodynamic criteria for the reactant assisted Ostwald ripening and induced disintegration are formulated, and the influence of reactants on sintering kinetics and redispersion are mapped out. Most energetics and kinetics barriers in the theory can be obtained conveniently by first-principles theory calculations. This allows for the rapid exploration of sintering and disintegration of supported metal particles in huge phase space of structures and compositions under various reaction environments. General strategies of suppressing the sintering of the supported metal particles and facilitating the redispersions of the low surface area catalysts are proposed. The theory is applied to TiO(2)(110) supported Rh particles in the presence of carbon monoxide, and reproduces well the broad temperature, pressure, and particle size range over which the sintering and redispersion occurred in such experiments. The result also highlights the importance of the metal-carbonyl complexes as monomers for Ostwald ripening and disintegration of supported metal catalysts in the presence of CO.

Ligand Effect in Platinum-Catalyzed Cycloisomerization of 1,6-Enynes: Water or Carbon Monoxide, a Similar Role despite Distinct Electronic Properties?

The PtCl2-catalyzed cycloisomerization of 1,6-enynes is considerably accelerated in the presence of carbon monoxide. The effect of CO has been explained by the reinforcement of the electrophilicity of the alkyne moiety once ligated to the π-acidic [PtCl2(CO)] fragment. However, platinum is also described as weakly capable of back-donation toward CO. A theoretical study has been carried out to shed light on this apparent contradiction. An alternative explanation based on the approach of CO onto the [PtCl2(η4-(1,6-enyne))] complex is proposed. When CO is ligated to PtCl2, the triple-bond coordination is favored, yet there is no positive influence on the formation of the cyclopropylcarbene key intermediate. The role of CO is actually comparable to that of a water molecule.

Slaughter of Atlantic salmon (Salmo salar L.) in the presence of carbon monoxide

The different stunning methods for Atlantic salmon can still be improved with regard to animal welfare. Salmon exposed to carbon monoxide expressed no aversive reactions towards CO as such. CO exposed fish showed an earlier onset of rigour mortis and a faster decrease in muscle pH due to depletion of oxygen during the treatment. Exposure to CO did increase the level of cortisol compared to undisturbed control fish, but the increase was less than in the water only control group. Neuroglobin, a CO binding globin, was found in salmon brain and Saccus vasculosus, a richly vascularized sac connected to the fish brain. Binding of CO to neuroglobin during sedation might possibly improve animal welfare.

CO-Induced Scavenging of Supported Pt Nanoclusters: A GISAXS Study

Supported platinum nanoparticles in the presence of carbon monoxide in the 10–6–103 Pa CO pressure range were studied by grazing incidence small-angle X-ray scattering. Disruption and aggregation of platinum nanoparticles upon CO exposure are shown to occur in parallel. Particles smaller than a critical size of 1 nm undergo scavenging after disruption in the form of carbonyls at CO pressure as low as 10–1 Pa. Mobile carbonyls then agglomerate to larger clusters. Upon annealing, a CO-driven diffusion and agglomeration of clusters of size ranging between the critical size and 2 nm is observed. These phenomena are discussed in relation to the CO–metal, metal–metal, and metal–substrate relative bond strengths. Similar mechanisms are suggested to hold for other supported metal catalysts.

Numerical Investigation of Safety Aspects of Hydrogen/Carbon Monoxide Mixture Release

Research into the performance of proton exchange membrane fuel cell (PEMFC) and its degradation (“poisoning”) by the presence of carbon monoxide, a common byproduct of most common hydrogen production methods, requires storage of a large quantities of hydrogen/carbon monoxide mixture in high pressure tanks. The possibility of unintended release of the gas calls for a safety study of H2/CO mixture leaks, as well as potential higher rate releases. This presentation covers the safety aspects of the numerical study of a H2/CO mixture release at a wide range of release parameters, including release velocity, orientation, initial diameter, and initial gases fraction ratio. The study provides a simulation of a) the extent of flammable concentrations of H2, corrected for the presence of CO; b) the extent of CO concentration exceeding OSHA recommended health safety limits. The presence of CO in the mixture required reassessment of hydrogen flammability limits, although the correction proved to be relatively small for the CO fractions used in the present. The maximum extents and evolution of H2 and CO envelops had been modeled and compared. An important conclusion is the possibility of using hydrogen detectors to predict CO concentration levels with accuracy sufficient for practical purposes.

Quantitative trace analysis of benzene using an array of plasma-treated metal-decorated carbon nanotubes and fuzzy adaptive resonant theory techniques

The functionalization of carbon nanotube sidewalls with metal nanoparticles is exploited here to improve the sensitivity and selectivity of gas sensors operated at room temperature. An array of sensors using oxygen plasma treated multiwalled carbon nanotubes (bare and decorated with Pt, Pd or Rh nanoparticles) is shown to selectively detect traces of benzene (i.e., 100 ppb) in the presence of carbon monoxide, hydrogen sulfide or nitrogen dioxide at different humidity levels. Employing a quantitative fuzzy adaptive resonant theory (ART) network whose inputs are the responses of the sensor array, it is possible to accurately estimate benzene concentration in a changing background. The quantitative fuzzy ART is especially suited for compensating the nonlinear effects in sensor response caused by changes in ambient humidity, which explains why this method clearly outperforms partial least squares calibration models at estimating benzene concentration. These results open the way to design new affordable, wearable, sensitive and selective detectors aimed at the personal protection of workers subject to occupational exposure to benzene, toluene, ethyl benzene and xylenes.

N‐Heterocyclic Carbene (NHC)‐Rhodium‐Catalyzed Carbonylative CC Bond Formation of Allenols with Arylboronic Acids under Carbon Monoxide

Abstract(3‐Butyl‐1‐methylimidazole)(1,5‐cyclooctadiene)rhodium chloride [Rh(Ibm)(cod)Cl] was found to be an efficient catalyst in the carbonylative arylation of allenols with arylboronic acids in the presence of carbon monoxide. Efficient, simple, and versatile methods for the synthesis of 2‐methylene‐1‐arylbut‐3‐en‐1‐ones have thus been developed.

Modular Synthesis of Conjugated Imidazole-Based Oligomers

An innovative procedure for the synthesis of imidazole-based oligomers is presented. The multicomponent, one-pot reaction combines two different imines and an acyl chloride in the presence of carbon monoxide and a palladium catalyst. The reaction proceeds under mild conditions and affords moderate to good yields of the target compounds.

Molecular Mapping of the Catalytic Cycle of the Cobalt-Catalyzed Hydromethoxycarbonylation of 1,3-Butadiene in the Presence of Pyridine in Methanol

High-pressure in situ IR and NMR investigations of the hydromethoxycarbonylation of 1,3-butadiene (1) to methyl 3-pentenoate (2) in methanol in the presence of Co2(CO)8 and pyridine under carbon monoxide has revealed that the reaction starts by the methanol- and/or pyridine-assisted disproportionation of Co2(CO)8, followed by the establishment of equilibria involving the ionic species [Co(Py)6]2+{[Co(CO)4]−}2, [Co(Py)6]2+[MeO]−[Co(CO)4]−, [PyH]+[Co(CO)4]−, and [MeOH2]+[Co(CO)4]−. The addition of HCo(CO)4 (3) to pyridine or methanol results in the formation of [PyH]+[Co(CO)4]− and [MeOH2]+[Co(CO)4]−, respectively, and 3 is not detectable by either IR or NMR. The ionic 1,4-addition of [MeOH2]+[Co(CO)4]− to 1 is the only pathway to 2-butenylcobalt tetracarbonyl, CH3CH═CHCH2Co(CO)4 (4), via the protonation of 1 followed by the reaction of the C4 carbocation with the counteranion tetracarbonylcobaltate. In the absence of carbon monoxide, 4 could lose a coordinated carbon monoxide to form (η3-C4H7)Co(CO)3 (7) in a reversible reaction. In the presence of carbon monoxide, 4 is converted to the acylcobalt tetracarbonyl species 5 via CO insertion into the Co–carbon bond of 4 followed by the reaction with CO. The pyridine-assisted methanolysis of 5 leads to the formation of the product methyl 3-pentenoate (2) and pyridinium tetracarbonylcobaltate. The key intermediates of the catalytic cycle were isolated and characterized.

The selective hydrogenation of acetylene in the presence of carbon monoxide over Ni and Ni–Zn supported on MgAl 2O 4

The effect of gaseous carbon monoxide on the hydrogenation of acetylene over Ni supported on MgAl 2O 4 in the presence and absence of zinc dopants has been investigated. Both carbon monoxide and zinc inhibit activity to a considerable extent. Carbon monoxide also lowers the selectivity to ethane substantially. Zinc causes some reduction in selectivity in the absence of carbon monoxide but only at very high conversions when it is present.

Ni-Coated Polyaniline Nanowire As Chemical Sensing Material for Cigarette Smoke

PANI-CSA-Ni composite nanowire was successfully synthesized using camphor sulfonic acid (CSA) as dopant as well as surfactant. In this process, CSA-ANI micelles act as soft template facilatating the formation of PANI nanowire. PANI-CSA-Ni nanowire composite was characterized by transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The use of PANI-CSA-Ni composite nanowire as sensing material was also investigated. It was observed that PANI-CSA-Ni nanowire composite shows nearly four order decrease in ac impedance in the presence of cigarette smoke. Therefore, such material has potential for use in cigarette smoke detector. Impedance response in the presence of controls like carbon dioxide and carbon monoxide was also measured. It was observed that whereas carbon dioxide gas has a negligible role in the change in ac impedance, there was a half-order change in impedance response in the presence of carbon monoxide (CO), hinting the possi...

ChemInform Abstract: Palladium‐Catalyzed Carbonylative Suzuki Coupling of Benzyl Halides with Potassium Aryltrifluoroborates in Aqueous Media.

AbstractVarious benzyl halides are converted into diarylethanones in the presence of carbon monoxide using different aryl trifluoroborates.

Growth of single-walled carbon nanotubes with controlled diameters and lengths by an aerosol method

On the basis of combined study of the transmission electron microscopy, scanning electron microscopy, Raman spectroscopy and ultraviolet–visible–near infrared absorption spectroscopy, the properties of the single-walled carbon nanotubes (SWCNTs), synthesized by aerosol (floating catalyst) chemical vapor deposition method by ferrocene vapor decomposition in the presence of carbon monoxide, are studied in details. The results show that increasing the temperature gives rise to the formation of high quality and large diameter SWCNTs. By monitoring the water-cooled probe position, both the bundle length and the diameter of the SWCNTs are effectively tuned due to the variation of the residence time and temperature profile in the reactor. An introduction of a small amount of CO 2 suppresses the growth of small diameter nanotubes and enlarges the mean diameter of SWCNT samples. The mean diameter of SWCNTs could be easily altered in a broad range from 1.1 to 1.9 nm during growth, which is essential for the SWCNT applications in optical and electronic devices.

LEDs based on InAsSbP/InAsSb heterostructures (λ = 4.7 μm) for carbon monoxide detection

Light-emitting diodes (LEDs) operating in the 4.4–4.8-μm wavelength range have been developed for detecting the presence of carbon monoxide (CO) in air. The proposed LEDs are based on InAsSbP/InAsSb heterostructures with InAs0.85Sb0.15 active region, which were grown by metalorganic vapor-phase epitaxy. The electrolumuinescent properties of LEDs have been studied. The output power of LED operating in a pulsed mode reaches 50 μW at a current pulse amplitude of 2 A, and that in a quasi-continuous wave mode is 1 μW at a current of 200 mA. The absorption of LED radiation in a gaseous medium containing 10% CO has been studied. The proposed LEDs can be used to simultaneously detect both CO2 (absorbing at λ = 4.3 μm) and CO (λ = 4.67 μm).

Electricity generation from carbon monoxide and syngas in a microbial fuel cell

Electricity generation in microbial fuel cells (MFCs) has been a subject of significant research efforts. MFCs employ the ability of electricigenic bacteria to oxidize organic substrates using an electrode as an electron acceptor. While MFC application for electricity production from a variety of organic sources has been demonstrated, very little research on electricity production from carbon monoxide and synthesis gas (syngas) in an MFC has been reported. Although most of the syngas today is produced from non-renewable sources, syngas production from renewable biomass or poorly degradable organic matter makes energy generation from syngas a sustainable process, which combines energy production with the reprocessing of solid wastes. An MFC-based process of syngas conversion to electricity might offer a number of advantages such as high Coulombic efficiency and biocatalytic activity in the presence of carbon monoxide and sulfur components. This paper presents a discussion on microorganisms and reactor designs that can be used for operating an MFC on syngas.

Liquid-phase hydrogenation of acetylene on the Pd/sibunit catalyst in the presence of carbon monoxide

The liquid-phase catalytic hydrogenation of acetylene into ethylene in the presence of CO over palladium supported on the graphite-like material Sibunit has been investigated. Carbon monoxide is an effective modifier of the selective hydrogenation process, exerting its effect by competing with acetylene and ethylene for chemisorption sites on the palladium surface. Under the optimum conditions (T = 90°C; N-methylpyrrolidone solvent; feed consisting of 2 vol % C2H2, 90 vol % H2, and He balance), the introduction of 2 vol % CO ensures a high ethylene selectivity of 89.6 ± 1.5% at an acetylene conversion of 95.8 ± 1.3%, with the acetylene converted into hydrooligomers taken into account.