Presence Of Carbon Monoxide Research Articles

Synthesis of Pt nano catalyst in the presence of carbon monoxide: Superior activity towards hydrogen evolution reaction

The effect of carbon monoxide (CO) on the reduction of Pt ion to metallic Pt is studied. The modified GC electrode with platinum metal synthesized in the presence of CO shows excellent activity for hydrogen evolution reaction (HER). Despite the decrease in the loading of platinum (4.5 × 10−4 mg cm−2) a substantial increase in its electrocatalytic activity towards HER is observed in a sulfuric acid environment. The observed electrocatalytic activity is comparable to available commercial catalysts like Pt/C. Tafel slope was obtained to be 34 mV.dec−1, and the overpotential was acquired to be 31 mV at the mass activity of 10 mA mg−1 were observed which was very close to kinetic parameters of Pt/C catalyst.

Acetylene Hydrogenation to Ethylene in a Hydrogen-Rich Gaseous Mixture on a Pd/Sibunit Catalyst

The reaction of the gas-phase hydrogenation of acetylene on a Pd/Sibunit catalyst was studied depending on the H2 : C2H2 molar ratio, the process temperature, and the presence of carbon monoxide. It was shown that for the reaction mixture of the composition H2 : C2H2 20, on the contrary, the order in hydrogen becomes zero and the reaction rate is determined by the acetylene content in the reaction mixture. It was found that an increase in the reaction temperature (from 30 to 85°C) leads to an increase in the contribution of complete hydrogenation to ethane. The introduction of CO into the reaction mixture up to a molar ratio of CO : C2H2 = 0.1 is accompanied by the almost complete blocking of the C2H4 readsorption sites, which results in a sharp increase in ethylene selectivity from 4 to 73%. With a further increase in the CO : C2H2 ratio, the number of sites available for hydrogen adsorption gradually decreases, and, correspondingly, the conversion decreases.

Surface Segregation in CuNi Nanoparticle Catalysts During CO2 Hydrogenation: The Role of CO in the Reactant Mixture.

Surface segregation and restructuring in size-selected CuNi nanoparticles were investigated via near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) at various temperatures in different gas environments. Particularly in focus were structural and morphological changes occurring under CO2 hydrogenation conditions in the presence of carbon monoxide (CO) in the reactant gas mixture. Nickel surface segregation was observed when only CO was present as adsorbate. The segregation trend is inverted in a reaction gas mixture consisting of CO2, H2, and CO, resulting in an increase of copper concentration on the surface. Density functional theory calculations attributed the inversion of the segregation trend to the formation of a stable intermediate on the nanocatalyst surface (CH3O) in the CO-containing reactant mixture, which modifies the nickel segregation energy, thus driving copper to the surface. The promoting role of CO for the synthesis of methanol was demonstrated by catalytic characterization measurements of silica-supported CuNi NPs in a fixed-bed reactor, revealing high methanol selectivity (over 85%) at moderate pressures (20 bar). The results underline the important role of intermediate reaction species in determining the surface composition of bimetallic nanocatalysts and help understand the effect of CO cofeed on the properties of CO2 hydrogenation catalysts.

Polymer supported triazine based palladium complex catalyzed double carbonylation reaction of halo aryl compounds for the synthesis of α-ketoamides

Novel polystyrene incorporated Palladium (II) catalyst was developed and well characterized. The efficiency of the supported Pd(II) catalytic material was checked for double carbonylation reaction of 2° amines and aryl iodides to their corresponding α-ketoamides under high pressure reaction conditions. The reaction was carried out in 60 psi carbon monoxide pressure. An extensive variety of aryl iodides in combination with 2° amines in presence of carbon monoxide can produce the respective α-ketoamides with superb chemoselectivity. Effect of solvents, bases, time and amount of catalyst for the production of α-ketoamides were reported. This supported Pd(II)complex was highly catalytically active and recyclable. The developed catalytic material was regenerated by filtration. It could be recycled further six times with no such profound loss in its activity.

Surface reconstruction of Pt–Sn nanoparticles supported on Al2O3 in the presence of carbon monoxide

FTIR spectroscopy and volumetric measurements are used to study the adsorption of CO (mainly 1% CO/He) in the temperature range 300–713 K on a 1.2% Pt–2.7% Sn/Al2O3 solid reduced in H2 at 713 K leading from XRD to PtSn bimetallic particles. This reveals the changes in the adsorption properties of the Pt sites for CO adsorption by comparison with monometallic Pt/Al2O3 solids and the stability of the Pt–Sn bimetallic particles in the presence of CO. At 300 K, FTIR spectroscopy shows that the insertion of Sn leads to (a) the total disappearance of the Pt sites forming bridged CO species (ascribed to a geometric effect of Sn) and (b) a significant shift in the position of the IR band of linear CO species on Pt sites from 2066 to 2044 cm−1 on Pt and Pt–Sn particles, respectively, ascribed to different adsorbed species, namely LPt and L1Pt–Sn, respectively. Moreover, it is shown that the insertion of Sn is associated with the decrease in the amount (in µmol/g of platinum) of Pt adsorption sites for CO adsorption. The evolution of the IR band of the L1Pt–Sn CO species with the increase in Ta in isobaric conditions reveals a modification of the surface of the Pt–Sn particles for Ta > ≈ 460 K ascribed to enrichment in Pt° due to a surface reconstruction. The Pt sites of the reconstructed surface are characterized by an IR band at 2057 cm−1 after adsorption of CO at 300 K ascribed to a linear CO species named L2Pt–Sn. The reconstructed surface is stable in the presence of CO in the range 300–713 K and disappears by hydrogen reduction at 713 K. Successive surface reconstruction/hydrogen reduction at 713 K cycles lead to an ageing of the Pt–Sn particles associated with a progressive decrease in the amount of Pt° sites on the freshly prepared and reconstructed Pt–Sn particles. It is shown that the reconstruction of the Pt–Sn particles is probably due to the formation of SnOx species via oxygen species coming mainly from the hydroxyls groups of the support.

A New Tool in the Quest for Biocompatible Phthalocyanines: Palladium Catalyzed Aminocarbonylation for Amide Substituted Phthalonitriles and Illustrative Phthalocyanines Thereof

The amide peptide bond type linkage is one of the most natural conjugations available, present in many biological synthons and pharmaceutical drugs. Hence, aiming the direct conjugation of potentially biologically active compounds to phthalocyanines, herein we disclose a new strategy for direct modulation of phthalonitriles, inspired by an attractive synthetic strategy for the preparation of carboxamides based on palladium-catalyzed aminocarbonylation of aryl halides in the presence of carbon monoxide (CO) which, to our knowledge, has never been used to prepare amide-substituted phthalonitriles, the natural precursors for the synthesis of phthalocyanines. Some examples of phthalocyanines prepared thereof are also reported, along with their full spectroscopic characterization and photophysical properties initial assessment.

Enabling CO Insertion into o-Nitrostyrenes beyond Reduction for Selective Access to Indolin-2-one and Dihydroquinolin-2-one Derivatives

The transition metal-catalyzed reductive cyclization of o-nitrostyrene in the presence of carbon monoxide (CO) has been developed to be a general synthetic route to an indole skeleton, wherein CO w...

Spectroscopical Investigations on the Redox Chemistry of [FeFe]-Hydrogenases in the Presence of Carbon Monoxide.

[FeFe]-hydrogenases efficiently catalyzes hydrogen conversion at a unique [4Fe–4S]-[FeFe] cofactor, the so-called H-cluster. The catalytic reaction occurs at the diiron site, while the [4Fe–4S] cluster functions as a redox shuttle. In the oxidized resting state (Hox), the iron ions of the diiron site bind one cyanide (CN−) and carbon monoxide (CO) ligand each and a third carbonyl can be found in the Fe–Fe bridging position (µCO). In the presence of exogenous CO, A fourth CO ligand binds at the diiron site to form the oxidized, CO-inhibited H-cluster (Hox-CO). We investigated the reduced, CO-inhibited H-cluster (Hred´-CO) in this work. The stretching vibrations of the diatomic ligands were monitored by attenuated total reflection Fourier-transform infrared spectroscopy (ATR FTIR). Density functional theory (DFT) at the TPSSh/TZVP level was employed to analyze the cofactor geometry, as well as the redox and protonation state of the H-cluster. Selective 13CO isotope editing, spectro-electrochemistry, and correlation analysis of IR data identified a one-electron reduced, protonated [4Fe–4S] cluster and an apical CN− ligand at the diiron site in Hred´-CO. The reduced, CO-inhibited H-cluster forms independently of the sequence of CO binding and cofactor reduction, which implies that the ligand rearrangement at the diiron site upon CO inhibition is independent of the redox and protonation state of the [4Fe–4S] cluster. The relation of coordination dynamics to cofactor redox and protonation changes in hydrogen conversion catalysis and inhibition is discussed.

Resistance to Plasmodium falciparum in sickle cell trait erythrocytes is driven by oxygen-dependent growth inhibition

Sickle cell trait (AS) confers partial protection against lethal Plasmodium falciparum malaria. Multiple mechanisms for this have been proposed, with a recent focus on aberrant cytoadherence of parasite-infected red blood cells (RBCs). Here we investigate the mechanistic basis of AS protection through detailed temporal mapping. We find that parasites in AS RBCs maintained at low oxygen concentrations stall at a specific stage in the middle of intracellular growth before DNA replication. We demonstrate that polymerization of sickle hemoglobin (HbS) is responsible for this growth arrest of intraerythrocytic P. falciparum parasites, with normal hemoglobin digestion and growth restored in the presence of carbon monoxide, a gaseous antisickling agent. Modeling of growth inhibition and sequestration revealed that HbS polymerization-induced growth inhibition following cytoadherence is the critical driver of the reduced parasite densities observed in malaria infections of individuals with AS. We conclude that the protective effect of AS derives largely from effective sequestration of infected RBCs into the hypoxic microcirculation.

Nonlinear Impedance Spectra Analysis of CO Poisoning on PEM Fuel Cell Performance

In polymer electrolyte membrane (PEM) fuel cells, hydrogen is the preferred fuel with air or oxygen as oxidant. However, many a time, the presence of carbon monoxide (CO), even at low ppm levels, inhibits the hydrogen oxidation reaction [1, 2]. In this work, we describe nonlinear impedance spectra analysis (NLEIS) of CO poisoning in PEM fuel cells. In NLEIS method, large amplitude perturbations are employed and the resulting signal have significant higher harmonic components, which, if acquired, can provide additional information about the system under investigation. Here we illustrate a NLEIS methodology in which governing equations were solved without linearization, using numerical method. The response signal was subjected to fast Fourier transform (FFT) to extract magnitude and phase at fundamental and higher harmonics. In this study, linear adsorption model, in which a CO molecule occupies one adsorption site was employed to generate NLEIS data [3]. Figure 1 shows the concentration effect on NLEIS results, simulated under galvanostatic mode employing large (Iac = 200 mA) amplitude perturbation at Idc =200 mA.cm-2 . The results show that the CO poisoning effects are more easily distinguishable at higher harmonics, when compared to the response at fundamental frequency. Key words: Nonlinear EIS, PEM fuel cell, CO poisoning, linear adsorption model

First-principles kinetics study of carbon monoxide promoted Ostwald ripening of Au particles on FeO/Pt(111)

Abstract The dynamic and kinetic evolution of supported metal particles in the presence of reactants is decisive in shaping the nature of the catalytic active sites and the deactivation process. Ostwald ripening of FeO/Pt(111) supported Au particles in the presence of carbon monoxide is addressed here by first-principles kinetics. It is found that CO stabilizes the ripening monomer (Au atom) by forming favorable Au carbonyls with lower total activation energy, and corresponding phase diagram at wide range of temperature and CO pressures is constructed. Evolution of particle number, dispersion and particle size distribution of supported Au particles are explored. Great influence of CO promotion on ripening kinetics is revealed and explored in details, and mbar range of CO can lower the onset temperature of ripening by a few hundred kelvins. The present work reveals the crucial role of the metal-reactant complexes formed under reaction conditions on ripening of metal catalysts.

α-Substituted Benzylic Complexes of Palladium(II) as Precursors of Palladium Hydrides

The adoption of a pseudoallylic (η3) form makes palladium benzylic derivatives a class of stabilized palladium alkyls that can undergo β-H elimination reactions in a more controlled way. α-(Pentafluorophenylmethyl)benzyl palladium complexes have been studied, and they decompose by β-H elimination to give palladium hydrides that, depending on the auxiliary ligands, can: (a) transmetalate to another palladium atom and, by reductive elimination, give hydrogenated products; this process is favored for a combination of bridging ligands (i.e., halogens) and low coordinating ligands. (b) Be used as a hydride source and get trapped by a diene to give palladium allylic derivatives. The presence of carbon monoxide does not induce a β-H elimination reaction, and only CO insertion into the Pd–benzyl bond to give acyl derivatives is observed.

Studies on the effect of heterogeneous catalysts on the hydrothermal liquefaction of sugarcane bagasse to low-oxygen-containing bio-oil

ABSTRACTDevelopment of suitable catalysts having deep deoxygenation activity is the key for the hydrothermal liquefaction (HTL) of biomass to auto fuels directly. In this study 12 catalysts, namely Fe-MCM-41, Co-MCM-41, Mo-MCM-41, Ti-MCM-41, and oxides of Fe, Co, Mo, Ti, Fe-Mo, Fe-Co, Co-Mo and Ti-Zr, were synthesised, and characterised by X-Ray Diffraction (XRD), textural analysis, Fourier Transform Infra Red (FTIR) and Scanning Electron Microscope (SEM). They were evaluated for HTL of sugarcane bagasse to bio-oil in the presence of hydrogen and carbon monoxide. For non-catalytic HTL, oil obtained in the presence of hydrogen contained less oxygen, whereas for catalytic HTL oil obtained in the presence of carbon monoxide contained less oxygen. Among the catalysts studied, iron-cobalt oxide was found to be the most selective as it gave the highest oil yield of 57.6 weight% containing the least oxygen of 10.8 weight% in the presence of CO. Co-MCM-41 and cobalt oxide yielded bio-oil with the least oxygen among the metal-substituted MCM-41 and metal oxides studied, indicating that cobalt may be the most active catalytic species for strong deoxygenation activity. Metal-substituted MCM-41 yielded oil with less oxygen compared to its simple metal oxides except Ti, which may be due to very high surface area owing to its mesoporous structure.

An Optimized Platinum (Pt) Doped Tin-oxide(SnO2) Ink for Deposition of Gas Sensing Thick Film on LTCC Micro-hotplate

An optimized platinum (Pt) doped tin oxide (SnO2) ink was prepared by chemical route and was deposited on low temperature co-fired ceramics (LTCC) micro-hotplate by screen printing. An alkoxide ink was prepared by mixing tin(II) 2-ethylexanoate (17 wt%) with isopropanol (27 wt%) and SnO2 powder (55 wt%). Doping of the ink was done using Pt (1 wt%) which increased the resistance of SnO2 film at room temperature and also reduced the operating temperature. The temperature of ensor was obtained and stabilised using MOSFET based temperature stability circuit. Film characterization was performed using Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) technique. Small grain size and high porosity is the requirement for good sensing. The grain size was found to be in the range of 150-180 nm and the film was sufficiently porous. Resistance change of the film was also investigated in the presence of carbon monoxide (CO) to assure gas sensing.

Study of the Influence Exerted by Zinc Additive on the Structure and Catalytic Properties of Pd/Al2O3 Catalysts for Liquid-Phase Hydrogenation of Acetylene

Effect of the phase composition of aluminum oxide [γ- and (δ + θ) phase] and introduction of zinc additives on the catalytic properties of 0.5% Pd/Al2O3 systems in the reaction of liquid-phase hydrogenation of acetylene into ethylene under an elevated pressure in a flow-through mode was studied. An increase in the activity of the Pd catalyst upon modification with zinc is only observed in the case of a system supported by the mixed phase of (δ + θ) aluminum oxide. XAFS spectroscopy was used to find that the increase in the activity and selectivity with respect to ethylene (in the presence of carbon monoxide) on the (0.5% Pd–0.62% Zn)/(δ + θ)-Al2O3 catalyst is correlated with the formation of the PdZn intermetallic compound.

Reduction of $$\hbox {CO}_{2}$$ CO 2 to CO in presence of $$\hbox {H}_{2}$$ H 2 on strontium doped lanthanum manganite cathode in solid oxide electrolysis cell

Electrochemical performance of $$\hbox {La}_{0.8}\hbox {Sr}_{0.2}\hbox {MnO}_{3-\delta }$$ (LSM) for $$\hbox {CO}_{2}$$ reduction in solid oxide cell is studied by performing impedance spectroscopy measurement and current-voltage characterizations for varying ratio of $$\hbox {CO}_{2}/\hbox {H}_{2}$$ . Ohmic resistance $$(\hbox {R}_{\Omega })$$ is observed to be slightly increased from 2.59 to $$2.70\, \Omega \hbox { cm}^{2}$$ , however; the cathode polarization resistance $$(\hbox {R}_{2})$$ decreased significantly from 16.20 to 4.70 $$\Omega \hbox { cm}^{2}$$ as the $$\hbox {H}_{2}$$ percentage increased from 8 to 82%, respectively. As the $$\hbox {H}_{2}$$ content increased in feed gas, the improved polarization resistance indicated an enhanced activity of LSM for $$\hbox {CO}_{2}$$ reduction reaction. Furthermore, the cathode polarization resistance for $$\hbox {CO}_{2}/\hbox {H}_{2}$$ of 92/08, is observed to be decreased from 16.20 $$\Omega \hbox { cm}^{2}$$ (OCV 0.89 V) to 1.90 $$\Omega \hbox { cm}^{2}$$ (2.0 V) as the applied potential increased in the electrolysis mode of operation. A maximum conversion of $$\hbox {CO}_{2}$$ of 6.0% with 55% of faradaic efficiency for the production of CO is achieved for $$\hbox {CO}_{2}/\hbox {H}_{2}$$ ratio of 38/62, which is supported by improved current-voltage polarization, i.e., an increase in reduction current from $$-0.28$$ to $$-0.32\hbox { A cm}^{-2}$$ (at 2.5 V) as the $$\hbox {CO}_{2}/\hbox {H}_{2}$$ ratio decreased from 92/08 to 38/62 respectively. These results demonstrate LSM as an active electrocatalyst to reduce $$\hbox {CO}_{2}$$ , which could further be improved by increasing the $$\hbox {H}_{2}$$ concentration in the feed composition to the cathode. Synopsis: Solid oxide cell is fabricated with strontium doped lanthanum manganite electrodes and yttria stabilized zirconia electrolyte. Electrochemical performance in terms of impedance spectroscopy and current-voltage characteristics of the cell are reported for the reduction of carbon dioxide into carbon monoxide in presence of hydrogen with varying ratio of $$\hbox {CO}_{2}/\hbox {H}_{2}$$ .

Iridium Halide Complexes [1,1‐X2‐8‐SMe2‐1,2,8‐IrC2B9H10]2 (X = Cl, Br, I): Synthesis, Reactivity and Catalytic Activity

The reactions of thallium salt Tl[7‐SMe2‐7,8‐C2B9H10] with [(cod)RhCl]2 and [Cp*RuCl]4 are accompanied by room‐temperature polyhedral rearrangement, giving rhoda‐ and ruthenacarboranes 1‐cod‐8‐SMe2‐1,2,8‐RhC2B9H10 (2) and 1‐Cp*‐8‐SMe2‐1,2,8‐RuC2B9H10 (3), respectively. According to DFT calculations, the rearrangement could be attributed to the triangular face rotation mechanism. The reaction of iridium derivative 1‐cod‐8‐SMe2‐1,2,8‐IrC2B9H10 (1) with anhydrous hydrohalic acids HX (X = Cl, Br, I) results in the dimeric halide iridacarboranes [1,1‐X2‐8‐SMe2‐1,2,8‐IrC2B9H10]2 [4a–c; X = Cl (a), Br (b), I (c)]. Bromide 4b reacts with Tl[Tl(η‐7,8‐C2B9H11)] and TlCp giving iridacarboranes 8′‐SMe2‐1,1′‐Ir(2,3‐C2B9H11)(2′,8′‐C2B9H10) (5) and 1‐Cp‐8‐SMe‐1,2,8‐IrC2B9H10 (6). The formation of the latter compound is accompanied by demethylation of the SMe2 substituent. The structures of 2, 3, 5 and 6 were determined by single‐crystal X‐ray diffraction. Iridacarboranes 4b and [1,1‐Br2‐4‐SMe2‐1,2,3‐IrC2B9H10]2 (7) catalyze the dimerization of diphenylacetylene, giving 1,2,3‐triphenylnaphthalene in 20–24 % yields. Compounds 4b and 7 also effectively catalyze the reductive amination reaction between aldehydes (or ketones) and primary (or secondary) amines in the presence of carbon monoxide, giving the corresponding secondary and tertiary amines in high yields (60–85 %).

Access to Perfluoroalkyl-Substituted Enones and Indolin-2-ones via Multicomponent Pd-Catalyzed Carbonylative Reactions.

A simple method for accessing perfluoroalkyl-substituted enones is described applying a four-component palladium-catalyzed carbonylative coupling of aryl boronic acids together with terminal alkynes and perfluoroalkyl iodides in the presence of carbon monoxide. A wide range of highly functionalized enones can thus be prepared in a single operation in good yields. With 2-aminophenylalkynes, an intramolecular aminocarbonylation event overrules providing the indolin-2-one framework. Finally, adaptation of the two-chamber technology expands the method to the synthesis of the aforementioned structures with 13C-isotope labeling.

Nonlinear algorithm of PEM fuel cell catalyst poisoning progress in the presence of carbon monoxide in anode fuel: A computational study using OpenFOAM

This paper presents a model to theoretically study the key poisoning-related concepts including Dimensionless Cell Voltage (DCV), nonlinear algorithm of poisoning progress, smooth and accelerated poisoning progress regions, intensification point, and the rate of poisoning progress. A 3-D multicomponent transient solver, based on a comprehensive mathematical model including reaction kinetics, governing equations, boundary conditions and constitutive relations, in the open source code package, OpenFOAM, has been developed that has the capability of simulating anode side of PEM fuel cell in poisoning condition. This study suggests an optimum parametric voltage range for choosing purge characteristics of fuel cells operated in dead ended mode as well as an optimum range of efficient oxygen bleeding that must be used to cure or prevent CO poisoning. Studying the effects of key operating conditions on the poisoning progress algorithm showed that increasing the CO concentration, current density and operating temperature, and also lowering the catalyst Pt loading can all reduce the poisoning period and speed up its progress rate. The results also showed that poisoning progress follows a nonlinear algorithm. Based on the Response Surface Method (RSM), a series of parametric correlations were extracted to predict the poisoning progress algorithm according to above-mentioned operating conditions.

Some Aspects of Reductive Amination in the Presence of Carbon Monoxide: Cyclopropyl Ketones as Bifunctional Electrophiles

We conducted detailed studies on CO-assisted reductive chemistry with cyclopropyl ketones as a special type of substrate. Multiple factors influencing the outcome of the reaction have been studied for both ruthenium and rhodium catalysis. An unusual rearrangement of aminomethylcyclopropanes was found. We showed that some reductive reactions, which were believed to proceed through a water–gas shift reaction pathway, can nonetheless take place even without an external or internal water source, indicating a more interesting reaction mechanism. Cyclopropylketones were employed as bifunctional electrophiles and, depending on the conditions, the reaction with an amine can lead to a number of products, including aminoketones, cyclopropyl methylamines, pyrrolidines or 1,4-diaminopentanes.