The Oxidation of Carbon Monoxide as an Integrated Part of the Coupled Alkane Oxidation Process: Gas-Phase Oxidation over Supported Metal-Complex Catalysts

Heterogeneous rhodium–copper chloride catalysts for gas-phase oxidation processes were prepared via the cold impregnation of γ-Al₂O₃ with aqueous RhCl₃ and CuCl₂ solutions. Heptafluorobutyric or pentafluorobenzoic acids were additionally deposited onto these catalysts to simulate the action of homogeneous rhodium–copper chloride catalytic systems in the coupled alkane–carbon monoxide oxidation reaction. The catalysts were studied in the reactions of carbon monoxide oxidation and coupled propane–CO oxidation with dioxygen by diffuse reflectance IR Fourier transform spectroscopy (DRIFTS) and electron paramagnetic resonance (EPR). The obtained data indicate the probable transfer of electrons between rhodium and copper compounds.     

CO oxidation over Co3O4/SiO2 catalysts: Effects of porous structure of silica and catalyst calcination temperature

The catalytic performances of Co3O4/SiO2 catalysts prepared by incipient wetness impregnation for CO oxidation were investigated using three kinds of silica as carriers with different pore sizes of 7.7, 14.0 and 27.0 nm. The effects of calcination temperature on the catalyst surface and micro structure properties as well as catalytic performance for the oxidation of carbon monoxide were also studied. All catalysts were characterized by N2 adsorption-desorption, XRD, XPS, FTIR, H2-TPR and O2-TPD. It was found that the properties and crystal size of cobalt-containing species strongly depended on the pore size of silica carrier. While the silica pore size increased from 7.7 to 27.0 nm, the Co3O4 crystal size increased from 8.5 to 13.5 nm. Moreover, it was demonstrated that if the spinel crystal structure of Co3O4 was obtained at a calcination temperature as low as 150 ℃, the catalyst sample would have a high Co3O4 surface dispersion and a increase of surface active species, and thus exhibit a high activity for the oxidation of carbon monoxide.     

Thermal characterisation of molybdenum and platinum-molybdenum catalysts

Alumina supported Mo and Pt-Mo catalysts was subject to temperature programmed reduction (TPR) using H₂ and CO. After earlier oxidation step TPR–H₂ profiles shows different surface species, which depends on the composition of the catalysts and reduction temperature. Change in reducing gas from H₂ into CO results in significant changes in catalyst system. Hydrogen causes a decrease in oxidation number of metals, while carbon monoxide reacts with chemisorbed chemicals.     

Thermal characterisation of the non-stoichiometry and catalytic activity of BaxLn1−xCoO3 (Ln = La,Nd, Sm and Dy) compounds

The compounds Ba_xLn_1?xCoO₃ (Ln = La, Nd, Sm and Dy) were prepared by ceramic technique. They were characterised for oxygen non-stoichiometry using isothermal DTA under varying oxygen partial pressure and TG in air. Isothermal DTA was also employed to study the catalytic activity of the compounds towards CO oxidation. For a given compound, the oxygen deficiency increases with increasing temperature and decreasing oxygen partial pressure. For a given Ba_xLn_1?xCoO₃ series, in general barium-rich compounds were more oxygen deficient. Isothermal DTA study of CO oxidation over Ba_xLa_1?xCoO₃ compounds at 600 K suggested that the carbon monoxide takes up lattice-labile oxygen from the sample and is oxidised to CO₂, the percent CO conversion being higher for barium-rich samples.     

Study of the mutual influence of hydrogen and carbon monoxide in their joint oxidation on palladium

The joint oxidation of hydrogen and carbon monoxide in excess oxygen on palladium was investigated in a reactor for separate calorimetry and a gradientless microreactor at atmospheric pressure. An initiating influence of hydrogen m the oxidation of carbon monoxide, as well as inhibitory effect of carbon monoxide on the heterogeneous-homogeneous oxidation of hydrogen, was detected. The conditions of transition of the reactions into the volume according to a heterogeneous-homogeneous mechanism were determined. It is suggested that the joint oxidation of CO and H₂ occurs with the participation of the same active intermediate products formed from hydrogen and oxygen.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 4, pp. 504–508, July–August, 1985.     

Characteristics of the Oxidation of Carbon Monoxide on Platinum and Palladium Acetylacetonates Immobilized on a Silica Surface

Characteristics of the kinetics of the oxidation of carbon monoxide on acetylacetonates of palladium and platinum immobilized on a silica surface have been studied. The bound metal complexes show no hysteresis in the dependence of the rate of reaction on the concentration of CO and O₂ and have a higher catalytic activity than Pt/SiO₂ and Pd/SiO₂. A mechanism is proposed for the oxidation of carbon monoxide on platinum and palladium complexes bound to a SiO₂ surface.     

Substitution of silver for copper in the binuclear Mo/Cu center of carbon monoxide dehydrogenase from Oligotropha carboxidovorans

Carbon monoxide dehydrogenase from Oligotropha carboxidovorans catalyzes the aerobic oxidation of carbon monoxide to carbon dioxide, providing the organism both a carbon source and energy for growth. The active site of the native enzyme is a unique binuclear molybdenum- and copper-containing center. Here we show that silver can be substituted for copper in the active site to yield a functional enzyme. The characteristic hyperfine coupling of the I = ? nucleus of Ag is evident in the EPR signal of the binuclear active site observed upon reduction with CO, indicating both the incorporation of silver into the active site and, remarkably, retention of the catalytic activity. The silver-substituted enzyme is reduced by CO with an observed limiting rate constant of 8.1 s(-1), which can be compared with the value of 51 s(-1) for the wild-type enzyme. Steady-state kinetics for the Ag-substituted enzyme yielded k(cat) = 8.2 s(-1) and K(m) = 2.95 μM at pH 7.2.     

A CO Adsorption Site Change Induced by Copper Substitution in a Ruthenium Catalyst for Enhanced CO Oxidation Activity

Ru is an important catalyst in many types of reactions. Specifically, Ru is well known as the best monometallic catalyst for oxidation of carbon monoxide (CO) and has been practically used in residential fuel cell systems. However, Ru is a minor metal, and the supply risk often causes violent fluctuations in the price of Ru. Performance‐improved and cost‐reduced solid‐solution alloy nanoparticles of the Cu‐Ru system for CO oxidation are now presented. Over the whole composition range, all of the Cu_xRu_1?x nanoparticles exhibit significantly enhanced CO oxidation activities, even at 70 at % of inexpensive Cu, compared to Ru nanoparticles. Only 5 at % replacement of Ru with Cu provided much better CO oxidation activity, and the maximum activity was achieved by 20 at % replacement of Ru by Cu. The origin of the high catalytic performance was found as CO site change by Cu substitution, which was investigated using in situ Fourier transform infrared spectra and theoretical calculations.     

A MECHANISTIC STUDY OF THE FORMATION OF [Ru6C(CO)16]2− FROM [Ru6(CO)18]2−

Abstract

The kinetics of the transformation of [Ru₆(CO)₁₈]^2? into [Ru₆C(CO)₁₆]^2? in diglyme over the temperature range 130–160°C have been determined. The results are consistent with reversible loss of a carbonyl ligand from [Ru₆(CO)₁₈]^2?, followed by formation of carbon dioxide and reassociation of carbon monoxide to give the observed product. Mass spectral analysis of the evolved carbon dioxide trapped as barium carbonate supports an intramolecular pathway for the disproportionation of carbon monoxide.     

Preparation,Characterization, and Catalytic Behavior of Nanostructured Mesoporous CuO/ZrO2 Catalysts for Low-Temperature CO Oxidation

High-surface area mesoporous 20 mol% CuO/ZrO₂ catalyst was prepared by a surfactant-assisted method of nanocrystalline particle assembly, and characterized by x-ray powder diffraction (XRD), N₂ adsorption, transmission electron microscopy (TEM), H₂-TPR, TG-DTA, and x-ray photoelectron spectra (XPS) techniques. The catalytic properties of the CuO/ZrO₂ nanocatalysts calcined at different temperature were evaluated by low-temperature carbon monoxide oxidation using a CATLAB system. The results showed that these mesoporous nanostructured CuO/ZrO₂ catalysts were very active for low-temperature CO oxidation and the CuO/ZrO₂ catalyst calcined at 400°C exhibited the highest catalytic activity.     

Carbon monoxide :acceptor oxidoreductase from Pseudomonas thermocarboxydovorans strain C2 and its use in a carbon monoxide sensor

The carbon monoxide:acceptor oxidoreductase from autotrophically-grown Pseudomonas thermocarboxydovorans strain C2 was purified to 95% homogeneity and found to contain fiavin, iron, acid-labile sulphide and possibly molybdenum; its molecular weight was 2.7 × 10⁵. The enzyme catalyzed the oxidation of CO to CO₂ with various electron acceptors including phenazine ethosulphate, methylene blue, hexacyanoferrate(III) and ferrocene derivatives (ferrocene monocarboxylic acid, 1,1′dimethylferrocene and horse heart cytochrome C) but not viologen dyes, NAD(P) and oxygen. The optimum pH and temperature for enzyme activity in the in vitro assay were 7.5 and 80°C, respectively. Carbon monoxide is the only known electron donor (apparent K_m 5 × 10^?7 M) and acetylene, cyanide, 8-quinolinol and sulphydryl reagents inhibited the enzyme. Second-order homogeneous rate constants for the reaction between the reduced enzyme and either cytochrome C (3.0 × 10⁴ l mol^?1 s^?1) or the ferricinium ion of ferrocene monocarboxylic acid (4.0 × 10⁵ l mol^?1 s^?1) were calculated by using cyclic voltammetry. The latter reaction was exploited by incorporating 1,1′-dimethylferrocene in a carbon electrode and retaining carbon monoxide oxidoreductase behind a membrane at the surface. The probe gave a linear current response to aqueous concentrations of carbon monoxide up to 65 μM and achieved a steady current in < 15 s. A similar configuration was used to detect gaseous carbon monoxide. With a fuel cell mode, 20 nmol could be detected.     

Continuous hot electron generation in Pt/TiO2, Pd/TiO2, and Pt/GaN catalytic nanodiodes from oxidation of carbon monoxide

Thin films (<10 nm) of platinum or palladium were deposited on TiO2 or GaN to form Schottky diodes. We detected and monitored the continuous electron flow across the metal-oxide interfaces of Pt/TiO2, Pd/TiO2, and Pt/GaN during the catalytic oxidation of carbon monoxide. The electron excitation and flow in the metals were due to conversion of energy released by the oxidation of carbon monoxide into the kinetic energy of free electrons in platinum and palladium. The best conversion of three electrons per four CO2 molecules was observed from 5 nm Pt/TiO2.     

片层WC/C的原位合成及其在甲醇氧化中的应用

以片层二硫化钨(WS2)为前驱体,氯化钠(Na Cl)为介质,CO为气体碳源,采用程序升温法一步合成片层碳化钨/碳复合材料(WC/C)。通过X射线衍射(XRD),X射线近边吸收谱(XANES)和扫描电镜(SEM)等一系列手段对样品的化学组成、形貌、结构等进行表征。研究发现,在高温渗碳过程中,不仅利用WS2的片层结构和Na Cl的锚定作用合成了具有薄层孔洞的WC,而且Na Cl和WS2金属面对碳膜生长的催化作用使WC表面覆有原位生长的碳膜,为电子传输提供了有效通道。将该材料作为载体材料进行电化学性能测试,结果表明:负载少量Pt后制得的Pt/WC/C电催化剂,在甲醇氧化反应(MOR)中表现出良好的电催化活性、稳定性及优异的抗CO中毒能力。     

Co3O4/CeO2 CO氧化的原位红外光谱研究

采用沉淀氧化法制备了Co₃O₄/CeO₂催化剂。分别在干、湿条件下进行了一氧化碳氧化反应研究。运用FT-IR表征手段,在钴铈复合氧化物上进行了CO吸附及CO/O₂共吸附研究。结果表明,与纯的Co₃O₄样品相比,Co₃O₄/CeO₂具有明显的抗湿气能力。Co₃O₄/CeO₂催化剂在进行CO氧化时,表面形成了类碳酸盐物种。当环境温度低于453 K时,催化剂上类碳酸盐的生成与形成类碳酸盐物种后受热分解存在着动态平衡。当环境温度高于493 K,催化剂上生成的类碳酸盐物全部受热分解。氧化铈的加入提高了催化剂的抗湿气性能。较小粒径的Co₃O₄与CeO₂产生的强相互作用可使CeO₂向Co₃O₄提供氧,因而间接提供了CO氧化需要的氧。     

基于席夫碱配体的锰羰基配合物可见光诱导释放一氧化碳性能

利用五羰基溴化锰和2-吡啶甲醛以及卤代苯胺通过一步法合成得到了3个含席夫碱配体的锰羰基配合物[Mn(CO)₃(py(CH=N)ph-X)Br],其中X=Cl (1)、Br (2)、I (3),并采用核磁、X射线单晶衍射、红外光谱、紫外可见光谱和荧光光谱对其进行了表征。这类配合物在非光照下稳定,在可见光(LED蓝光、绿光和红光)作用下分解释放CO,可以作为光诱导的一氧化碳释放剂(photoCORMs)。研究表明蓝光是促进配合物分解释放CO的最有效光源。此外,CO释放动力学分析显示配合物分解释放CO过程符合一级动力学模型。配合物3的释放研究表明脱氧肌红蛋白能够捕捉所释放的CO。尽管这些配合物本身的细胞毒性(IC50)达到微摩尔级,但光照下的细胞兼容性有显著改善,上升为接近100微摩尔级。这些配合物具有荧光性质,在450 nm激发波长下在500～700 nm范围内发射一定强度的荧光,可以作为荧光标记物用以监测细胞或生物体内释放剂分布及CO释放情况。     

基于席夫碱配体的锰羰基配合物可见光诱导释放一氧化碳性能

利用五羰基溴化锰和2-吡啶甲醛以及卤代苯胺通过一步法合成得到了3个含席夫碱配体的锰羰基配合物[Mn (CO)₃(py (CH=N) ph-X) Br],其中X=Cl (1)、Br (2)、I (3),并采用核磁、X射线单晶衍射、红外光谱、紫外可见光谱和荧光光谱对其进行了表征。这类配合物在非光照下稳定,在可见光(LED蓝光、绿光和红光)作用下分解释放CO,可以作为光诱导的一氧化碳释放剂(photoCORMs)。研究表明蓝光是促进配合物分解释放CO的最有效光源。此外,CO释放动力学分析显示配合物分解释放CO过程符合一级动力学模型。配合物3的释放研究表明脱氧肌红蛋白能够捕捉所释放的CO。尽管这些配合物本身的细胞毒性(IC₅₀)达到微摩尔级,但光照下的细胞兼容性有显著改善,上升为接近100微摩尔级。这些配合物具有荧光性质,在450 nm激发波长下在500~700 nm范围内发射一定强度的荧光,可以作为荧光标记物用以监测细胞或生物体内释放剂分布及CO释放情况。     

A Device for Preparing Standard Mixtures of Carbon Monoxide

Abstract

Accurate low concentrations of carbon monoxide, at levels comparable with those found in ambient air, are prepared by permeation through a thin silicone membrane at a constant temperature. The lowering in CO pressure into a diffusing phial is a measure of permeation rate. The device described permits the dynamic calibration and testing of atmospheric CO analyzers.     

Experimental and theoretical studies of carbon monoxide oxidation over W/Cu/Ce trimetallic oxides: the effect of W addition

It is a significant method to prepare highly dispersed polymetallic oxides using in-situ doping metal organic frameworks as precursors. Herein, a series of straw-like W/Cu/Ce trimetallic oxides were prepared by using phosphotungstic ionic liquid@Ce-based metal organic framework adsorbing with copper acetylacetonate as precursors. The effect of W content on catalytic activity of W/Cu/Ce trimetallic oxides for carbon monoxide (CO) oxidation was well-investigated. Comprehensive characterization methods and density functional theory calculations were adopted to reveal the property changes of Cu/CeO₂ catalyst by the addition of W. The results demonstrated that W, Cu, and Ce are highly dispersed in the prepared W/Cu/Ce trimetallic oxides, and adding proper amount of W can improve the activity of the catalyst. H₂ temperature-program reduction profiles, X-ray photoelectron spectroscopy, in-situ diffuse reflectance infrared Fourier transform spectroscopy, and density functional theory calculations clearly revealed that after the addition of W, the strength of Ce-O bond is weakened, the oxygen vacancy is increased, and the adsorption of CO is enhanced, respectively, which are vital reasons for its high catalytic activity. In addition, the CO oxidation reaction pathway over prepared W/Cu/Ce trimetallic oxides based on the Mars-van Krevelen mechanism was studied, and the results exhibited that CO can wrest the lattice oxygen of W/Cu/Ce trimetallic oxides to form CO₂, which is also proved to be the rate-determining step in reaction process.     

One Model,Two Enzymes: Activation of Hydrogen and Carbon Monoxide

The ability to catalyze the oxidation of both H₂ and CO in one reaction pot would be a major boon to hydrogen technology since CO is a consistent contaminant of H₂ supplies. Here, we report just such a catalyst, with the ability to catalyze the oxidation of either or both H₂ and CO, based on the pH value. This catalyst is based on a NiIr core that mimics the chemical function of [NiFe]hydrogenase in acidic media (pH 4–7) and carbon monoxide dehydrogenase in basic media (pH 7–10). We have applied this catalyst in a demonstration fuel cell using H₂, CO, and H₂/CO (1/1) feeds as fuels for oxidation at the anode. The power density of the fuel cell depends on the pH value in the media of the fuel cell and shows a similar pH dependence in a flask. We have isolated and characterized all intermediates in our proposed catalytic cycles.     

One Model,Two Enzymes: Activation of Hydrogen and Carbon Monoxide

The ability to catalyze the oxidation of both H₂ and CO in one reaction pot would be a major boon to hydrogen technology since CO is a consistent contaminant of H₂ supplies. Here, we report just such a catalyst, with the ability to catalyze the oxidation of either or both H₂ and CO, based on the pH value. This catalyst is based on a NiIr core that mimics the chemical function of [NiFe]hydrogenase in acidic media (pH 4–7) and carbon monoxide dehydrogenase in basic media (pH 7–10). We have applied this catalyst in a demonstration fuel cell using H₂, CO, and H₂/CO (1/1) feeds as fuels for oxidation at the anode. The power density of the fuel cell depends on the pH value in the media of the fuel cell and shows a similar pH dependence in a flask. We have isolated and characterized all intermediates in our proposed catalytic cycles.