The non-isothermal kinetics of zinc ferrite reduction with carbon monoxide

Journal of Thermal Analysis and Calorimetry - This study aims to reduce zinc ferrite using carbon monoxide in the temperature range of 25–1000 °C using temperature-programmed...     

The isothermal kinetics of zinc ferrite reduction with carbon monoxide

Journal of Thermal Analysis and Calorimetry - The reduction kinetics of zinc ferrite in CO was investigated under isothermal conditions at different CO concentration and roasting temperature with...     

The radiolysis of mixtures of carbon monoxide and hydrogen

The self-radiolysis of mixtures of CO and tritium (³H₂) has been studied at pressures of 0.25 to 1.0 atmospheres, temperatures of ?198° to +100°C, and in the presence of added H₂O or CO₂. The products of decomposition are CO₂, ³H₂O, C³H₄, C₂³H₄, and a white polymer believed to be polyformaldehyde. Initial rates and G values were measured and compared with rates of ion pair formation. The rates of formation of both CO₂ and C³H₄ are independent of temperature and proportional to the energy absorbed in the ³H₂.     

The second limit of hydrogen + carbon monoxide + oxygen mixtures

Previous studies by Buckler and Norrish of the second limit of CO and O₂ mixtures containing small amounts (0.25–10%) of H₂ have been used to obtain the velocity constant of the reaction These estimates of k₃₃ = 3.9 × 10⁸ and 3.5 × 10⁸ liter² mole^?2 sec^?1 (M ? H₂) at 500° and 560°C, respectively, have been combined with other estimates over the range 300°–3500°K to give k₃₃ = 3.0 × 10⁸ exp (?3000/RT) for M ? Ar; the considerable scatter in the available points does not encourage any great confidence in this expression and may be attributed at least partly to the different molecules used as M by different workers. For KCl-coated and CsCl-coated vessels at 540°C, studies of the second limit of H₂ + O₂ mixtures, to which CO has been added, have indicated that with both the surfaces, the effect of CO on the limit is masked by changes in the surface nature. In the case of CsCl, the results have enabled a lower limit of about 0.6 to be obtained for the efficiency of CO relative to H₂ in the reaction Use of a computer treatment to interpret the second limit of CO + H₂ + O₂ mixtures in aged boric-acid-coated vessels at 500°C gives a value of m_CO = 0.74 ± 0.04 together with an estimate of k₃₂ (H + CO + M″ = HCO + M″)/k₄ = 0.022 ± 0.003, which leads to k₃₂ = 2.3 × 10⁸ liter² mole^?2 sec^?1 (M ? H₂) at 500°C.     

Platinum and molybdenum oxide deposited carbon electrocatalyst for oxidation of hydrogen containing carbon monoxide

Carbon-supported Pt/MoO_x catalysts for use in PEFC anodes were prepared and their catalytic activity for the oxidation of CO-contaminated H₂ was examined based on the fuel cell performance in PEFC single cell arrangements. Based on the XRD pattern and XPS measurements of the prepared Pt/MoO_x/C catalysts, it was found that the deposited MoO_x exists as an amorphous oxide phase. The MoO_x phase shows a redox peak at around 0.45 V, which was revealed by the cyclic voltammogram of the Pt/MoO_x/C in sulfuric acid solution. The PEFC performance of the cell with Pt/MoO_x/C was improved under 100 ppm CO-contaminated H₂ conditions compared to the Pt/C catalyst, and was almost comparable to the PtRu(1:1)/C catalyst.     

The oxidation of carbon monoxide on a catalyst with a spinel structure containing Mg ferrite

The oxidation of carbon monoxide on xMgO · yFe₂O₃ catalysts was studied over the temperature range 440–660 K. The catalysts contained 5, 40, and 75 at % Fe and the spinel MgFe₂O₄ and MgO phases. Complete CO conversion on compact and deposited (on γ-Al₂O₃) catalysts containing 75 at. % Fe occurred at 650–660 K. The kinetics of interaction of CO with adsorbed oxygen was studied on catalysts with 5 and 40 at % Fe below and above the Curie point (T _c = 593 ± 10 K). The differences in the reaction orders with respect to gaseous CO and adsorbed oxygen below and above T _c were explained as follows. In the ferromagnetic state of the active MgFe₂O₄ phase, oxidation involved adsorbed oxygen localized at oxygen vacancies in the environment of Fe³⁺ ions, whereas, in the paramagnetic state, superexchange interactions were absent in spinel structure fragments.     

Spectroscopic investigations of high-power laser-induced dielectric breakdown in gas mixtures containing carbon monoxide

Large-scale plasma was created in gas mixtures containing carbon monoxide by high-power laser-induced dielectric breakdown (LIDB). The composition of the mixtures used corresponded to a cometary and/or meteoritic impact into the Earth's early atmosphere. A multiple-centimeter-sized fireball was created by focusing a single 85 J, 450 ps near-infrared laser pulse into the center of a 15 L gas cell. The excited reaction intermediates that formed in various stages of the LIDB plasma chemical evolution were investigated by optical emission spectroscopy (OES) with temporal resolution. Special attention was paid to any OES signs of molecular ions. However, carbon monoxide cations were registered only if their production was enhanced by Penning ionization, i.e., excess He was added to the CO. The chemical consequences of laser-produced plasma generation in a CO-N 2-H 2O mixture were investigated using high resolution Fourier-transform infrared absorption spectroscopy (FTIR) and gas chromatography (GC). Several simple inorganic and organic compounds were identified in the reaction mixture exposed to ten laser sparks. H 2 (18)O was used to avoid possible contamination. The large laser spark triggered more complex reactivity originating in carbon monoxide than expected, when taking into account the strong triple bond of carbon monoxide causing typically inefficient dissociation of this molecule in electrical discharges.     

Catalytic reduction of dinitrogen monoxide by carbon monoxide over various metal oxides

A volcano-shaped relationship was obtained between the temperature Tc, where a given conversion (per unit surface area of the catalyst) attained, and the heat of formation, Q, of metal oxide, suggesting that the mechanism of the reaction depended upon Q-value.

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T_c, ( ), , Q, , Q.

     

The microdetermination of carbon dioxide,oxygen, carbon monoxide,and hydrogen in gaseous mixtures Krogh method

Summary The analysis of gases by theKrogh technique of entrapping a bubble under glycerol and exposing it to selective absorbents has been examined to assess its value as a means of determining quantitatively oxygen, carbon dioxide, carbon monoxide and hydrogen in volumes of sample of the microlitre order. The method, after modifications to accommodate for non-specificity of the absorption reagents, has given satisfactory performance, and it possesses the additional advantage of simplicity of apparatus.

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Zusammenfassung Das gasanalytische Verfahren vonKrogh, wonach eine Gasblase in Glycerin eingeschlossen und unter dem Mikroskop der Einwirkung selektiver Absorptionsmittel ausgesetzt wird, wurde geprüft, um seine Eignung zur quantitativen Bestimmung von Sauerstoff, Kohlendioxyd, Kohlenmonoxyd und Wasserstoff in Proben der Größenordnung von Mikrolitern festzustellen. Das Verfahren wurde modifiziert, um es der Verwendung nicht spezifischer Absorptionsreagenzien anzupassen, und läßt sich nun in befriedigender Form durchführen. Es bietet den zusätzlichen Vorteil der Einfachheit in apparativer Hinsicht.

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Résumé La technique d'analyse de gaz deKrogh qui consiste à emprisonner une bulle de gaz sous du glycerol et à l'exposer à des réactifs absorbants sélectifs a été éprouvée pour le dosage de l'oxygène, du gaz carbonique, de l'oxyde de carbone et de l'hydrogène sur des échantillons dont le volume est de l'ordre de grandeur du microlitre. La méthode a fourni des résultats satisfaisants après certaines modifications destinées à tenir compte de la non spécificité des réactifs absorbants; elle présente l'avantage complémentaire de la simplicité de l'appareillage mis en oeuvre.

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The author wishes to thank Mr.F. J. Woodman who initiated this work, and Mr.I. Waide for technical co-operation. This paper is published by permission of the Managing Director, United Kingdom Atomic Energy Authority (Industrial Group).     

Routes of nitrogen formation in reduction of nitrogen oxide by carbon monoxide and hydrogen over nickel chromite catalyst

The route of NO reduction to N₂ over nickel chromite catalyst is dependent on the nature of the reducing agent. NO reduction by dihydrogen proceeds mainly through the step of N₂O formation, whereas NO reduction to N₂ by carbon monoxide is mainly direct without a step of N₂O formation.

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NO N₂ NO , , N₂O, NO , , NO N₂, . . N₂O.

     

Influence of oxygen on reduction of NO by carbon monoxide

Experimental data on the influence of oxygen on the rate of formation of N₂, N₂O, and CO₂ were obtained for a wide range of conditions, the goal being to substantiate and develop a previously proposed mechanism and reaction kinetics for the reaction of CO with NO and O₂. The effect of the reversibility of the NO adsorption step on the kinetics of the process was also analyzed. The conditions necessary for acceleration of the reaction of CO + NO by oxygen were obtained. Good correspondence was also obtained between the calculated and experimental kinetic dependences.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 3, pp. 289–294, May–June, 1989.     

Thermodynamic properties of liquid mixtures of carbon monoxide and methane

The equations of state of liquid methane at 125.00 K and of six liquid mixtures of carbon monoxide and methane at 116.30, 120.00 and 125.00 K have been measured from just above the saturation vapour pressure to the freezing pressure of methane. The results show that the excess volume V^E is large and negative at low pressures but becomes less negative as the pressure is increased, being almost zero at the highest pressures. The curve of V^E against the mole fraction x is very asymmetrical at low pressures, but becomes more symmetrical with rising pressure.The effect of pressure on the excess functions G^E, H^E and T·S^E has been calculated. H^E and T·S^E prove to be much more sensitive to pressure than G^E.Conformal solution theory, in the van der Waals one-fluid form, reproduces the experimental results very successfully.     

Thermodynamics of liquid mixtures of argon+ carbon monoxide

The heat of mixing of liquid argon (component 1) and liquid carbon monoxide has been measured by direct calorimetry for several mixtures of composition ranging from x₁ ? 0.2 to x₁ ? 0.8 at 85.79 K. At this temperature H^E is positive and an almost parabolic function of mole fraction, with a maximum value of H^E = 95.9 J mol^?1 at x₁ = 0.569.The experimental results are compared with those derived from the Gibbons-Rigby equation of state, and from conformal solution theory.     

Molecular simulation and macroscopic modeling of the diffusion of hydrogen, carbon monoxide and water in heavy n-alkane mixtures

The self-diffusion coefficient of hydrogen (H(2)), carbon monoxide (CO) and water (H(2)O) in n-alkanes was studied by molecular dynamics simulation. Diffusion in a few pure n-alkanes (namely n-C(8), n-C(20), n-C(64) and n-C(96)) was examined. In addition, binary n-C(12)-n-C(96) mixtures with various compositions as well as more realistic five- and six-n-alkane component mixtures were simulated. In all cases, the TraPPE united atom force field was used for the n-alkane molecules. The force field for the mixture of n-alkanes was initially validated against experimental density values and was shown to be accurate. Moreover, macroscopic correlations for predicting diffusion coefficient of H(2), CO and H(2)O in n-alkanes and mixtures of n-alkanes were developed. The functional form of the correlation was based on the rough hard sphere theory (RHS). The correlation was applied to simulation data and an absolute average deviation (AAD) of 5.8% for pure n-alkanes and 3.4% for n-alkane mixtures was obtained. Correlation parameters vary in a systematic way with carbon number and so they can be used to provide predictions in the absence of any experimental or molecular simulation data. Finally, in order to reduce the number of adjustable parameters, for the n-alkane mixtures the "pseudo-carbon number" approach was used. This approach resulted in relatively higher deviation from MD simulation data (AAD of 18.2%); however, it provides a convenient and fast method to predict diffusion coefficients. The correlations developed here are expected to be useful for engineering calculations related to the design of the Gas-to-Liquid process.