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 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).     

Vapor—liquid equilibrium in ternary mixtures of hydrogen + carbon dioxide + 1-methylnaphthalene

Compositions of saturated vapor and liquid phases at equilibrium were measured for hydrogen + carbon dioxide + 1-methylnaphthalene mixtures at 543 and 704 K over a pressure range of 50–250 atm. Measurements were made at three relative concentrations of hydrogen to carbon dioxide at each condition of temperature and pressure. A significant variation of the K-value of 1-methylnaphthalene with gas composition was observed in the high pressure region.     

High temperature separation of carbon dioxide/hydrogen mixtures using facilitated supported ionic liquid membranes

Efficiently separating CO₂ from H₂ is one of the key steps in the environmentally responsible uses of fossil fuel for energy production. A wide variety of resources, including petroleum coke, coal, and even biomass, can be gasified to produce syngas (a mixture of CO and H₂). This gas stream can be further reacted with water to produce CO₂ and more H₂. Once separated, the CO₂ can be stored in a variety of geological formations or sequestered by other means. The H₂ can be combusted to operate a turbine, producing electricity, or used to power hydrogen fuel cells. In both cases, only water is produced as waste. An amine-functionalized ionic liquid encapsulated in a supported ionic liquid membrane (SILM) can separate CO₂ from H₂ with a higher permeability and selectivity than any known membrane system. This separation is accomplished at elevated temperatures using facilitated transport supported ionic liquid membranes.     

The solubility of water in mixtures of dimethyl ether and carbon dioxide

This paper reports measurements of the solubility of water in liquid and supercritical fluid mixtures of dimethyl ether and carbon dioxide. The measurements were made by extracting water under saturation conditions using premixed liquid dimethyl ether–carbon dioxide mixtures. Results are reported for temperatures of 313.8 K and 333.3 K at 9.0 MPa and 15.0 MPa. Results are fitted to the Peng–Robinson cubic equation of state with mixing rules according to Wong and Sandler, using binary interaction parameters fitted to the literature data for the respective binary systems: dimethyl ether–water; dimethyl ether–carbon dioxide; and carbon dioxide–water. Liquid densities for dimethyl ether–carbon dioxide mixtures, measured using a coriolis flow instrument, are also reported.     

Photoreduction of carbon dioxide by hydrogen and methane

Zirconium oxide is active for photoreduction of gaseous carbon dioxide to carbon monoxide with hydrogen. A stable surface species arises under the photoreduction of CO₂ on zirconium oxide, and it is identified as surface formate by infrared spectroscopy. Adsorbed CO₂ is converted to formate by photoreaction with hydrogen. The surface formate is a true reaction intermediate since CO is formed by the photoreaction of formate and CO₂; surface formate works as a reductant of carbon dioxide to yield carbon monoxide. The dependence on the wavelength of irradiation light shows that a bulk ZrO₂ is not a photoactive species. When ZrO₂ adsorbs CO₂ a new band appears in photoluminescence excitation spectrum. The photoactive species in the reaction that CO₂+H₂ yields HCOO⁻ is presumably formed by the adsorption of CO₂ on ZrO₂ surface. Hydrogen molecules play a role to supply an atomic hydrogen. Therefore, methane molecules can also be used as a reductant of carbon dioxide.     

Thermodynamics of supercritical steam + carbon dioxide mixtures

Measurements of the excess enthalphy of steam + carbon dioxide have been made at temperatures from 363 to 698 K at pressures up to 6 MPa. Analysis of the measurements at low pressures yields values of the cross term second virial coefficient B₁₂. Evidence for a specific interaction between water and carbon dioxide is found, the enthalpy of association is ΔH = − 14 ±2 kJ mol⁻¹. The measurements at high pressures are fitted by the Peng-Robinson equation of state using values of the interaction parameter k_ij which are temperature dependent.     

Hydrate dissociation conditions for gas mixtures containing carbon dioxide,hydrogen, hydrogen sulfide,nitrogen, and hydrocarbons using SAFT

A new method, a molecular thermodynamic model based on statistical mechanics, is employed to predict the hydrate dissociation conditions for binary gas mixtures with carbon dioxide, hydrogen, hydrogen sulfide, nitrogen, and hydrocarbons in the presence of aqueous solutions. The statistical associating fluid theory (SAFT) equation of state is employed to characterize the vapor and liquid phases and the statistical model of van der Waals and Platteeuw for the hydrate phase. The predictions of the proposed model were found to be in satisfactory to excellent agreement with the experimental data.     

Enhancement of gamma-ray radiolysis of carbon dioxide with the assistance of solid materials

This work is devoted to enhance gamma-ray radiolysis of CO₂ with the assistance of coexisting metal materials. It is found that lower energy electrons which are generated through interactions of γ-photons with the coexisting metal materials and ejected to CO₂ gas actually enhance decomposition of CO₂ to produce CO. The increment of CO production agrees well with the increment of the deposited energy in CO₂, given by the lower energy electrons emitted from the materials, which is calculated by a numerical simulations code MCNP. It is also suggested that the volumetric decomposition of CO₂ dominates the decomposition at the material’s surface.     

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.     

Conversion of methane/carbon dioxide mixtures on vermiculite

A study has been made of the conversion of methane/carbon dioxide mixtures on a vermiculite catalyst of composition 22MgO·22SiO₂·5Al₂O₃·Fe₂O₃·4OH₂O. It has been established that at 900–970°C with molar ratios of CO₂/CH₄ of 0.5–1.5 and contact times of 10.5–21 sec the conversion proceeds quantitatively but the main products, H₂ and CO, are formed in varying proportions. An explanation has been given for the effect of the process parameters on the conversion and selectivity.Chernogolovka Institute of Chemical Physics, Russian Academy of Sciences, 142432 Chernogolovka. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 7, pp. 1511–1515, July, 1992.     

Phase behavior of diisobutyl adipate–carbon dioxide mixtures

Phase equilibrium data are reported for diisobutyl adipate (DiBA) in CO₂ at temperatures from 25 to 150 °C. This system exhibits a continuous mixture-critical curve with a maximum near 200 °C and 260 bar. The phase behavior of the DiBA–CO₂ system is well characterized and modeled with the Peng–Robinson equation of state using a single, fixed binary interaction parameter, k_ij. The DiBA–CO₂ data are compared to other solute–CO₂ systems with structures similar to DiBA to demonstrate the impact of the diester end groups in DiBA, which enhance DiBA solubility in CO₂ at low temperatures, relative to a single (ethyl laurate) or no ester end groups (tetradecane), and a single acid end group (tetradecanoic acid). DiBA–CO₂ data are also compared to data for two compounds each with diester groups but one containing an interior aromatic group (dibutyl phthalate) and the other containing the same number of interior carbon groups but with two less carbon groups at either end of the chain (divinyl adipate).     

The deactivation of the asymmetric stretch mode of carbon dioxide by hydrogen

The deactivation of CO₂(00⁰1) by H₂ is shown to involve a near-resonance transfer of vibrational to rotational energy.     

Solubility of thiophene in carbon dioxide and carbon dioxide + 1-propanol mixtures at temperatures from 313 to 363 K

Solubility measurements of sulfur compounds in supercritical fluids are required in order to determine the feasibility of supercritical extraction for removing them from gasoline and diesel fuel. In this work, solubility of thiophene in CO₂ and in CO₂ + 1-propanol mixtures were measured from 313 to 363 K using an apparatus based on the static–analytical method. Vapor–liquid equilibria (VLE) data of binary mixtures were fitted to the Peng–Robinson equation of state (EoS) with classical mixing rules. The binary interaction parameters (k_ij) obtained were used to predict the VLE data of ternary systems. The calculated values given by this simple model agree well to the experimental data.     

Dew points of binary carbon dioxide + water and ternary carbon dioxide + water + methanol mixtures: Measurement and modelling

Dew points for four carbon dioxide + water mixtures between 1.2×10⁵ and 41.1×10⁵ Pa in the temperature range from 251.9 to 288.2 K, and eight carbon dioxide + water + methanol mixtures between 1.2×10⁵ and 43.5×10⁵ Pa and temperatures from 246.0 to 289.0 K were experimentally determined. The experimental results obtained on the binary and ternary systems were analysed in terms of a predictive excess function–equation of state (EF–EOS) method, which reproduced the experimental dew point temperature data with absolute average deviation (AAD) between 0.8 and 1.8 K for the systems with water, and from 0.0 to 2.7 K for the systems with water and methanol. The experimental results obtained for carbon dioxide + water mixtures, with molar fraction of water lower than 0.00174, at pressure values higher than 5×10⁵ Pa were also compared to a predictive equation of state model. It reproduced experimental dew point temperature data with AAD between 0.2 and 0.6 K.     

The mechanism of carbon dioxide catalysis in the hydrogen peroxide N-oxidation of amines

The reactivity of the peroxymonocarbonate ion, HCO4- (an active oxidant derived from the equilibrium reaction of hydrogen peroxide and bicarbonate), has been investigated in the oxidation of aliphatic amines. Tertiary aliphatic amines are oxidized to the corresponding N-oxides in high yields, while secondary amines give corresponding nitrones. A closely related mechanism for the H2O2 oxidation of tertiary amines catalyzed by CO2 (under 1 atm) and H2O2 at 25 degrees C is proposed. The rate laws for the oxidation of N-methylmorpholine (1) to N-methylmorpholine N-oxide and N,N-dimethylbenzylamine (2) to N,N-dimethylbenzylamine N-oxide have been obtained. The second-order rate constants for the oxidation by HCO4- are k1 .016 M(-1) s(-1) for 1 in water and k1=0.042 M(-1) s(-1) for 2 in water/acetone (5:1). The second-order rate constants for tertiary amine oxidations by HCO4- are over 400-fold greater than those for H2O2 alone. Activation parameters for oxidation of 1 by HCO4- in water are reported (DeltaH=36+/-2 kJ mol(-1) and DeltaS=-154+/-7 J mol(-1) K(-1)). The BAP (NH4HCO3-activated peroxide) or CO2/H2O2 oxidation reagents are simple and economical methods for the preparation of tertiary amine N-oxides. The reactions proceed to completion, do not require extraction, and afford the pure N-oxides in excellent yields in aqueous media.     

Spectroscopic identification of the mixed hydrogen and carbon dioxide clathrate hydrate

In this contribution, we first found the novel clathrate hydrate containing two gaseous guests of hydrogen and carbon dioxide by spectroscopic analysis. X-ray powder diffraction and NMR spectroscopy were used to identify structure and guest distribution of the mixed H2 + CO2 hydrate. X-ray diffraction result confirmed that the unit cell parameter was 11.8602 +/- 0.0010 A, and the formed hydrate was identified as structure I hydrate. 1H magic angle spinning (MAS) NMR and 13C cross-polarization (CP) NMR spectroscopy were used to examine the distribution of hydrogen and carbon dioxide molecules in the cages of structure I, respectively. These NMR spectra showed that carbon dioxide molecules occupied both small 512 cages and large 51262 cages, and hydrogen molecules only were occluded in small 512 cages of structure I. The new finding of the mixed hydrogen hydrate is expected to contribute toward the development of hydrogen production technology and, particularly, inclusion chemistry.