The radiolysis of mixtures of carbon dioxide and hydrogen

The self-radiolysis of CO₂ in excess tritium (³H₂) has been studied at pressures of 0.1 to 1.0 atm, temperatures of ?80° to +100°C, and in the presence of added H₂O, He, or Ar. The primary products of decomposition are CO and ³H₂O. Secondary products are C³H₄, C₂³H₄, and a white polymer. The rates of disappearance of CO₂ and formation of products and G-;values were measured. The disappearance of CO₂ initially obeys first-order kinetics, then slows down with time at a rate depending upon the initial pressure of ³H₂. The initial rates are proportional to pressures of CO₂ and ³H₂. They are independent of temperature, decreased by addition of H₂O vapor, and increased by addition of He or Ar. The proposed mechanism of decomposition of CO₂ and formation of products involves ionization of CO₂ followed by dissociative recombination forming CO and O. Then the O reacts with a hydrogen-containing species forming OH and H₂O, and a back reaction forms CO₂ from CO and OH.     

Modeling the phase equilibria of hydrogen sulfide and carbon dioxide in mixture with hydrocarbons and water using the PCP-SAFT equation of state

The perturbed-chain polar statistical associating fluid theory (PCP-SAFT) equation of state is applied to correlate phase equilibria for mixtures of hydrogen sulfide (H₂S) and carbon dioxide (CO₂) with alkanes, with aromatics, and with water over wide temperature and pressure ranges. The binary mixtures of H₂S–methane and CO₂–methane are studied in detail including vapor–liquid, liquid–liquid and fluid–solid phase equilibria. Very satisfying results were obtained for the binary mixtures as well as for the ternary mixture of H₂S–CO₂–methane using the (constant) interaction parameters of the binary pairs.     

GCA-EoS: A SAFT group contribution model—Extension to mixtures containing aromatic hydrocarbons and associating compounds

GCA-EoS is the first equation of state that takes into account association using a SAFT-like group contribution term. It has been recently upgraded to deal simultaneously with multiple associating and solvating groups. In this work a review of applications and parameters revisions are presented and the GCA-EoS extension to aromatic hydrocarbons is discussed. These compounds are important in different industrial fields (textile, fine chemicals, pharmaceutical, petrochemicals, materials, etc.). Moreover, compounds like phenol play a major role not only in several polymers syntheses but also in biomass processing mixtures. Specifically, the extension to systems containing aromatic hydrocarbons (BETX and alkylbenzenes), water and alkanols is discussed.     

Critical phenomena in a mixture of methane,carbon dioxide and hydrogen sulfide

Ng, H.-J., Robinson, D.B. and Leu, A.-D., 1985. Critical phenomena in a mixture of methane, carbon dioxide and hydrogen sulfide. Fluid Phase Equilibria, 19:273-286.The two- and three-phase boundaries for a mixture containing nominally 0.50 mole fraction methane, 0.10 mole fraction carbon dioxide and 0.40 mole fraction hydrogen sulfide were determined experimentally for a range of temperatures from c. 29 to – 83°C at pressures up to c. 13 MPa.The two-phase boundary curve commences with a conventional hydrogen-sulfide-rich liquid dew point locus which passes through an upper retrograde region and terminates at a vapor-hydrogen-sulfide-rich liquid critical point at ? 16.9°C and 11.03 MPa. The phase boundary then follows a bubble point locus which terminates at a hydrogen-sulfide-rich liquid-methane-rich liquuid critical point at ?45.6°C and 8.79 MPa. After this the boundary turns sharply upwards to higher pressures at lower temperatures. This separates the single phase from a second retrograde-like two-liquid region.The three-phase boundary enclosing a hydrogen-sulfide-rich liquid-methane-rich liquid—vapor region terminates when the methane-rich liquid dew point locus and the three-phase bubble point locus meet at a third critical point occurring at ?57.5°C and 6.62 MPa.The measurements and observations were made using a sapphire cylinder as an equilibrium cell. Phase compositions and phase volume percentages were measured under a number of selected conditions in both the two- and three-phase regions.     

Micro gas analysis system for measurement of atmospheric hydrogen sulfide and sulfur dioxide

A honeycomb structure microchannel scrubber was developed to achieve efficient and stable gas collection. A thin porous membrane was pasted on a microchannel by the adhesive force of a fresh polydimethylsiloxane surface. The microchannel scrubber achieved much more efficient gas collection than conventional impingers and diffusion scrubbers. Two sets of the microchannel scrubbers and detectors were integrated in a 10 cm x 9 cm plastic board to create a micro gas analysis system (microGAS) for simultaneous measurements of H2S and SO2. The whole system including a battery was incorporated in a carrying case 34 cm W x 16 cm D x 17 cm H for use in the field. Liquid flows at 30 microl min(-1) were obtained by bimetal micropumps. The estimated detection limits were 0.1 ppbv for H2S and 1 ppbv for SO2. The system was demonstrated for real atmospheric gas analysis, and the results agreed well with data concurrently obtained by ion chromatography coupled with a cylindrical diffusion scrubber. The system we developed allowed automated continuous analyses in the field and achieved a much higher time resolution compared to those by ion chromatographic analysis.     

The excess enthalpy of gaseous mixtures of nitrogen and carbon dioxide

A flow calorimeter has been designed for the direct determination of the excess enthalpy of gaseous mixtures at elevated pressures over a range of temperatures. The calorimeter was tested by determination of the excess enthalpy of mixtures of hydrogen and nitrogen, mixtures for which experimental results are available. New measurements were made on mixtures of nitrogen and carbon dioxide at 40 °C over the pressure range from 4 to 131 atm. The results were compared with predictions based on equations of state and the theory of corresponding states.     

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.     

Predictive use of a SAFT EOS for phase equilibria of some hydrocarbons and their binary mixtures

A systematic study of several hydrocarbons with a SAFT equation of state (EOS) is presented. First, it is shown that the phase behavior of the whole family of n-alkanes may be represented with the use of only three parameters. The approach is then extended to moderately branched alkanes, alkenes and ring compounds using one additional property, namely normal boiling point. Binary mixtures are also investigated and reasonable results are obtained with no additional binary parameters.     

Inhibition of corrosion and hydrogenation of carbon steel in media containing hydrogen sulfide and carbon dioxide with low concentrations of salts of oxyethylated amines

Impedance spectroscopy was used to study the protective action of salts of higher aliphatic oxyethylated amines as universal inhibitors of the hydrogen sulfide and carbon dioxide corrosion and hydrogenation of carbon steel.     

Determination of carbon monoxide,methane and carbon dioxide in refinery hydrogen gases and air by gas chromatography

This paper illustrates a method for determining trace amounts of CO, CH4 and CO2 with the detection limit of 0.15, 0.15 and 0.20 microg/l, respectively, in refinery hydrogen gases or in air. A simple modification of a gas chromatograph equipped with a flame-ionization detector is presented. A Porapak Q column, additionally connected with a short molecular sieve 5A packed column and a catalytic hydrogenation reactor on the Ni catalyst have been applied. The principle of the analytical method proposed is the separation of CO from O2 before the introduction of CO to the methanizer. The analytical procedure and examples of the results obtained have been presented. The modification applied makes it possible to use the GC instrument for other determinations, requiring utilization of the Porapak Q column and the flame-ionization detector. In such cases, the short molecular sieve 5A column and the methanizer can be by-passed.     

Enthalpies of dissociation of clathrate hydrates of carbon dioxide,nitrogen, (carbon dioxide + nitrogen), and (carbon dioxide + nitrogen + tetrahydrofuran)

A calorimetric technique is described for measuring the enthalpy of dissociation liberated from solid hydrates. In this study, the enthalpies of dissociation were determined at T =  273.65 K andp =  0.1 MPa for simple and mixed hydrates of carbon dioxide, nitrogen, (carbon dioxide  +  nitrogen), and (carbon dioxide  +  nitrogen  +  tetrahydrofuran) using an isothermal microcalorimeter. The addition of tetrahydrofuran (THF) promoted hydrate stability and increased the number of guest molecules encaged in the small and large cavities of the hydrate lattice, resulting in lower enthalpy of dissociation, compared with structure II hydrate. The composition ratio of guest molecules did not affect the enthalpy of dissociation, which was found to be nearly constant for the same mixture.     

Single-walled carbon nanotubes as stationary phase in gas chromatographic separation and determination of argon, carbon dioxide and hydrogen

A chromatographic technique is introduced based on single-walled carbon nanotubes (SWCNTs) as stationary phase for separation of Ar, CO₂ and H₂ at parts per million (ppm) levels. The efficiency of SWCNTs was compared with solid materials such as molecular sieve, charcoal, multi-walled carbon nanotubes and carbon nanofibers. The morphology of SWCNTs was optimized for maximum adsorption of H₂, CO₂ and Ar and minimum adsorption of gases such as N₂, O₂, CO and H₂O vapour. To control temperature of the gas chromatography column, peltier cooler was used. Mixtures of Ar, CO₂ and H₂ were separated according to column temperature program. Relative standard deviation for nine replicate analyses of 0.2 mL H₂ containing 10 μL of each Ar or CO₂ was 2.5% for Ar, 2.8% for CO₂ and 3.6% for H₂. The interfering effects of CO, and O₂ were investigated. Working ranges were evaluated as 40-600 ppm for Ar, 30-850 ppm for CO₂ and 10-1200 ppm for H₂. Significant sensitivity, small relative standard deviation (RSD) and acceptable limit of detection (LOD) were obtained for each analyte, showing capability of SWCNTs for gas separation and determination processes. Finally, the method was used to evaluate the contents of CO₂ in air sample.     

Simultaneous determination of carbon,hydrogen, and nitrogen

Summary It was shown that carbon, hydrogen, and nitrogen can be determined simultaneously by the pyrolytic decomposition of the organic substance in a stream of oxygen in an empty combustion tube. Carbon and hydrogen are determined in the usual way, and nitrogen is determined from the sum of the amounts present as nitrogen oxides and as elementary nitrogen.     

Submilligram determination of carbon,hydrogen, and nitrogen

Summary The procedure described byFrazer ^4,6 for the simultaneous determination of carbon, hydrogen, and nitrogen has been scaled down to the submilligram level with no serious loss of accuracy. Approximately six complete determinations can be made in an eight-hour day. Whereas the accuracy depends to a large extent upon the analyst's technique, the method presented is comparatively straightforward. Analysts with no previous microanalytical training have been able to obtain results equivalent to the accuracy shown in Table I after two weeks of experience with the procedure.

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Zusammenfassung Die Methode vonFrazer ^4,6 für die gleichzeitige manometrische Bestimmung von Kohlenstoff, Wasserstoff und Stickstoff wurde ohne merkliche Einbuße an Genauigkeit in den Submilligramm-Maßstab übertragen. Ungefähr sechs vollständige Bestimmungen können innerhalb 8 Stunden ausgeführt werden. Obschon die erzielbare Genauigkeit stark von der Erfahrung des Analytikers abhängt, ist das Verfahren verhältnismäßig einfach. Analytiker ohne mikrochemische Erfahrung konnten nach zweiwöchentlicher Einübung Resultate erhalten, deren Genauigkeit denen der Tabelle 1 entspricht.

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Résumé Le procédé décrit parFrazer ^4,6 pour le dosage simultané du carbone, de l'hydrogène et de l'azote a été appliqué jusqu'à l'échelle du submilligramme sans perte sérieuse de précision. On peut effectuer approximativement six déterminations complètes en une journée de travail de huit heures. Comme la précision dépend dans une large mesure de la technique de l'analyste, la méthode présentée est relativement simple.Des analystes sans entraînement préalable en microchimie ont été capables d'obtenir des résultats avec la précision montrée sur le Tableau I, après deux semaines d'essai sur ce procédé.

     

Thermodesorption of mixtures. Hydrocarbon, hydrogen sulfide and oxygen from the surface of molybdenum sulfide

The presence of hydrogen sulfide and oxygen in mixtures increases the number of sites for dissociative desorption on the surface of MoS₂ as compared with the adsorption of individual hydrocarbons. This phenomenon can be explained by a change in the coordination state of the active sites (molybdenum ions) upon the adsorption of the gases mentioned.

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, MoS₂ . .

     

Closing the automation loop for carbon,hydrogen and nitrogen analyses

Summary The automation of carbon, hydrogen, and nitrogen (CHN) microanalysis has been extended to include software control of two Perkin Elmer Elemental Analyzers (a 240A and 240C), electronic weight transfer from a Mettler UM3 Ultra-Microbalance, and electronic preparation of formalized reports. This highly automated closed loop system minimizes the sources of human error and maximizes the efficiency of CHN analyses. The precision and accuracy of data is comparable to values previously reported.

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Vervollständigung der Automatisierung der C-, H-und N-Bestimmung

Zusammenfassung Die Automatisierung der CHN-Mikrobestimmung wurde durch Software-Kontrolle zweier Perkin-Elmer Analysatoren (240 A und 240 C), durch elektronische Übertragung der Daten einer Mettler-Waage UM 3 sowie elektronische Herstellung der Resultat-Formulare erweitert. Dadurch werden die Fehlerquellen vermindert und der Gütegrad der CHN-Analysen erhöht. Richtigkeit und Genauigkeit der Ergebnisse entsprechen den an anderer Stelle angegebenen Werten.

     

Methanol synthesis from carbon dioxide and hydrogen using a ceramic memebrane reactor

Methanol was synthesized from CO₂ and H₂ using a silica/alumina composite membrane reactor, which improved methanol conversion to 150% of the value in conventional reactor, by in situ removal of water formed in catalytic reaction. This revised version was published online in June 2006 with corrections to the Cover Date.