Phase equilibrium isotope effects in molecular solids and liquids. Vapor pressures of the isotopic nitrous oxide molecules

1975 ◽  
Vol 63 (4) ◽  
pp. 1555-1563 ◽  
Author(s):  
Yumio Yato ◽  
Myung W. Lee ◽  
Jacob Bigeleisen
Keyword(s):  
Nitrous Oxide ◽  
Phase Equilibrium ◽  
Isotope Effects ◽  
Molecular Solids ◽  
Vapor Pressures

scholarly journals Continuous measurements of nitrous oxide isotopomers during incubation experiments

2016 ◽  
Author(s):  
Malte Winther ◽  
David Balslev-Harder ◽  
Søren Christensen ◽  
Anders Priemé ◽  
Bo Elberling ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Greenhouse Gas ◽  
Isotope Effect ◽  
Atmospheric Chemistry ◽  
Isotope Effects ◽  
Denitrifying Bacteria ◽  
Central Position ◽  
Site Preference ◽  
Continuous Measurements ◽  
Incubation Experiments

Abstract. Nitrous oxide (N2O) is an important and strong greenhouse gas in the atmosphere and part of a feed-back loop with climate. N2O is produced by microbes during nitrification and denitrification in terrestrial and aquatic ecosystems. The main sinks for N2O are turnover by denitrification and photolysis and photo-oxidation in the stratosphere. The position of the isotope 15N in the linear N = N = O molecule can be distinguished between the central or terminal position (isotopomers of N2O). It has been demonstrated that nitrifying and denitrifying microbes have a different relative preference for the terminal and central position. Therefore, measurements of the site preference in N2O can be used to determine the source of N2O i.e. nitrification or denitrification. Recent instrument development allows for continuous (on the order of days) position dependent δ15N measurements at N2O concentrations relevant for studies of atmospheric chemistry. We present results from continuous incubation experiments with denitrifying bacteria, Pseudomonas fluorescens (producing and reducing N2O) and P. chlororaphis (only producing N2O). The continuous position dependent measurements reveal the transient pattern (KNO3 to N2O and N2, respectively), which can be compared to previous reported site preference (SP) values. We find bulk isotope effects of −5.5 ‰ ± 0.9 for P. chlororaphis. For P. fluorescens, the bulk isotope effect during production of N2O is −50.4 ‰ ± 9.3 and 8.5 ‰ ± 3.7 during N2O reduction. The values for P. fluorescens are in line with earlier findings, whereas the values for P. chlororaphis are larger than previously published δ15Nbulk measurements from production. The calculations of the SP isotope effect from the measurements of P. chlororaphis result in values of −6.6 ‰ ± 1.8. For P. fluorescens, the calculations results in SP values of −5.7 ‰ ± 5.6 during production of N2O and 2.3 ‰ ± 3.2 during reduction of N2O. In summary, we implemented continuous measurements of N2O isotopomers during incubation of denitrifying bacteria and believe that similar experiments will lead to a better understanding of denitrifying bacteria and N2O turnover in soils and sediments and ultimately hands-on knowledge on the biotic mechanisms behind greenhouse gas exchange of the Globe.

Phase equilibrium in n-octane/water separation units: vapor pressures, vapor and liquid molar fractions

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Jeonghoon Kong ◽  
Salvador Escobedo ◽  
Sandra Lopez-Zamora ◽  
Hugo de Lasa
Keyword(s):  
Phase Equilibrium ◽  
Liquid Phase ◽  
Thermodynamic Model ◽  
Vapor Pressures ◽  
Auxiliary Equipment ◽  
Water Separation ◽  
Aspen Hysys ◽  
Special Value ◽  
Accurate Procedure ◽  
High Level

Abstract The present study reports result from research into vapor–liquid–liquid phase equilibrium for n-octane highly diluted in water and water highly diluted in n-octane blends, using a dynamic method implemented in a constant volume CREC-VL-Cell. In the CREC-VL-Cell, a very high level of mixing is achieved, allowing for dispersions to be formed in the liquid phase and good mixing in the gas phase. This VL-Cell and its auxiliary equipment provide an increasing temperature ramp in the 30–110 °C range. It is found that the CREC-VL-Cell is of special value, for studying immiscible or partially miscible blends, such as is the case of n-octane in water. With the data obtained, which includes vapor pressures and temperatures, data analyses involving mass and molar balances, allow establishing overall liquid and vapor molar fractions. The recorded vapor pressures together with the calculated liquid and vapor molar fractions offer valuable data for VL thermodynamic model discrimination. For instance, it can be shown that vapor pressures, vapor and liquid molar fractions, as calculated with the Aspen-Hysys Peng Robinson Equation of State (Hysys-Aspen PR-EoS) provide only a first approximation of the experimental data, with significant discrepancies in the prediction of an n-octane disengagement temperatures. Thus, the determination of combined measured vapor pressures and calculated overall liquid molar fractions in the CREC-VL-Cell, offers a valuable and accurate procedure for thermodynamic model validation and discrimination.

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