Theoretical and experimental study of chemical equilibrium in the systems Si-Cl and Si-Cl-H. Calculation of chemical equilibrium in the systems Si-Cl and Si-Cl-H

1989 ◽  
Vol 54 (11) ◽  
pp. 2896-2909 ◽  
Author(s):  
Jindřich Leitner ◽  
Čestmír Černý ◽  
Petr Voňka ◽  
Jan Mikulec
Keyword(s):  
Gas Phase ◽  
Chemical Equilibrium ◽  
Atmospheric Pressure ◽  
Total Pressure ◽  
Equilibrium Composition ◽  
Molar Ratio ◽  
Initial Composition ◽  
Chemical Equilibria ◽  
First Time ◽  
Equilibrium Calculations

From the calculations of heterogenous chemical equilibria in the systems Si-Cl and Si-Cl-H the equilibrium composition of the gas phase and the amount of deposited or reacted solid silicon have been determined. For these calculations, the method based on the minimization of the Gibbs energy of the system and critically judged and selected values of input thermodynamic data have been used. The calculations have been performed for the temperature range 1 000-1 600 K, for the pressure 101.325 kPa and 10.133 kPa and for various input compositions of the gaseous phase. In the case of the system Si-Cl, the reaction of solid leading to the formation of silicon subchlorides takes place at all conditions investigated. At atmospheric pressure and at temperatures in the neighbourhood of 1 300 K, the dominant components of the gas phase are the following substances: SiCl4, SiCl3 and SiCl2. The dependence of the amount of deposited solid silicon on temperature and on the initial composition of the gas phase in the system Si-Cl-H shows–in the investigated range of variables – a maximum, the position of which depends on the total pressure of the system. At atmospheric pressure, at temperatures around 1 300 K and at the initial molar ratio Cl/H = 0.01, the dominant components of the gas phase are the following substances: SiCl4, SiCl3, SiCl2, SiHCl3, SiH2Cl2 and HCl. The substance SiHCl which has been included into the equilibrium calculations for the first time, is present in a significant amount at higher temperatures and especially at lower pressure.

scholarly journals Chemical equilibrium in AGB atmospheres: successes, failures, and prospects for small molecules, clusters, and condensates

2020 ◽  
Vol 637 ◽  
pp. A59 ◽  
Author(s):  
M. Agúndez ◽  
J. I. Martínez ◽  
P. L. de Andres ◽  
J. Cernicharo ◽  
J. A. Martín-Gago
Keyword(s):  
Gas Phase ◽  
Chemical Equilibrium ◽  
Equilibrium Composition ◽  
Building Blocks ◽  
Carbon Clusters ◽  
Agb Stars ◽  
Circumstellar Envelopes ◽  
General Chemical ◽  
First Time ◽  
Equilibrium Calculations

Chemical equilibrium has proven extremely useful for predicting the chemical composition of AGB atmospheres. Here we use a recently developed code and an updated thermochemical database that includes gaseous and condensed species involving 34 elements to compute the chemical equilibrium composition of AGB atmospheres of M-, S-, and C-type stars. We include for the first time TixCy clusters, with x = 1–4 and y = 1–4, and selected larger clusters ranging up to Ti13C22, for which thermochemical data are obtained from quantum-chemical calculations. Our main aims are to systematically survey the main reservoirs of each element in AGB atmospheres, review the successes and failures of chemical equilibrium by comparing it with the latest observational data, identify potentially detectable molecules that have not yet been observed, and diagnose the most likely gas-phase precursors of dust and determine which clusters might act as building blocks of dust grains. We find that in general, chemical equilibrium reproduces the observed abundances of parent molecules in circumstellar envelopes of AGB stars well. There are, however, severe discrepancies of several orders of magnitude for some parent molecules that are observed to be anomalously overabundant with respect to the predictions of chemical equilibrium. These are HCN, CS, NH3, and SO2 in M-type stars, H2O and NH3 in S-type stars, and the hydrides H2O, NH3, SiH4, and PH3 in C-type stars. Several molecules have not yet been observed in AGB atmospheres but are predicted with non-negligible abundances and are good candidates for detection with observatories such as ALMA. The most interesting ones are SiC5, SiNH, SiCl, PS, HBO, and the metal-containing molecules MgS, CaS, CaOH, CaCl, CaF, ScO, ZrO, VO, FeS, CoH, and NiS. In agreement with previous studies, the first condensates predicted to appear in C-rich atmospheres are found to be carbon, TiC, and SiC, while Al2O3 is the first major condensate expected in O-rich outflows. According to our chemical equilibrium calculations, the gas-phase precursors of carbon dust are probably acetylene, atomic carbon, and/or C3, while for silicon carbide dust, the most likely precursors are the molecules SiC2 and Si2C. In the case of titanium carbide dust, atomic Ti is the major reservoir of this element in the inner regions of AGB atmospheres, and therefore it is probably the main supplier of titanium during the formation of TiC dust. However, chemical equilibrium predicts that large titanium-carbon clusters such as Ti8C12 and Ti13C22 become the major reservoirs of titanium at the expense of atomic Ti in the region where condensation of TiC is expected to occur. This suggests that the assembly of large TixCy clusters might be related to the formation of the first condensation nuclei of TiC. In the case of Al2O3 dust, chemical equilibrium indicates that atomic Al and the carriers of Al-O bonds AlOH, AlO, and Al2O are the most likely gas-phase precursors.

scholarly journals Thermodynamic characterization of Mexico City aerosol during MILAGRO 2006

2007 ◽  
Vol 7 (3) ◽  
pp. 9203-9233 ◽  
Author(s):  
C. Fountoukis ◽  
A. Nenes ◽  
A. Sullivan ◽  
R. Weber ◽  
T. VanReken ◽  
...  
Keyword(s):  
Gas Phase ◽  
Mexico City ◽  
Thermodynamic Equilibrium ◽  
Phase State ◽  
Molar Ratio ◽  
Inorganic Species ◽  
Equilibrium Calculations ◽  
Thermodynamic Equilibrium Model ◽  
Thermodynamic Equilibrium Calculations

Abstract. Fast measurements of aerosol and gas-phase constituents coupled with the ISORROPIA-II thermodynamic equilibrium model are used to study the partitioning of semivolatile inorganic species and phase state of Mexico City aerosol sampled at the T1 site during the MILAGRO 2006 campaign. Overall, predicted semivolatile partitioning agrees well with measurements. PM2.5 is insensitive to changes in ammonia but is to acidic semivolatile species. Semi-volatile partitioning equilibrates on a timescale between 6 and 20 min. When the aerosol sulfate-to-nitrate molar ratio is less than 1, predictions improve substantially if the aerosol is assumed to follow the deliquescent phase diagram. Treating crustal species as "equivalent sodium" (rather than explicitly) in the thermodynamic equilibrium calculations introduces important biases in predicted aerosol water uptake, nitrate and ammonium; neglecting crustals further increases errors dramatically. This suggests that explicitly considering crustals in the thermodynamic calculations are required to accurately predict the partitioning and phase state of aerosols.

scholarly journals Measurements of OH and HO<sub>2</sub> yields from the gas phase ozonolysis of isoprene

2010 ◽  
Vol 10 (3) ◽  
pp. 1441-1459 ◽  
Author(s):  
T. L. Malkin ◽  
A. Goddard ◽  
D. E. Heard ◽  
P. W. Seakins
Keyword(s):  
Gas Phase ◽  
Atmospheric Pressure ◽  
Room Temperature ◽  
Recent Literature ◽  
Direct Detection ◽  
Kinetic Method ◽  
Oh Radicals ◽  
First Order ◽  
Gas Expansion ◽  
First Time

Abstract. The reactions of ozone with alkenes are an important source of hydroxyl (OH) radicals; however, quantification of their importance is hindered by uncertainties in the absolute OH yield. Hydroxyl radical yields for the gas-phase ozonolysis of isoprene are determined in this paper by four different methods: (1) The use of cyclohexane as an OH scavenger, and the production of cyclohexanone, (2) The use of 1,3,5-trimethylbenzene as an OH tracer, and the diminution in its concentration, (3) A kinetic method in which the OH yield was obtained by performing a series of pseudo-first-order experiments in the presence or absence of an OH scavenger (cyclohexane), (4) The OH and HO2 yields were determined by fitting the temporal OH and HO2 profiles following direct detection of absolute OH and HO2 concentrations by laser induced fluorescence at low pressure (Fluorescence Assay by Gas Expansion- FAGE). The following OH yields for the ozonolysis of isoprene were obtained, relative to alkene consumed, for each method: (1) Scavenger (0.25±0.04), (2) Tracer (0.25±0.03), (3) Kinetic study (0.27±0.02), and (4) Direct observation (0.26±0.02), the error being one standard deviation. An averaged OH yield of 0.26±0.02 is recommended at room temperature and atmospheric pressure and this result is compared with recent literature determinations. The HO2 yield was directly determined for the first time using FAGE to be 0.26±0.03.

Hydrogenation of CO2 over 15% Fe/SiO2 Catalyst under Sub- and Supercritical Conditions

2018 ◽  
Vol 18 (4) ◽  
pp. 57-63
Author(s):  
N. D. Evdokimenko ◽  
K. O. Kim ◽  
G. I. Kapustin ◽  
N. A. Davshan ◽  
A. L. Kustov
Keyword(s):  
Gas Phase ◽  
Atmospheric Pressure ◽  
Iron Nanoparticles ◽  
Catalyst Surface ◽  
Phase Reaction ◽  
Supercritical Conditions ◽  
Gas Phase Reaction ◽  
Xrd Studies ◽  
First Time ◽  
Hydrogenation Of Co

The results of comparative studies of CO2hydrogenation over 15% Fe/SiO2catalyst under sub- and supercritical conditions are presented for the first time. The reaction was studied at 300–500 °C and atmospheric pressure in gas phase and at 95 atm under supercritical conditions. The molar H2: CO2ratio was 2 : 1. Under supercritical conditions, the selectivity to CO2decreased from 90–95 to 30–50 % at all temperatures, while the selectivity to hydrocarbons increased up to 60 %. The reaction under supercritical conditions, unlike gas-phase hydrogenation, produced alcohols. TG-DTG-DTA techniques were used to demonstrate 2.2-fold decrease in the quantity of carbon-like deposits in comparison to that in the gas-phase reaction. XRD studies revealed the formation of graphite-like species on the catalyst surface under gas-phase but not supercritical conditions. The developed process and catalyst for hydrogenation of CO2can be recommended to be further modified in order to improve the catalyst based on iron nanoparticles that is as expensive as 0.1–0.01 of the known catalysts for CO2hydrogenation.

Degradation mechanism of 2-fluoropropene by Cl atoms: experimental and theoretical products distribution studies

2021 ◽  
Author(s):  
Cynthia Rivela ◽  
Alejandro L. Cardona ◽  
Maria B Blanco ◽  
Ian Barnes ◽  
Martina Kieninger ◽  
...  
Keyword(s):  
Gas Phase ◽  
Quartz Glass ◽  
Atmospheric Pressure ◽  
Degradation Mechanism ◽  
Phase Reaction ◽  
Reaction Products ◽  
Gas Phase Reaction ◽  
Distribution Studies ◽  
First Time ◽  
Cl Atoms

The gas-phase reaction products of 2-fluoropropene (2FP) with Cl atoms has been determined for the first time at 298 K and atmospheric pressure using a 1080 L quartz-glass photoreactor coupled...

Some Condensation Calculations Using Chemical Equilibria

1989 ◽  
Vol 106 ◽  
pp. 379-379
Author(s):  
Christopher M. Sharp
Keyword(s):  
Free Energy ◽  
Chemical Equilibrium ◽  
Gaseous Species ◽  
Chemical Equilibria ◽  
Gibb’S Free Energy ◽  
Equilibrium Calculations

A number of extensive chemical equilibrium calculations have recently been performed for temperatures below 2000 K, with mixtures containing over 200 gaseous species and the allowance for the formation of over 60 condensates. These calculations were based on the minimization of the Gibb's free energy.

scholarly journals Measurements of OH and HO<sub>2</sub> yields from the gas phase ozonolysis of isoprene

2009 ◽  
Vol 9 (4) ◽  
pp. 17579-17631 ◽  
Author(s):  
T. L. Malkin ◽  
A. Goddard ◽  
D. E. Heard ◽  
P. W. Seakins
Keyword(s):  
Gas Phase ◽  
Atmospheric Pressure ◽  
Room Temperature ◽  
Recent Literature ◽  
Direct Detection ◽  
Kinetic Method ◽  
Oh Radicals ◽  
First Order ◽  
Gas Expansion ◽  
First Time

Abstract. The reactions of ozone with alkenes are an important source of hydroxyl (OH) radicals; however, quantification of their importance is hindered by uncertainties in the absolute OH yield. Hydroxyl radical yields for the gas-phase ozonolysis of isoprene are determined in this paper by four different methods: (1) The use of cyclohexane as an OH scavenger, and the production of cyclohexanone, (2) The use of 1,3,5-trimethylbenzene as an OH tracer, and the diminution in its concentration, (3) A kinetic method in which the OH yield was obtained by performing a series of pseudo-first-order experiments in the presence or absence of an OH scavenger (cyclohexane), (4) The OH and HO2 yields were determined by fitting the temporal OH and HO2 profiles following direct detection of absolute OH and HO2 concentrations by laser induced fluorescence at low pressure (Fluorescence Assay by Gas Expansion-FAGE). The following OH yields for the ozonolysis of isoprene were obtained, relative to alkene consumed, for each method: (1) Scavenger (0.25 ± 0.04), (2) Tracer (0.25 ± 0.03), (3) Kinetic study (0.27 ± 0.02), and (4) Direct observation (0.26 ± 0.02), the error being one standard deviation. An averaged OH yield of 0.26 ± 0.02 is recommended at room temperature and atmospheric pressure and this result is compared with recent literature determinations. The HO2 yield was directly determined for the first time using FAGE to be 0.26 ± 0.03.

Fluorescence of BODIPY Dyes in Gas Phase at near Ambient Conditions

2020 ◽  
Author(s):  
Kseniya A. Mariewskaya ◽  
Denis Larkin ◽  
Yuri Samoilichenko ◽  
Vladimir Korshun ◽  
Alex Ustinov
Keyword(s):  
Gas Phase ◽  
Molecular Interactions ◽  
Atmospheric Pressure ◽  
Fluorescence Spectra ◽  
Visible Range ◽  
Intrinsic Properties ◽  
Ambient Conditions ◽  
Ideal Model ◽  
Molecular Fluorescence ◽  
Tesla Coil

Molecular fluorescence is a phenomenon that is usually observed in condensed phase. It is strongly affected by molecular interactions. The study of fluorescence spectra in the gas phase can provide a nearly-ideal model for the evaluation of intrinsic properties of the fluorophores. Unfortunately, most conventional fluorophores are not volatile enough to allow study of their fluorescence in the gas phase. Here we report very bright gas phase fluorescence of simple BODIPY dyes that can be readily observed at atmospheric pressure using conventional fluorescence instrumentation. To our knowledge, this is the first example of visible range gas phase fluorescence at near ambient conditions. Evaporation of the dye in vacuum allowed us to demonstrate organic molecular electroluminescence in gas discharge excited by electric field produced by a Tesla coil.

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