Desorption rate of volatile compounds in polishing ponds

2011 ◽  
Vol 63 (6) ◽  
pp. 1177-1182
Author(s):  
Eudes M. Alves ◽  
Paula F. C. Cavalcanti ◽  
Adrianus van Haandel
Keyword(s):  
Carbon Dioxide ◽  
Experimental Investigation ◽  
Volatile Compounds ◽  
Rate Constants ◽  
Driving Force ◽  
Co2 Removal ◽  
Desorption Rate ◽  
Order Process ◽  
First Order ◽  
Co2 Desorption

Increase of pH in polishing ponds can be predicted quantitatively from variations in alkalinity and acidity. These variables are affected by processes that develop simultaneously in ponds: (1) CO2 desorption, (2) biological CO2 removal by photosynthesis and (3) NH3 desorption. An experimental investigation was carried out to determine the desorption rate of carbon dioxide and ammonium. It is shown that CO2 and NH3 desorption can be described by Fick’s law, which describes desorption of a gaseous compounds from water as a first order process with respect to the degree of oversaturation, which is the driving force of the process. An experimental investigation was carried out to determine the desorption rate constants. The value of the constant proved to be inversely proportional to the depth of the pond (H) and its value for H=1 m and at 26°C was established as KCO2=0.34/H d−1 for carbon dioxide and KNH3=0.33/H d−1 for ammonium.

The thermal decompositions of carbamates. I. Ethyl N-Methyl-N-phenylcarbamate

1971 ◽  
Vol 24 (12) ◽  
pp. 2541 ◽  
Author(s):  
NJ Daly ◽  
F Ziolkowski
Keyword(s):  
Carbon Dioxide ◽  
Gas Phase ◽  
Rate Constants ◽  
Volume Ratio ◽  
Reaction Vessel ◽  
First Order ◽  
Order Rate

Ethyl N-methyl-N-phenylcarbamate decomposes in the gas phase over the range 329-380� to give N-methylaniline, carbon dioxide, and ethylene. The reaction is quantitative, and is first order in the carbamate. First-order rate constants are described by the equation ������������������� k1 = 1012.44 exp(-45,380/RT) (s-1) and are unaffected by the addition of cyclohexene or by increase in the surface to volume ratio of the reaction vessel. The reaction is considered to be unimolecular and likely to proceed by means of a mechanism of the type represented by the pyrolyses of acetates, xanthates, and carbonates.

An Electron Spin Resonance Study of Some Reactions of Pentafluorosulfuranyl (SF5)

1975 ◽  
Vol 53 (16) ◽  
pp. 2361-2364 ◽  
Author(s):  
John Charles Tait ◽  
James Anthony Howard
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Rate Constants ◽  
Arrhenius Equation ◽  
Kinetic Studies ◽  
Electron Spin Resonance Study ◽  
Order Process ◽  
First Order ◽  
Spin Resonance ◽  
Spin Resonance Study

A kinetic electron spin resonance study of the self-reaction of SF5 and a spectroscopic and kinetic e.s.r. study of the reaction of SF5 with 1,1-di-t-butylethylene are reported. This radical undergoes self-reaction by a second-order process and the rate constants are given by the Arrhenius equation log 2k1(M−1 s−1) = (10.3 ± 0.5) − (1.7 ± 0.5)/θ where θ = 2.303RT kcal mol−1. It adds to 1,1-di-t-butylethylene to give (t-Bu)2CCH2SF5 which decomposes by a first-order process with rate constants that obey the expression log k2(s−1) = (13 ± 0.4) − (10 ± 0.2)/θ. Both these rate constants are pertinent to kinetic studies of the photoinduced addition of SF5C1 to olefins.

scholarly journals Gas-Phase Photocatalytic Oxidation of Dimethylamine: The Reaction Pathway and Kinetics

2007 ◽  
Vol 2007 ◽  
pp. 1-4
Author(s):  
Anna Kachina ◽  
Sergei Preis ◽  
Juha Kallas
Keyword(s):  
Carbon Dioxide ◽  
Gas Phase ◽  
Continuous Flow ◽  
Kinetic Data ◽  
Photocatalytic Oxidation ◽  
Reaction Pathway ◽  
Tubular Reactor ◽  
Order Process ◽  
First Order ◽  
Long Run

Gas-phase photocatalytic oxidation (PCO) and thermal catalytic oxidation (TCO) of dimethylamine (DMA) on titanium dioxide was studied in a continuous flow simple tubular reactor. Volatile PCO products of DMA included ammonia, formamide, carbon dioxide, and water. Ammonia was further oxidized in minor amounts to nitrous oxide and nitrogen dioxide. Effective at 573 K, TCO resulted in the formation of ammonia, hydrogen cyanide, carbon monoxide, carbon dioxide, and water. The PCO kinetic data fit well to the monomolecular Langmuir-Hinshelwood model, whereas TCO kinetic behaviour matched the first-order process. No deactivation of the photocatalyst during the multiple long-run experiments was observed.

ABSOLUTE RATE CONSTANTS FOR HYDROCARBON AUTOXIDATION: III. α-METHYLSTYRENE, β-METHYLSTYRENE, AND INDENE

1966 ◽  
Vol 44 (10) ◽  
pp. 1113-1118 ◽  
Author(s):  
J. A. Howard ◽  
K. U. Ingold
Keyword(s):  
Isotope Effect ◽  
Rate Constant ◽  
Rate Constants ◽  
Propagation Rate ◽  
Absolute Rate ◽  
Order Process ◽  
Deuterium Isotope Effect ◽  
First Order ◽  
Process Rate Constant ◽  
Propagation Rate Constant

Absolute rate constants for the copolymerization of α-methylstyrene and oxygen have been measured from 13 to 50 °C. The propagation and termination rate constants can be represented by[Formula: see text]Experiments with 2,6-di-t-butyl-4-methylphenol at 65 °C have shown that C6H5C(CH3):CH2 and C6H5C(CD3):CD2 have the same propagation rate constant but that chain termination involves a deuterium isotope effect (kt)H/(kt)D ≈ 1.5.Absolute rate constants for the copolymerization of oxygen with β-methylstyrene and with indene at 30 °C showed that a significant fraction of the oxidation chains were terminated by a kinetically first order process (rate constant kx). The rate constants for β-methylstyrene and indene at 30 °C are kp = 51 and 142 l mole−1 s−1, kt = 1.6 × 107 and 2.5 × 107 l mole−1 s−1, and kx = 0.61 and 1.2 s−1, respectively. The propagation rate constant for indene can be separated into a rate constant for the copolymerization with oxygen (kadd = 128 l mole−1 s−1) and a rate constant for hydrogen atom abstraction (kabstr = 14 l mole−1 s−1). In the presence of heavy water the first order process for indene had a deuterium isotope effect (kx)/(kx)D2O ≈ 3.

scholarly journals Reaction Kinetics of Carbon Dioxide in Aqueous Diethanolamine Solutions Using the Stopped-Flow Technique

2012 ◽  
Vol 19 (1) ◽  
pp. 55-66 ◽  
Author(s):  
Marta Siemieniec ◽  
Hanna Kierzkowska-Pawlak ◽  
Andrzej Chacuk
Keyword(s):  
Carbon Dioxide ◽  
Reaction Kinetics ◽  
Rate Constants ◽  
Reaction Rate ◽  
Reaction Rate Constant ◽  
Stopped Flow ◽  
First Order ◽  
Pseudo First Order ◽  
Kinetics Of ◽  
Good Agreement

Reaction Kinetics of Carbon Dioxide in Aqueous Diethanolamine Solutions Using the Stopped-Flow Technique The pseudo-first-order rate constants (kOV) for the reactions between CO2 and diethanolamine have been studied using the stopped-flow technique in an aqueous solution at 293, 298, 303 and 313 K. The amine concentrations ranged from 167 to 500 mol·m-3. The overall reaction rate constant was found to increase with amine concentration and temperature. Both the zwitterion and termolecular mechanisms were applied to correlate the experimentally obtained rate constants. The values of SSE quality index showed a good agreement between the experimental data and the corresponding fit by the use of both mechanisms.

Mechanism of decarboxylation of substituted salicylic acids. I. Kinetics in quinoline solution

1968 ◽  
Vol 46 (18) ◽  
pp. 2905-2909 ◽  
Author(s):  
G. E. Dunn ◽  
E. G. Janzen ◽  
W. Rodewald
Keyword(s):  
Carbon Dioxide ◽  
Aromatic Ring ◽  
Rate Constants ◽  
Substituent Effect ◽  
The Other ◽  
Carboxyl Group ◽  
Isokinetic Relationship ◽  
First Order ◽  
Hammett Relationship ◽  
Salicylic Acids

First-order rate constants for the decarboxylation of fourteen 4- and 5-substituted salicylic acids have been determined in quinoline solution in the temperature range 90–230 °C. Substituents have almost no effect on the rate constants, except those with large negative σ-constants: p-amino, p-hydroxy, p-ethoxy. The enthalpies and entropies of activation do not fit the isokinetic relationship, with the same three substituents deviating. It is suggested that the decarboxylation involves a preliminary ionization of the carboxyl group, followed by protonation of the aromatic ring of the anion so formed, and then loss of carbon dioxide. The isokinetic relationship fails because substituents affect all three steps differently, and the Hammett relationship fails because the substituent effect on the ionization is related to σ while that on the other two steps follows σ+. The three substituents which deviate are those for which σ and σ+ differ widely.

Kinetics and mechanism of the decarboxylation of pyrimidine-2-carboxylic acid in aqueous solution

1977 ◽  
Vol 55 (13) ◽  
pp. 2478-2481 ◽  
Author(s):  
Gerald E. Dunn ◽  
Edward A. Lawler ◽  
A. Brian Yamashita
Keyword(s):  
Carbon Dioxide ◽  
Aqueous Solution ◽  
Carboxylic Acid ◽  
Rate Constants ◽  
Kinetics And Mechanism ◽  
First Order ◽  
Order Rate ◽  
Pseudo First Order ◽  
Positively Charged

Pseudo-first-order rate constants for the decarboxylation of pyrimidine-2-carboxylic acid have been determined at 65 °C in aqueous solution over the acidity range pH = 2 to H0 = −9.5. Rate constants increase rapidly from pH = 2 to H0 = −3, then remain constant. This behaviour can be accounted for by a Hammick-type mechanism in which monoprotonated pyrimidine-2-carboxylic acid loses carbon dioxide to form an ylide (stabilized by the adjacent positively charged nitrogens) which rapidly converts to pyrimidine.

THE THERMAL DECOMPOSITION OF PHENYLACETIC ACID

1960 ◽  
Vol 38 (8) ◽  
pp. 1261-1270 ◽  
Author(s):  
Margaret H. Back ◽  
A. H. Sehon
Keyword(s):  
Carbon Dioxide ◽  
Activation Energy ◽  
Thermal Decomposition ◽  
Carbon Monoxide ◽  
Rate Constant ◽  
Phenylacetic Acid ◽  
Order Process ◽  
First Order ◽  
Kinetics Of ◽  
Dissociation Step

The thermal decomposition of phenylacetic acid was investigated by the toluene-carrier technique over the temperature range 587 to 722 °C. The products of the pyrolysis were carbon dioxide, carbon monoxide, hydrogen, methane, dibenzyl, and phenylketene. From the kinetics of the decomposition it was concluded that the reaction[Formula: see text]was a homogeneous, first-order process and that the rate constant of this dissociation step was represented by the expression k = 8 × 1012.e−55,000/RT sec−1. The activation energy of this reaction may be identified with D(C6H5CH2—COOH). The possible reactions of carboxyl radicals are discussed.

Spin trapping for hydroxyl in water: a kinetic evaluation of two popular traps

1980 ◽  
Vol 58 (8) ◽  
pp. 803-807 ◽  
Author(s):  
Paul R. Marriott ◽  
M. John Perkins ◽  
David Griller
Keyword(s):  
Rate Constants ◽  
Half Life ◽  
Biological Systems ◽  
Spin Trapping ◽  
Order Process ◽  
Kinetic Evaluation ◽  
Spin Traps ◽  
First Order ◽  
Tert Butyl

Two spin traps, 4-(N-methylpyridinium)tert-butyl nitrone (4-MePyBN) and 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) were examined for their effectiveness at trapping hydroxyl in water. At pH 6 and 22 °C, rate constants for trapping hydroxyl were found to be 0.5 × 109 M−1 s−1 (4-MePyBN) and 2.0 × 109 M−1  s−1 (DMPO). The hydroxyl adduct of DMPO decayed by a first order process with a half-life of 870 s. This was at least three times greater than that of the 4-MePyBN adduct. These and other results suggest that DMPO is the superior trap for this particular application and is well suited for use in biological systems.

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