High temperature–pressure aqueous oxidations. IV. A kinetic study of the oxidation and enolization of cyclohexanone in the presence of catalytic metal ions

1989 ◽  
Vol 67 (1) ◽  
pp. 165-170 ◽  
Author(s):  
John W. Thomas ◽  
Jay E. Taylor
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Kinetic Study ◽  
Metal Ion ◽  
Copper Ions ◽  
Copper Ion ◽  
Oxidation Products ◽  
Initial Reaction ◽  
Temperature Oxidation ◽  
First Order

The aqueous high pressure–temperature oxidation of cyclohexanone was found to be strongly catalyzed by silver, iron(III), and copper ions but not by aluminum, cobalt, manganese(II), or nickel ions. The reactivities of the catalytic ions were inhibited by the acidic oxidation products. Accordingly, initial reaction velocities were determined and used to correlate the kinetic data. A detailed kinetic study of copper ion catalysis has shown that in the presence of that ion the reaction was first order in cyclohexanone, one-half order in copper ion, and zero order in oxygen. The rate of enolization of cyclohexanone appeared to be unaffected by the presence of copper ion under conditions of constant acidity but was strongly catalyzed by both deuterium ion and acetate ion. Further, the rate of oxidation exceeded the rate of enolization at higher copper ion concentrations. These data contrast with the uncatalyzed oxidation, for which the kinetic reaction was first order in cyclohexanone, one-half order in oxygen, and the rate of oxidation was much less than the rate of enolization. The activation energies for the catalyzed and uncatalyzed oxidations were about the same, but the entropies of activation were quite different. From these data it is concluded that the enol is not a major intermediate for the catalyzed reaction. It is suggested that the copper ion may form an active peroxy complex with the oxygen molecule to serve as the reactive oxidant. Keywords: metal ion catalysis, kinetics, cyclohexanone, high temperature oxidation, high pressure oxidation.

scholarly journals Harnessing of Newly Tailored Poly (Acrylonitrile)-Starch Nanoparticle Graft Copolymer for Copper Ion Removal via Oximation Reaction

2021 ◽  
Author(s):  
khaled Mostafa ◽  
H. Ameen ◽  
A. Ebessy ◽  
A. El-Sanabary
Keyword(s):  
Experimental Data ◽  
Adsorption Capacity ◽  
Graft Copolymer ◽  
Adsorption Kinetics ◽  
Copper Ions ◽  
Copper Ion ◽  
Second Order ◽  
First Order ◽  
Pseudo Second Order ◽  
Pseudo First Order

Abstract Our recently tailored and fully characterized poly (AN)-starch nanoparticle graft copolymer having 60.1 G.Y. % was used as a starting substrate for copper ions removal from waste water effluent after chemical modification with hydroxyl amine via oximation reaction. This was done to change the abundant nitrile groups in the above copolymer into amidoxime one and the resultant poly (amidoxime) resin was used as adsorbent for copper ions. The resin was characterized qualitatively via rapid vanadium ion test and instrumentally by FT-IR spectra and SEM morphological analysis to confirm the presence of amidoxime groups. The adsorption capacity of the resin was done using the batch technique, whereas the residual copper ions content in the filtrate before and after adsorption was measured using atomic adsorption spectrometry. It was found that the maximum adsorption capacity of poly (amidoxime) resin was 115.2 mg/g at pH 7, 400ppm copper ions concentration and 0.25 g adsorbent at room temperature. The adsorption, kinetics and isothermal study of the process is scrutinized using different variables, such as pH, contact time, copper ion concentration and adsorbent dosage. Different kinetics models comprising the pseudo-first-order and pseudo-second-order have been applied to the experimental data to envisage the adsorption kinetics. It was found from kinetic study that pseudo-second-order rate equation was better than pseudo-first-order supporting the formation of chemisorption process. While, in case of isothermal study, the examination of calculated correlation coefficient (R2) values showed that the Langmuir model provide the best fit to experimental data than Freundlich one.

Kinetics of reconstitution of apotyrosinase by copper

1990 ◽  
Vol 68 (2) ◽  
pp. 476-479
Author(s):  
Donald C. Wigfield ◽  
Douglas M. Goltz
Keyword(s):  
Rate Constant ◽  
Copper Concentration ◽  
Copper Ions ◽  
Copper Ion ◽  
Order Rate Constant ◽  
First Order ◽  
Order Rate ◽  
Pseudo First Order ◽  
Rate Limiting ◽  
Kinetics Of

The kinetics of the reconstitution reaction of apotyrosinase with copper (II) ions are reported. The reaction is pseudo first order with respect to apoenzyme and the values of these pseudo first order rate constants are reported as a function of copper (II) concentration. Two copper ions bind to apoenzyme, and if the second one is rate limiting, the kinetically relevant copper concentration is the copper originally added minus the amount used in binding the first copper ion to enzyme. This modified copper concentration is linearly related to the magnitude of the pseudo first order rate constant, up to a copper concentration of 1.25 × 10−4 M (10-fold excess), giving a second order rate constant of 7.67 × 102 ± 0.93 × 102 M−1∙s−1.Key words: apotyrosinase, copper, tyrosinase.

scholarly journals Kinetic Study of Photocatalytic Degradation of Tolonium Chloride Under High Pressure Irradiation in Aquatic Buffer Systems

2011 ◽  
Vol 8 (s1) ◽  
pp. S19-S26 ◽  
Author(s):  
M. Montazerozohori ◽  
S. Nezami ◽  
S. Mojahedi
Keyword(s):  
High Pressure ◽  
Photocatalytic Degradation ◽  
Kinetic Study ◽  
Rate Constants ◽  
Order Kinetic ◽  
Optimum Conditions ◽  
First Order ◽  
Reactor Cell ◽  
Order Kinetic Model ◽  
Tolonium Chloride

Anatase titanium dioxide catalyzed photodegradation of tolonium chloride at various bufferic pH of 2, 7, 9 and 12 in aqueous solution is presented. The effect of some physicochemical parameters such as initial concentration of dye, catalyst amount and reaction time on photocatalytic degradation has been investigated in a photo-reactor cell containing high pressure mercury lamp to obtain the optimum conditions in each bufferic pH at constant temperature. A complete spectrophotometric kinetic study of tolonium chloride under high pressure irradiation at buffer media was performed. The photocatalytic degradation observed rate constants (kobs) were found to be 2.90×10-3, 3.30×10-3, 3.20×10-3and 5.20×10-3min-1for buffer pH of 2-12 respectively. It was found that a pseudo-first-order kinetic model based on Langmuir-Hinshelwood one is usable to photodegradation of this compound at all considered buffer pH. In addition to these, the Langmuir-Hinshelwood rate constants, krfor the titled compound at various pH are reported.

scholarly journals Oxidation and Characterization of Low Concentration Gas in High-Temperature Reactor

2020 ◽  
Author(s):  
Jinhua Chen ◽  
Guangcai Wen ◽  
Song Yan ◽  
Xiangyun Lan ◽  
Lu Xiao
Keyword(s):  
High Temperature ◽  
High Temperature Oxidation ◽  
Air Pressure ◽  
Oxidation Products ◽  
Heating Process ◽  
Temperature Oxidation ◽  
Low Concentration ◽  
Temperature Environment ◽  
Explosion Limit ◽  
High Temperature Environment

To achieve efficient utilization of low-concentration mine gas, reduce resource waste, and alleviate environmental pollution, high-temperature oxidation of low-concentration gas at a concentration range of 1.00% to 1.50% that is directly discharged into the atmosphere during coal mine production was oxidized to recover heat for reuse. The gas oxidation equipment was improved for the heating process, and the safety of low-concentration gas oxidation under high-temperature environment was evaluated. Experimental results showed that the reactor could provide a 1000 ℃ high-temperature oxidation environment for gas oxidation after installing high-temperature resistant ceramics. The pressure variation curves of the reactor with air and different concentrations of gas were similar. Due to the thermal expansion, the air pressure slightly increased and then returned to normal pressure. In contrast, the low-concentration gas exhibited a stable pressure response in the high-temperature environment of 1000 ℃. The outlet pressure was significantly greater than the inlet pressure, and the pressure difference between the inlet and outlet exhibited a trend to increase with the gas concentration. The explosion limit varied with the temperature and the blend with oxidation products. The ratio of measured gas pressure to air pressure after oxidation was below the explosion criterion, indicating that the measured concentration gas is still safe after the shift of explosion limit, which provides a safe concentration range for efficient use of low-concentration gas in the future.

Kinetic Study of the Epimerization of 1,1,1-Trichloro-2-hydroxy-3-methyl-4-hexanone

1973 ◽  
Vol 51 (19) ◽  
pp. 3182-3186 ◽  
Author(s):  
Eberhard Kiehlmann ◽  
Fred Masaro ◽  
Frederick J. Slawson
Keyword(s):  
Activation Energy ◽  
Acetic Acid ◽  
Kinetic Study ◽  
Glacial Acetic Acid ◽  
Initial Reaction ◽  
First Order ◽  
Kinetically Controlled ◽  
Different Temperatures ◽  
Pseudo First Order

The acetate-catalyzed epimerization of 1,1,1-trichloro-2-hydroxy-3-methyl-4-hexanone has been studied in glacial acetic acid as solvent at five different temperatures. The reaction follows pseudo first-order, reversible kinetics and is associated with an activation energy of 24.0 ± 0.4 kcal/mol. Rate and product studies have shown that epimerization occurs by an enolization–ketonization pathway rather than dehydration–rehydration or retroaldol–aldolization. The ratio of diastereomeric ketols formed by condensation of 2-pentanone and 2-heptanone with chloral does not change as a function of time while the stereochemistry of the chloral addition to cyclohexanone is kinetically controlled during the initial reaction period.

High Temperature Oxidation Behaviour of Detonation-Gun-Sprayed Cr3C2-NiCr-CeO2 Coatings on Inconel-718 at 900°C

2014 ◽  
Author(s):  
Sekar Saladi ◽  
Jyoti V. Menghani ◽  
Satya Prakash
Keyword(s):  
High Temperature ◽  
Inconel 718 ◽  
High Temperature Oxidation ◽  
Parabolic Rate Constant ◽  
Coated Specimen ◽  
Oxidation Products ◽  
Temperature Oxidation ◽  
X Ray ◽  
Heating And Cooling ◽  
Detonation Gun

The high temperature oxidation behavior of detonation-gun sprayed Cr3C2-NiCr coatings with and without 0.4 wt. % CeO2 additive on Ni-based superalloy inconel-718 is comparatively discussed in the present study. Oxidation studies were carried out at 900°C for 100 cycles in air under cyclic heating and cooling conditions on bare and coated superalloys. The thermo-gravimetric technique was used to establish kinetics of oxidation. X-ray diffraction, SEM/EDAX and X-ray mapping techniques were used to analyze the oxidation products of bare and coated samples. The results indicate that Cr3C2-NiCr-CeO2 coated specimen showed better oxidation resistance. The overall weight gain and parabolic rate constant of Cr3C2-NiCr-CeO2 coated specimen was found to be lowest in the present study signifying that the addition of CeO2 in Cr3C2-NiCr powder has contributed to the development of adherent and dense oxide scale on the coating at elevated temperature.

High pressure–temperature aqueous oxidations. III. A kinetic study of the enolization and oxidation of cyclohexanone

1988 ◽  
Vol 66 (2) ◽  
pp. 294-299 ◽  
Author(s):  
John W. Thomas ◽  
Jay E. Taylor
Keyword(s):  
High Pressure ◽  
Kinetic Study ◽  
Aqueous Media ◽  
Activation Parameters ◽  
Oxygen Molecule ◽  
First Order ◽  
Partial Pressures ◽  
Butanedioic Acid ◽  
Pentanedioic Acid ◽  
Hexanedioic Acid

The rates of enolization of cyclohexanone have been determined at 145 and 172 °C in D2O and with buffers. The rates of oxidation were evaluated at temperatures of 145, 172, and 193.5 °C with oxygen partial pressures of 20.4 to 131 atm. The rate of enolization was 10–160 times faster than the rate of oxidation thereby supporting the previously proposed concept of enol intermediacy for the oxidation of ketones. The oxidation was first order in cyclohexanone and 1/2 order in oxygen. The rate of oxidation was increased by the addition of traditional phenolic inhibitors. The products isolated were formic, acetic, butanedioic, pentanedioic, hexanedioic, and 5-oxohexanoic acids. The activation parameters were calculated to be ΔH≠, 22 kcal/mol; ΔS≠, −27 eu, log A, 7.6 for the oxidation and ΔH≠, 12 kcal/mol; ΔS≠, −42.3 eu, log A, 4.13 for the enolization. Based on these observations a mechanism has been postulated whereby an oxygen molecule forms a transitory adduct with two enolates of cyclohexanone. The latter may then split by a reversible reaction to form an intermediate which may then isomerize or oxidize to either 2-hydroxycyclohexanone or 1,3-cyclohexanedione. Upon further oxidation the former yields hexanedioic acid. The latter then undergoes a reverse condensation in the aqueous media to 5-oxohexanoic acid which upon further oxidation yields formic plus pentanedioic acid and acetic plus butanedioic acid.

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