A high temperature, pressure study of the comparative rates of enolization and oxidation of acetone in aqueous solution

1986 ◽  
Vol 64 (11) ◽  
pp. 2235-2237 ◽  
Author(s):  
John W. Thomas ◽  
Jay E. Taylor
Keyword(s):  
Aqueous Solution ◽  
High Temperature ◽  
Partial Pressure ◽  
Oxygen Concentration ◽  
Total Pressure ◽  
Room Temperature ◽  
Isotopic Exchange ◽  
Partial Pressure Of Oxygen

The rate of enolization and acetone has been determined as 6.6 × 10−4 s−1 at 193.5 °C under nitrogen at 136 atm total pressure via isotopic exchange. The rate of oxidation was determined to be 8.8 × 10−6 s−1 at 193.5 °C in 123 atm partial pressure of oxygen (136 atm total pressure). In a previous study it was shown that the rates of oxidation of several ketones correlated with the extents of enolization at room temperature. This prompted the suggestion that the enol is an intermediate in the oxidation. Since the rate of enolization exceeded the rate of oxidation by a factor of 75, this suggestion is further supported. A dependence of the rate of oxidation of acetone on oxygen concentration was also demonstrated.

Effect of Oxygen Concentration on Aging of Rubber Vulcanizates. II. Effect of Partial Pressure of Oxygen on Changes in Physical Properties Accompanying Oxidation

1953 ◽  
Vol 26 (3) ◽  
pp. 643-654 ◽  
Author(s):  
J. Reid Shelton ◽  
William L. Cox
Keyword(s):  
Physical Properties ◽  
Partial Pressure ◽  
Oxygen Concentration ◽  
Chain Scission ◽  
Cross Linking ◽  
Partial Pressure Of Oxygen ◽  
Aging Behavior ◽  
Storage Temperatures ◽  
Normal Storage ◽  
Oxygen Concentrations

Abstract The over-all rate of deterioration of physical properties increases with the oxygen concentration, as would be expected from the increased rate of oxygen absorption: The nature of the deterioration resulting from a given amount of oxygen absorbed is influenced also by changes in the partial pressure of oxygen in the aging atmosphere. It appears that chain scission is favored at higher oxygen concentrations, while cross-linking becomes of greater relative importance at lower oxygen concentrations. These data suggest that R⋅ radicals are more effective than RO2⋅ radicals in reacting with double bonds to form crosslinks. Heat aging in the absence of oxygen, as observed by heating a vulcanizate in lamp-grade nitrogen, results in considerable stiffening, particularly in the case of a GR-S black stock. This effect is observed primarily in the first few hours of heating, and may account for some of the erratic behavior observed in the early stages of aging when changes in physical properties are compared on the basis of amount of oxygen absorbed. Higher oxygen concentration brings about a more rapid oxidation, and also results in a higher proportion of chain scission compared to cross-linking for a given amount of oxygen absorbed. As tensile decay is the most evident sign of deterioration of Hevea stocks, it follows that the aging behavior of natural rubber in air at normal storage temperatures will be better than that predicted by high temperature testing in oxygen. In the case of GR-S stocks, on the other hand, oxidative hardening is the most serious result of aging, and consequently, the aging behavior of GR-S stocks in air at normal storage temperatures is poorer than would be expected on the basis of comparative tests in oxygen at higher temperatures.

Al2O3 Microspheres Prepared by Cathode Plasma Electrolysis

2017 ◽  
Vol 70 (1) ◽  
pp. 120 ◽  
Author(s):  
Chenxu Liu ◽  
Jin Zhang ◽  
Yedong He ◽  
Peng Wang ◽  
Shunjie Deng ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Surface Tension ◽  
High Temperature ◽  
Formation Mechanism ◽  
Room Temperature ◽  
Cathode Plasma ◽  
Plasma Electrolysis ◽  
High Concentrations ◽  
Α Al2o3 ◽  
High Temperature Calcination

Al2O3 microspheres were prepared by cathode plasma electrolysis (CPE) in an aqueous solution of Al(NO)3·9H2O. Compared with high-temperature calcination methods, the CPE method afforded the preparation of microspheres directly at room temperature. The results showed that regular microspheres formed under relatively high concentrations of Al(NO)3·9H2O. The microspheres, with diameters mostly in the range of 5–30 μm, consisted of γ-Al2O3 and α-Al2O3. The possible formation mechanism included the following processes: (1) Al(OH)3 intermediate was formed during the cathodic reactions; (2) plasma energized the intermediate to Al2O3; and (3) microspheres formed under the effect of the surface tension.

Action Mechanism of β-Si3N4 in Bauxite Sintering

2014 ◽  
Vol 543-547 ◽  
pp. 3834-3838
Author(s):  
Jun Hong Chen ◽  
Bin Li ◽  
Hua Sheng Zhan ◽  
Jin Dong Su ◽  
Ming Wei Yan ◽  
...  
Keyword(s):  
High Temperature ◽  
Melting Point ◽  
Partial Pressure ◽  
Sodium Oxide ◽  
Potassium Oxide ◽  
Oxide Content ◽  
Partial Pressure Of Oxygen ◽  
Action Mechanism ◽  
High Potassium ◽  
High Partial Pressure

In this paper, we added silicon nitride in the samples of common bauxite and the bauxite with high potassium and sodium oxide content, treated them at the high temperature of 1,400°Cand 1,500°C, and then conducted analysis with XRD, SEM and EDS. The results are as follows: After adding β-Si3N4 in sintered bauxite, the partial pressure of oxygen in the composite materials will be reduced, the decomposition and volatilization of compounds with high partial pressure of oxygen (such as potassium oxide and sodium oxide) will be promoted, the content of these compounds in the bauxite will be lowered, and the hazards of the compounds with low melting point will be weakened; meanwhile, with the reduction of potassium, sodium and iron oxide, the lattice of alumina will be activated, the β-Sialon phase will be easily formed and the high temperature properties of sintered bauxite materials will be strengthened.

scholarly journals The Physiological Action of Abnormally High Temperatures on Poikilotherm Animals

1940 ◽  
Vol 17 (4) ◽  
pp. 386-395
Author(s):  
G. S. FRAENKEL ◽  
G. V. B. HERFORD
Keyword(s):  
Oxygen Consumption ◽  
High Temperature ◽  
Partial Pressure ◽  
High Temperatures ◽  
Oxygen Pressure ◽  
Partial Pressure Of Oxygen ◽  
Waste Products ◽  
Physiological Action ◽  
Very High ◽  
Acid Waste

The oxygen consumption of blowfly larvae at sublethal and lethal high temperatures at the beginning of the determination is entirely dependent on the oxygen pressure, but after about 1 hr. at 42°C. it is higher at 20 and 10% partial pressure of oxygen than at either 100 or 5%. Death at high temperatures is not due to lack of oxygen, but may be due to the accumulation of acid waste products of the metabolism. The basal oxygen consumption remains unchanged for some time after the organism has been irreversibly injured by the high temperature. Blowfly larvae resist the damaging effect of high temperatures slightly better in air (20% oxygen) than in either very high (100%) or very low (less than 10%) concentrations of oxygen.

scholarly journals The oxidation of haemoglobin to methaemoglobin by oxygen - II—The relation between the rate of oxidation and the partial pressure of oxygen

1935 ◽  
Vol 118 (811) ◽  
pp. 560-577 ◽  
Keyword(s):  
Aqueous Solution ◽  
Dissolved Oxygen ◽  
Partial Pressure ◽  
Oxygen Pressure ◽  
Phosphate Buffer ◽  
Maximum Rate ◽  
The Other ◽  
Partial Pressure Of Oxygen ◽  
Oxidation Reduction ◽  
Single Oxygen

Neill and Hastings (1925) found that the rate of oxidation of haemoglobin by dissolved oxygen in aqueous solution was maximal at a small partial pressure of oxygen; a similar result was obtained (Brooks, 1929) for the oxidation of haemoglobin in pigmented muscle. In both cases the rate was determined approximately. A possible explanation of the effect was suggested to Neill and Hastings by the work of Conant (1923, 1924-25, 1926, 1928) who had shown that methaemoglobin and reduced haemoglobin formed an oxidation-reduction system of the ferri-ferro type. If only reduced haemoglobin reacts with oxygen to give methaemoglobin, increasing the oxygen pressure decreases the concentration of the other reactant (by the formation of oxyhaemoglobin), and a maximum rate of oxidation might be obtained. The rate of oxidation of haemoglobin, using ox-blood diluted in a phosphate buffer, was measured at a single oxygen pressure (Brooks, 1931) and found to be unimolecular with respect to the concentration of haemoglobin. Similar measurements at 30° C and p h 5·69 have now been made at other oxygen pressures; the concentration of oxy-and reduced haemoglobin in the system has also been determined. Fortunately, the establishment of equilibrium between oxygen and haemoglobin is very rapid in comparison with the rate of oxidation (Hartridge and Roughton, 1923, 1925).

Interaction of H2O, O2 and H2 with Proton Conducting Oxides Based on Lanthanum Scandates

2019 ◽  
pp. 88-100
Author(s):  
A. S. Farlenkov ◽  
N. A. Zhuravlev ◽  
Т. A. Denisova ◽  
М. V. Ananyev
Keyword(s):  
Water Vapor ◽  
Partial Pressure ◽  
Gas Phase ◽  
Molecular Hydrogen ◽  
Proton Magnetic Resonance ◽  
Partial Pressure Of Oxygen ◽  
Proton Conducting ◽  
Conducting Oxides ◽  
Temperature Range ◽  
Apparent Level

The research uses the method of high-temperature thermogravimetric analysis to study the processes of interaction of the gas phase in the temperature range 300–950 °C in the partial pressure ranges of oxygen 8.1–50.7 kPa, water 6.1–24.3 kPa and hydrogen 4.1 kPa with La1–xSrxScO3–α oxides (x = 0; 0.04; 0.09). In the case of an increase in the partial pressure of water vapor at a constant partial pressure of oxygen (or hydrogen) in the gas phase, the apparent level of saturation of protons is shown to increase. An increase in the apparent level of saturation of protons of the sample also occurs with an increase in the partial pressure of oxygen at a constant partial pressure of water vapor in the gas phase. The paper discusses the causes of the observed processes. The research uses the hydrogen isotope exchange method with the equilibration of the isotope composition of the gas phase to study the incorporation of hydrogen into the structure of proton-conducting oxides based on strontium-doped lanthanum scandates. The concentrations of protons and deuterons were determined in the temperature range of 300–800 °C and a hydrogen pressure of 0.2 kPa for La0.91Sr0.09ScO3–α oxide. The paper discusses the role of oxygen vacancies in the process of incorporation of protons and deuterons from the atmosphere of molecular hydrogen into the structure of the proton conducting oxides La1–xSrxScO3–α (x = 0; 0.04; 0.09). The proton magnetic resonance method was used to study the local structure in the temperature range 23–110 °C at a rotation speed of 10 kHz (MAS) for La0.96Sr0.04ScO3–α oxide after thermogravimetric measurements in an atmosphere containing water vapor, and after exposures in molecular hydrogen atmosphere. The existence of proton defects incorporated into the volume of the investigated proton oxide from both the atmosphere containing water and the atmosphere containing molecular hydrogen is unambiguously shown. The paper considers the effect of the contributions of the volume and surface of La0.96Sr0.04ScO3–α oxide on the shape of the proton magnetic resonance spectra.

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