The mechanism of the Pinacol-Pinacone rearragement. VI. Low temperature kinetics

The low temperature rearrangement of pinacol to pinacone appears to be second order with respect to the hydrogen ion concentration. The activation energy is, however, similar to that of the high temperature reaction. This is interpreted as indicating that in the low temperature reaction the synartetic step is formed by a two stage process, through a stable intermediate, and each stage requires the participation of a hydrogen ion.

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Study of high-pressure air jet controlled compression ignition with compound thermodynamic cycle for combustion and emission formation process

International Journal of Engine Research ◽

10.1177/1468087420969337 ◽

2020 ◽

pp. 146808742096933

Author(s):

Xiangyu Meng ◽

Sicheng Liu ◽

Jingchen Cui ◽

Jiangping Tian ◽

Wuqiang Long ◽

...

Keyword(s):

High Pressure ◽

High Temperature ◽

Low Temperature ◽

Formation Process ◽

Combustion Process ◽

Thermodynamic Cycle ◽

Compression Ignition ◽

Temperature Reaction ◽

Air Jet ◽

High Temperature Reaction

A novel method called high-pressure air (HPA) jet controlled compression ignition (JCCI) based on the compound thermodynamic cycle was investigated in this work. The combustion process of premixed mixture can be controlled flexibly by the high-pressure air jet compression, and it characterizes the intensified low-temperature reaction and two-stage high-temperature reaction. The three-dimensional (3D) computational fluid dynamics (CFD) numerical simulation was employed to study the emission formation process and mechanism, and the effects of high-pressure air jet temperature and duration on emissions were also investigated. The simulation results showed that the NOx formation is mainly affected by the first-stage high-temperature reaction due to the higher reaction temperature. Overall, this combustion mode can obtain ultra-low NOx emission. The second-stage high-temperature reaction plays an important role in the CO and THC formation caused by the mixing effect of the high-pressure air and original in-cylinder mixture. The increasing air jet temperature leads to a larger high-temperature in-cylinder region and more fuel in the first-stage reaction, and therefore resulting in higher NOx emission. However, the increasing air jet temperature can significantly reduce the CO and THC emissions. For the air jet duration comparisons, both too short and too long air jet durations could induce higher NOx emission. A higher air jet duration would result in higher CO emission due to the more high-pressure air jet with relatively low temperature.

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737. The heat coagulation of milk: II. variations in sensitivity of casein to calcium ions

Journal of Dairy Research ◽

10.1017/s0022029900009523 ◽

1958 ◽

Vol 25 (3) ◽

pp. 467-474 ◽

Cited By ~ 42

Author(s):

G. T. Pyne

Keyword(s):

High Temperature ◽

Calcium Ions ◽

Serum Proteins ◽

Significant Part ◽

Hydrogen Ion ◽

Ion Concentration ◽

Temperature Stabilization ◽

Phosphate Content ◽

Hydrogen Ion Concentration ◽

Phosphate Complex

1. The sensitivity to calcium of the caseinate-phosphate complex of milk heated at 120°C., increases to an early maximum and thereafter steadily declines, apparently in consequence of parallel changes in the sensitivity of its caseinate constituent.2. A simultaneously developed capacity of the heated complex to bind additional colloidal phosphate appears to be unrelated to these changes in casein sensitivity.3. Colloidal phosphate content is confirmed as a factor in the heat coagulation of milk.4. Heat-developed acidity contributes to the heat coagulation of milk primarily by increasing hydrogen-ion concentration and only slightly, if at all, through release of calcium ions from insoluble combinations.5. Neither serum proteins nor protein-lactose combinations play any significant part in the heat coagulation of milk.6. The bearing of these results on the heat coagulation of milk in general and on the operation of certain high-temperature stabilization treatments is discussed.

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Mastication of Rubber a Study of Some of the Oxidation Rocesses Involved

Rubber Chemistry and Technology ◽

10.5254/1.3546422 ◽

1939 ◽

Vol 12 (2) ◽

pp. 163-175 ◽

Cited By ~ 2

Author(s):

W. F. Busse ◽

E. N. Cunningham

Keyword(s):

High Temperature ◽

Low Temperature ◽

Thermal Oxidation ◽

Oxygen Concentration ◽

High Temperatures ◽

Nitroso Compounds ◽

Temperature Reaction ◽

Vulcanized Rubber ◽

High Temperature Reaction ◽

Internal Mixer

Abstract The rate of breakdown of smoked sheet, pale crepe, and sprayed-latex rubber in a laboratory internal mixer is a minimum at temperatures around 240° F., and the rate may be increased as much as four- or five-fold by either raising or lowering the temperature 80° F. The high-temperature reaction (above 240° F.) probably is similar to the thermal oxidation which occurs when rubber is heated in air, since the rates of both reactions are increased by increasing the oxygen concentration, and they are reduced by adding antioxidants. The low-temperature reaction (below 240° F.) may involve a mechanical acti-vation of the rubber, as in milling. The rate of this reaction first increases and then remains constant or decreases slightly as the oxygen concentration in the temperature during mastication is increased from about 0.5% to 20% to 100%. Some nitroso compounds are powerful stiffeners of rubber, and they change the softness-retentivity relation, making it more like that of reclaim or semi-vulcanized rubber. The effect of most commonly used “softeners” on the plasticity of rubber is small compared with the effect of changing the mastication temperature ±40° F. Exceptions to this are certain vulcanization accelerators (at high temperatures), hydrazine compounds and thiophenols, which appear to be true mastication acelerators or oxidation catalysts.

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