Low temperature -high pressure

Use of high or low temperature, high pressure, vacuum or possible hazardous reactions (polymerization, oxidation, halogenation, hydrogenation, alkylation, nitration, etc.)... 

Low-temperature, high-pressure gases at moderate to low temperatures can be expanded by the use of an expansion turbine (very similar to a steam turbine or even by reciprocating or screw-type compressors) or by the use of a throt-... 

Low-temperature/high-pressure distillation. Rather than use a low-temperature single-stage condensation or refluxed condenser, a conventional distillation can be used. To carry out the separation under these circumstances will require a low-temperature condenser for the column, or operation at high pressure, or a combination of both. 

L = PPh3, P(p-MeCgH4)3, or P(p-FC6H4)3]. Of more fundamental interest was i.r. evidence for the formation of the hitherto unknown Rh2(CO)g from the low -temperature (high-pressure) reaction between Rh4(CO)i2 and CO. Whereas Rh (CO)j2 catalyses the hydroformylation of propene in toluene, the use of more polar solvents such as methanol and acetone has been shown to yield instead RhglCO) , and the first reported acyl clusters [NR4][Rhg-(CO)is(COR)] [R = Et(ethylene) or Pr(propene)]. The presence of the acyl group was confirmed from the i.r. spectra (1655—1670 cm ). ... 

Change-over from first to second order, and the pressure at which this occurs, depends mainly on three factors. Low temperatures, high pressures and increasing complexity all favour first order kinetics, while high temperatures, low pressures and small numbers of atoms in the reactant favour second order. 

This reaction is just similar to the synthesis of ammonia described above. So, the effect of pressure, temperature and concentration will be the same as mentioned in the synthesis of ammonia. Low temperature, high pressure and increased concentrations of S02 and 02 will favour the formation of sulphur trioxide. 

The number of low-temperature, high-pressure (LT + HP) structure determinations of organic conductors is not yet very large, but a number of other crystallographic studies under constraint have also been reported. To limit the field of the discussion below, we consider only the case of techniques allowing for the measurement of full crystal structures, since collecting a three-dimensional diffraction data set is more demanding than simple observation of a few main or satellite reflections. 

In some cases, the low-temperature high-pressure cycle can be anticipated to be the most damaging to the product because it can create conditions where the rate of ice sublimation is slowed down, thus resulting in product overwarming, collapse, and high residual moisture. 

Eeehan J. G. and Brandon M. T. (1999) Contribution of ductile flow to exhumation of low-temperature, high-pressure metamorphic rocks San Juan-Cascade nappes, NW, Washington State. J. Geophys. Res. 104, 10883-10902. 

The production of fluids and melts during subduction (the latter occurring in strictly prograde, relatively low-temperature-high-pressure conditions compared to typical crustal anatepis) is dominated by a succession of continuous and discontinuous reactions that are of comparatively equal importance in terms of fluid productivity in... 

Three properties of fluids under shear are discussed in detail flow boundary condition, friction, and shear viscosity. It has been shown that the no-slip boundary condition assumed in fluid mechanical formulations of Newtonian flow past solids can fail at the molecular level. The velocity profiles deviate most from the continuum linear form at small pore separations, low temperatures, high pressures, and high shear rates. Friction is controlled by two factors - interfacial strength and in-plane ordering. 

Blueschist facies low-temperature/high-pressure metamorphism. 

Two other metamorphic facies are formed on a regional scale and under unique circumstances. The blueschist facies forms in the low-temperature, high-pressure environment in the upper portion of a subduc-tion zone. Land-derived sediments accumulated deep on the cold ocean floor are driven into an area of high pressure during subduction of an oceanic plate. These rocks often look blue when seen in outcrops. 

Figure 8 Illustration of the scanning transitiometry technique for low-temperature, high-pressure investigation of polymers glass transition. The pressure coefficient of the glass transition temperature is given in the inset...

The absorption of the nitrous gases in the process water is favored by low temperatures, high pressures and longer contact times. The quantity of process water, of which the acid condensate is a part, is dependent upon the required nitric acid concentration. Higher pressures permit the production of higher nitric acid concentrations (up to 70% HNO3), since under pressure almost complete absorption of nitrous gases can be attained in a small quantity of process water with low emission of residual gas. Only 45 to 50% nitric acid can be produced at atmospheric pressure. 

Ikeda T, Kobayashi T, Takata M, Takayama T, Sakata M (1998) Charge density distributions of strontium titanate obtained by the maximum entropy method. Solid State Ion 108 151-157 Imai M, Mitamura T, Yaoita K, Tsuji K (1996) Pressure-induced phase transition of crystalline and amorphous silicon and germanium at low temperatures. High Pressure Res 15 167-189... 

The advantage of such devices is that they are light (< 10 kg) and can easily be cooled to cryogenic temperatures. They also allow a large-angle access in the equatorial plane, and in directions normal to this plane. Their main drawback is the limited volume of the samples, which, at the present time does not allow profile-refinement procedures to be carried out above 10 GPa. Nevertheless, they are extremely useful for low-temperature, high-pressure work, such as the study of magnetic phase transitions. ... 

Fig. 4.36 A low-temperature, high-pressure probe for solid-state NMR (a) an overall cross-sectional view and (b) details of the high-pressure seal and feedthrough. ...

Effect of Operating Variables. The direct hydration of ethylene is an equilibrium i eaction (see Sec. V) which is favored by low temperatures, high pressures, and high steam. ethylene ratios. He catalytic activity of the phosphoric acid catalyst increases with increasing temperature, decreases with increasing pressure because of lower concentration, and decreases with high steam ethylene ratios at hi pressures because of moisture absorption. Thus, the process conditions that favor ethanol production adversely affect the catalyst activity. For this reason, operating conditions must necessarily be chosen on the basis of economic considerations. 

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