Volatility temperature and

The JANAF tables specify a volatilization temperature of a condensed-phase material to be where the standard-state free energy A Gf approaches zero for a given equilibrium reaction, that is, M/fyl), M/)y(g). One can obtain a heat of vaporization for materials such as Li20(l), FeO(l), BeO(l), and MgO(l), which also exist in the gas phase, by the differences in the All" of the condensed and gas phases at this volatilization temperature. This type of thermodynamic calculation attempts to specify a true equilibrium thermodynamic volatilization temperature and enthalpy of volatilization at 1 atm. Values determined in this manner would not correspond to those calculated by the approach described simply because the procedure discussed takes into account the fact that some of the condensed-phase species dissociate upon volatilization. 

Although many reports are available on deposition performed at atmospheric pressure, low pressure operation is convenient in order to obtain satisfactory molar fractions of the precursor (of the order of 10 ) at relatively low (if possible less than 100°C) volatilization temperature, and also to achieve improved conformal coverage of the substrates. Only few investigations have been performed with varying deposition pressure."" It is worth noting that Ni(HL ) and NiCp have been decomposed in molecular beam epitaxy (MBE) conditions, but with a high carbon contamination for the latter." ... 

The V/L ratio is a volatility criterion seldom used in France but is used in Japan and in the United States where it has been standardized as ASTM D 2533. At a given temperature and pressure, the V/L ratio represents the volume of vapor formed per unit volume of liquid taken initially at 0°C. 

It is possible to modify the quality of the coke by calcination at high temperatures (1200-1400°C) this has the effect of reducing the volatile material and to increase the density. 

Me Arragher, J.S. and al. (1990), The effects of temperature and fuel volatility on evaporative emissions from european cars . /. Mech. Eng., No. 394/028, London. 

The four vertical lines on the diagram show the isothermal depletion loci for the main types of hydrocarbon gas (incorporating dry gas and wet gas), gas condensate, volatile oil and black oil. The starting point, or initial conditions of temperature and pressure, relative to the two-phase envelope are different for each fluid type. 

For both volatile oil and blaok oil the initial reservoir temperature is below the critical point, and the fluid is therefore a liquid in the reservoir. As the pressure drops the bubble point is eventually reached, and the first bubble of gas is released from the liquid. The composition of this gas will be made up of the more volatile components of the mixture. Both volatile oils and black oils will liberate gas in the separators, whose conditions of pressure and temperature are well inside the two-phase envelope. 

Although Pd is cheaper than Rh and Pt, it is still expensive. In Pd(0)- or Pd(ll)-catalyzed reactions, particularly in commercial processes, repeated use of Pd catalysts is required. When the products are low-boiling, they can be separated from the catalyst by distillation. The Wacker process for the production of acetaldehyde is an example. For less volatile products, there are several approaches to the economical uses of Pd catalysts. As one method, an alkyldi-phenylphosphine 9, in which the alkyl group is a polyethylene chain, is prepared as shown. The Pd complex of this phosphine has low solubility in some organic solvents such as toluene at room temperature, and is soluble at higher temperature[28]. Pd(0)-catalyzed reactions such as an allylation reaction of nucleophiles using this complex as a catalyst proceed smoothly at higher temperatures. After the reaction, the Pd complex precipitates and is recovered when the reaction mixture is cooled. 

The halothiazoles are distillable oils under reduced pressure. The 2-fluOrothiazole is extremely volatile at room temperature and must be handled with care. 

Thermogravimetry The products of a thermal decomposition can be deduced by monitoring the sample s mass as a function of applied temperature. (Figure 8.9). The loss of a volatile gas on thermal decomposition is indicated by a step in the thermogram. As shown in Example 8.4, the change in mass at each step in a thermogram can be used to identify both the volatilized species and the solid residue. 

A laser beam is capable of putting so much energy into a substance in a very short space of time that the substance rapidly expands and volatilizes. The resulting explosive shock wave travels through the sample, subjecting it to high temperatures and pressures for short times. This process is also known as ablation. 

Genera.1 Ca.se, The simple adiabatic model just discussed often represents an oversimplification, since the real situation implies a multitude of heat effects (/) The heat of solution tends to increase the temperature and thus to reduce the solubihty. 2) In the case of a volatile solvent, partial solvent evaporation absorbs some of the heat. (This effect is particularly important when using water, the cheapest solvent.) (J) Heat is transferred from the hquid to the gas phase and vice versa. (4) Heat is transferred from both phase streams to the shell of the column and from the shell to the outside or to cooling cods. 

Deodorization can be carried out ki batch, continuous, or semicontkiuous systems. Figure 4 shows a typical design for a semicontkiuous deodorizer. The heated ok is passed through a series of trays under vacuum. Steam is passed through the ok through a steam sparge ki the bottom of the tray. Volatiles are carried through the headspace and condensed. In addition to fatty acids and compounds responsible for odor, some tocopherols and sterols are also distilled kito the condensate. The amount of tocopherols distilled depends on deodorization temperature and vacuum. 

Pulp-like olefin fibers are produced by a high pressure spurting process developed by Hercules Inc. and Solvay, Inc. Polypropylene or polyethylene is dissolved in volatile solvents at high temperature and pressure. After the solution is released, the solvent is volatilised, and the polymer expands into a highly fluffed, pulp-like product. Additives are included to modify the surface characteristics of the pulp. Uses include felted fabrics, substitution in whole or in part for wood pulp in papermaking, and replacement of asbestos in reinforcing appHcations (56). 

Borane—dimethyl sulfide complex (BMS) (2) is free of these inconveniences. The complex is a pure 1 1 adduct, ca 10 Af in BH, stable indefinitely at room temperature and soluble in ethers, dichioromethane, benzene, and other solvents (56,57). Its disadvantage is the unpleasant smell of dimethyl sulfide, which is volatile and water insoluble. Borane—1,4-thioxane complex (3), which is also a pure 1 1 adduct, ca 8 Af in BH, shows solubiUty characteristics similar to BMS (58). 1,4-Thioxane [15980-15-1] is slightly soluble in water and can be separated from the hydroboration products by extraction into water. 

Reaction with Meta/ Oxides. The reaction of hydrogen chloride with the transition-metal oxides at elevated temperatures has been studied extensively. Fe202 reacts readily at temperatures as low as 300°C to produce FeCl and water. The heavier transition-metal oxides require a higher reaction temperature, and the primary reaction product is usually the corresponding oxychlorides. Similar reactions are reported for many other metal oxides, such as Sb202, BeO, AI2O2, andTi02, which lead to the formation of relatively volatile chlorides or oxychlorides. 

In 1974 a 1000 t/d ammonia plant went into operation near Johaimesburg, South Africa. The lignitic (subbituminous) coal used there contains about 14% ash, 36% volatile matter, and 1% sulfur. The plant has six Koppers-Totzek low pressure, high temperature gasifiers. Refrigerated methanol (—38° C, 3.0 MPa (30 atm)) is used to remove H2S. A 58% CO mixture reacts with steam over an iron catalyst to produce H2. The carbon dioxide is removed with methanol (at —58° C and 5.2 MPa (51 atm)). Ammonia synthesis is carried out at ca 22 MPa (220 atm) (53) (see Ammonia). 

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