Pseudo-boiling

The volatilization or pseudo-boiling point temperature and the corresponding enthalpies of decomposition and volatilization of all the systems examined as a function of total pressure are reported in Table 9.2. The variation in the enthalpy of volatilization as a function of pressure is generally less than 7%. The Ti-02 system (Fig. 9.8) shows an anomalous rise in AH°ol with pressure. 

Considering that dissociation occurs upon volatilization, the temperatures can be correlated extremely well on a In P vs (1/rd.voi) plot, where P is the total system pressure and T a.voi decomposition temperature, as the case dictates. Such a plot is shown in Fig. 11. Since the Clausius-Clapeyron relation for vapor pressure of pure substances shows an exponential dependence on temperature, TVoi was considered a pseudo-boiling point at the respective system pressure. For a substance that vaporizes congruently to its gaseous state, the slope of lines on a In P vs (l/Tvoi) plot represents the enthalpy of vaporization. Indeed, the enthalpy of vaporization calculated from the slope on a In P vs (l/TVoi) plot for the B-O2 system (360 kJ/mol) agrees exactly with the value calculated by using... 

Also, two special phenomena (for their definitions, see the beginning of this appendix) may appear along a heated surface (1) pseudo-boiling and (2) pseudo-film boiling. 

A4.2.2 Pseudo-boiling and pseudo-film boiling phenomena... 

Using the principle of corresponding states requires knowledge of pseudo-critical constants of petroleum fractions these should be estimated starting from characteristic properties which are the normal boiling temperature and the standard specific gravity. 

Residue curve maps exist for mixtures having more than three components but cannot be visualized when there are more than four components. However, many mixtures of industrial importance contain only three or four key components and can thus be treated as pseudo-temary or quaternary mixtures. Quaternary residue curve maps are more compHcated than thek ternary counterparts but it is stiU possible to understand these maps using the boiling point temperatures of the pure components and azeotropes (31). 

In crude distillation, there are thousands of different compounds present having a virtually continuous spectrum of boiling points. It would be impractical to consider each of these compounds in describing the crude or designing the equipment to process it. Instead the crude is treated as if it were composed of a manageable number (< 50) of pseudo components. These are defined by dividing the crude distillation curve into a series of adjacent boiling cuts. 

Usually, product specifications for a crude distillation unit are expressed in terms of the products 15/5 or ASTM distillation curves. The prediction of a product 15/5 distillation is accomplished simply by blending the quantities of the pseudo components in the stream so as to form a true boiling point, 15/5 equivalent, distillation curve. This curve can then be converted to an ASTM type distillation using an empirical method. Figure 5 illustrates how a typical ASTM curve compares to the 15/5 curve for the same material. 

The ketone derivatives of the pseudo-ionone are converted under similar conditions into ketone-derivatives of the ionone. The pure ionone corresponds to the formula CjjHjjO, it boils under a pressure of 12 mm. at a temperature of about 128° 0., its specific weight is 0-935, and its index of refraction mD = 1-507. 

Although the odour of the pseudo-ionone does not appear to render it of great importance for its direct use in perfumery, it is capable of serving as raw material lor the production of perfumes, the pseudo-ionone being converted by the action of dilute acids into an isomeric ketone, which I term lonone, and which has most valuable properties for perfumery purposes. This conversion may be effected, for example, by heating for several hours in an oil-bath 20 parts of pseudo-ionone with 100 parts of water, 2-5 parts of sulphuric acid, and 100 parts of glycerine, to the boiling-point of the mixture. 

When a very large number of reactants occurs, as in the treatment of petroleum fractions with a virtually continuous spectrum of boiling points, the problem is made more tractable by lumping the composition. The lumps are made up of pseudo components with limited boiling ranges and of partcular chemical types such as aromatics, paraffins, naphthenes, olefins and so on. 

Pseudo-ionone is the first prodnct, and this is then converted to a mixture of a- and /3-ionone by boiling with dilute sulphuric acid ... 

The boiling point is the last data herein sought out however, it is indeed the most important data to secure for a discrete pure component or a pseudo-crude cut component. Since the discrete pure components are generally a known type of molecular structure, their boiling points may readily be obtained or estimated from data sets such as Table 1.3. The crude oil components are left, unfortunately, undefined. Therefore, this section is dedicated to defining the boiling points of crude oil and its products. 

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