True boiling point naphtha

The design methods considered for multicomponent mixtures in Chap. 9 were based on a limited number of definitely known components. In some cases, the mixtures are so complex that the composition with reference to the pure component is not known. This is particularly true of the petroleum naphthas and oils which are mixtures of many series of hydrocarbons, many of the substances present having boiling points so close together that it is practically impossible to separate them into the pure components by fractional distillation or any other means. Even if it were possible to determine the composition of the mixture exactly, there are so many components present that the methods of Chap. 9 would be too laborious. It has become customary to characterize such mixtures by methods other than the amount of the individual components they contain, such as simple distillation or true-boiling-point curves, density, aromaticity (or some other factor related to types of compounds), refractive index, etc. 

Figure 11.31 shows that this is indeed true. The responses with temperature control are represented by solid lines. The responses with 95% boiling point control are represented by dashed lines. The disturbance is a swing in crude oils to less OlL-1 and more OIL-2. The process steadies out in about 90 min with temperature control. The naphtha boiling point is not held exactly at 191 °C, but ends up at about 189.3 °C. The naphtha yield is somewhat smaller, with more bottoms. 

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