Separation of hydrocarbons by azeotropic distillation

The following topics are discussed: the principles involved in azeotropic distillation; the substances that form azeotropic mixtures with hydrocarbons; the separation of hydrocarbons by azeotropic distillation, including aromatics from naphthenes and paraffins, naphthenes from paraffins, aromatic hydrocarbons having different numbers and kinds of rings, naphthene hydrocarbons having different numbers of naphthene rings, olefin hydrocarbons, and isomeric hydrocarbons; the differences in the change of boiling point with pressure for the difl"erent types of hydrocarbons; and the benefits of distillation at reduced pressure prior to azeotropic distillation at the normal operating pressure. A general procedure is outlined for separating a given (gasoline or kerosene) fraction of petroleum by means of distillation alone in its several variations (at the normal distilling pressure, at reduced pressure, and with an azeotrope-forming substance). A list is given of the hydrocarbons which are known to be separable in a substantially "pure" state by distillation alone from petroleum or its products.