Isolation of an isononane from petroleum - Its fractionation from naphthenes by distillation with acetic acid

Abstract

A nonane boiling at 135.20 C, probably a dimethylheptane, has been isolated from Oklahoma petroleum. It was found closely associated with naphthenic hydrocarbons in a distillation fraction boiling normally between 135 and 136 0 C from which aromatic hydrocarbons had already been removed. Separation of the mixture by distillation with glacial acetic acid yield~d a fraction highly concentrated in the nonane from which the compound was finally isolated by crystallization from solution in liquid dichlorodifluoromethane. It constitutes about 0

2,6-Dimethylheptane: its synthesis, properties, and comparison with an isononane from petroleum

“…The indication from the correlation of physiCllI properties that the compound might be 2,6-dimethylheptane was in keeping with a suspected dimethylheptane structure, a supposition based on the fact that all of the isoparaffinic hydrocarbons previously isolated from the 1 Financial assistance has been received from the research fund of the American Petroleum Institute . This work is part of Project 6, The Separation, Identification, and Determination of the Constituents of Petroleum.…”

“…The properties previously reported for the isononane from petroleum [1] are listed in table 1. A calculation of the purity, made in a manner similar to that for the synthetic 2,6-dimethylheptane, yielded a value of 98.8 ± 0.2 mole percent.…”

“…In connection with another investigation [12), the heat of fusion of the isononsne from petroleum was calculated to be 2.5 ±O.2 keal/mole, from values of the molecular depression of the freezing point produced by the addition, to the isononane, of known quantities of ethylcyclohexane. • For values of the coefficients of these properties with temperature or pressure see table 1. b These uncertainties are relative.…”

“…Table 2 gives values of the properties of the hydrocarbon, 100.0 mole percent pure, obtained by extrapolation of measurements actually made on synthetic 2,6-dimethylheptane, 99.6 mole percent pure, and on the isononane from petroleum, 98.8 mole percent pure. The extrapolations were made on the assumptions that the impurity in the synthetic material was normal nonane and that in the Isononane from petroleum was a nonanaphthene [1,10,12], and that, WIthin the small range involved, the values of density and refractive index are linear functions of the mole fractions of the components. The freezing point was calculated according to the procedure previously mentioned.…”

“…The isolation from a midcontinent petroleum of an isomeric nonane boiling at 135.2° C has been described in an earlier paper by White and Rose [1]. 6 The identification of the compound was attempted at the time, by comparing the physical constants of the hydrocarbon from petroleum with those reported for the few nonanes known to boil near 135° C. The compound had properties most nearly like those reported for 2,6-dimethylheptane [2,3], but the agreement was not sufficient, in the absence of knowledge concerning 1 9 of the 35 structurally possible isomers of C9H 20 , to make the identification complete.…”