Seperation of 1,2,4-trimethylcyclohexane and an isononane from a midcontinent petroleum

Abstract

A fraction of Oklahoma petroleum boiling at 141° C, from which the aromatic hydrocarbons previously had been removed, was separated by distillation at 215 mm Hg into a fraction containing the bulk of a naphthene constituent and one enriched in paraffins. From the former, nearly pure 1,2,4-trimethylcyclohexane was isolated by crystallization from solution in liquid dichlorodifluoromethane. Continued distillation of the paraffinic fraction at normal pressure, alternated with distillation at 215 mm Hg, yielded a fraction containing 85 mole percent of an isononane, probably 2,3-dimethylheptane. The 1,2,4-trimethylcyclohexane constitutes about 0.1 percent, and the isononane about 0.05 percent of the original petroleum.Effective separation of a paraffin-naphthene mixture, constant-boiling at normal pressure, by distillation at a different pressure arises from the greater change in boiling point with pressure of the naphthene component. For hydrocarbons normally boiling near 140° C, the mean interval between boiling points at 760 mm Hg and 215 mm Hg is about 42° C for paraffins, and about 43.2° C for naphthenes. The boiling points at the two pressures were determined for six hydrocarbons, 2,6-dimethylheptane, a nonanaphthene (boiling at 136.7° C), 1,2,4-trimethylcyclohexane, 4-methyloctane, 3-methyloctane, and 2-methyloctane. The boiling points at these pressures for the "2,3-dimethylheptane" were estimated from values for an impure sample.The boiling point, freezing point, density, refractive index, and critical solution temperature in aniline have been determined for the 1,2,4-trimethylcyclohexane and the isononane. Comparison of the properties of the 1,2,4-trimethylcyclohexane with those reported for its synthetic stereoisomers indicates that the petroleum hydrocarbon is either lei., 2,r.n • .4ci.-trimethylcyclohexane or 1, • .,2'r.n" 4 tr• n.-trimethylcyclohexane.

Isolation of 3-methylhexane, trans-1,2-dimethylcyclopentane, and trans-1,3-dimethylcyclopentane from petroleum

“…The fact that a change in pressure sometimes produces a favorable advantage in separation [37,38] prompted a study of the change in boiling point, between 760-and 215-mm pressure, of the naphthenic and paraffinic constituents in this fraction. The difference in boiling temperature between the two pressures was found to be 37.4 0 C for the paraffinic constituents and 38.5 0 C for the naphthenic constituents.…”

Highly Aromatic Petroleum Solvent Naphthas

“…Further, should occasion demand, the petroleum industry has the materials and processes for the separation and commercial production of a number of individual aromatics of any required degree of purity. PETROLEUM crudes are exceedingly complex mixtures, but much has been learned of their composition in recent years, Rossini and co-workers (5,10,11,18,27,28,29), Fenske et al (20,21), and others (8,6) have separated and identified over seventy hydrocarbons in the gas and gasoline boiling ranges. These include all the normal paraffins, a good number of the possible isoparaffins, the simple naphthenes, cyclopentane and cyclohexane, and several alkylated cyclopentanes and cyclohexanes.…”