Chemical Structure of Lubricating Oils

Abstract

This report presents a study of the structure of lubricating oils on the basis of synthetical rather than analytical work. Several series of hydrocarbons consisting of alkyl derivatives of benzene, naphthalene, and diphenyl have been prepared to determine the effect of chemical structure on their chemical and physical properties. A relationship is established for these hydrocarbons between their viscosity characteristics and chemical structure. This study includes such structural factors as length, unsaturation, and branching of side chains.The effects on viscosity of other characteristics such as cyclization, reduction of aromatic to hydroaromatic rings, multiplicity of side chains, and allocation of the latter in the nucleus, are also considered.© •IHE interest of chemists in the composition 1 of petroleum oils has remained unabated

Relationships between physical properties and chemical constitution of lubricating oil fractions

“…The physical properties of the synthetic hydrocarbons used in this comparison are principally those reported by Mikeska [1]. In addition, values for 16-butylhentriacontane from Suida and Planckh [6], dimethyl-9,12-di-n-hexyl-9,1O-octadecane from Lerer [7], 1,I-dicyclohexylhexadecane and l-cyclohexyl-2-hexahydro benzylheptadecane from Landa and Cech [8] have been used in the charts of specific refraction and density.…”

“…Also used in the density chart is · the value for 1-phenyl-2-benzylheptadecane from Landa and Cech [8]. In addition to Mikeska's [1] values, the viscosity and viscosity-index charts contain values for 1,I-dicyclohexylhexadecane and l-cyclohexyl-2-hexahydrobenzylheptadecane. The aniline-point chart contains values determined in this laboratory for two normal paraffins.…”

“…Yet, in attempting to relate the chemical constitution and the physical properties, it is extremely important to know how much of this deficiency is attributable to naphthene rings and how much to aromatic rings. For example, as shown by the work of Mikeska [1], an aromatic with one ring and a long paraffin side chain may be expected to have a much lower viscosity and a lower temperature coefficient of viscosity (higher viscosity index) than a four-ring naphthene with the same number of carbon atoms. Yet both these compounds are represented by the same empirical formula, CnH 2n -6• In the following attempt to correlate physical properties and constitution, it was consequently of importance to decide how much of the change in empirical formula was due to a change in aromatic concentration or unsaturation, and how much to a separation into fractions containing, respectively, more or fewer naphthene rings.…”

“…The literature dealing with the constitution of the lubricant fraction of petroleum has recently been reviewed by Mikeska [1] 3 and Rossini [2]. An examination of these and other articles shows a considerable divergence of opinion as to what types of hydrocarbons are present and what relationships exist between chemical constitution and physical properties.…”

“…Recently a large number of hydrocarbons of high molecular weight have been synthesized, principally by Mikeska [1], and many of their physical properties determined, so that a direct comparison of their properties with those of petroleum fractions is now possible.…”