Oxidation of mineral base oils of petroleum origin: The relationship between chemical composition, thickening, and composition of degradation products

Abstract

The aim of this study was to improve understanding of high-temperature oxidation of base oils used in automobile engine oil formulations. Various oils were investigated: oils from the Middle East and the North Sea, with high and low aromatic and sulphur contents respectively; a hydro-isomerised polyalphaolefin oil with no aromatic or sulphur content; and a hydrocracked oil of intermediate composition.The influence of the aromatic and sulphur content and composition of the oils on thermo-oxidative degradation is investigated. These compoundsgive base oils natural protection from oxidation, but, under severe oxidation conditions, in the presence of a catalyst such as iron, which is always present i n a n engine, they become precursors of deposits.The action of two types of additive, radical inhibitors and hydroperoxide decomposers, was studied through oxygen consumption and thin-film oxidation tests.The oxidation products were identified; these provide insight into the degradation processes of the compounds during oxidation. They show too the influence of these processes on the formation of oxidised volatile species, on the increase in viscosity of the oil, and on the formation of oxidised species of high molar mass which, as they condense, contribute to the formation of insoluble compounds and deposits. RIrefractive index SEM scanning electron microscopy TFOUT uv ultraviolet (spectrometry) ZDTP thin film oxygen uptake test zinc alkyldithiophosphate (2 methyl, 4 pentyl)

Proposal of an FTIR Methodology to Monitor Oxidation Level in Used Engine Oils: Effects of Thermal Degradation and Fuel Dilution

“…To avoid possible external factors affecting degradation such as the catalysis effect of metal components, this process was performed in a glass beaker and samples were collected every six hours. Temperature selected for the thermal bath was higher than those in other standard oxidation tests 15,[22][23][24] with the purpose of simulating strong thermal oxidation, similar to those situations where engine oils can rise to over 250-260°C in real operation, due to hot spots in the engine in contact with the lubricant, as in the first piston groove near the combustion chamber 25 .…”

“…In all lubricating systems and, perhaps even more, in internal combustion engines, organic compounds exposed to the presence of oxygen, high temperatures and pressures will partially oxidize into a large variety of by-products (react chemically with the oxygen), such as: ketones, esters, aldehydes, carbonates and carboxylic acids, that exhibit characteristic IR absorptions [3][4] . .…”

Investigation of Liquid-Phase Oxidation of Naphthene-Paraffinic Hydrocarbons of Balakhany Oil

“…It may be noted, in particular, the studies of the catalytic oxidation of petroleum pharaffinic fraction [1], oil fraction from the oil with low and high sulfur and aromatics content [2], naphthene and naphthene -paraffinic hydrocarbons of oil [3][4][5][6].…”

Discoloration of Hydrotreated Naphthenic Rubber Base Oil at High Temperature

“…Many articles have reported the influence of base oil composition on thermo-oxidative stability (Sharma et al, 2004;Suchada et al, 2004;Chawlar, 2003;Yoshida et al, 1998;Bergeron et al, 1999;Maleville et al, 1996;Stipanovic et al, 1996;Igarashi et al, 1992aIgarashi et al, , 1992bIgarashi et al, , 1995Batts and Zuhnan, 1991;Zuhnan and Batts, 1992;Michael and Murphy, 1991;; however, previous studies have generally defined thermo-oxidative stability in term of formed deposits under high temperature. There has been very little work to address the influence of base oil composition on discoloration.…”