Oxidation of Lubricating Oils. Factors Controlling Oxidation Stability

Abstract

A study of the oxygen absorption characteristics and the nature of the products obtained from oils oxidizing under controlled conditions has permitted the evaluation of a number of factors involved in lubricating oil deterioration.Investigation of selected fractions of a distillate stock has shown considerable variations in reactivity toward oxygen.The rate of oxygen absorption approximately doubles for each 100 C. temperature increase over the interval 140°to 180°C ., provided it is not limited by physical factors. The presence or absence of water vapor in the oxidizing atmosphere has little effect on the oxidation of one type of oil.The oxidation of certain oils can be reduced greatly by adding natural or synthetic inhibitors.

Liquid Phase Hydrocarbon Oxidation

“…This higher stability of the over-all neutral corresponds to the results obtained in a previous study (8) with portions separated by distillation and extraction from a light mineral oil.…”

Oxidation of Lubricating Oils.

“…Thus, formic, acetic, and propionic acids would be expected in order of decreasing concentration. Fenske et al (19,20) actually found this to be the case in an analysis of the volatile products resulting from the oxidation of a lubricating oil at temperatures of 130-180°C. George, Rideal, and Robertson (22) found that Gis and C26 paraffins and alkylbenzenes are oxidized at 100-120°C.…”

“…Similar results have been reported by Domte (14) and by Denison (13) regarding the oxidation of white oils. Several investigators have shown that water is one of the principal oxidation products of lubricating oils (14,19,31,32). Fenske and coworkers (19) report that water can account for as much as 44 to 70 per cent of the oxygen absorbed by an oil.…”

Lubricating Oil Oxidation and Stabilisation

“…Many factors, which include refining conditions, viscosity index (VI), sulphur content, clay treatment, catalysis by metals and hydrocarbon struc ture, were all investigated in the 1940s and led to the development of relationships between mineral oil composition and oxidisability [7][8][9][10][11][12][13]. Solvent extraction removes aromatic components and improves the VI and the colour of oils and reduces the tendency to form sludge.…”