The relationship between oxidation stability and antioxidant depletion in turbine oils formulated with Groups II, III and IV base stocks

Abstract

Using simple turbine oil formulations, we studied the effects of different antioxidant systems on oxidation behaviour. Fourier transform infrared was used as a sensitive probe to monitor the depletion of different antioxidant types present in turbine oils based on Group II, III and IV base stocks. It was found that the depletion of alkylated diphenylamine antioxidants from turbine oil systems is generally slower when hindered phenolics are present in the formulation. Furthermore, the type of hindered phenolic used in the formulation is critical for preserving this amine activity, with the bis-phenolic 4,4-methylenebis(2,6-di-tert-butylphenol) showing superior performance over a phenolic ester of approximately the same molecular weight. This effect was explained by the higher hindered phenolic activity of the bis-phenolic relative to the phenolic ester. The ability of the bis-phenolic to preserve or protect the amine antioxidant, combined with its higher hindered phenolic activity, was shown to improve the oxidation resistance of turbine oils. The results also showed a surprisingly high oxidation stability for turbine oils formulated with Group III base stock, with the oxidation resistance of the Group III systems exceeding that of the equivalent Group II and Group IV systems.

Molecular Science of Lubricant Additives

“…Fine particles of calcium carbonate could be dispersed in hydrocarbons with the aid of surfactant. This releases the alkali salt upon formation of Different types of AOs are frequently used together in a lubricant [81]. Since tribological processes usually induce different causes of autoxidation, different AO complement each other to prevent the ageing processes happening simultaneously.…”

“…Different types of AOs are frequently used together in a lubricant [81]. Since tribological processes usually induce different causes of autoxidation, different AO complement each other to prevent the ageing processes happening simultaneously.…”

Utilising Fenton reagent to simulate oxidation processes in turbine oil

“…According to the mechanism of oxidative degradation of the lubricant antioxidants alkylated diphenylamine, oxidation products of dialkylanilines in 80–120 C have a conjugate structures similar to indophenol (Reaction 1). In acidic condition, the oxidation product from alkylated diphenylamine presents a blue or blue‐violet colour. The acidic condition is related to the level and chemical structure of additives, such as antirust alkenyl succinic acid, as well as, the oxidation products from hydrocarbons, such as carboxylic acid.…”

Monitoring of oxidation behavior in mineral base oil additized with biomass derived antioxidants using FT-IR spectroscopy

“…While the peaks in the same wave number range are distinct in case of the plain MBO sample aer oxidation which may be due to high concentration of carbonyl compounds and olens formed as oxidized products. 45 The FTIR spectra of the RHE-and SDE-additized MBO samples aer oxidation are given in Fig. 4(c and d), respectively.…”