Special features of use of phenolic inhibitors in mineral oils

Abstract

The effectiveness (performance) of various phenolic inhibitors in medium-viscosity base mineral oils under high-temperature catalytic oxidation conditions has been studied. It has been proved that all the studied base oils possess differing catalytic activity whose quantitative value determines the effectiveness of the phenolic inhibitors. Under specific conditions, in the presence of inhibitors, oxidation of the oil increases rather than decreases.Substituted phenols are classic inhibitors, which are being used for a long time in compositions of various types of mineral hydrocarbon lubricating oils. Several investigators have indicated high effectiveness of phenolicIn [3], data were reported on the investigations of the effectiveness (performance) of various oxidation inhibitors, including phenolic, in hydrocarbon base oils under conditions of high-temperature catalytic oxidation (HTCO) in a Papok-R apparatus. The oxidation of the oils having varying inhibitor contents was carried out in activated crucibles at 180°C for 3 h. The crucibles were activated by cleaning their inner surfaces with finegrained emery paper in order to remove lacquered or other depositions (incrustations).The effectiveness of oxidation inhibitors is assessed from the change in the oil of the amount C ox of the oxidation products formed after addition of the inhibitor. The effectiveness coefficient K ef (rel. unit) was determined by the formula ox ox ox efwhere ox C′ and ox C ′ ′ are the amounts of oxidation products formed in the oil without and with the inhibitor.The content of oxidation products were determined from the integral absorption area in the wavelength region 1645-1825 cm -1 on the differential IR spectrum obtained by abstracting the IR spectrum of the unoxidized oil from the IR spectrum of the oxidized oil. A Bruker-made Tensor-27 Fourier IR spectrometer was used to record and process the spectra. The OPUS program was used to process the spectra.