Studies have been made on the effectiveness of amine and phenolic inhibitors, including mixtures of them, in MS-8 mineral oil under conditions of high-temperature catalytic oxidation. It is found thatmineral oils containing simultaneously amine and phenolic inhibitors have oxidation rates that are determined only by the content of the amine inhibitor, while the phenolic inhibitor partially determines the secondary oxidation-destruction processes.It is usually considered that joint use of amine (A) and phenolic (P) antioxidants results in synergism of their properties and thus reduces the oxidation of the oil better than does separate use. Consequently, many lubricating oils contain antioxidants of both types, e.g., MS-8p mineral aviation oil and semisynthetic Petrim oil for gas-turbine engines (GTE). Many firms specializing in additives for lubricating oils such as the Swiss firm of Ciba provide ready-made packages of additives containing mixtures of amine and phenolic antioxidants (Irganox L64, Irganox L150, and so on).There is a study [1] of estimating the performance of various inhibitors under conditions of high-temperature catalytic oxidation (HCO) for hydrocarbon oils. Some interest attaches to the interaction of amine and phenolic antioxidants as regards the oxidation rate of mineral oil such as MS-8p under conditions of HCO, since those conditions most closely correspond to the actual working conditions of oils in GTE lubrication.As the oxidation rate we took the constant quantity obtained on testing these in the presence of a catalyst at high temperatures, which is virtually equal to the amount of O C C = > in the oxidation products formed in a fixed time interval.Lubricating oil specimens were oxidized as described in [2]. The contents of oxidation products were determined by IR spectroscopy from the integral absorption area in the region of wavelengths 1645 -1825 cm -1 in the differential spectrum obtained by subtracting the IR spectrum of the unoxidized oil from the IR spectrum of the oxidized oil. The performance of the oxidation inhibitors was estimated from the change in the amount of oxidation products formed in the oil after adding to the oil the inhibitor at various concentrations. The effectiveness coefficient K ef can be determined for each inhibitor concentration from

The efficacy of different inhibitors in mineral and synthetic base oils in conditions of high-temperature catalytic oxidation was investigated. It was found that all of the inhibitors investigated only slowed the oxidation reaction in mineral oils, while three of the inhibitors totally stopped the reaction in synthetic oil. The efficacy factors of the inhibitors for different base oils were determined. T h e s t a b i l i t y o f t h e p r o p e r t i e s o f l u b e o i l s d u r i n g u s e i n t h e r m a l l y s t r e s s e d g a s -t u r b i n e engines (GTE) used as drives for gas-pumping units (GPU) is determined by the thermooxidative stability of the oils in conditions of high-temperature catalytic oxidation (HCO), which is a function of the efficiency of the oxidation inhibitors they contain to a great degree. The theoretical principles of oxidation of hydrocarbons were laid out by N. N. Semenov, who created the theory of slow branched chain reactions, to explain the special features of these processes [1]. A number of later theoretical and experimental studies [2-5] elucidated the features of the effect of inhibitors on degenerative branched chain reactions. The efficacy of inhibitors was assessed in [5] with respect to the rate constants of the corresponding chemical reactions.In practice, the efficacy of inhibitors is determined as follows. An inhibitor is added to a model system (individual hydrocarbon or treated crude cut) and oxidation is conducted in standard conditions. The efficacy of the inhibitor is characterized by the absolute value of the induction period or its ratio to the induction period of some inhibitor used as the standard. It is necessary to take the oxidation kinetic curve to determine the induction period, but this is somewhat laborious.Evaluating the antioxidative efficacy E (%) of inhibitors in motor oils with the following equation was proposed in [6] 100, GOI GOI E GOI

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.

It is proved experimentally that structural factor is a measure of homogeneity or inhomogeneity of structural-group and fractional compositions of hydrocarbon oils, and the dynamics of its variation characterizes the initiation of secondary oxidative degradation processes. It is shown by IR-spectral analysis that carboxylic acid anhydrides are formed under conditions of high-temperature catalytic oxidation due to secondary processes. The nature of the secondary processes that occur in laboratory conditions and during use is identical.