Thermal degradation behavior of zinc dialkyldithiophosphate in presence of catalyst and detergents in neutral oil

Abstract

Thermal decomposition of zinc dialkyldithiophosphate (ZDDP) is examined in presence of a noble catalyst iron fluoride (FeF 3 ), using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The influence of heating rate, isothermal holding period and catalyst concentration was verified. The role of FeF 3 on ZDDP decomposition mechanism was analyzed using 31 P-NMR. This study also focused on the effect of FeF 3 on ZDDP decomposition in combination with detergents (Ca-sulfonate, Mg-sulfonate and Cophenates). The decomposition temperature of ZDDP is reduced significantly in presence of FeF 3 . Thanks to FeF 3 , the ZDDP decomposition temperature is lower even in the presence of the detergents, while the detergents greatly retard the ZDDP decomposition. The 31 P-NMR studies confirmed a faster decomposition and a different decomposition mechanism of ZDDP in presence of FeF 3 .

Synthesis of Fluorinated ZDDP Compounds

“…The series of peaks at *82-83 and *43 ppm are found to be stronger in intensity in presence of FeF 3 than when ZDDP is baked alone indicating that the decomposition of ZDDP is more rapid in presence of FeF 3 . Earlier DSC studies have shown that the decomposition of ZDDP is accelerated in presence of FeF 3 by at least 10-15% [9]. Compounds of type (RO) 2 P(S)O -(*46 ppm) are not formed here unlike in case of baked ZDDP; however, the other small impurity peaks still remain unchanged.…”

“…The temperatures reached in an engine are usually in the range of 120-200°C. In this study, the DSC data indicated that both in the case of ZDDP as well as in a mixture of ZDDP and FeF 3 , the decomposition commences at a temperature between 160 and 170°C at heating rates of 0.5°C/min [9]. A temperature of 150°C was chosen for all the degradation experiments.…”

“…All decomposition experiments were conducted in hermitically sealed containers in an environment of flowing nitrogen to minimize outgassing of H 2 S. The DSC plots are shown in the temperature range of 150-250°C, the range at which ZDDP decomposes. The decomposition of ZDDP is endothermic and was found to depend significantly upon heating rates [9]. As the heating rate was decreased, the peaks were shifted to lower temperatures.…”

“…The approach adopted involves thermal degradation of ZDDP in which temperature solely triggers chemical reactions and this route as opposed to a tribological one helps us understand the underlying mechanism in terms of the products that are formed in the presence and absence of FeF 3 . This approach has been used by several investigators in the past [8][9][10][11][12][13][14][15][16][17][18]. 31 P NMR and 19 F NMR have been principally used to identify these products.…”

The tribological performance of a long chain alkyl phenylboric ammonium derivative and its interaction with ZDDP

“…It can be seen that DBBM begins to decompose around 150 C, which is similar to ZDDP. 23 It has been reported that the lower the decomposition temperature, the higher the reactivity of the additive to react with a metal surface to form a protective film. From this point of view, it can be considered that the synthesized additive is suitable for using as AW additive.…”