Transformer oils prepared from the vacuum distillates of Egyptian crude paraffinic petroleum

Vacuum gas oil and spindle oil obtained from the vacuum distillation of paraffinic crude oil from the Western Desert region of Egypt were utilized for transformer oils production. The vacuum gas oil, spindle oil and blends therefrom containing different percentages of these oils and were subjected to aromatic extraction, dewaxing catalytic hydrogenation processes. The aromatic extraction process used N-methyl-2-pyrrolidone as solvent, for a feed ratio of 0.7:1 (wt/wt) at an extraction temperature of 55 °C, while in the dewaxing process the wax is removed by chilling the raffinate at − 42 °C using MEK-toluene (60:40,vol/vol). The hydrofinishing process was achieved in a pilot plant using NiO–MoO3/Al2O3 catalyst. These refining processes improved the viscosity indices and the pour points of the resulting oils and removed most of the polar impurities. It was found that, the transformer oil formulated from 7:3 b.w. vacuum gas oil:spindle oil respectively meets the IEC 60296-2003 standard specifications requirements. Its sulfur content is very low and non-corrosive. The gassing tendency is also low due to its low aromatic content. Further, the electrical properties which are significant for transformer oils fulfill the standard specifications as a result of the low water content and polar contaminants. Moreover, addition of 2,4-dimethyl-6-tertiary butyl phenol increases the oxidation stability of the produced oil, by acting as a free radical inhibitor.