675.    DAZELEY, G. H., GALL, D., AND HALL, C. C.  Production of Olefin-Polymer Lubricating Oils of Satisfactory Oxidation Stability.  Jour. Inst. Petrol., vol. 34, 1948, pp. 647-653.

     Attempts have been made to increase the oxidation stability (as measured by the B.A.M. oxidation-number test) of olefin-polymer lubricating oils derived from the products of the Fischer-Tropsch synthesis.  A controlled hydrogenation of the oils in the presence of MoS₂ at 200° and 200 atm. pressure yields an oil with an oxidation number of 1.8.  The effect is the result of saturation by H₂ coupled with the formation of S-containing inhibitors and can be accurately reproduced by hydrogenation in the presence of Ni catalyst followed by heating with MoS₂ in the absence of H₂.  Treatment of the oil with AlCl₃ at 180° produces some improvement in oxidation stability, but the effect is small and is accompanied by a serious loss of oil.  Naphthalene added to the olefins before polymerization is chemically incorporated in the resulting oil and leads to an increase in oxidation stability, an increased conversion of the olefins to lubricating oil, and a decrease in the viscosity index of the oil.  About 15% napthalene is required to produce an oil with an oxidation number below 2.0; this causes a fall in viscosity index from 100 to a value in the range 80-85.