Response to different oxidation inhibitors for industrial lube base stocks

The response to antioxidants of different types (aminic, phenolic and sulphur-based) has been evaluated for three base stocks intended for industrial lube production: a paraffinic solvent neutral, a hydrotreated naphthenic, and a naphthenic technical white oil. Furthermore, three different oxidation test methods were used: IP 280, DSC (in-house), and ASTM D 1934 (open beaker). A statistical experimental design was used to evaluate the effects of the different inhibitors. For the naphthenic base stocks tested, the higher degree of refining, the better response to oxidation inhibitors. Since the test methods differ in severity, different inhibitors will be those giving the best effects in different tests. Severe tests require peroxide-destroying inhibitors, while aminic or phenolic inhibitors show effects in milder tests. High oxidation stability can be achieved for various types of base stocks, naphthenic as well as paraffinic, if the right inhibitor system is chosen.