INHIBITING ABILITIES OF HYDROAROMATICS AGAINST DETERIORATION OF HYDROCARBON PRODUCTS .1. INHIBITION OF THERMAL DETERIORATION AND ITS APPLICATION TO OIL PRODUCTS

It was found that the hydrogen donating properties of hydroaromatics can act as deterioration inhibitors for hydrocarbon products. The inhibiting abilities of hydroaromatics [tetralin and 1,2,3,4,5,6,7,8-octahydrophenanthrene (OHP)] against thermal deterioration of oil (SAE-50) were examined; the addition of the hydroaromatics (5 wt.%) was very effective in inhibiting such deterioration, and the hydrogen donating abilities of hydroaromatics were shown to be closely related to the deterioration inhibiting effects. The relation between the inhibiting ability and oxygen partial pressure was examined by using oxygen-nitrogen mixtures with several mixing ratios. It was found that the inhibiting abilities of hydroaromatics (both tetralin and OHP) were noticeably decreased by raising the oxygen partial pressure; however, their effectiveness remained even at higher oxygen partial pressure than expected. It was also clear that the formation of naphthalene, tetrahydrophenanthrene and phenanthrene was increased by raising the oxygen partial pressure and with increasing hydrogen donation from the hydroaromatics. A synthetic additive containing various hydroaromatics produced by the hydrogenation of decrystallized anthracene oil obtained from a coal tar fraction was added as an inhibitor to electric discharge machining oil, and it was observed that carbon deposits on the electrode were markedly reduced. It was also confirmed that the additive was an effective inhibitor for the oxidation of grease.