Impact of wash oil composition on degradation: a comparative analysis of "light" and "heavy" oils

Abstract

This study examines the degradation of wash oils in benzene units by analyzing fresh and operating oils from different manufacturers. Gas chromatography/mass spectrometry and Brookfield viscometry were used to assess composition and viscosity. During operation, heavy oil (HO) becomes less volatile, and light oil (LO) becomes slightly more volatile. HO's viscosity increases by 1.25 times, while LO has a higher alkyl derivative concentration (48 wt.% vs. 44 wt.% for HO). LO is enriched with naphthalene and indene, while HO loses certain methylnaphthalenes and shows an increase in dibenzofuran, fluorene, anthracene, and phenanthrene. LO's oxidation products are oxidized alkyl groups, while HO shows oxidized non-substituted hydrocarbons. These findings help guide the selection of oil for current operating conditions, with LO being more resistant to degradation than HO.