PCA reduction in naphthenic base oils by optimizing HDT conditions

Abstract

Polycyclic Aromatics (PCA) are aromatic hydrocarbons and related sulphur and nitrogen compounds, containing three or more fused aromatic rings, which are considered as toxic compounds. PCA control is a complex task because the Base Oil production involves different processes with many variables such as pressure, temperature, feedstock quality, catalyst, etc. This study focuses on controlling the hydrotreating temperature as main variable in the reduction of PCA in Naphthenic Bases. Two Naphthenic distillate fractions taken from an industrial plant were hydrotreated in pilot plant at different temperatures. The results show that PCA are reduced as hydrotreating temperature increases; however there is an optimum temperature above it, the thermodynamic equilibrium of aromatic hydrogenation reverses, increasing as a result, the PCA content. These results were implemented in the industrial Unit by installing a hydrogen quench between the two industrial reactors to guarantee that the profile of temperature, due to exothermic character of some reactions, be always in the optimun operating range.