Chemical Transformations of Components of Raffinates from Selective Refining of Sulfurous Crude Oils in the Process of Hydrotreating in Production of Base Oils of API Group II

Variation of the chemical composition and properties of raffinates from selective refining of sulfurous crude oils in the course of hydrofining in the presence of a zinc-modified catalyst was studied. In hydrofining of the raffinate obtained at the N-methylpyrrolidone: distillate weight ratio of 1.2: 1 at 360°C, “light” aromatic hydrocarbons (n D 20 = 1.4900–1.5100) start to undergo hydrogenation with the formation of high-index paraffin-naphthene hydrocarbons. At the same temperature, tetra-, penta-, and hexacyclic naphthenes undergo active hydrodecyclization with the formation of high-index mono-, bi-, and tricyclic structures. From the hydrogenizates obtained at 360 and 380°C, after dewaxing, base oil samples were obtained with the sulfur content of 0.020–0.024 wt %, content of saturated compounds of 91.2–91.4 wt %, and viscosity index of 88–91, meeting the requirements of API group II. There are prospects for further improving the quality of the hydrogenizates by varying the hydrofining process parameters (decreasing the space velocity to 0.5–0.75 h−1, increasing the hydrogen circulation factor).