Effect of Wax Content in Hydrocracker Unconverted Oil on Viscosity Index and Yield of Lubricant Base Oil 150N

Hydroprocessing has become the main technology for the production of API Group II and III base oils. One of the key properties is viscosity index for Group II and III base oils. The effect of wax content in hydrocracker unconverted oil on viscosity index and yield was studied in a 400 kton/year hydroisomerization dewaxing plant at a total pressure of 15 MPa, a feed rate of 38 ton/hour, and a gas to oil ratio of 710 Nm3(H2)/m3(feed). The contribution of wax hydroisomerization to the viscosity index of the main product 150N base oil increases with the wax content in the 11-19% range and reaches a constant value of 6 VI units rather than continuously rising with the wax content. The 150N yield decreases about 1.3%, when the wax content increases by 1%. This is related to a higher dewaxing temperature required at increased wax contents in order to keep the low pour point of 150N, which results in more multi-branched compounds with a low viscosity index in the base oils and more light hydrocracking products.