Abstract: Pre-qualification API II+ base oil was produced from CNOOC Xijiang VGO#3 and VGO#4 using CLG high pressure all-hydroprocessing technologies and catalysts. Test results indicate that the all- hydroprocessing technology can successfully produce base oil to meet the API Ⅱ+ 4 cSt and API Ⅱ+ 8 cSt specifications. The two products have viscosity index of more than 118, cloud point of lower than -10 ℃, and pour point of lower than -28 ℃. These two products are excellent base oil for engine oil and industrial oilformulation.Hydrocracking and dewaxing reaction temperatures are the most important factors on base oil yield, kinematic viscosity, viscosity index, pour point, cloud point and other significant performance. When reaction temperature exceeds a certain value, product yield decreases rapidly. Under an appropriate reaction temperature, 4cSt oil yield of VGO #3 is about 64%,8cSt oil yield of VGO #4 is about 54%.

Key words: Xijiang crude, hydroprocess, isodewaxing, base oil