Chinese refiners have built a lot of capacity to produce API Group II base stocks, but the viscosity indices of the oils from those plants are largely lower than blenders want. This is a major reason that the country imports large volumes of base stocks, according to speakers at an industry summit in Xiamen last month, who added that the situation is unlikely to change in the next few years.
Through upgrades and new construction, Chinese refiners have added large amounts of Group II capacity in recent years – to the point that Group II now accounts for just over half (4.3 million metric tons per year) of the countrys 8.5 million t/y of base oil capacity. But the viscosity indices of those oils are largely less than those demanded in China, especially as the market trends toward higher-quality finished products. Group II base stocks by definition contain at least 90 percent saturates, no more than 0.3 percent of sulfur content, and have viscosity index of between 80 and 120.