Introduction of the legal requirement for <10-ppm sulfur in diesel fuels is intended to help reduce diesel exhaust emissions, such as nitrogen oxide and particulate matter, as well as CO₂ emissions depending on the improvement of mileage.
Development of highly active HDS catalysts for five years has resulted in new CoMo HDS catalysts for the production of ultra-low sulfur diesel fuels. The developed catalyst, C-606A, has three times higher HDS activity compared with the conventional CoMoP/Al₂O₃ catalyst, which enables <10-ppm sulfur content in products using a commercial diesel hydrotreater designed to produce 500-ppm sulfur diesel fuels. The new catalysts were prepared by coimpregnation using an aqueous solution containing Co, Mo, orthophosphoric acid and carboxylic acid on a support consisting of HY-Al₂O₃. After impregnation, these catalysts were air-dried only without calcination. The new catalyst preparation method could increase the formation of the active phase, Co-Mo-S phase, and provide more highly active Co-Mo-S Type II, which is located at the edges of the MoS₂ multi-layers.
Based on the environmental and economical advantages, Cosmo Oil Co., Ltd. has utilized C-606A in all diesel hydrotreaters at its refineries. High catalyst performance has been demonstrated for each application. This HDS catalyst technology is expected to be introduced worldwide to encourage energy conservation, minimum capital investment, and reduction of CO₂ emissions.