To overcome the inhibition of aromatic compounds in low nitrogen light cycle oil (LCO) on its deep hydrodesulfurization (HDS), CoMo and NiMo sulfide catalysts supported on γ-alumina, alumina coated zeolite (ACZ) and TiO2 were investigated with the objective of achieving ultra-low sulfur through direct desulfurization route at relatively high temperature of 360 °C. Higher temperature certainly accelerated the HDS probably through direct desulfurization route over all the catalysts studied. It also resulted in reduction of total aromatics by about 50% leading to a significant cetane number improvement. Conventional Al2O3-supported CoMo and NiMo catalysts were quite active for HDS, hydrogenation and hydrogenolysis, but they could not meet the demand of deep HDS to achieve 10-15 ppm sulfur in hydrotreated products, even at higher reaction temperatures of 340-360 °C. Higher acidity alumina coated zeolite (ACZ)-supported catalysts exhibited higher HDS activity compared to Al2O3-supported catalysts. However, they also exhibited highest cracking activity and coke formation, which make them unsuitable for deep HDS at high temperatures. Low-acidic, non-polar (TiO2 and powdered activated carbon (PAC)) supported catalysts could achieve the deep HDS of LCO at 350-360 °C. The HDS activity of TiO2-based catalysts was better than Al2O3-supported catalysts and their cracking activity was significantly lower than Al2O3- and ACZ-supported catalysts. When the LCO was hydrotreated over CoMo/PAC at 350 °C, the product contains only 12 ppm sulfur. Hence, it is concluded that low-acidic, non-polar supports (such as TiO2 and PAC) are more suitable for CoMo and NiMo catalysts to achieve deep HDS of aromatic-rich feedstock such as LCO.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)
- Fuel Technology
- Energy Engineering and Power Technology