Adsorptive pretreatment of light cycle oil and its effect on subsequent hydrodesulfurization

Adsorptive denitrogenation of light cycle oil (LCO) over the carbon-based adsorbents was conducted in both batch and flow adsorption systems. The effects of the physical and chemical properties of the carbon materials as well as the adsorption conditions on the adsorption performance were examined. It was found that some activated carbons could efficiently remove the nitrogen compounds from LCO. Oxidative modification of the activated carbons greatly enhanced the adsorption capacity and selectivity for nitrogen compounds, but not for the coexisting sulfur compounds. The regeneration of the spent activated carbon by solvent washing was also studied. The results indicate that the majority of the capacity of the adsorbents can be recovered by washing the spent adsorbents with toluene. In addition, the effect of the pre-denitrogenation on the performance of the subsequent HDS was examined. It was confirmed that the pretreatment of LCO by adsorption over the activated carbon improved the HDS performance significantly, especially for removing the refractory sulfur compounds that have one or two alkyl groups at the 4- and/or 6-positions of dibenzothiophenes, due to the substantial pre-removal of the coexisting carbazole compounds from LCO.