Chapter 4 Increasing LCO yield and quality in the FCC: cracking pathways analysis

Owing to automotive fuels market and environmental regulations, FCC unit operators are looking for a step increase of diesel yield and quality. In this manuscript, the conversion of vacuum gas oil (VGO) is discussed from the point of view of the relative cracking rates of VGO and LCO for the different class of components present in the feed. Although the cracking of paraffinic feeds has the potential for forming high quality diesel, they are not well suited for the operation since they give low yield of LCO with common FCC catalysts. Feeds containing one and two-ring molecules may be the best options for acceptable diesel yield and quality if the unit at moderate VGO conversion, through low temperature and recycle operation. Finally, feeds containing molecules with three and more rings should be avoided since the concentration of aromatic cores in the cracked diesel is hardly avoided, conducing to the worst light cycle oil (LCO) quality regards to cetane and particulate emissions.