Study On Composition And Structures Of The FCC Diesel In Hydrotreating Process

With crude oil is becoming more and more worse and the upgrading of clean fuel quality standards,which has become a huge challenge to the production of hydrotreated LCO.We used FCC diesels as raw materials to investigate the composition and structures of the FCC diesel in hydrotreating process.Established the relationships among the density,cetane number,hydrogen chemical consumption and hydrocarbon compositions of FCC diesel.Explored the knietic models of hydrogenation desulfurization,denitrification and dearomatization.Besides,on the basis of studying on the structures and changes of each narrow fraction of Qingdao FCCdiesel and its products,a two-stage hydrotreating process of FCC diesel was designed.It will provide theoretical guidance for inexpensive and efficient use of FCC diesel.We used FDS-1A as catalyst and Qingdao diesel as raw material to investigate the effect of process parameters on hydrotreating process.The results showed that raising temperature and pressure,reducing space velocity and increasing hydrogen/oil ratio are methods to promote deep hydrotreating.As a result,the density of product was reduced and saturation rate of sulfides,nitrides,aromatics were increased.Among all these factors,hydrogen/oil ratio had little effect on hydrogenation reaction.On this basis,superior optimized principles were put forward.It makes sense for the optimization of hydrogenation process and reactor.The optimal reaction conditions are as follows:the reaction temperature is 350³60?,the reaction pressure is 8⁹ MPa,the hydrogen/oil ratio is 600⁷00,the space velocity is 0.8¹.2h^-1.The properties of the hydrotreated LCO from FCC diesel catalytic hydrotreating under a series of reaction conditions were analyzed.The established correlation equations could provide evidence for predicting the properties of the products and reducing consumption.Based on the former data,the knietic models of FCC diesel were established.Kinetics research data suggested that hydrogenation desulfurization can be divided into two parts.When the space velocity was higher than 2.5 h^-1,the knietic model of HDS was first-order knietic model,the apparent activation energy in the first stage was 39.20 kJ/mol.When the space velocity was lower than 2.5 h^-1,the n-order kinetic model was established.It had been corrected by space velocity,hydrogen/oil ratio and pressure and their index had been obtained.The apparent activation energy in the second stage was 135.68 kJ/mol.The HDN reaction knietic parameter were determined by a first-order reaction model.The apparent activation energy was 103.19 kJ/mol.The HDA experimental data were fitted by an n-order kinetic model.The apparent activation energy was 118.35 kJ/mol.The experimental data were in agreement with the calculated results of model.The result of exploring the structures and changes of each narrow fraction of Qingdao FCC diesel and its products showed that lots of sulfides and nitrides as well as aromatics in each narrow fraction of the products were removed.The higher reaction temperature was,the more obvious the change was.The mass yields of the products were normally distributed.The mass yields of the light composition in the products were higher than the raw material.Nitrides were mainly enriched in heavy fractions compared with sulfides.The fraction of the boiling point exceeding 325?in raw material had a large quantity of sulfides,nitrides and aromatics.It is difficult to process to meet the standard.On this basis,an effective lowcost processing technology were raised.