Study On Hydrogenation Reaction Of Catalytic Cracking Diesel And Catalyst Grading Method

The key to the VI clean diesel production technology is to simultaneously reduce the polycyclic aromatic hydrocarbons and sulfur content and maintain the long-term stable operation of the catalyst.Many existing diesel fuels use catalyst combination technology.The development of a suitable catalyst and its compounding technology and process are inseparable from the deep understanding of the hydrodesulfurization kinetics and the conversion law of oil hydrogenation reaction in different reaction zones,so as to optimize the overall activity and stability of the catalyst.In this paper,catalytic cracking diesel oil was used as raw material to study the reaction law of reactants along the axial direction of the reactor,and the hydrogenation reaction characteristics of traditional Ni Mo catalyst and Co Mo catalyst.The catalyst grading optimization scheme was proposed to provide deep hydrotreating for diesel.Technical Support.The reaction law of the typical reactants in the catalytic cracking diesel oil along the axial direction of the reactor was studied,and the hydrogenation reaction kinetic model was established.The results show that the depth of hydrogenation of sulfides,nitrides and PAHs in the axial direction of the reactor is gradually increased.When passing through the first 20% of the bed,the removal rates of sulfides and nitrides are more than 50%,thick.The conversion of cycloaromatic hydrocarbons is greater than 55%;the hydrogenation of aromatic hydrocarbons to monocyclic aromatic hydrocarbons occurs primarily in the first 40% of the bed of the reactor,and the subsequent beds are primarily subjected to the excessive hydrogenation of PAHs to naphthenes.The characteristics of hydrogenation reaction of Ni Mo catalyst and Co Mo catalyst were studied by using catalytic cracking diesel form Qingdao Refinery as raw materials,and the influence of reaction conditions was investigated.The results show that the Ni Mo catalyst has higher hydrodesulfurization,denitrification and dearomatization properties,while the Co Mo catalyst has higher selectivity for hydrogenation of fused aromatic hydrocarbons to monocyclic aromatic hydrocarbons.In addition,as the reaction temperature increases or the space velocity decreases,the hydrogenation performance of the Ni Mo catalyst and the Co Mo catalyst gradually increases.The effects of three catalyst grading schemes of Co Mo//Ni Mo,Ni Mo//Co Mo and Ni Mo&Co Mo(fully mixed)on the hydrogenation performance of diesel were studied.It was found that the Co Mo//Ni Mo scheme has the highest hydrogenation performance of fused aromatic hydrocarbons and higher PAHs at the same time,Ni Mo&Co Mo solution has the highest hydrodesulfurization,denitrification performance and single aromatic ring cycloalkane hydrogenation selectivity,especially suitable for the low consumption hydrogen production of national VI clean diesel.