Study On The Catalyst And Process For Hydrogenation Of Coker Naphtha

Coker naphtha can be used as raw material for ethylene steam cracking and catalytic reforming after hydrotreating.However,the content of conjugated diene in the coker naphtha is high,and the conjugated diene is prone to coking during the Hydrogenation process,which reduces the operation cycle of the unit.Therefore,this paper studied the effect of Mo content on the performance of Ni/γ-Al₂O₃ catalyst for pre-hydrogenation dediene reaction and investigated the effect of NiMoP,CoMoP catalyst grading on the olefin saturation,desulfurization,and denitrification reaction of coker naphtha.Finally,the coker naphtha hydrogenation process parameters were optimized on the pilot unit,providing guidance for the long-term operation of the hydrotreating unit of coker naphtha.The effect of Mo content on the selective hydrogenation performance of coker naphtha was investigated.It was found that with the increase of Mo content,the amount of medium-strong acid decreased,and the interaction force between the metal Ni and the support decreased.The evaluation results showed that with the increase of Mo content,the conjugated diene removal rate gradually increased,and the selective hydrogenation performance of conjugated diene increased at first and then decreased.When the Mo content was 6 wt%,the catalyst had the highest selective hydrogenation performance of conjugated diene.The conjugated diene removal rate was 81%,and the olefin saturation was 7.2%.The optimal reaction conditions were as followed:the reaction temperature was 150℃,the pressure was 3 MPa,the space velocity was 3 h^-1,the hydrogen-oil ratio was 50(V_H2/V_oil).The effect of CoMoP and NiMoP catalyst grading in the coker naphtah deep hydrotreating performance was investigated.It was found that the olefin saturation performance of the NiMoP catalyst was better than CoMoP catalyst,but the desulfurization performance was not better.The desulfurization effect of the upper bed layer filled with NiMoP catalyst and the lower bed layer filled with CoMoP catalyst（NiMoP//CoMoP）was better than the opposite gradation method（CoMoP//NiMoP）,proving that there was a synergistic effect between the catalysts and improving the reaction activity of the catalyst.But the order of grading of the catalyst limited the synergistic effect.Furthermore,the CoMoP and NiMoP catalysts were uniformly mixed to achieve a high degree of synergy between the two catalysts,thereby showing the best hydrodesulfurization,hydrodenitrogenation,and olefin saturation performance.Finally,the coker naphtha was used to pre-hydrogen-deep hydrotreating double reactor series process,and the reaction process conditions were optimized with Qingdao refining coker naphtha as the raw material.The results showed that the pre-hydrogenation conditions were as followed:the reaction temperature was 150℃,the pressure was 3 MPa,the space velocity was3 h^-1,hydrogen-oil ratio was 50(V_H2/V_oil),the product diene value was reduced to 1.91 g I/100g,the conjugated diene removal rate was 81%,the olefin saturation was less than 15%.Hydrotreating conditions were as followed:the reaction temperature was 300℃,the pressure was 3 MPa,the space velocity was 1.5 h^-1,the hydrogen-oil ratio was 400(V_H2/V_oil).The bromine value of product was 0.04 g Br/100g,the sulfur content was 8.5μg·g^-1,and the nitride content was 0.4μg·g^-1.