Preparation Of ZSM-5 Molecular Sieve Modified With Carbon And Nitrogen For Aromatization Of FCC Gasoline

FCC gasoline hydro-upgrading technology is an important means to produce clean gasoline blending components that meet the national VI standard.The commonly used ZSM-5molecular sieve catalyst has relatively high cracking activity in the initial stage of construction,and requires a long activity stable period.In addition,the strong acid sites on the outer surface of the molecular sieve inevitably lead to the side reaction of the alkylation of light aromatics and olefins,which increases the dry point of gasoline,thereby reducing the economics of FCC gasoline hydro-upgrading technology.This thesis designs and synthesizes a vulcanization impregnation solution with high vulcanization activity and moderate passivation function.By optimizing the key process parameters of the pretreatment process,a carbon nitride modified ZSM-5 molecular sieve is constructed,which preliminarily reveals the vulcanization-passivation of the catalyst The mechanism can provide guidance for the design of high-performance hydro-upgrading catalysts.Using active metal salt and nitrogen-containing vulcanizing agent to configure vulcanization impregnation solution,a carbon nitride modified ZSM-5 catalyst was prepared through a simple vulcanization process,and the effect of the amount of vulcanizing agent on the aromatization performance of the catalyst FCC gasoline was investigated.The research results show that the nitrogen-containing vulcanizing agent can generate hydrogen sulfide gas at high temperature to complete the sulfidation of the metal,and at the same time,it can generate the macromolecular compound of carbon nitride to complete the passivation of the catalyst,thereby optimizing the catalyst vulcanization-passivation process.After using a nitrogen-containing vulcanizing agent to vulcanize the passivation catalyst,the specific surface area and pore volume of the catalyst are reduced,and the acid strength is significantly reduced;the activity stability period of the catalyst is shortened,the olefin conversion rate is reduced,and the aromatization rate can reach 50%;When the nitrogen vulcanizing agent content is 1.6 times the metal sulfur requirement,the 1,3,5-triisopropylbenzene conversion rate is reduced to 1%,which realizes the passivation of the external surface acidity,thus reducing the generation of C9⁺aromatics and improving the second Toluene selectivity.The effect of temperature on the aromatization performance of the catalyst during the vulcanization-passivation process and its action law were further investigated.As the treatment temperature increases,the acid content and acid strength of the catalyst have a decreasing trend,and the number of B acid sites and L acid sites are both significant.cut back.When the calcination temperature is 300～400℃,the catalyst has a higher degree of sulfidization,and at the same time it shows a better aromatization rate,the acid content can be reduced by 48%,and the stable period of activity is shortened from 6 days for in-vessel vulcanization to 2 days,Which greatly improves the economy.The optimized sulfidation-passivation catalyst is used,and the reaction process conditions are optimized using Fushun Petrochemical FCC gasoline as raw material.The research results show that under the conditions of reaction temperature of 380°C,reaction pressure of 1.5 MPa,reaction space velocity of 1.5 h^-1,and hydrogen-to-oil volume ratio of 300:1,the aromatization rate of the catalyst can reach 51%,and the aromatic content can be increased 2wt%.