Research Of Hydrocracking Catalytic Performance Of Hierarchical Y And Beta Zeolites

With the large number of consumption of petroleum resources,the phenomenon of the quality and deterioration of crude oil was continued to intensify.At the same time,the increasingly stringent environmental regulations make the effective use of petroleum products and clean production gradually attract attention.Hydrocracking technology,as an important means of light heavy oil,low quality oil refining and refining and chemical integration of the important means of processing,as a wide range of applications because of the flexible production equipments,raw materials adaptability,the high target product selectivity,high product quality and other advantages.The catalyst is the key of the hydrocracking technology.Hydrocracking catalyst is a typical dual-function catalyst,of which the zeolite provides the acid sites and the metal species are the active sites for the hydrogenation.The ringopening reaction of aromatics and naphthenes and the hydrocracking,dealkylation and isomerization reaction of n-alkane mainly occur on acid sites.In this paper,the Ni-Mo bimetallic component is used as the hydrogenation component of the hydrocracking catalyst,and hierarchical Y and Beta zeolites are used as the cracking active component of the hydrocracking catalyst.Y zeolite has excellent adsorption,acidity,ion exchange performance and selectivity due to its FAU topology,and exhibits excellent catalytic performance in various catalytic reactions.Although the Y zeolite has a relatively large supercage structure,the macromolecular reactants can not effectively diffuse in the pores due to their relatively small openings and narrow elongated channels,thus reducing the use ratio on the catalyst's inner surface.While,the product of the reaction is also difficult to diffuse out from the channel,which will easily leads to secondary cracking and resulting in coking.Beta zeolite has a cage-like structure,which is the only high-silica zeolite with a three-dimensional twelve-member pore structure.The ring-opening products are more likely to diffuse,reducing the probability of secondary cracking.The Beta catalyst shows advantages of good thermal stability,acid resistance and anti-coking.And the Beta catalysts have excellent hydroisomerization activity,good product quality,strong ability to resist nitrogen and low inactivation rate.The addition of Beta zeolite in the hydrocracking reaction promotes the occurrence of ring-opening reactions.The middle distillate of hydrocracking reaction,in which the catalyst prepared with Beta zeolite,is selectively increased and the freezing point of diesel is reduced.Hierarchical Beta zeolite in the hydrocracking reaction can exhibit better cracking performance,higher selectivity of gasoline and middle distillate,thus Beta zeolite is widely used in industry.Beta and Y zeolites have the advantages of high cracking activity,low reaction temperature and good stability because of their inherent microporous structure and suitable acidity as the carrier and acidic center of hydrocracking catalyst.However,the pore size of the zeolite limits the proximity of macromolecular hydrocarbons and the diffusion of molecules in the pores,leading to excessive cracking and coking.In this study,Beta and Y zeolites with hierarchical pore structure were used to replace the microporous zeolite as hydrocracking catalysts to improve the accessibility and diffusion of zeolite due to the introduction of secondary mesopores.Three kinds of hierarchical zeolite Y(prepared by Fushun Petrochemical Research Institute and use the post-treatment method)and two kinds of Beta zeolites with different Si/Al ratios(synthesized by our group).Five kinds of hydrocracking catalyst were prepared by zeolites mixed with alumina,nickel nitrate and molybdenum oxide.The catalytic cracking diesel was used as raw material and the microreactor was used in the laboratory to evaluate the catalysts.And the effect of temperature,volume space velocity and hydrogen / oil ratio on the hydrocracking performance of the catalyst were also investigated.The results showed that TSY-B and TSY-C zeolites were modified by posttreatment of TSY-A zeolite,and their BET specific surface area,external surface area,acidity and acid strength of modified Y zeolite were obviously improved.Although the crystallinity of the modified TSY-B and TSY-C zeolites decreased slightly,the mesoporous structure could be introduced into the zeolite crystal to obtain the hierarchical pores with the maintaining of the microporous structures.Two kinds of Beta zeolites of ?-1 and ?-2 with SiO2 / Al2O3 of 25.5 and 15.7 were prepared by soft template method.The pore size distribution was relatively concentrated with the relatively large average pore size and pore volume.The specific surface area of ?-2 zeolite reached 419 m2/ g with higher total acid quantity,B acid quantity and acid strength.By comparing the hydrocracking catalytic results of hydrocracking catalysts made from different types of zeolites.The results show that the BET surface area,external surface area,acid quantity and acid strength of the zeolite are related to the hydrocracking performance.The pore size and pore volume of the zeolite also have influence on the hydrocracking performance.The effect of hydrocracking on the hydrocracking performance was investigated under different experimental parameters including the temperature,volume space velocity and H2/oil ratio.The catalytic results showed that with the increase of temperature,the hydrogenation rate and the ring-opening rate of polycyclic aromatic hydrocarbons reaches the highest value at 340?.With the increase of volume space velocity,the hydrogenation rate and the ring-opening rate of polycyclic aromatic hydrocarbons are decreased.With the increase of the volume ratio of hydrogen and oil,the hydrogenation rate and the ring-opening rate of polycyclic aromatic hydrocarbons are increased.