Study On Preparation Of Pt-loaded Catalysts And Evaluation Of Hydroisomerization On F-T Light N-alkanes

As the core of the clean utilization of coal resources,the products of the Fischer-Tropsch synthesis reaction are mostly linear alkanes.The isomerization of lower alkanes can be used to produce high-octane gasoline with low sulfur content and no unsaturated hydrocarbons,which is a good quality clean energy.The currently used industrial hydroisomerization catalysts are metal bifunctional catalysts in which Pt or other transition metals are supported on alumina or molecular sieve supports.Micro-mesoporous composite molecular sieve combines the excellent mass transfer performance of mesoporous materials with the strong acidity and high hydrothermal stability of microporous molecular sieves.The introduction of mesopores can improve the mass transfer performance of traditional microporous catalysts,and can be designed by changing the synthesis conditions.A composite material having the desired pore properties and acid distribution is prepared to obtain a catalyst having good properties.In order to prepare Pt-based catalyst carrier with high isomerization performance,this paper explored the molecular sieve catalyst for preparing composite pore structure by micro-mesoporous composite route,and discussed the effect of micro-mesoporous composite ratio on the pore structure and acid properties of MOR molecular sieve.The post-treatment-cation exchange route can efficiently introduce MCM-41 molecular sieve into the MOR molecular sieve system;when the micro-mesoporous material doping ratio is the same,the mechanical mixture exhibits a relatively significant pore effect.The MOR/MCM-41 micro-mesoporous composites were prepared by in-situ recrystallization method.The composites were analyzed and characterized.The results show that the in-situ recrystallization method reduces the MOR molecular sieve by alkali-pretreatment.The degree of grain agglomeration increases the treatment concentration to make the specific surface area increase more significant.Micro-composite is mainly through the introduction of mesoporous structure,which regulates the acidity and pore structure parameters of the sample.By modification,the specific surface area and pore volume of the composite system increase,and the accessibility of the acidic sites and the pore diffusion are improved.The N-hexane was selected as the F-T low-carbon hydrocarbon model compound,and the prepared Pt-based micro-media composite material was applied to the isomerization of n-hexane.The results show that the selectivity of the composite at the same conversion level is increased compared to the original MOR.This study provides a reference for the preparation of low carbon normal paraffin hydroisomerization support,and it is expected to achieve efficient conversion of heterogeneous products through the regulation of mesoporous recombination.