Study Of N-heptane Hydrogen Isomerization On Cr₂O₃-Pt/WO₃/ZrO₂ Catalyst

Light naphtha isomerization oil,which does not contain sulfur,aromatics,and olefins,is one of the clean gasoline components with high octane number.The isomerization of n-pentane and n-hexane of light naphtha has been industrialized,while the isomerization of long-chain alkanes represented by n-heptane is difficult and not industrialized yet.If n-heptane isomerization is industrialized,it will bring tremendous technological advancement to the production of high-octane gasoline.The Pt/WO₃/ZrO₂ catalyst has good thermal stability,strong acidity,simple preparation method,regeneration and good isomerization reaction performance,and thus becomes a research focus as the n-heptane isomerization catalyst.In this paper,the Pt/WO₃/ZrO₂ catalyst was modified with various metals such as Cr to improve the catalyst performance.The main research results are as follows:?1?The Pt/WO₃/ZrO₂ catalyst was modified by rare earth metals including La,Ce,Pr and Rb,and transition metals including Cr,Co,Zn and Fe.Catalysts were prepared by the impregnation method,and characterized by XRD,BET,NH₃-TPD and SEM.The results show that the Cr₂O₃-Pt/WO₃/ZrO₂ catalyst exhibited a larger specific surface area,stronger acidity and better catalytic activity in the isomerization of n-heptane.?2?The effects of WO₃ content,Cr content,calcination temperature and calcination time on catalyst activity were investigated.The results show that Cr₂O₃-Pt/WO₃/ZrO₂ has the highest activity when the WO₃content was 18 wt%,the Cr content was 1.0 wt%,the calcination temperature was 800°C and the calcination time was 3 h.While the conversion of n-heptane reached 82%and the yield of n-heptane isomer reached 73%.?3?The effects of reaction condition such as temperature,pressure,LHSV and the mole ratio of hydrocarbon to hydrogen on n-heptane isomerization were discussed.Under the temperature of 220°C,the pressure of 1.0 MPa,the LHSV of 1.05¹.4 h^-1and the mole ratio of hydrocarbon to hydrogen of 9,the catalysts showed the highest isomerization activity with the yield of n-heptane isomer around 75%.?4?The stability of the Cr₂O₃-Pt/WO₃/ZrO₂ catalyst was investigated.The results show that the catalyst was not deactivated after 500 h of n-heptane isomerization reaction.The Cr₂O₃-Pt/WO₃/ZrO₂ catalyst was used in the isomerization of light naphtha feedstocks,and the octane number of the chromatogram increased by 28 units.