Study On Hydrogenation Catalysts For Raw Materials Of C5/C6 Isomerization

Isomerized gasoline,with the characteristics of high octane number and low contents of sulfur,olefin and aromatic hydrocarbon,is an excellent gasoline blending component.The C5/C6 distillates contain a certain amount of benzene and olefin.However,hydrogenation releases a large amount of heat in the process of isomerization,which will increase the temperature of the reaction.On one hand,the isomerization reaction will be inhibited.On the other hand,the coke will be produced on the surface of the catalyst,which makes the catalyst activity decrease or even deactivate.This experiment aims to develop an economic hydrogenation catalyst for isomerization that can be used at low temperatures.In this paper,alumina support was prepared by using carbonized aluminum hydroxide,and chloroplatinic acid was used as precursor of active component to prepare impregnation solution.A series of catalysts with different platinum contents and prepared at different catalyst calcination temperatures were prepared.The results show that using n-hexane containing 2wt%benzene as raw material,for the Pt/Al₂O₃ catalyst,when the content of platinum is 0.30%,the calcination temperature is 400°C,the hydrogenation activity of the catalyst is the optimum,the conversion of benzene is 88.30%,and the selectivity of cyclohexane is 100%.On the basis of optimizing Pt content and calcination temperature of catalysts,three series of catalysts were prepared by adding different concentrations of competitive adsorbents including hydrochloric acid,acetic acid and citric acid to the impregnation solution.By characterization and evaluation,the results show that the optimum hydrogenation activity of benzene for Pt/Al₂O₃ catalyst is 93.38%.When hydrochloric acid is used as competitive adsorbent and the concentration of hydrochloric acid in the impregnation solution is 1M.The selectivity of cyclohexane is 100%.The preferred catalyst is evaluated in different process conditions,using n-hexane containing 2wt%benzene as raw material,the reaction temperature is 75°C,the reaction pressure is 2MPa,the LHSV is 4h^-1,and the hydrogen-oil ratio is 600.The conversion of benzene is 100%,the selectivity of cyclohexane is 100%;The hexane containing 2wt%benzene and 1wt%1-hexene is used as raw material at the temperature of 110°C and under the pressure of 2MPa.When the LHSV is 4h^-1 and the hydrogen-oil ratio is 600,the conversion of benzene is 98.26%,the conversion of 1-hexene is 100%,and the selectivity of benzene to cyclohexane is 100%.The selectivity of the 1-hexene to n-hexane reaction is100%.