ZSM-5 Catalyst Preparation And The Application In Hexene Oligomerization

The preparation of ethylene from petroleum steam cracking and catalytic cracking(FCC)produces large amounts of low carbon olefins.With the increasingly strict environmental regulations,the olefin content of gasoline is strictly controlled,and the technology that mixed C₆ olefin with gasoline as a transportation fuel is seriously restricted by the low content requirement of olefin in gasoline.In recent years,the process of preparing clean liquid fuel by the oligomerization reaction of low-carbon olefins has attracted attention.The annual consumption of aviation fuel increases significantly year by year.Aviation fuel can be divided into aviation gasoline and aviation kerosene,and the carbon number distribution is between C₄?C₁₂ and C₉?C₁₆,respectively.The oligomerization of C₆olefin is a promising route for the synthesis of high-quality aviation fuel.Developing proper catalysts for the conversion of low carbon olefins can optimize the current refining technology and can improve the economic effectiveness,and the selection of a suitable catalyst is the key to the reaction.In this thesis,1-hexene is used as the raw material,and the ZSM-5 zeolite is used to investigate the catalytic activity in 1-hexene oligomerization reaction.The relationship between the structure and performance of the oligomerization catalyst was studied by adjusting the acidity of the zeolite and the existing state of the metal.ZSM-5 zeolite with different acid amounts was prepared by changing the number of ammonium exchange.The main conclusion is that,with a similar pore size structure,the conversion rate of 1-hexene increased with acid content,especially the weak acid content in the oligomerization reaction,but the selectivity of dimer decreased.Strong acid sites were necessary for the oligomerization of 1-hexene oligomers.However,high carbon oligomerization products and carbon are easily formed with strong acid sites.Therefore,the HZSM-5-EX2 sample with proper acid sites exhibited the highest conversion,with an initial conversion of 80.7%.The effects of different nickel states were further investigated.Ni/ZSM-5catalysts were prepared by in-situ synthesis,impregnation and ion-exchange.Catalysts synthesized by in-situ synthesis and impregnation showed the decrease of the pore volume.Compared to the zeolite support,the catalysts also showed less acid content.Therefore the conversion rate of 1-hexene was reduced,but the selectivity of the dimer was improved to a certain extent.However,the catalysts synthesized by the ion-exchange method exhibited a similar pore structure with the initial zeolite.The synergistic effect of the metal and the support was found in the oligomerization reaction.Finally,the reaction on the IM-5 zeolite in the 1-hexene oligomerization reaction was studied.The industrial ZSM-5 zeolite was selected as a contrast sample.IM-5 zeolite exhibited better activity for 1-hexene oligomerization reaction than commercial ZSM-5 zeolite under the same reaction condition.