Synthesis And N-Dodecane Hydroisomerization Properties Of ZSM-22 Zeolites

F-T synthesis as the core of coal-to-liquids technology,through Fischer-Tropsch synthesis Fischer-Tropsch wax upgrade into higher value added lubricant base oil,so as to realize changing the present status of lubricating oil mainly rely on import in our country,and the conversion process is mainly relies on the hydrogenation technology of heterogeneous,by is long straight chain alkanes into single chain or much branched chain isomerization alkane,and transform the features of the product,For example,product low temperature fluidity,product freezing point,octane number and so on.Hydrogen isomerization technology usually uses a dual-function catalyst consisting of zeolite molecular sieve and metal,which is composed of molecular sieve carrier part with acidic component and metal part of hydrogenation dehydrogenation component.ZSM-22 molecular sieve because of its excellent 10-rings one-dimensional pore structure and suitable acidic performance is usually selected as a catalyst carrier,the metal part of the general selection of Pt,Pd and other good hydrogenation dehydrogenation performance of precious metals.In this thesis,ZSM-22 molecular sieve was successfully synthesized by two different dynamic and static methods.With precious metal Pt as the active component,the morphology change,pore structure and acidity change of the molecular sieve under two different synthesis conditions were investigated,and the isomerization performance of the molecular sieve in the hydroisomerization reaction of n-dodecane was explored.The optimum synthesis method of molecular sieve was obtained by comparison.The results show that the ZSM-22 molecular sieve synthesized at 70r/min in a homogeneous reactor has the best hydroisomerization performance.ZSM@γ-Al₂O₃ core-shell catalyst was successfully prepared by introducing different contents ofγ-Al₂O₃ into ZSM-22 zeolite after post-treatment under hydrothermal treatment.The performance of n-dodecane isomerization reaction was investigated by loading Pt noble metal.The results show that core-shell zeolite can cover some acidic components on the surface of ZSM-22 zeolite,which reduces the cracking reaction in the reaction process,but also reduces the conversion rate of the reaction,and the product distribution of the product is also changed due to the change of the contact distance between reactants,Different from pure ZSM-22 molecular sieve product distribution,core-shell molecular sieve single chain isomerism product 2-methylunalkane changes,showing a trend of first increase and then decrease,and different content ofγ-Al₂O₃ core-shell catalyst catalytic performance is different.The industrial ZSM-22 zeolite was treated with NH₄F and NH₄F-HF aqueous solution and impregnated with 0.5wt%Pt to prepare dual-function catalyst.The hydroisomerization performance of n-dodecane was evaluated before and after treatment.Through a series of characterization,ZSM-22 zeolite treated with different concentrations has different pore structure and properties,and its morphology also has a certain change.Catalytic results show that the ZSM-22 after treatment has higher conversion,selectivity and yield than the original sample.