ZSM-22/ZSM-23共晶分子筛的合成及其正十六烷加氢异构催化性能

Synthesis of ZSM-22/ZSM-23 intergrowth zeolite as the catalyst support for hydroisomerization of n-hexadecane

在二甲胺与二乙胺双模板剂体系中,通过控制二甲胺/二乙胺的摩尔比为24,动态水热合成了ZSM-22/ZSM-23共晶分子筛。采用XRD、FE-SEM、TEM、N2物理吸附、NH3-TPD和吡啶吸附红外等表征手段,考察了ZSM-22/ZSM-23共晶分子筛样品的物理化学性质,并对其负载Pt后在正十六烷加氢异构化反应中的催化性能进行了研究。结果表明,针状的ZSM-22/ZSM-23分子筛具有与ZSM-22和ZSM-23不同的拓扑结构,其Brönsted酸量及中强酸比例较高。对于正十六烷加氢异构化,相比于单一分子筛和机械混合分子筛催化剂,采用共晶分子筛通过浸渍法制备的双功能Pt/ZSM-22/ZSM-23催化剂同时具备Pt/ZSM-22高选择性以及Pt/ZSM-23高转化率的优势,表现出更高的异构体收率,并具有一定的择形效应,异构化产物以单甲基异构体为主。

ZSM-22/ZSM-23 intergrowth zeolite was successfully synthesized by hydrothermal method with diethylamine and dimethylamine as co-structure directing agents at a dimethylamine/diethylamine molar ratio of 24.The physicochemical properties of ZSM-22/ZSM-23 intergrowth zeolite including the crystallinity,crystal morphology,texture and acidity were determined by XRD,FE-SEM,TEM,N2-physisorption,NH3-TPD,Py-FTIR,and so on;the performance of Pt/ZSM-22/ZSM-23 catalyst prepared by impregnation in the hydroisomerization of n-hexadecane was then investigated.The results indicate that the ZSM-22/ZSM-23 intergrowth zeolite displays the needle-like morphology with the topological structures of both ZSM-22 and ZSM-23,which is rather different from pure ZSM-22 and ZSM-23 and their mechanical mixture.After loading 0.5%Pt,the bi-functional Pt/ZSM-22/ZSM-23 catalyst exhibits excellent performance in the hydroisomerization of n-hexadecane,with a much higher yield of i-C_(16)products(dominated by mono-branched isomers)than those obtained over Pt supported on ZSM-22 and ZSM-22 and their mechanical mixture.