多级孔HZSM-5分子筛的制备及其催化合成聚甲氧基二甲醚的性能

Synthesis of Hierarchical HZSM-5 and Its Catalytic Performance in the Synthesis of Polymethoxy Dimethyl Ether

采用两步结晶法,用不同硅源铝源在无介孔模板剂的情况下,直接合成具有多级孔结构的ZSM-5分子筛;利用XRD、SEM、N_(2)吸附/脱附、Py-IR等技术对合成的多级孔ZSM-5分子筛结构、形貌、织构和酸性质进行表征,并考察其催化甲缩醛和三聚甲醛合成聚甲氧基二甲醚(PODE)的催化性能。结果表明:硅源铝源会影响分子筛结晶过程的晶体尺寸,粒径小的纳米粒更容易相互堆叠形成晶间孔隙;以正硅酸乙酯为硅源,分别以硝酸铝、偏铝酸钠和硫酸铝为铝源合成的3个多级孔ZSM-5分子筛具有较大的介孔体积和较高的B酸/L酸值,在催化合成PODE反应中表现出较好的催化性能;三者对三聚甲醛的转化率均达90%以上,对PODE_(3~8)选择性分别为62.22%、62.35%和62.12%。

A two-step crystallization method was used to directly synthesize hierarchical ZSM-5 zeolite using different silicon sources and aluminum sources without mesoporous template;XRD,SEM,N_(2) adsorption/desorption,Py-IR were used to characterized the structure,morphology,texture and acid properties of the hierarchical ZSM-5 zeolite.And its performance in catalyzing the synthesis of polymethoxy dimethyl ether from methylal and trioxymethylene was investigated.The results showed that the silicon and the aluminum source will affect the crystal size of the zeolite during the crystallization process,and the small-sized nanoparticles are more likely to stack on each other to form intercrystalline pores.Three hierarchical ZSM-5 zeolites synthesized with tetraethyl orthosilicate as the silicon source and aluminum nitrate,sodium metaaluminate and aluminum sulfate as the aluminum source respectively had larger mesopore volume and higher B acid/L acid ratio,which showed a good catalytic performance in the catalytic synthesis of polymethoxy dimethyl ether.The conversion rate of paraformaldehyde were above 90%,whose yield of PODE_(3~8) were 62.22%,62.35 and 62.12%,respectively.