ZSM-5沸石大单晶的生长  

THE GROWTH OF LARGE SINGLE CRYSTALS OF ZEOLITE ZSM-5

作　　者：龙英才[1] Long Yingcai(Department of Chemistry,Fudan University,Shanghai)

机构地区：[1]复旦大学化学系

出　　处：《高等学校化学学报》1982年第2期275-278,共4页Chemical Journal of Chinese Universities

摘　　要：ZSM-5是近十年来发展的具有广泛应用前景的高硅沸石分子筛。其骨架主要由五元环连结而成,具有十元环孔道(直径约6Å)。空间群为P_(nma)。大于40μm的均匀完美沸石单晶体,为晶体结构的测定以及与催化性质有密切关系的阳离子交换、扩散、吸附等重要性质的研究所必须。在通常的条件下获得大而完美的沸石单晶体是困难的。单晶的合成,有利于研究沸石晶体的形成与生长机理,是沸石结晶动力学研究的重要课题之一。According to the patent[5],the size of zeolite ZSM-5 crystals obtained in the system of(TPA)_(2)O-Na3 O-Al_(2)O_(3)-SiO_(2)-H_(2)O is merely about 1 Mm.The growth of ZSM-5 single crystals is investigated by the author in the system diethanolamine(DEA)-Na_(2)O-Al_(2)O_(3)-SiO_(2)-H_(2)O and batch samples(3 g each)of maximum size 50×50×120μmi(Fig.1)can be obtained,They are transparent and perfect,suitable for X-ray crystal structure determination and diffusion measurement.Raw materials used are water glass,Al_(2),(SO_(4))_(3),H_(2)SO_(4),and DEA.Proper amount of DEA is added to 30g of water glass,which has been filtered carefully beforehand.Gel(1)is formed.Fixed amounts of Al_(2)(SO_(4))_(3),H_(2)O and DEA are mixed,forming gel(2).Then gel(1)and(2)are mixed again.The mixture is poured into a hard glass tube and crystallized statically at about 160 to 220℃in a small autoclave for 50 to 300 hours until crystallization is completed.DEA not only acts as the"template"to initiate the formation of ZSM-5 but also serves as a buffering or complexing agent.However,the spontaneous crystallization in the DEA system always contains Mordenite and a-SiO_(2).Adding seeds(<1μm in size)obtained by grinding the single crystals of ZSM-5 can obviously improve the purity of ZSM-5.Pure ZSM-5 of 20×20×50μm in size is produced by adding more seeds.The size is obviously increased by adding fewer seeds.Small Amounts of other phase appeared during the later period of crystallization can be removed by elutriation and shifting.The perfection of the single crystals can be improved by adding glycerine to the reacting mixture.In the system of DEA,the compositions of reaction mixture for growth of single crystals have the following ranges(in terms of mole ratios):H_(2)O:SiO_(2)=200 to 600;OH:SiO_(2)=5 to 20;SiO_(2):Al_(2)O_(3)=50 to 150;DEA:SiO_(2)=0.4 to 4.Better materials for the autoclave wall are hard glass(GGl7),quartz glass and high purity graphite.Stainless steel produces smaller crystals while Teflon forms large quantities of a-SiO

关 键 词：结晶动力学 催化性质 晶体结构 五元环 沸石晶体 阳离子交换 单晶体 高硅沸石 

分 类 号：O64[理学—物理化学]