硅酸为硅源合成丝光沸石晶体

SYNTHESIS OF MORDENIT CRYSTALS WITH SILICIC ACID POWDER AS SILICON SOURCE

合成尺寸较大、形状均一的丝光沸石（MOR）晶体对于研究分子在MOR晶体中的吸附和扩散有重要意义。笔者采用硅酸作为硅源水热法合成了丝光沸石晶体，以XRD和SEM手段对所合成的丝光沸石进行表征，考察硅酸焙烧温度、硅酸粉末颗粒大小、体系Si／Al摩尔比（n（SiO2）／n（Al2O3））以及碱度对合成丝光沸石晶体的影响。结果表明，减小硅酸粉末的颗粒大小、提高体系n（SiO2）：n（Al2O3）、适当降低体系碱度均可抑制杂晶相（ANA和PHI）的产生，同时得到尺寸较大、形状均一的纯相丝光沸石晶体。采用200～250目的硅酸粉末作为硅源，在n（Na2O）：n（Al2O3）：n（SiO：）：n（H2O）=5：1：25：293．6的合成体系中，合成了晶体大小均一（约为23μm×13μm）的六方棱柱状MOR晶体，且不伴有杂晶产生。

To synthesize mordenite （MOR） crystals with large size and uniform shape is of utmost important to study their adsorption and diffusion properties. In the current study, large mordenite crystals were synthesized hydrothermally with silicic acid powder as a silica source, and the synthesized crystals were characterized by XRD and SEM techniques. The influence of several synthetic parameters, such as the heat pretreatment of silicic acid, the particle size of silicic acid powder, the Si/Al molar ratio （n （SiO2）/n（Al2O3 ）） and alkalinity in the synthesis solution, on the formation of the mordenite crystals was symmetrically investigated. The results indicated that reducing the particle size of silicic acid powder, increasing the n（SiO2 ） ： n（Al2O3）, and lowering the alkalinity in the synthesis solution properly can prevent from the formation of hybrid phases such as ANA and PHI zeolites, and pure MOR crystals with uniform shape and large size can be synthesized. Under the optimized conditions such as silicic acid powder with 200--250 mesh as silicon source, molar composition in the synthesis solution： n（Na2O） ： n（Al2O3） ： n（SiO2） ： n（H2O）=5 ： 1 ： 25 ： 293.6, prismatic mordenite crystals without any hybrid crystals with a uniform size of 23 μ/~m in length and of 13 μm in width can be obtained.