微波辅助水热合成条件对直接合成纳米HZSM-5晶体性质的影响

发布时间：2018-08-03 13:24

【摘要】：利用微波辅助水热合成法直接制备了纳米HZSM-5晶体。采用XRD、FT-IR、SEM、BET和NH_3-TPD等手段对合成样品进行了分析表征,研究了晶化温度和时间对合成产物晶体性质的影响。结果表明,晶化温度和时间对微波辅助水热直接合成产物微观形貌、晶粒尺寸和分散度影响明显。较低的晶化温度和较短的晶化时间均难以形成形貌规则的HZSM-5晶体。随着晶化温度的升高,合成样品逐渐变为球形晶粒、晶粒尺寸逐渐增大、分散度逐渐提高,继续提高晶化温度达180℃时,晶粒长大使比表面积稍有降低;随着晶化时间的延长,样品的微孔和介孔增多,比表面积和孔容逐渐增大,继续延长晶化时间,晶体内微孔可能的收缩和晶粒的长大使得样品孔容和比表面积减小。160℃和1.5 h条件下制备的HZSM-5分子筛晶体形貌呈球形,晶粒尺寸约为60 nm,分散程度较好;其比表面积、孔容和平均孔径分别为398.45 m~2·g~(-1)、0.63 cm~3·g~(-1)和6.27 nm;晶体表面具有弱酸特征。
[Abstract]:Nanocrystalline HZSM-5 crystals were prepared by microwave-assisted hydrothermal synthesis. The synthetic samples were characterized by XRDD-FT-IRT-SEMT-BET and NH_3-TPD, and the effects of crystallization temperature and time on the crystal properties of the synthesized products were studied. The results show that the effect of crystallization temperature and time on the microstructure, grain size and dispersion of microwave-assisted hydrothermal direct synthesis products is obvious. It is difficult to form HZSM-5 crystal with regular morphology at lower crystallization temperature and shorter crystallization time. With the increase of crystallization temperature, the synthesized samples gradually become spherical grains, the grain size increases gradually, and the dispersity increases gradually. When the crystallization temperature continues to increase to 180 鈩，

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