Role of Defects in Pore Formation in MFI Zeolites

被引:39
作者
Fodor, Daniel [1 ]
Redondo, Amaia Beloqui [1 ]
Krumeich, Frank [1 ,2 ]
van Bokhoven, Jeroen A. [1 ,3 ]
机构
[1] Swiss Fed Inst Technol, Inst Chem & Bioengn, CH-8093 Zurich, Switzerland
[2] Swiss Fed Inst Technol, Inorgan Chem Lab, CH-8093 Zurich, Switzerland
[3] Paul Scherrer Inst, Lab Catalysis & Sustainable Chem, CH-5232 Villigen, Switzerland
关键词
POWDER DIFFRACTION; ZSM-5; SILICALITE-1; DESILICATION; ADSORPTION; ALUMINUM; HYDROXYSODALITE; TRANSFORMATION; MESOPOROSITY; DEACTIVATION;
D O I
10.1021/jp5117933
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Silica lite crystals, crystallized With fluoride ions in the synthesis mixture; are stable in alkaline solution for at least 1 week of base treatment. Nuclear magnetic reasonance (NMR) and infrared (IR) spectroseopy evidence that silicaLite is essentially free of defect sites. MFI crystals with decreasing aluminum content it the order ZSM-5 (Si/Al = 14) > ZSM-5 (Si/Al = 50) > silicalite were base leathed. Based on X-ray diffrattion (XRD) patterns only silicalite and ZSM-5 (Si/Al = 14) retain the MFI morphology for as long as 1 week in alkaline solution (0.1 M NaOH at 80 degrees C), while that of ZSM-5 With Si/Al= 50 is completely destroyed. The modulating effect of aluminum sites is excluded in silicalite, and its lack of defects explains the stability. Scanning elettrart,microscopy (SEM) images show that leaching takes place in the center of the crystals preferentially in the [010] directionThe preferential pore forthation indicates that structural properties have an effect on creation of porosity upon alkaline treatment.
引用
收藏
页码:5447 / 5453
页数:7
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