Effect of synthesis pH and H2O molar ratio on the structure and morphology of aluminum phosphate (AlPO-5) molecular sieves

被引:31
作者
Chen, CM [1 ]
Jehng, JM [1 ]
机构
[1] Natl Chung Hsing Univ, Dept Chem Engn, Taichung 402, Taiwan
关键词
AlPO-5 molecular sieve; H2O concentration; pH control; hexagonal pillar crystal; tridymite structure;
D O I
10.1023/A:1022120824681
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
AlPO-5 molecular sieves were prepared by the hydrothermal reaction of a gel mixture with the following compositions: Al2O3:P2O5:Et3N:H2O = 1:1:1.5:x, where x is between 100 and 750 H2O molar ratio. The structure and morphology of the AlPO-5 molecular sieves depend on the gel mixture's composition, hydrothermal temperature, hydrothermal reaction time, and H. Without H control, the AlPO-5 structure changed from a spherical shape at H2O = 100 to a hexagonal pillar shape at H2O = 450. With pH control in the range of about 2.5-3.5, the hexagonal pillar crystals began to form at H2O = 100 and an island of hexagonal pillars with radiation form appeared at H2O = 300-450 due to the formation of a tridymite type of dense AlPO4 phase. It appears that the formation rate of hexagonal pillar crystals to form a dense AlPO4 phase is favorable under acidic conditions, and an amorphous AlPO-5 structure forms under basic conditions. Thus, the H2O concentration and pH value have a dramatic effect on the AlPO-5 structure.
引用
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页码:73 / 80
页数:8
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