摘要
通常用NH_4Y作原料与(NH_4)_2SiF_6反应进行脱铝补硅,因为NaY与(NH_4)_2SiF_6反应生成的NaF和Na_3AlF_6沉淀不易从沸石中洗除.高温下,氟化物将破坏沸石的晶体结构.如果能用NaY直接脱铝,则在生产中可简化操作过程,节省铵盐用量.为此,本文研究了NaY及不同交换度的(NH_4Na)Y脱铝反应.以及反应生成物中难溶氟化物从沸石中洗除的可能性.
Isomorphous substitution of (NH4Na)Y with different Na contents and NaY by (NH4)2SiF6 and the solubilities of fluorides were studied. When buffered with NH4Ac, 50% of the framework Al of NaY can be dealuminated and the crystallinity is higher than 90%. In the dealumin-ation of (NH4Na)Y, NaF can not precipitate. The solubility of Na3AlF6 in water is very low, however, its solubility increases obviously in aqueous electrolyte solution. In the dealumination of NaY, some Na3AlF6 precipitate will be formed, which is difficult to be removed from D-A1Y zeolite. The difference is small between sodium contents of D-AlY zeolites prepared by (1 ) (NH4Na)Y( Ⅰ) dealumination then exchanged with (NH4)2SO4 once, (2 ) (NH4Na)Y(Ⅱ) dealumination, and ( 3 ) (NH4Na)Y (Ⅲ) dealumination, though the processes (1 ) and (2 ) can cut down the NH4+ exchange once.
基金
国家自然科学基金
