摘要
在典型的(NH_4)_2SiF_6与(NH_4Na)Y反应条件下分别研究了(NH_4Na)Y与NH_4F、HCl和NH_4F+HCl以及HY与NH_4F的作用。发现F^-单独不能使(NH_4Na)Y脱骨架铝,HCl也不能使其脱铝(在NH_4Ac缓冲液中),而HCl+NH_4F可使其脱铝并保持较高的结晶度。据此认为(NH_4)_2SiF_6与沸石反应时,沸石的骨架铝是在H^+和F^-的共同作用下逐步脱出的,而不是被F^-抽取掉。根据反应机理提出脱铝沸石中有少量组分性氟存在,水洗不能将其除去。
Under typical reaction conditions,(NH_4)SiFe with (NH4Na)Y,especially using NH4Ac as buffer,the reaction of (NH4Na)Y with NH4F,HCl,NH4F + HC1 and HY with NH4F was studied separately.It is found that F- or H+ itself can not make the zeolite dealuminated,whereas (H++F~) is able to do so.According to these results,it is suggested that when (NH4)2SiF6 reacted with faujusite,the framework A13+ of the zeolite can be removed by reaction with (H++F-) alternately rather than being extracted by F- alone.Therefore,it can be deduced that the dealuminated zeolite prepared by isomorphous substitution with (NH4) 2 SiF6 contains a small amount of structural fluorine which can not be removed by washing.
基金
国家自然科学基金
关键词
八面沸石
脱铝补硅
氟硅酸铵
Faujusite
isomorphous substitution
ammonium fluorosilicate
reaction mechanism
