偏高岭土转化为A沸石的结晶动力学

Studies on the crystallization kinetics of zeolite A from metakaolinite conversion

研究了不同粒径偏高岭土向Ａ沸石转晶的动力学．该偏高岭土是由结晶良好、不含杂质的硬质高岭土经预处理获得的．偏高岭土中，硅铝摩尔比与理论值一致．预处理时焙烧温度、所用的ＨＣｌ溶液浓度及ＮａＯＨ溶液浓度对Ａ沸石的结晶动力学及所获得的Ａ沸石相对结晶度有很大的影响．粒径为２～３μｍ及２５～３０μｍ的偏高岭土转化为Ａ沸石的成核活化能分别为１０．８ｋＪ／ｍｏｌ及１６．６ｋＪ／ｍｏｌ．这表明由偏高岭土转化为Ａ沸石较之后者从硅铝酸盐凝胶中形成要容易．

The conversion kinetics into zeolite A of several hard kaolinite withdifferent particle size have been investigated in temperature range 70 - 95 C' Thekaolinite is well crystallized without impurity, and has theoretical chemicalcomposition of St and Al. The concen iration of HCI solution for pretreating,Thecalcination temperature and the concentration of NaOH solution used for con if'sion greatly influence the crystallization kinetics and relative crystallinity of zeo.'tkA obtained. The active energy of nucleation of zeolite A from the conversionof metakaolinite with particle size 2- 3am are 10.skJ/mol (i.e. 2.58heal/mol) and16.6kJ/mol (i.e. 3.96 heal/mol) respectively. This indicates that metakaolinite conversion into zeolite A is much easier than the formation of zelolite A fromalumino - silicate gel.