Study on the mechanism of zeolite Y formation in the process of liquor recycling

Crystallization of zeolite Y formation in the process of mother liquor recy cling (MLR) has been studied. The zeolite crystallization mother liquor com prises a little sodium silicate as well as minor zeolite, Upon addition of aluminum sulfate, the silicate existed in the mother liquor reacts to form finely divided silica-alumina hydrogel (MLHG) which can be utilized later i n zeolite Y formation. The particle of MLHG is relatively small and Si/Al o f the gel's framework is a little great. Since amorphous aluminosilicate ge l passes through two stages of gelation, the pseudoequilibrium between soli d phase and liquid phase of gel is attained rapidly and the time of zeolite Y formation is much reduced. In addition, experiments have also showed tha t the quantities and the properties of zeolite Y added affect the process o f crystallization heavily. Minor quantities of zeolite in the mother liquor have detrimental effect on the zeolite Y formation. Based on studies of cr ystallization from recycling mother liquor, a model of two-phase transforma tion for zeolite Y formation has been proposed. (C) 1998 Elsevier Science B .V. All rights reserved.