胶体二氧化硅
硅酸铝
化学
溶解
沸石
胶体
化学工程
铝酸钠
硅酸钠
铝酸盐
吸附
絮凝作用
沉淀法白炭黑
无定形固体
无机化学
铝
材料科学
有机化学
催化作用
天然橡胶
水泥
冶金
涂层
工程类
作者
D.M. Ginter,Gregory T. Went,Alexis T. Bell,Clayton J. Radke
出处
期刊:Zeolites
[Elsevier]
日期:1992-07-01
卷期号:12 (6): 733-741
被引量:73
标识
DOI:10.1016/0144-2449(92)90125-9
摘要
An investigation was carried out to determine the effects of room-temperature aging on the structure and composition of NaY zelite synthesis gels prepared from colloidal silica. Alkaline solutions containing varying amounts of sodium aluminate were added to a colloidal silica sol to produce gels of composition 4 Na2O, x Al2O3, 10 SiO2, 180 H2O (x = 0.0 –1.5). Each of the gels was homogenized and then allowed to age at room temperature. Changes in the composition and structure of the solid and liquid phases of zeolite synthesis gels were followed as a function of time using elemental analysis; n.m.r., i.r. and Raman spectroscopies; and X-ray diffraction. Initial mixing of the colloidal silica, caustic, and aluminate has no noticeable chemical or structural effects beyond gelation via flocculation of the silica particles and adsorption of AI and Na onto the surface of the particles. The colloidal silica dissolves during aging as a consequence of successive cleavage of siloxane bonds. Adsorption of AI reduces the rate of silica dissolution. The slow dissolution of the silica releases monomeric silicate anions that rapidly react with aluminate anions to form an aluminosilicate precipitate, estimated to have a SiAi ratio of 1. Once the dissolved aluminum is depleted from the liquid phase, the remaining colloidal silica dissolves away, leaving only an amorphous aluminosilicate in the solid phase, which can then rearrange through interaction with the silicates anions in solution. As discussed in a companion study, the aluminosilicate precipitate formed during aging serves as the precursor for nuclei which induce the cyrstallization of NaY zeolite.
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